Interactive input systems that allow users to inject input such as for example digital ink, mouse events etc., into an application program using an active pointer (e.g., a pointer that emits light, sound or other signal), a passive pointer (e.g., a finger, cylinder or other object) or other suitable input device such as for example, a mouse or trackball, are well known. These interactive input systems include but are not limited to: touch systems comprising touch panels employing analog resistive or machine vision technology to register pointer input such as those disclosed in U.S. Pat. Nos. 5,448,263; 6,141,000; 6,337,681; 6,747,636; 6,803,906; 6,972,401; 7,232,986; 7,236,162; and 7,274,356 and in U.S. Patent Application Publication No. 2004/0179001 assigned to SMART Technologies ULC of Calgary, Alberta, Canada, assignee of the subject application, the contents of which are incorporated by reference; touch systems comprising touch panels employing electromagnetic, capacitive, acoustic or other technologies to register pointer input; tablet personal computers (PCs); laptop PCs; personal digital assistants (PDAs); and other similar devices.
Above-incorporated U.S. Pat. No. 6,803,906 to Morrison, et al. discloses a touch system that employs machine vision to detect pointer interaction with a touch surface on which a computer-generated image is presented. A rectangular bezel or frame surrounds the touch surface and supports digital cameras at its four corners. The digital cameras have overlapping fields of view that encompass and look generally across the touch surface. The digital cameras acquire images looking across the touch surface from different vantages and generate image data. Image data acquired by the digital cameras is processed by on-board digital signal processors to determine if a pointer exists in the captured image data. When it is determined that a pointer exists in the captured image data, the digital signal processors convey pointer characteristic data to a master controller, which in turn processes the pointer characteristic data to determine the location of the pointer in (x,y) coordinates relative to the touch surface using triangulation. The pointer coordinates are then conveyed to a computer executing one or more application programs. The computer uses the pointer coordinates to update the computer-generated image that is presented on the touch surface. Pointer contacts on the touch surface can therefore be recorded as writing or drawing or used to control execution of application programs executed by the computer.
Above-incorporated U.S. Pat. No. 6,972,401 to Akitt, et al. discloses an illuminated bezel for use in a touch system such as that disclosed in above-incorporated U.S. Pat. No. 6,803,906. The illuminated bezel comprises infrared (IR) light emitting diodes (LEDs) that project infrared light onto diffusers. The diffusers in turn, diffuse the infrared light so that the intensity of backlighting provided over the touch surface by the illuminated bezel is generally even across the surfaces of the diffusers. As a result, the backlight illumination provided by the bezel appears generally continuous to the digital cameras. Although this illuminated bezel works very well, it adds cost to touch system.
In some environments, users interact with the touch surface using a single pointer. In some other environments, such as that described in U.S. patent application Ser. No. 10/750,219 to Hill, et al., assigned to SMART Technologies ULC, the content of which is incorporated by reference, multiple users may interact with the touch surface simultaneously, or a single user may interact with the touch surface using a plurality of pointers.
As will be appreciated, in machine vision touch systems, when a single pointer is in the fields of view of multiple imaging devices, the position of the pointer in (x,y) coordinates relative to the touch surface typically can be readily computed using triangulation. Difficulties are however encountered when multiple pointers are in the fields of view of multiple imaging devices as a result of pointer ambiguity and occlusion. Ambiguity arises when multiple pointers in the images captured by the imaging devices cannot be differentiated. In such cases, during triangulation a number of potential positions for the pointers can be computed but no information is available to the system to allow the correct pointer positions to be resolved. Occlusion occurs when one pointer occludes another pointer in the field of view of an imaging device. In such an instance, an image captured by an imaging device includes only one pointer. As a result of occlusion, the correct positions of all of the pointers relative to the touch surface cannot be disambiguated.
According to U.S. patent application Ser. No. 12/501,088 to Chtchetinine, et al., assigned to SMART Technologies ULC, the content of which is incorporated by reference, the placement of additional imaging devices with different vantages improves disambiguation and reduces difficulties with occlusion, because the field of view of each imaging device looks at the pointers from a different angle. The additional imaging devices enable improvements in accuracy of the triangulation. Although increasing the number of imaging devices allows pointer ambiguity and occlusion to be resolved, this of course results in increased touch system cost and complexity.
U.S. patent application Ser. No. 12/369,473 to McGibney, et al., assigned to SMART Technologies ULC, the content of which is incorporated by reference, describes a method for distinguishing between a plurality of pointers in an interactive input system. The method comprises calculating a plurality of potential coordinates for a plurality of pointers in proximity of an input surface of the interactive input system, displaying visual indicators associated with each potential coordinate on an input surface, and determining real pointer locations and imaginary pointer locations associated with each potential coordinate from the visual indicators.
While the above provides a useful method, improvements are of course desirable. It is therefore an object of the present invention to provide a novel interactive input system.