By Roland Piquepaille
A flexible image scanner that you could roll up and carry in your pocket along with your cell phone will soon help you to capture an accurate image of a curved surface such as the label on the wine bottle you just shared with friends. In "Flexible scanner works on curved surfaces," New Scientist writes that a recently introduced prototype weighs less than 1 gram. Its dimensions are 50 by 50 millimeters and it's only 0.4 millimeter thick. You connect it to your phone, which acts both as a power provider and as a display. So far, this flexible scanner can only capture images of its own size and has only a resolution of 36 dots per inch. But more advanced scanners should be on the market within three years, with better resolutions and in various sizes. The Japanese inventors say that a 7-centimeter-square scanner should cost about $10. Read more...Here is the description of this flexible scanner by New Scientist.
The new device, developed in Japan by electrical engineer Takao Someya and colleagues at the University of Tokyo, comprises a polymer matrix in which thousands of light-sensitive plastic photodiodes have been deposited 700 micrometres apart beneath a grid of plastic transistors.
Each photodiode produces a current in response to light input, which its accompanying transistor stores as a charge. This can then be read into the memory of a mobile phone and converted into an image.
To use the sheet image scanner, it has to be placed on the area of interest, such as a bottle or an open book. It can only capture the image it covers; it cannot be swiped across it like an office hand scanner.
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Here is a picture of the device scanning the label of a wine bottle (Credit: Takao Someya Group). |
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And here the flexible scanner is easily bent around the open page of a book.(Credit: Takao Someya Group). |
The above images were also shown in "Flexible image scanner," published by ElectronicsWeekly.com, which adds a few details about the resolution of the device.
Each pixel in the device consists of an organic transistor and organic photodetector with an effective sensing area of 50x50µm and the 0.4mm thick imager has a 50x50mm sensing area and resolution of 36 dots per inch (dpi) "with the potential to go up to 250 dpi", said Someya.
In this other article, "Image scanner fits in a pocket," optics.org brings additional information.
The device consists of a polymer laminate sheet containing a two-dimensional array of light sensor cells, each featuring an organic transistor and an organic photodiode.
Unlike conventional image scanners which mechanically scan a linear array of photodetectors over an object, the new Japanese design does not require any moving parts or internal optics to capture an image. Instead, the sheet is simply placed over the target object in ambient light conditions and the transistors are probed to reveal to the light intensity of each photodetector. Each sensor cell is also covered with an opaque light shield to prevent incident light from above distorting the signal generated by the object below.
Someya's current prototype has an effective sensing area of 2x2 inches and is just 0.4 mm thick and 1 g in weight. It features an array of 72x72 (5184) sensor cells, each 700 µm in size, giving a scan resolution of 36 dpi.
This flexible scanner was recently introduced during a presentation at the International Electron Devices Meeting (IEDM 2004), which was held in December in San Francisco. Here is a link to the press kit for this organic sheet-image scanner.
For more information, you can visit the Takao Someya Group website, which contains an abstract of the IEDM presentation.
A large-area, flexible, and lightweight sheet image scanner has been successfully manufactured on a plastic film, for the first time, integrating high-quality organic transistors and organic photodetectors. Since this area-type image-capturing device does not require any optics or any mechanical scanning devices, it is innovatively light to carry, shock-resistant and potentially inexpensive to manufacture.
Finally, I already mentioned here a previous work from the Takao Someya Group, "Flexible Sensors Make Robot Skin."
Sources: Celeste Biever, New Scientist, December 23, 2004; Steve Bush, ElectronicsWeekly.com, December 14, 2004; Oliver Graydon, optics.org, December 22, 2004; and various websites
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