SPring-8, the large synchrotron radiation facility

Speaker : Takeharu Goji Etoh

Language : JAPANESE

Affiliate : Ritsumeikan University

Title : Ultra-high-speed video cameras-toward 1Gfps

Abstract :
In 1991, we developed a high-speed video camera operating at 4,500 frames per second (fps), which was later marketed as Photron FASTCAM, the 1st generation; KODAK EKTAPRO HS4540. Since then, we have been updating the highest frame rate of video cameras in the world. We achieved 1 Mfps in 2002 (SHIMADZU HPV 1&2), and 16Mfps in 2011. The theoretical highest frame rate is more than 1Gfps. History of development of the high-speed image sensors is reviewed, and the future evolution is forecasted.
[Technologies]
(1) In-situ Storage Image Sensor operating at 1Mfps (2002)1): A slanted linear storage CCD was mounted for each pixel as in-situ storage of image signals. Simultaneous recording of image signals at all pixels enabled image capturing at the frame interval equal to the time required for an image signal to be transferred to the neighboring storage element. It achieved one million frames per second. However, the fill factor was only 15% due to the light shield which covers the storage area to prevent direct intrusion of incident light to the storage.
(2) Backside Illuminated CCD operating at 16Mfps (2011)2): The fill factor is nearly 100%. The EM-CCD was mounted on the readout HCCD. Therefore, the sensitivity is very high. If we mount in-situ storage for each pixel on the front side of a backside-illuminates (BSI) image sensor with a standard structure, false signals are generated in the storage area by direct intrusion of residual of incident light after the absorption in the silicon layer and by migration of generated photoelectrons to the storage. To prevent these effects, we developed a special cross-sectional structure. The starting material is a wafer with thick p-/n- double epi-layers. In the n- epi-layer, a p-well is made by implanting from the front side, and the CCD memories are made in the p-well. In the p-well, various functional circuits can be installed, instead of the simple CCD memories, which may provide ultra-high-speed functional image sensors.
(3) Image sensor technologies toward 1Gfps : It is possible by using currently available technology to achieve more than 100 Mfps, by introducing a new concept, an image sensor with multi-collection gates at the center of each pixel, in addition to the above-mentioned special BSI structure. The multi-collection gates collect image signal packets in turn and each transfers a signal packet to the neighboring memory element during the others collecting the signals. It may be possible to achieve 1Gfps by using this technology in the near future.
[Reference]
1) Etoh, et al, A CCD image sensor of 1,000,000 fps for continuous image capturing more than 100 consecutive frames, ISSCC2002, 45, 46-47.
2) Etoh, et al, A 16 Mfps 165 kpixel backside-illuminated CCD, ISSCC2011, 54, 406-407.

Organizer : Hidenori Toyokawa
Mail : toyokawa@spring8.or.jp
PHS : 3865