In the spirit of the recently dissected Fly Pen Computer, let's look at another device in the gadget space that embodies clever design. The iTech Virtual Keyboard aims to solve the problem of serious text entry on a handheld by replacing a physical keypad with a projected QWERTY layout whose "keystrokes" are read and translated to real input. At least technically, this is some pretty slick stuff.
The Virtual Keyboard weighs a little more than 3 ounces, measures just over an inch wide and deep, and is slightly more than 3.5 inches high. It stands on end to beam a laser-generated, trapezoidal image of a keyboard onto almost any flat surface. The manufacturer said the device can handle up to 400 keystrokes per minute while providing two hours of continuous typing between internal battery charges. The product comes with interface adapter cables for the most popular lines of PDAs, and one version is Bluetooth-equipped to end the wired hassle factor. In our limited testing, the device worked surprisingly well and the design concept seems quite solid.
So how does all this work? While our assessments often contain an element of speculation, it seems the core principle of operation here is straightforward--pro- ject the keyboard image and take a picture to see what's being "typed."
Virtual Keyboard projects a QWERTY layout, reads input.
The enclosure contains a single circuit board with two laser assemblies at each end. One laser plugs into the top of the pc board and projects the keyboard down to a flat surface. To project a rather complex QWERTY pattern, the beam of the keyboard's upper laser diode is projected through diffractive optics, or a holographic optical element, to generate the keyboard image. The optical element contains microscopic patterns that transform the point source of the laser diode into a precise two-dimensional image. Novelty laser pointers often come with similar optics to project more fanciful imagery like hearts, messages and smiley-faces, but the principle remains the same.
Projecting an image is one thing, but knowing when a key has been "pressed" is essential to the design. Here, a second laser--plugged into the lower end of the pc board and located on the bottom of the stand-up design--projects an invisible horizontal plane a few mil- limeters above the projection surface. When a finger passes through the lower plane, the laser light is reflected back toward the unit for detection. Here, a functional analogy with the high-end intrusion sensors of Mission: Impossible is more appropriate, as disruption of the laser plane means it is time now for some image sensing to take over.
The laser light reflected back from the keyboard sense plane by a user's finger arrives at an Omnivision CIF-resolution CMOS image sensor. Upon detection of reflected light, the sensor is then asked to capture a view of the projected keyboard. We are guessing a bit here, but it is presumed that the captured image is analyzed to detect what portions of the QWERTY pattern are blocked/visible, allowing the user's finger position to be inferred and thus, more specifically, to determine the appropriate "keystroke" for output.
Atmel's AT94S10AL microcontroller integrates FPGA logic and E2PROM and is responsible for essentially all the processing and control of the Virtual Keyboard. The Omnivision image sensor outputs digital image data to the Atmel part for analysis. A serial 8-bit A/D converter (thought to monitor the laser diode drive level), a temperature sensor chip, two LDO regulators and two op amps, all from National Semiconductor, provide essential small-scale functions, and a Sipex serial transceiver acts as serial interface to host PDAs. The battery and plug-in upper- and lower-laser diode units are the system's only remaining electronics. Though the boards contain identical laser diodes, the difference in function dictates that their electronics and optics are entirely different. Optics for the CMOS image sensor are fairly simple given the modest resolution of the captured image (288 x 352 pixels), with only a single glass lens and coated IR filter contained in the factory-focused optics module.
Although the iTech Virtual Keyboard performs a complicated function, it contains only 11 chip packages. The estimated total manufacturing cost is about $44, including more than $5 in accessories that ship with the product. Given a suggested retail price of $100, sustainable margins are suggested, and the Bluetooth variation of the product is likely to further enhance profits for the manufacturer.
The Virtual Keyboard could go beyond the PDA to become part of a more-integrated and subtle approach to personal computing, where "light-duty" keyboards can come and go as needed, all without ever cluttering a living space. No more spilled-coffee issues either.
By David Carey, president of Portelligent. The Austin, Texas, company produces teardown reports and related industry research on wireless, mobile and personal electronics (www.teardown.com)
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