Toshiba and Sharp have both made advances in technology related to the optical sensor that is one of the most important components in a digital still camera, they said this week. The optical sensor sits behind the lens and is the device that converts light into electronic data.

Sharp said it has developed a CCD (charge-coupled device) sensor that has 6 million pixels but is the same physical size as sensors containing 4 or 5 million pixels. The company achieved this by making the individual pixels smaller so it could fit them into the required space, said Masaaki Takeda, a spokesman for Sharp in Tokyo.

The advantage of this is that camera makers can produce higher resolution cameras with less effort — delivering an image that measures 2,872 pixels by 2,160 pixels.

Samples of the sensor are just becoming available and Sharp said it would begin mass production at a level of 100,000 units per month in January 2004. The company would not disclose the volume price or how it compares to existing sensors.

Toshiba has also been making ground in the development of more advanced sensors although these are based on CMOS (complementary metal-oxide semiconductor) technology. Such sensors are generally considered to be inferior to CCD sensors, but Toshiba said its latest sensor matches or betters them in several areas.

The company made changes to two parts of the sensor to combat current leaking from defects and the surface layer, and in doing so produced a higher-quality sensor, said Fumio Izawa, chief specialist at Toshiba's image sensor marketing and engineering group, in an interview.

A prototype of the new sensor demonstrated by Izawa had 1.3 million pixels to produce an SXGA resolution (1,280 pixels by 1,024 pixels) image, according to the company. The sensor has a light sensitivity of 2 lux at five frames per second, which is equivalent to CCD, said Izawa. It also draws less power, consuming 150 milliwatts at 15 frames per second or roughly one-quarter that of a CCD sensor, according to Toshiba.

The company is planning to begin shipping the megapixel-class CMOS sensors in volume in 2004.

The development of better quality CMOS sensors doesn't mean that Izawa thinks camera makers will start switching from CCD en masse. He concedes the general image in many people's minds of CMOS sensors is one of lower quality and that will be hard to turn around. He hopes Toshiba's new sensors will help to address this.