As is well known, a drop of water falling onto a water surface forms a “water crown.” This is caused by a phenomenon occurring beneath the water’s surface. To begin with, the air enclosed between the drop and the water surface instantly forms a ring of small air bubbles similar in appearance to a pearl necklace. Then, as the diameter of this ring decreases, individual air-bubble diameters increase as air bubbles unite eventually forming one bubble that finally separates into two separate upper and lower bubbles.This phenomenon was discovered with the aid of an ultrahigh-speed video camera featuring image-capturing speeds of 1,000,000 frames per second (fps).

The camera was developed and built by Professor Takeharu Etoh of the School of Science and Engineering, Kinki University, in cooperation with Shimadzu Corporation and other organizations.

Professor Etoh’s specialty is hydraulic engineering. In 1991, to visualize water flow in detail, his research group developed a camera that captures 256×256-pixel images at 4500 fps or 64×64-pixel images at 40,500 fps. Ten years later in 2001, the group developed an experimental video camera capable of capturing 312×260-pixel images at 1,000,000 fps.

 Professor Etoh and his group are presently developing an ultrahigh-speed, high-resolution 1,000,000-fps video camera system applicable to digital high-definition television (HDTV) broadcasts. With Assistance Grant for 2002/2003 grant cycle provided by the Hoso-Bunka Foundation, the group’s research continues toward a practical professional system.

 The In-situ Storage Image Sensor (ISIS) developed by Professor Etoh and his group has made this ultrahigh-speed image capturing possible. When this sensor is used, each pixel has multiple image signal storage and the image signals are stored consecutively during shooting instead being read out to an external device. The image signals are collectively output from the device at low speed only after shooting is completed. This scheme achieves heretofore-impossible ultrahigh-speed capture while maintaining high picture quality. To incorporate many tiny storage spaces within a small pixel, this image sensor employs the world’s simplest and smallest storage structure (slanted CCD storage); this structure was proposed by Professor Etoh.

 At present, however, with the aim of creating an HDTV system, Professor Etoh and his group are developing the “terraced image sensor” with a new image-sensor structure. This work is being done in conjunction with research on packaging technology, image trigger and other related technologies.

 To give another example of research aimed at an ultrahigh-speed HDTV camera system, Professor Etoh and his group have teamed with NHK Science and Technical Research Laboratories to develop an experimental 1,000,000-fps color video camera featuring three 80,000-pixel ISIS image sensors. Field trials are currently being held that use this video camera for night baseball game broadcasts and others.

 For further information about this reserch project, please make contact with Prof. Takeharu Etoh of the School of Science and Engineering, Kinki University (mail to : best2010@civileng.kindai.ac.jp ), or Mr. Hirotaka Maruyama, Senior research engineer (Advanced Imaging Devices) of NHK Science & Technical Research Laboratories (mail to : maruyama.h-hy@nhk.or.jp ).