Fig 1
Fig 1
[Click to enlarge image]
Fig 2
Fig 2
[Click to enlarge image]

Fujifilm Corp will release the "FinePix F70EXR," a digital camera that features a 10x optical zoom lens and is as thin as 22.7mm, Aug 8, 2009.

One of the possible competing products is Olympus Corp's "μ-9000," a 10x zoom camera that is 31mm in thickness.

The street price of the F70EXR is about ¥40,000 (approx US$421). It took over most of the functions of the FinePix F200EXR, which achieved one of the highest image qualities as a compact camera by using the "Super CCD Honeycomb EXR" (See related article). The F200EXR features a 5x optical zoom and 23.4mm thickness.

Fujifilm gave the brand name "Fujinon," a famous brand for broadcast equipment, to the F70EXR's lens and claims that it achieved a high resolution that can live up to the brand. But how could the company thin the 10x zoom lens and realized the slim body of the camera. There are three answers to that question.

First, Fujifilm downsized the image pickup device, knowingly sacrificing the pixel count. One of the most important factors in the size of a lens unit is image sensor size. For the F70EXR, the company reduced the sensor size (diagonal length of the imaging area) of the image pickup device from 1/1.6 inch (diagonal length: 10.0mm) to 1/2.0 inch (diagonal length: 9.0mm).

As a result, the effective pixel count decreased from 12 million to 10 million. The pixel pitch remained at 2.0μm.

The second answer is a bold optical design including a sliding lens, which is a lens stored in a space made by removing some lenses from the optical axis. Hoya Corp is known to be good at making such a design.

"We use a different method for retracting lenses," Fujifilm said. "So, we do not infringe on their patents."

Furthermore, the company improved the refracting power by increasing the thickness of the spherical lens to be retracted and drastically enlarging its curvature radius. As a result, other lenses could be thinned (their curvatures were reduced).

The shape of the retractable lenses can be seen in Fig 2. In the left cut model, the retractable lenses are located obliquely above the image pickup device.

There are three other lenses that contributed to reducing the size of the lens unit, according to Fujifilm. In Fig 2, the second lens from the left is made of an anomalous dispersion glass material with a large Abbe number.

The first and second lenses from the side of the image pickup device have aspheric surfaces. The aspheric surface was designed by using high-order aspheric coefficients including odd orders, according to the company.

Third, Fujifilm made small but many improvements to the manufacturing process of the lenses, which, except for the retractable lenses, are much thinner than other lenses used for digital cameras. This means that the lenses of the F70EXR are more likely to be broken in the manufacturing process.

We could not know what kind of measures Fujifilm took to solve that problem. But the company said, "We are planning to use the new lens unit for many of our future products," showing confidence that it developed a reliable manufacturing process.