Solar-powered cellphones
In "Self-powered displays keep gadgets alive," New Scientist describes two new patents granted to Nokia and Motorola which plan to improve the batteries of our favorite handhelds (see below for tips on how to find a full version of a patent). While Nokia wants to develop self-powered billboards, Motorola is building a liquid crystal display (LCD) that incorporates a solar panel behind the screen of a phone. Other companies have tried to put solar cells behind phones' screens without success. Motorola says its approach is different because this new LCD will act both as a display and a light collecting device for the solar cell. No date is given about the availability of such a solar-powered phone.
New Scientist was kind enough to give us the U.S. patent number (7206044), so here is a description of the figure on the left extracted from this patent. "Many solar cells are provided in an integrated package that does not offer a uniformly colored active surface area. Instead, [in the figure on the left,] many such packages provide a plurality of solar cells 15 that are separated by inactive areas made of, for example, copper or other metal. Not only are such materials usually comprised on a color that does not match the color of the active surface regions, but such materials are also usually relatively reflective. As a result, when placing such a package behind a display surface as taught above, under at least some viewing conditions these inactive surface regions can be visible through the display. When visible in this way, the resultant display can be very distracting to a user."
The patent goes on an on (more on this below), so let's return to New Scientist for a more concise description of what Motorola engineers have done.
To give batteries a longer lifetime between charges without adding to their size and weight, manufacturers have tried fitting solar cells behind phones' LCD displays. Till now this has not been successful, because the LCD absorbs most of the incoming light before it can reach the solar cell, says Motorola engineer Zili Li.
Li's answer has been to propose building the LCD with colour filters made from a polymer film that reflects only narrow bands of red, blue and green light. This is enough to provide an adequate colour picture, while allowing through enough energy at other wavelengths for the solar cell to generate power to charge the phone's battery. Motorola will not say when the technology might reach the shops, but Li says the patent takes the company a step closer to developing mobile devices that need charging far less often than they do now.
I want to come back now at how you can find a U.S. patent. Of course, you can visit the United States Patent and Trademark Office (USPTO) and use its multiple and awkward various search engines. Eventually, you'll find a link to the "Display and solar cell device" patent. But first, the URL is so obfuscated that it might not be available tomorrow. And second, you cannot see the full images used in the patent except if your browser has an add-on which supports the "image file format called 'TIFF,' using CCITT Group 4 compression." You can read the USPTO explanations here.
Fortunately, there are several free -- and better -- services to find a patent online, and which don't need additional software installed on your system. For example, you can use FreePatentsOnline.com (link to their page about the Motorola patent) or PatentMonkey.com (link to their page about the Motorola patent). Or you can use pat2pdf.org which creates a PDF version of the patent very easily, but is not as good as the two above sites for searches.
Sources: Paul Marks, New Scientist magazine, Issue 2602, Page 30, May 2, 2007; and various websites
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