Architecture of a digital pixel sensor array using 1-bit Hilbert predictive coding

In this paper, the architecture of a digital pixel sensor (DPS) array with an online 1-bit predictive coding algorithm using Hilbert scanning scheme is proposed. The architecture of the sensor array reduces by more than half the silicon area of the DPS by sampling and storing the differential values between the pixel and its prediction, featuring compressed dynamic range and hence requiring limited precision (only 1-bit signed value in the proposed architecture as compared to 8-bit unsigned full precision). Hilbert scanning is used to read-out the pixel's value, hence avoiding discontinuity in the read-out path, which is shown to improve the quality of the reconstructed image. The Hilbert scanning path is all carried out by hardware wire connection without increasing the circuit complexity of the sensor array. Reset pixels are inserted into scanning path to overcome the error accumulation problem inherent in predictive coding. System level simulation results show a PSNR of around 25dB can be reached while using the proposed 1-bit Hilbert predictive coding algorithm. VLSI implementation results illustrate a pixel level implementation featuring a pixel size reduction of 67% with a fill-factor of 40% compared with a standard PWM DPS architecture.