Optical pseudo trackball controls the operation of an appliance or machine

An optical fingertip tracker, which may be a pseudo trackball, responds to the motion of the texture on one of the user's digits pressed against an image input aperture to produce motion signals processed within an appliance to be controlled. The appliance may have a minimal GUI, such as an LCD display having only a modest number of low resolution pixel locations and/or preestablished characters or icons. An appliance control parameter is set or adjusted in response to translation ofthe fingertip along a particular axis. E.g., to enter a parameter value (volume) a changing bar graph can be displayed. The display might even be omitted; to set the tone control of an audio appliance it can be sufficient to simply adjust the tone until the result is as desired. A numeric display of control parameter digits may be desirable, as when moving the fingertip tunes a receiver. There can be several particular axes along which fingertip movement changes an associated appliance control parameter. Other appliances can include character recognition of input characters traced by the fingertip. A pressure sensitive switch coupled to the fingertip tracker can serve as a delimiting mechanism useful in ratification of interpreted results and in editing strings that have been input. Excursions is a loss-of-correlation signal can be detected and interpreted as tapping the image input aperture with the fingertip. Such "taps" and "double taps" can be defined, and have selected meanings associated therewith that may be used in conjunction with, or in place of, the pressure sensitive switch.