High Sampling Rate Smartphone-PPG via Built-in Rolling Shutter Image Sensor

Abstract

Recent advancement of CMOS image sensor (CIS) on smartphone brings a significant improvement to IoT-based mobile healthcare technology in the form of CISphotoplethysmography (CPPG). Nevertheless, most of the available smartphone is equipped with a limited sampling rate (Fs), typically 30 frame per second (fps), thus often resulting in a distorted CPPG signal acquisition. This distorted signal is hard to be utilized for different types of advanced PPG-derived physiological analysis, and only useful in a simple pulse rate monitoring system. In this paper, the rolling-shutter camera mechanism has been exploited to extract CPPG data points from CIS-pixel rows, thus allowing high-Fs CPPG signal extraction from a common built-in, low-fps smartphone CIS. Multiple experiments were conducted to prove the reliability of RSCPPG signal. Firstly, we conduct iterative experiments with different CIS parameters to find their correlation to the acquired RSCPPG signal quality. Results indicate that the short exposure time produces a high-SNR CPPG signal up to 25 ± 2.38 dB, and highly correlated signal morphology (average r = 0.95) compared to the reference PPG signal. Then, we also demonstrated the proposed RSCPPG algorithm allowing a high CPPG data sampling with Fs = 150 Hz (that is ≥ 5 times CIS fps). Finally, feasibility study has been conducted on multiple features extracted from RSCPPG that are potentially implemented for further physiological analysis application. These findings suggest that the proposed RSCPPG algorithm is a reliable bio-signal acquisition technique in smartphone-based healthcare technology.

Tingkatkan Kamera Smartphone Tipe Entry Level Dan Mid Range Untuk Menghitung Denyut Jantung Dan Saturasi Oksigen Berbasis Photoplethysmogram Kontak

“…Sayangnya, banyak kamera smartphone kelas konsumen yang dibatasi pada sampling rate hanya 25-30 frame per detik (fps). Kesenjangan ini telah dikuatkan oleh beberapa penelitian [17], [18] yang mencapai hasil dengan akurasi tinggi menggunakan kamera dengan tingkat pengambilan sampel yang lebih tinggi. Oleh karena itu, penerapan metode ini pada kamera dengan laju pengambilan sampel yang lebih rendah pasti akan menghasilkan hasil yang bervariasi.…”