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CMOS Image Sensors for a Capsule Endoscope

Recent interest in human activity monitoring has spurred a great deal of research into the implantable sensor devices. The integration of an ultra-low power wireless transmitter has become a crucial factor in the design of implantable devices. We have developed a new design method of an extremely low-power transmitter using inductive coupling. Our approach makes it possible to integrate wireless components into a single silicon chip. It also provides a low cost and small-size implementation of next-generation medical instruments such as capsule endoscopes.

Developed CMOS one-chip wireless camera with digital image transmission function. The chip specifications and the measured performance summary.
Miniaturized wireless camera module. Captured image.

A prototype image sensor chip which has 320x240 effective pixels was fabricated using 0.25um CMOS image sensor process. With a 2.0 V power supply, the analog part consumes 950uW and the total power consumption is about 2.6mW. This extremely low power consumption is useful for long life battery operation. Error-free image transmission over a distance of 48cm at the data rate of 2.5Mbps corresponding to 2 fps has been demonstrated.

References

  1. Shinya Itoh, Shoji Kawahito and Susumu Terakawa,"A 2.6mW 2fps QVGA CMOS One-Chip Wireless Camera with Digital Image Transmission Function for Capsule Endoscopes", Proc. 2006 IEEE International Symposium on Circuits and Systems B3P-Z, pp.3353-3356, 2006.
  2. Shinya Itoh, Shoji Kawahito and Susumu Terakawa,"A CMOS One-chip Wireless Camera with Digital Image Transmission Function for Capsule Endoscopes", IEEJ Trans. SM, Vol. 126, No. 7, pp.318-324, 2006.
  3. Shinya Itoh and Shoji Kawahito, "A low-power transmitter design for inductive data link with class-F switching operation", IEICE Electronics Express, vol.4, No.2, 42-47, 2007.

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