KEYWORDS: Light emitting diodes, Signal to noise ratio, Photoacoustic spectroscopy, Photoacoustic imaging, Pulse signals, Signal processing, Laser systems engineering, Autocorrelation
Photoacoustic imaging is a new imaging technique that can measure optical absorbers with high resolution. Lasers are commonly used as light sources for photoacoustic imaging, but there are many safety restrictions. Therefore, devices in which the light source is replaced by LEDs, which have fewer safety restrictions, are attracting attention. However, LED light sources have very low energy, and the photoacoustic signal generated is correspondingly small. Therefore, the photoacoustic signal is buried in noise, resulting in a low signal-to-noise ratio (SNR). Averaging can also improve SNR, but it is difficult to maintain a high frame rate. M-sequence signal processing can improve SNR while maintaining a high repetition rate, and its effectiveness has been demonstrated in photoacoustic measurements of laser light sources. However, LED power supplies have time delays in emission and circuit jitter, which affect decoding. Therefore, we propose a new decoding algorithm that compensates for LED jitter. We then experimentally verified the SNR improvement using this signal processing in practice.
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