25 August 2007

A new optic design promises better zoom capability for even the thinnest cameraphones!

A new design could put the power of a telephoto lens into thin cameras.

The mega pixel race on the digital cameras of the last years seems to have settled down now but in the mobile phone world it seems that there is a completely different trend.

While each generation of mobile phone cameras captures more megapixels, the image quality basically remains the same and still can't match the quality of those taken with stand-alone cameras.

The major reason is the quality and size of the sensor and the lens. In most of current mobile phones, the embedded lenses are frozen in place, without the ability to physically zoom in on a subject, sure there are some exceptions from this rule, and the Nokia N93 with its 3x optical zoom is nice example.

Sure, as the pour lovely phones are getting smaller, thinner and sleeker, engineering are getting less and less room to work wit which is the crucial problem in making camera phones and unfortunately it is nearly impossible to put the decent optic.

Instead of the optical zoom, to zoom in, cellphone cams sue the digital equivalent and simply stretch pixels, which kills image quality completely. In matter of fact digital zoom is completely useless thing, I’m only using it when I want to impress my friends and that’s the only real purpose. In my personal opinion digital zoom only benefits the manufacturer, because it’s another big number to stick on a spec sheet and another nasty trick how to attract more consumers and convince them to thinking they’ve did a good deal because they have a cam with 20x digital zoom

Digital zoom actually digitally enlarge photos by adding missing pixels via the interpolation, it enlarge a part of the image and on that way simulates optical zoom. In other words, the camera crops a portion of the image and then enlarges it back to size and the result is the blurry pictures with less details and pretty bad quality.

This novel lens design has the zooming capabilities of a telephoto lens 40 millimeters long, even though it’s only 5 millimeters thick. The trick is to collect light from the outer edge; reflect it within the lens eight times, using mirrors on the front and in the back; and focus it onto a camera sensor.

Anyway, lets go back to the point, because all of the mentioned problems, researchers at the University of California, San Diego (UCSD), working with Illinois-based optics company Distant Focus, have developed a new type of lens that could let mobile-phone cameras take close-up shots.

Joseph Ford, professor of electrical and computer engineering at UCSD, and his group have developed a five-millimetre-thick lens that has the power of an optical system that is usually 40 millimetres long. The group's novel design collects light and reflects it within the lens to obtain the full 40-millimeter optical path, and then it focuses the light onto the camera's sensor.

The research is based on technology called a folded optical system, which can be found in some telescopes today. In these telescopes, a series of separate lenses and mirrors are used to increase the distance that light travels before it reaches the imaging sensor, a distance known as the focal length.

Light is collected using a lens at one end, reflected between mirrors, and then focused onto a sensor. The longer the focal length of a system, the larger the final image will appear. Ford's group compressed this idea into a novel thin lens and designed it in such a way that light reflects inside the lens eight times before hitting the sensor.

To do this, the researchers made extreme modifications to a traditional lens. First, they used diamond machining to carve mirror surfaces out of a lens material called calcium fluoride. The mirrors steer the light, altering its path so that all the light converges onto the camera's sensor. Second, they coated both the front and the back of the calcium fluoride with mirrors so that the light reflects inside the lens. The key to making this lens work is precise alignment between the mirrors, which is accomplished by machining them all from a single piece.

Slimming Mirrors: The reflective rings on this crystal increase the optic's focal length to enable high-quality zoom.

The mirror on the front of the lens blocks roughly 90 percent of the light from entering, says Ford, which can reduce the contrast in an image.However, even with so much light blocked, he says, the group's camera was able to perform almost as well as a conventional lens almost ten times as long, producing images that are only slightly less crisp than those created using a traditional camera, in which 100 percent of the light from an image passes through the lens.