Sony Unveils CCD with Dual-Layer Microlenses

This month's Sony semiconductor and component newsletter gives details of how the brand's new 14-Megapixel CCD sensors are designed. The new sensors use an interesting technological development, which we're surprised hasn't featured in some of the brand's previous sensors: a double layer of microlenses.

When the first 14-Megapixel compact cameras began to appear, we were all concerned that it wouldn't be possible to achieve the same sensitivity levels with photodiodes that would inevitably be 15% smaller, especially when sensitivity was already teetering on the edge of acceptability in the previous 12-Megapixel model.

For a few months now, several manufacturers (Canon in particular) have been talking a lot about microlenses, the small lenses that cover the light-sensitive photodiodes that make up the sensor. Microlenses concentrate light onto the sensor by channelling it onto the photodiodes.

The new 1/2.3" sensors with 14 Megapixels have a pixel size of 1.43 µm, compared with 1.55 µm for the previous 12-Megapixel sensor. In other words, effectively directing each and every photon of light onto the photodiodes is more important than ever. The Sony Ericsson Satio mobile phone, which featured a 12-Megapixel 1/2.5" sensor with an almost identical pixel size, failed to impress on photo quality, with a slight gain in detail but poorly reproduced black tones.


To limit the impact of reducing the size of the light-sensitive areas, Sony has stacked two microlenses on top of one another. The new 14-Megapixel sensor therefore has two microlens layers, which helps channels light onto the light-sensitive photodiodes more effectively.

It's difficult to say whether all 14-Megapixel 1/2.3"compact cameras use this type of sensor technology or whether it's brand new, as most manufacturers generally prefer to keep this kind information under lock and key. In any case, the first 14-Megapixel compacts we've tested have given fairly mixed results, usually with a slight improvement in sharpness but a fairly average sensitivity.

The Panasonic TZ7 vs TZ10 (which feature 10- and 12-Megapixel sensors respectively) is currently the only comparison we can make between different resolution sensors with the same lens. At 80 ISO, the 12-Megapixel TZ10 takes shots that are much more detailed. However, it's not possible to directly compare the two cameras' sensitivities, as Panasonic's TZ10 is much more heavy handed with its image processing.

The Sony newsletter also said that the new 14-Megapixel sensor can handle 1.6 frames per second in full definition. If many recent models of compact can only manage less than one frame per second, even in burst mode, then it's almost certainly down their internal electronics.

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