Patent Application
20070291008
Inverted Touchtable
As used herein throughout, “front” means on a side facing the user(s), and “back” means the opposite side facing away from the user(s). For a tabletop device these correspond to “top” and “bottom”.
The touch sensitive surface 230 geometrically coincides with the display surface 220. That is, locations on the touch sensitive surface have a one-to-one correspondence with positions on the display surface, making this a direct touch input device.
In order to maintain the sense of direct-touch input for a user while touching the back of the table, the thickness of the table front is minimized. For example, a distance between the front to the back is about 1 cm, so that an actual point of touch is as close to the displayed target as possible. It should be noted, that this thickness is significantly less than most conventional touch sensitive display surfaces. In one embodiment of our invention the antenna arrays of the DiamondTouch sensor are mounted on opposition sides of a thin sheet of opaque Lucite plastic. The sensors are coupled to a single controller to ensure synchronized timing of input data.
When a user sitting in one of the chairs 240 touches 270 the surface 230 a capacitive coupling is induced between the surface and the user. As a unique feature, multiple touches or gestures can be detected concurrently for a single user or multiple users because the chairs are individually coupled to the touch sensitive surface.
During operation, images are displayed on the surface 220 by the projector 250. The processor coordinates and controls the displayed images according to the touching. As a unique feature of our invention, the touching 270 in this case does not occlude the displayed images.
Two-Sided Touchtable
It should also be noted, that the touch sensitive surface on the front of the device, that is the side facing the user, can also be an indirect touch surface such as a touchpad. Thus, touching either touch sensitive surfaces still does not occlude the display.
The two-sided direct touch input devices according to the embodiments of our invention provides a number of novel and interesting properties. Although the touch and display surfaces are separated, by ensuring exact registration between the geometrically coincident input surfaces and the display surface, an inverted touchtable is able to maintain many properties of a conventional direct-touch interface.
When interacting with a direct touch-sensitive display device that only have a touch sensitive surface on the front, occlusion of the display surface is unavoidable. Pointing at a displayed image requires the user to put a hand between the display surface and the eyes. By having a touch-sensitive surface on the back of the display surface, we eliminate this occlusion. This is desirable both for users working with intricate data and groups where one user may wish to observe displayed imagery currently under manipulation by another user.
With traditional tabletop interfaces, touching using a finger is difficult to do with a high degree of precision. Although systems typically enable pixel-level interaction, the precise pixel being targeted by a touch is hard for the user to determine or control, because multiple pixels are typically within the bounds of the touch area. It is impossible to offer in-place feedback to the user during the touch, because the selection point is generally occluded by the hand or at least a finger until it is removed.
Touch Strategies
Three strategies have been described for touch interaction, land-on, first-contact, and take-off, Potter, R. L., Weldon, L. J., and Shneiderman, B., “Improving the accuracy of touch screens: an experimental evaluation of three strategies,” In Proceedings of the SIGCHI Conference on Human Factors in Computing Systems, ACM/CHI '88. ACM Press, pp. 27-32, 1988. A land-on strategy selects the object immediately below the finger at the initial point of contact. First-contact selection selects the first-on screen object the user's finger touches as the finger is “dragged” around the screen following the initial contact. The take-off selection is done by selecting the object that was last touched before the finger was removed from the screen. The take-off strategy varies from the others in that its target of influence is not the point of contact of the finger on the display, but rather a cross-hair 500 displayed approximately 0.5 inches above the finger 501 as shown in
The inverted touchtable allows for a take-off strategy to be employed, including visualisation of the point of influence 502, while maintaining a direct-touch input paradigm, as shown in
Privacy of Input
On a shared direct-touch system, all three stages of input are public—the input target specification, the input action, and the consequential change to the system, are all visible to all users. This can be advantageous in circumstances where knowledge of other users' actions is desirable, such as when performing collaborative tasks.
In some circumstances, however, this may not be desirable: users may wish to “hide” one of the targets of the input, the input action, or the system's induced output.
The issue of providing private output on a shared display is described by Shoemaker et al., “Single display privacyware: augmenting public displays with private information,” In Proceedings of the SIGCHI Conference on Human Factors in Computing Systems, ACM/CHI '01, pp. 522-529, 2001, and Yerazunis et al., “Privacy-Enhanced Displays by Time-Masking Images,” 2001, and for touchtables in particular by Matsushita et al. above, and Wu et al., “Multi-finger and whole hand gestural interaction techniques for multi-user tabletop displays,” In Proceedings of the 16th Annual ACM Symposium on User interface Software and Technology, ACM/UIST '03, pp. 193-202, 2003, all incorporated herein by reference.
However, none of these techniques enable private input with a shared direct-touch input interface. With an inverted touchtable, both the input gesture and its graphical target can be kept private from other users. Because display surface occludes the back input surface from view, users are able to specify a point of input known only to them.
Without visual feedback, users are generally able to select within a few centimetres of a target while pointing under the table, so actual visual feedback of the touched location is necessary only to complete and confirm selections, or for fine-grained interactions.
Accidental Touches Less Likely
Users of shared touchtables often make pointing gestures to graphical objects while discussing the objects. This causes accidentally input to the system. This is less likely when the display surface and input surface are not the same, because pointing on the display for reference does not provide input.
Arm Fatigue
A disadvantage of large direct-touch display surfaces is the need to make elaborate arm movements, increasing fatigue. This might be especially problematic for interaction on the back of a table, because the table's support structure is not available to serve as an arm rest. To reduce problem, one embodiment of the invention provides a support arm rest surface 211.
Change in Bimanual Posture
With conventional touchtables, bimanual interaction is typically done with the hands flat on the table, thumbs pointing towards one another. Bimanual input to an inverted touchtable mirrors this, so that the thumbs face away from one another, as shown in
Properties of a Two-Surface Touchtable
The addition of a second input area for direct-touch interaction offers several compelling advantages for the development of interactive systems. Our focus here is on interactions that would otherwise not be possible without a one-sided input surface.
More Input Bandwidth
The second touch surface effectively doubles the bandwidth of the input device. This doubling enables richer interaction and an overall larger control space for one, or multiple users.
Number and Table-Side of Hands has Meaning
The side touched and number of hands being used for interaction is of importance for interaction, see
Sides Afford Modal Coupling
A two sided input can distinguish a dominant and non-dominant hand. This enables two modes to be maintained continuously, and can reduce errors with a moded interface. For example, the right hand can be considered dominant.
Co-Locality of Bimanual Interaction
For our purposes, we define co-locality as whether or not the hands are operating within the same physical space with respect to the virtual space of the displayed images. When working within a direct-touch input table, co-locality of the virtual hands necessitates co-locality of the physical hands. Thus, some forms of bimanual input are not possible, because the hands cannot occupy the same space at the same time. A two-sided touchtable allows for both hands to effectively target the same physical location simultaneously, in a way that is not possible without causing physical interference on a regular one-sided touchtable. In the case of our two-sided tabletop, co-locality is enabled by one hand operating above, and the other below the surface of the table, as shown in
Co-Locality of Interaction for Multiple Users
Not only does a two-sided touchtable enable co-locality for two hands of a single user, but it also enables co-locality of touch for multiple users. As shown in
New Type of Symmetry in Bimanual Interaction
Traditional touchtable interfaces, where both hands are oriented with the palms down, afford a certain kind of symmetry of bimanual interaction. A two-sided touchtable affords two new types of bimanual symmetry, see
Potential for Reduction of Physical Interference
Two types of physical interference can occur on a direct-touch interface. The first, described above, occurs when two users wish to interact in the same physical space. The other occurs when one or more user attempts to place their hands in such a way that would otherwise cause the arms to pass over one another, or actually collide. A two-sided device allows bimanual interaction without this type of interference.
Three-Dimensional Input
For designers, a conventional touchtable provides a flat interaction and display area, similar to a desktop computer's display. A two-sided touchtable, however, presents a natural mapping of a third dimension, i.e., depth, to the application, where touches on the back of the table map to the ‘back’ of the volume, and likewise for touches on the front surface.
Alternate Input
One use for indirect touch on the back of the touchtable is for input to virtual spaces other than the one being projected onto the front of the table. In order to maintain a direct-touch input paradigm, each of these techniques would require a visual representation of some kind on the surface of the table. In particular, a miniature version of the ancillary display is rendered on the table.
In application as shown in
In addition to this literal mapping of physical spaces, it is also possible to map input to the back surface of the table to other virtual paradigms such as aural spaces.
Although the invention has been described by way of examples of preferred embodiments, it is to be understood that various other adaptations and modifications may be made within the spirit and scope of the invention. Therefore, it is the object of the appended claims to cover all such variations and modifications as come within the true spirit and scope of the invention.
