Matsushita Electronic Corp., Sharp Corp. and Sony Corp., the top three suppliers of megapixel CCD sensors, showed samples with over 2 Mpixels at the Electronics Show last week.

Matsushita's sensor has 2.31 Mpixels, Sharp's has 2.14 Mpixels and Sony's contains 2.11 Mpixels.

When CCD resolution exceeds one million pixels, progressive scanning becomes impossible. All three of the 2-Mpixel CCDs, therefore, employ interlaced read-out systems. The optical format was enlarged from one-third to one-half inch to secure enough sensitivity for the one-million-plus pixel level.

The large optical format helps to improve performance, which was said to surpass existing megapixel sensors. Sharp and Sony's sensors achieve a sensor-saturation signal of 500 mV and a sensitivity of 300 mV, respectively. Matsushita's device has a sensitivity of 480 mV and a sensor-saturation signal of 600 mV.

"Sensitivity is largely dependent on cell size," said a spokesman for Sony CCD. Sharp and Sony's devices have cells of 3.95-mm² and 3.9-mm², respectively. Matsushita's device has larger, 4.2-mm² cells because it is about 1 mm larger than the other two sensors, measuring 9.1 mm diagonally. Matsushita's sensor features a 3:2 aspect ratio, the same as that of 35-mm files, while the devices from Sony and Sharp have an aspect ratio of 4:3.

Compact package
While the devices are larger, total package size was kept to almost that of the one-third-inch format sensors, thus retaining a compact consumer-camera size.

"To achieve the same package size as that of the one-third-inch format, we developed a plastic package for the one-half-inch format sensor," said a spokesman for Matsushita Electronic's CCD unit.

All three companies offer small-outline packages for surface mounting to a dual in-line package.

The resolution of digital still cameras is increasing so rapidly that Kodak projects that those with resolutions surpassing 1 Mpixel will account for more than 50 percent of the digital camera market this year.

"Two-megapixel cameras will appear as the high end of next spring's models. VGA-resolution cameras will form the low-end category. Cameras with 81,000 to 1.3 Mpixels will be in the popular price range and higher-resolution [cameras] will form the high end," said a Sharp CCD spokesman.

"The resolution is too much for PC displays. When 1.3 to 1.5 Mpixel cameras emerged, users were already starting to leave PC displays to view pictures. Instead, they preferred to have printouts of pictures from photo printers, like conventional film prints," said the Matsushita spokesman.

Sony and Matsushita started sampling last month and Sharp will follow this month. The three begin volume production in the first quarter of next year.