The current level of development of organic user interfaces is the equivalent of where the mouse was when it was first invented.

capacitively couples to the electrodes and drains the wave signal. As a result, the received signal amplitude becomes weak. Measuring this effect makes it possible to detect the proximity of a conductive object (such as a human hand).

Since the hand detection is done through capacitive sensing, all the necessary sensing elements can be completely embedded in the surface. Unlike camera-based systems, the SmartSkin sensor is not affected by changes in the intensity of the environmental lighting. The surface is also not limited to being flat; the surface of any object, including furniture and robots, potentially provides such interactivity, functioning like the skin of a living creature.

The system recognizes the effect of the capacitance change when the user’s hand is placed 5cm–10cm from the table. To accurately determine the hand’s position (the peak of the potential field), SmartSkin uses bi-cubic interpolation to analyze the sensed data. The position of the hand can be determined by finding the peak on the interpolated curve. The precision of the calculated position is much finer than the size of a grid cell (10cm). The current implementation has an accuracy of 1cm.

SmartSkin’s sensor configuration also enables shape-based manipulation that does not explicitly use the hand’s 2D position. A potential field created by sensor inputs is instead used to move objects. As the hand approaches the surface of the table, each intersection of the sensor grid measures the capacitance between itself and the hand. This field helps define various rules of object manipulation. For example, an object that descends to a lower potential area is repelled from the hand. The direction and speed of the object’s motion can be controlled by changing the hand’s position around the object.

In my lab’s tests, many SmartSkin users were able to quickly learn to use the interface even though they did not fully understand its underlying dynamics. Many users used two hands or even their arms. For example, one can sweep the table surface with an arm to move a group of objects, and two arms can be used to trap and move objects, and (see Figure 2b).

Using the same sensing principle with a more dense grid antenna layout, SmartSkin determines the shape of a human hand (see Figure 2c and Figure 2d). The peak detection algorithm can also be used; in it, the algorithm, rather than tracking just one position of the hand, is able to track multiple positions of the fingertips.

An algorithm known as As-Rigid-As-Possible Shape Manipulation deforms objects with multiple control points [ 4]; Figure 2e shows its implementation in SmartSkin. Users manipulate graphical objects directly with multiple finger control points.

 

DIAMONDTOUCH

Diamond Touch [ 1] developed at Mitsubishi Electric Research Laboratories is another interactive table system based on capacitive sensing. Its unique feature is the ability to distinguish among multiple users. The grid-shaped antenna embedded in the DiamondTouch table transmits a time-modulated signal. Users sit in a special chair with a built-in signal-receiving electrode. When a user’s finger touches the surface, a capacitive connection from the grid antenna to the signal-receiving chair is established through the user’s body. The connection information is then used to determine the user’s finger position on the surface, as well as the uniquely identified user manipulating the surface. Since the DiamondTouch table transmits a modulated signal, multiple users are able to operate the same surface simultaneously without the system losing track of the identity of any user. DiamondTouch also supports semi-multi-touch operation in which “semi” means (despite some ambiguity) the ability to detect multiple points. For instance, when a user touches two points—( 100, 200) and (300, 400)—the system is unable to distinguish them from another two points—( 100, 400) and (300, 200). However, performing simple multi-touch interactions (such as pinching, or controlling scale with the distance between two fingers), this ambiguity is not a problem.

 

PRESENSE: TOUCH- AND PRESSURE-SENSING INTERACTION Touch-sensing input [ 3] extends the mouse’s usability by adding a touch sensor. While the buttons of a normal mouse have only two states (nonpress and press),