System and method for reducing power consumption in an optical screen pointing device

• US 6,797,937 B2
• Filed: 10/20/2003
• Issued: 09/28/2004
• Est. Priority Date: 07/24/2001
• Status: Expired due to Term

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Anderson, Mark A., Norskog, Allen C.
• Primary Examiner(s): Allen, Stephone B.
• Application Number:
  US10/689,109
• Publication Number:
  US 20040079868A1
• Time in Patent Office: 344 Days
• Field of Search: 250/221, 250/221.1, 340/555-557, 345/158, 345/161, 345/165, 345/166, 345/168, 345/169
• US Class Current: 250/221
• CPC Class Codes: G06F 1/32 Means for saving power
• CPC Class Codes: G06F 1/3259 Power saving in cursor control device, e.g. mouse, joystick, trackball
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

An apparatus for controlling the position of a screen pointer for an electronic device having a display screen includes a light source for illuminating an imaging surface, thereby generating reflected images. The apparatus includes a motion transducer. A lens receives the reflected images and directs the reflected images onto the motion transducer. The motion transducer includes an electronic shutter for controlling the amount of time that light is collected for image frames. The motion transducer is configured to generate digital representations of the reflected images. The motion transducer is configured to generate movement data based on the digital representations of the reflected images. The movement data is indicative of relative motion between the imaging surface and the motion transducer. A controller coupled to the light source turns the light source on only during the time that light is being collected for an image frame.

Claims

1. A method of switching an optical screen pointing device from a low power mode to a full power mode, the method comprising:

detecting a first movement with the optical screen pointing device;

calculating a first value representing an amount of the first movement;

storing an accumulated movement value representing an accumulation of previously detected movements;

updating the accumulated movement value by adding the first value;

comparing the updated accumulated movement value to a threshold value;

determining whether to switch to the full power mode based on the comparison of the updated accumulated movement value and the threshold value.

2. The method of claim 1, and further comprising:

switching to the full power mode if the updated accumulated movement value is greater than the threshold value.

3. The method of claim 1, wherein the threshold value is one pixel per frame.

4.The method of claim 1, and further comprising:

reducing the updated accumulated movement value by a decay factor.

5. The method of claim 1, wherein the optical screen pointing device is configured to collect and process image data in each of a plurality of frame periods, each frame period including an integration phase during which light is collected, an analog to digital conversion phase during which collected light is converted into digital values, and an image processing phase during which image data is correlated with previous image data to determine movement information.

4. The method of claim 4, wherein the decay factor is 0.5.

6. The method of claim 6, wherein the optical screen pointing device includes a light source, the method further comprising:

turning the light source on only during the integration phase of frame periods.