Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2000-09-22
2001-07-03
Lee, John R. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S208100, C345S157000
Reexamination Certificate
active
06255643
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention provides a device which optically senses the presence and movement of an object in contact with an optically transmissive platen and generates a control signal indicative thereof. According to a specific embodiment of the invention, the control signal is for controlling the movement of a pointer or cursor on a display. According to another specific embodiment, the control signal is for controlling various functions of an apparatus such as, for example, volume and channel selection on a television.
There are currently a number of different technologies on the market for moving a pointer on a computer display screen, the most common being a “mouse”. The mouse employs a rubber ball in frictional contact with a flat surface. The rotation of the rubber ball caused by movement of the mouse across the surface is translated into movement of the pointer on the screen. Typically, the rotation of the ball is sensed using two wheels in contact with the ball, each of which tracks rotation of the ball in one dimension. The wheels generate electrical signals which are, in turn, combined to generate a composite signal for controlling movement of the pointer on the screen in the two dimensions. Selection of symbols or icons on the screen indicated by the pointer is effected by actuation of a switch on the mouse. Another type of mouse operates similarly to the typical mouse except that the rotation of the ball is tracked by optical sensors.
One alternative to the mouse is the Glidepoint pad manufactured by Alps Electronics. The Glidepoint is a touch sensitive pad which comprises a matrix of pressure sensitive switches across which the user moves a fingertip or other object such as, for example, a pencil. The matrix of switches tracks the movement of the fingertip across the surface of the pad and generates a two-dimensional control signal which controls the movement of the pointer. As with the mouse, a switch is provided for selection of items on the screen. Alternatively, selection may be effected by rapid, intermittent actuation of any portion of the switch matrix, i.e., tapping on the Glidepoint pad.
Another alternative to the mouse is the TrackPoint pointing stick provided by IBM with its Thinkpad line of laptop computers. The Trackpoint is essentially a miniature joystick which protrudes from the center of the laptop's keyboard. To move the pointer up and down, the user pushes the stick forward and backward. To move the pointer left and right, the user pushes the stick left and right. The Trackpoint senses the forces exerted against it, translating these forces into electrical signals corresponding to the directions in which the stick is pushed. These electrical signals are then used to control the movement of the pointer on the display.
In the field of television remote controls, control signals for volume control and channel selection are typically generated using mechanical switches. The control signals are then transmitted to the television using infrared energy. One type of remote control employs four mechanical momentary switches arranged in a diamond configuration with the left/right switches controlling channel selection and the up/down switches controlling the volume. Another type of remote control employs a four-position rocker switch (e.g., circular or cross-shaped) with similar functionality associated with the four positions.
The above-described pointing and remote control devices each have associated advantages for particular applications. However, all of them share the same disadvantage in that each includes components which require mechanical actuation to effect movement of the display pointer. Because of inherent reliability problems associated with mechanical components, pointing and control devices having no mechanical components are therefore desirable.
SUMMARY OF THE INVENTION
According to the invention a control device with no moving parts is provided for generating control signals for such applications as controlling movement of a pointer on a display, or, more generally, for controlling the various functions of an apparatus. The control device employs an optically transmissive platen upon which the user places a fingertip. From the opposite side of the platen, a light-emitting diode emits light through the platen which is diffused by the user's fingertip. A photodetector is disposed in such a manner as to only receive light diffused and/or reflected beyond the critical angle of the platen material. That is, the photodetector receives an image of an object, e.g., the fingertip, in contact with the platen and none of the ambient light because it cannot travel beyond the critical angle of the platen. According to some embodiments, a lens or system of lenses focuses the light from the fingertip onto the photodetector.
According to a specific embodiment, the photodetector is configured into quadrants, each of which receives a portion of the light corresponding to the fingertip image and generates charge in proportion to the amount received. That is, the light energy received in each quadrant and the resultant charge generation are a function of the contact area of the fingertip in the corresponding platen quadrant. Any slight motion of the fingertip on the platen affects the size, shape and location of the fingertip's contact area which is, in turn, tracked in substantially real time by corresponding changes in the charge generation in the photodetector quadrants. The charge generation and the changes therein caused by movement of the fingertip on the platen are then converted to a control signal which may be used, for example, to control movement of a pointer on a display screen. Because, in such an embodiment, each of the photodetector's quadrants corresponds to a particular pointer direction, the control signal combines information from the charge generated in each quadrant to determine the direction and speed of the pointer on the screen.
Therefore, by optically sensing minute movements of the user's fingertip on the platen using optical components, a control signal for the display pointer is generated without the use of mechanical components. Moreover, because inexpensive four quadrant photodetectors are commercially available, and because the other device components are inexpensive, the pointing device of the present invention may be manufactured at a very low unit cost.
According to another embodiment, a dual-mode control device is provided which employs a configurable matrix array as the detector. In one mode, the matrix array is biased so that it is divided into a plurality of multi-pixel sectors, each of which acts as a single photosensitive region from which stored charge can be downloaded in a single step. In this mode, the device acts like the control device described above. In the second mode, the matrix array is biased to act like a high resolution imaging device to capture a detailed image of the user's fingerprint.
Thus, according to the invention a method and apparatus for generating a control signal which corresponds to movement of an object in contact with a platen are described. The platen has a first surface and is characterized by a critical angle beyond which light incident upon the first surface is not transmitted. A source of electromagnetic radiation emits electromagnetic radiation through the platen which is diffused by the object. A detector having a plurality of sectors receives a portion of the electromagnetic radiation diffused by the object and transmitted through the platen beyond the critical angle. The sectors of the detector accumulate charge in response to the incident electromagnetic radiation. Conversion circuitry then converts the charge accumulated in the detector to the control signal.
According to a specific embodiment, the object comprises a fingertip and the control signal is for controlling movement of a pointer on a display in response to the movement of the fingertip on the platen. In this embodiment, the charge is converted to a digital seria
Beyer Weaver & Thomas LLP
Lee John R.
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