Apparatus for controlling a screen pointer that distinguishes between ambient light and light from its light source

• US 20040135825A1
• Filed: 01/14/2003
• Published: 07/15/2004
• Est. Priority Date: 01/14/2003
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Brosnan, Michael J.
• Granted Patent: US 7,295,186 B2
• Time in Patent Office: Days
• US Class Current: 345/857
• CPC Class Codes: G06F 3/0317 in co-operation with a patterned surface, e.g. absolute position or relative movement detection for an optical mouse or pen positioned with respect to a coded surface

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 with a plurality of light pulses, thereby generating reflected light pulses. A detection circuit is configured to sense light, distinguish between the reflected pulses and ambient light, and generate a low signal indication if the magnitude of the reflected pulses falls below a threshold value. An optical motion sensor generates digital images based on the reflected pulses. The motion sensor is configured to generate movement data based on the digital images. The movement data is indicative of relative motion between the imaging surface and the apparatus.

Claims

1. An apparatus for controlling the position of a screen pointer for an electronic device having a display screen, the apparatus comprising:

a light source for illuminating an imaging surface with a plurality of light pulses, thereby generating reflected light pulses;

a detection circuit configured to sense light, distinguish between the reflected pulses and ambient light, and generate a low signal indication if the magnitude of the reflected pulses falls below a threshold value; and

an optical motion sensor for generating digital images based on the reflected pulses, the motion sensor configured to generate movement data based on the digital images, the movement data indicative of relative motion between the imaging surface and the apparatus.

2. The apparatus of claim 1, wherein the motion sensor is configured to output movement data indicating no motion between the imaging surface and the apparatus when the low signal indication is generated.

3. The apparatus of claim 1, wherein the apparatus is configured to cause the screen pointer to freeze at its current position when the low signal indication is generated.

4. The apparatus of claim 1, wherein the apparatus is an optical mouse and the low signal indication indicates that the mouse has been lifted away from the imaging surface.

5. The apparatus of claim 1, and further comprising:

an oscillator for generating a modulation waveform;

a modulator coupled to the oscillator for generating a modulated light control signal based on the modulation waveform; and

wherein the light source is configured to generate the plurality of light pulses based on the modulated light control signal.

6. The apparatus of claim 5, wherein the detection circuit is configured to generate an electrical signal based on the sensed light, the apparatus further comprising:

a demodulator coupled to the oscillator for demodulating the electrical signal based on the modulation waveform.

7. The apparatus of claim 1, wherein the detection circuit is configured to generate an electrical signal based on sensed ambient light and sensed light pulses from the light source, and filter the electrical signal to reject components of the signal corresponding to the ambient light.

8. The apparatus of claim 7, wherein the detection circuit is configured to detect the magnitude of the reflected pulses based on the filtered electrical signal.

19. The method of claim 1S, and further comprising:

generating movement data indicating zero motion if the amount of sensed reflected light from the light source is less than a threshold value.

9. A method for detecting when an optical mouse has been lifted from an imaging surface, the method comprising:

illuminating the imaging surface with a modulated light signal output by the mouse, thereby generating a reflected modulated light signal;

generating an electrical signal based on sensed light, the sensed light including ambient light and the reflected modulated light signal;

processing the electrical signal to remove components corresponding to the ambient light; and

determining whether the mouse has been lifted from the imaging surface based on the processed electrical signal.

10. The method of claim 9, and further comprising:

detecting the magnitude of the sensed reflected modulated light signal based on the processed electrical signal; and

generating a mouse lifted indication if the magnitude of the sensed reflected modulated light signal falls below a threshold value.

11. The method of claim 9, and further comprising:

generating a modulation waveform;

generating a modulated light control signal based on the modulation waveform; and

outputting the modulated light control signal to a light source of the mouse to generate the modulated light signal.

12. The method of claim 11, and further comprising:

demodulating the electrical signal based on the modulation waveform.

13. A method for generating movement data with an optical pointing device for controlling the position of a screen pointer, the method comprising:

illuminating an imaging surface with a light source, thereby generating reflected light;

sensing a combination of reflected light from the light source and ambient light when the light source is on;

sensing ambient light when the light source is off;

generating digital images based on a difference between the sensed combination and the sensed ambient light; and

generating movement data based on the digital images, the movement data indicative of relative motion between the imaging surface and the pointing device.

14. The method of claim 13, and further comprising:

charging a first capacitor when the light source is on, thereby generating a first voltage representing an amount of combined reflected light from the light source and ambient light; and

charging a second capacitor when the light source is off, thereby generating a second voltage representing an amount of ambient light.

15. The method of claim 14, and further comprising:

providing a photo detector array with a plurality of pixel circuits, each pixel circuit including two capacitors configured to operate in the same manner as the first and the second capacitor.

16. The method of claim 14, and further comprising:

generating a first digital value based on the first voltage;

generating a second digital value based on the second voltage; and

calculating a difference between the first and the second digital values.

17. The method of claim 16, and further comprising:

generating movement data indicating zero motion if the difference between the first and the second digital values is less than a threshold value.

18. The method of claim 13, and further comprising:

charging a capacitor when the light source is off during a shutter interval;

discharging the capacitor when the light source is on during the shutter interval; and

wherein the difference between the voltage on the capacitor at the beginning of the shutter interval and the voltage on the capacitor at the end of the shutter interval represents an amount of sensed reflected light from the light source.

20. An optical mouse for generating movement data for controlling the position of a screen pointer, the device comprising:

a light source for illuminating an imaging surface; and

an optical motion sensor for generating movement data based on captured images of the imaging surface, wherein the optical motion sensor is configured to sense a combination of reflected light from the light source and ambient light when the light source is on, sense ambient light when the light source is off, detect a level of the reflected light from the light source based on the sensed combination and the sensed ambient light, and determine whether the mouse has been lifted from the imaging surface based on the detected level.

21. A method for rejecting ambient light in a digital imaging system, the method comprising:

illuminating an object with a modulated light signal, thereby generating a reflected modulated light signal;

generating an electrical signal based on sensed light, the sensed light including ambient light and the reflected modulated light signal; and

processing the electrical signal to remove components corresponding to the ambient light.

22. The method of claim 21, and further comprising:

detecting the magnitude of the sensed reflected modulated light signal based on the processed electrical signal.

23. The method of claim 21, and further comprising:

generating a modulation waveform;

generating a modulated light control signal based on the modulation waveform; and

outputting the modulated light control signal to a light source of the digital imaging system to generate the modulated light signal.

24. The method of claim 23, and further comprising:

demodulating the electrical signal based on the modulation waveform.