Kirana: a solid-state megapixel uCMOS image sensor for ultrahigh speed imaging

Abstract

This paper describes a solid-state sensor for ultra-high-speed (UHS) imaging. The 'Kirana' sensor was designed and manufactured in a 180 nm CMOS technology to achieve full-frame 0.7 Megapixel video capture at speeds at 2 MHz. The 30 µm pixels contain a pinned photodiode, a set of 180 low-leakage storage cells, a floating-diffusion, and a source follower output structure. Both the individual cells and the way they are arranged in the pixel are novel. The pixel architecture allows correlated double sampling for low noise operation.In the fast mode, the storage cells are operated as a circular buffer, where 180 consecutive frames are stored until receipt of a trigger; up to 5 video-bursts per second can be read out. In the 'slow' mode, the storage cells act like a pipeline; the sensor can be read out like a conventional sensor at a continuous frame rate of 1,180 fps. The sensor architecture is fully scalable in resolution since memory cells are located inside each pixel. The pixel architecture is scalable in memory depth (number of frames) as a trade-off with pixel size, dependent on application. The present implementation of 0.7 Mpixels has an array focal plane which is optimized for standard 35 mm optics, whilst offering a competitive 180-frame recording depth.The sensor described has been manufactured and is currently being characterized. Operation of the sensor in the fast mode at 2 million frames per second has been achieved. Details on the camera/sensor operation are presented together with first experimental results.

Probing the nanoscale: the first contact of an impacting drop

“…We use long-distance microscopes, primarily a Leica (Z16 APO), with pixel resolution down to 1.04 µm/px. The rapid surface motions during first contact require ultra-high-speed video, acquired with the Kirana-05M from Specialized Imaging in Tring, UK (Crooks et al (2013)), at frame rates up to 5 million fps. The extreme 200 ns time-resolution, allows us to follow individual fringes between video frames and eliminates some of the ambiguity at lower frame-rates, which has required color interferometry to get absolute layer thicknesses , de Ruiter et al (2012)).…”

A Novel Image-based Ultrasonic Test to Map Material Mechanical Properties at High Strain-rates

“…The advent of full-field optical metrology, such as digital image correlation [35] or the grid method [10], combined with the new developments in ultra-high speed imaging [2,29,36] provides a unique opportunity to revisit high strain-rate testing techniques. In particular, full-field of accelerations can be obtained which provides a powerful image-embedded load cell if the material density is known, which is usually the case.…”

Probing the nanoscale with high-speed interferometry of an impacting drop

“…However, in most of our work we use a different approach. With the 5 million fps Kirana video camera (16) we are able to follow interference fringes from one frame to the next and thereby keep track of absolute thicknesses, while using monochromatic light. This requires identifying the last fringe before the drop touches the solid surface, therefore allowing us to trace back the absolute thicknesses at earlier times, by keeping track of new fringe formations.…”

“…This requires identifying the last fringe before the drop touches the solid surface, therefore allowing us to trace back the absolute thicknesses at earlier times, by keeping track of new fringe formations. This camera is based on in-sensor image storage (3,4,16) and can acquire a sequence of 180 frames, which corresponds to a total clip duration of 36 µs at the highest frame-rate. This mandates the use of electronic triggering for which we use a laser/photo-diode circuit, which the drop interrupts during its free-fall.…”