A Dual-Mode 303-Megaframes-per-Second Charge-Domain Time-Compressive Computational CMOS Image Sensor.

Keiichiro Kagawa,Taishi Takasawa,Masaya Horio,Shoji Kawahito,Thoriq Ibrahim,Keita Yasutomi,Shin-Ichiro Okihara,Anh Ngoc Pham,Tatsuki Furuhashi,Hajime Nagahara

doi:10.3390/s22051953

Abstract

An ultra-high-speed computational CMOS image sensor with a burst frame rate of 303 megaframes per second, which is the fastest among the solid-state image sensors, to our knowledge, is demonstrated. This image sensor is compatible with ordinary single-aperture lenses and can operate in dual modes, such as single-event filming mode or multi-exposure imaging mode, by reconfiguring the number of exposure cycles. To realize this frame rate, the charge modulator drivers were adequately designed to suppress the peak driving current taking advantage of the operational constraint of the multi-tap charge modulator. The pixel array is composed of macropixels with 2 × 2 4-tap subpixels. Because temporal compressive sensing is performed in the charge domain without any analog circuit, ultrafast frame rates, small pixel size, low noise, and low power consumption are achieved. In the experiments, single-event imaging of plasma emission in laser processing and multi-exposure transient imaging of light reflections to extend the depth range and to decompose multiple reflections for time-of-flight (TOF) depth imaging with a compression ratio of 8× were demonstrated. Time-resolved images similar to those obtained by the direct-type TOF were reproduced in a single shot, while the charge modulator for the indirect TOF was utilized.

Highlights

Ultra-high-speed (UHS) cameras are utilized to observe ultrafast phenomena in the fields of science and industry [1]
We proposed a multi-aperture UHS image sensor that adopted an entirely different scheme using compressive sensing, which was motivated by computational photography [7,8]
The image acquisition tion scheme is based on compressive sensing, and signal compression is performed in the scheme is based on compressive sensing, and signal compression is performed in charge domain in pixels

Summary

Introduction

Ultra-high-speed (UHS) cameras are utilized to observe ultrafast phenomena in the fields of science and industry [1]. Solid-state UHS cameras are advantageous compared with other technologies based on streak cameras or ultra-short pulse lasers [2,3] in terms of compactness, durability, and mass productivity, increasing the frame rate is a challenge. To realize ultrafast frame rates that cannot be achieved by ordinary continuousreadout image sensors, the burst readout scheme is utilized. Burst readout UHS image sensors are equipped with on-chip frame memory, where images are stored for a short time. There are several implementations, such as CCD or CMOS, with pixelwise or columnwise memory. UHS image sensors with on-chip analog frame memory have achieved

Methods

Discussion

Conclusion