Ultra-low-light-level digital still camera for autonomous underwater vehicle

Abstract

In deep ocean applications, a camera’s viewing range is related to its low-light-level performance. Hence, a high-resolution ultra-low-light-level digital still camera (thereafter L3DSC), designed from the ground up for deep ocean autonomous underwater vehicle (AUV) imaging, is presented. A high-resolution (1024 × 1024) electron-multiplying CCD (EMCCD) is adopted as an image sensor to ensure low-light capability. A thermo electric cooler (TEC) is employed to lower image sensor temperature to promote low-light-level performance. Totem pole circuits that are able to generate 50-V pulse wave at 10 MHz are implemented to drive the EM pin, and power consumption of the circuit is optimized. An EMCCD digital image is buffered in a field-programmable gate array (FPGA) and then transferred through USB interface to a solid-state drive (SSD), which is installed in the image storage unit. The camera is controlled by AUV via Ethernet, and image data stored in the camera could be downloaded via the same interface after AUV retrieved from the sea. The camera module is mounted into a 6000-m depth-rate titanium alloy housing. The diagonal field of view is measured to be 58.4 deg in air. Experiments show that the minimum scene illumination of L3DSC is better than 5 × 10 − 4 Lux; underwater imaging distance is longer than 10 m, and total image data capacity is 200 gigabytes. These results demonstrate the camera’s low-light-level imaging performance and feasibility for AUV applications.