Display pointer tracking device

• US 6,377,242 B1
• Filed: 12/02/1999
• Issued: 04/23/2002
• Est. Priority Date: 12/02/1999
• Status: Expired due to Term

• Current Assignee: United States Air Force (Government of the United States of America)
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Sweed, Richard H.
• Primary Examiner(s): WU, XIAO MIN
• Application Number:
  US09/453,258
• Time in Patent Office: 873 Days
• Field of Search: 345/156, 345/157, 345/158, 345/169, 345/159, 345/160, 345/161, 345/162, 345/163, 345/173, 345/179, 345/180, 345/181, 345/182, 345/183
• US Class Current: 345/158
• CPC Class Codes: G06F 3/0386 for light pen

Abstract

A device for tracking a light pointer on a display. The device processes analog interlaced field video images from a video camera, seeking the point of brightest intensity, which is the current location of the pointer on the display. Synchronously operating counters and a latch count the lines and pixels of the video data until a high-speed comparator detects the brightest point of the video data. The comparator then sends a detect signal, causing control logic to freeze the counters, as well as freezing the latch, effectively storing in the counters and latch the line and pixel location of the pointer. The same detect signal from the comparator instructs a microcontroller to output the data from the counters in computer readable, digital data format. The device operates in substantially real time in either two or three-dimensional space, with greater speed and significantly reduced cost over the prior art, and an adjustable resolution.

Claims

1. An electronic tracking device whose output is absolute x and y coordinates of a light pointer'"'"'s image on a display and synchronization information, said device comprises:

a microcontroller;

video-processing logic,

wherein said video processing logic further comprises;

a processor for video data, and

a processor for timing data;

two synchronized counters;

a latch;

control logic,

wherein said control logic further comprises;

a high-speed comparator, and

an oscillator;

a counter control; and

a prescaler,

wherein said prescaler has a dividing ratio greater than zero but not greater than one-quarter.

2. The device as in claim 1, wherein said oscillator and said prescaler are replaced by an oscillator phase-locked to a video input horizontal synchronization signal.

3. The device as in claim 1, wherein said display is a one of an interactive display and a non-interactive display.

4. The device as in claim 1, wherein said display is a one of a two-dimensional display and a three-dimensional display.

5. The device as in claim 1, wherein said display is a one of a passive, non-radiating display and an active, self-radiating display.

6. The device as in claim 1, wherein said device tracks said image on a single display.

7. The device as in claim 1, wherein said device tracks said image on multiple displays.

8. A method for tracking a user-operated light pointer on a passive or active single display or passive or active multiple displays, comprising the steps of:

simultaneously inputting frames of video to a tracking device, said frames of video comprising interleaved fields;

detecting said light pointer'"'"'s image on said display;

counting lines and pixels in said frames of video until said pointer'"'"'s image is detected, wherein said step of counting further comprises;

prescaling said step of counting, said step of prescaling further comprising;

producing an oscillating signal for enabling said step of prescaling said step of counting, and dividing said oscillating signal by a number not less than four;

determining and storing a value of a current one of said interleaved fields, said value being odd or even, until said pointer'"'"'s image is detected;

stopping counting said lines and said pixels when said pointer'"'"'s image is detected;

producing a position of said pointer'"'"'s image, said position comprising absolute x and y coordinates of said position and a synchronization bit; and

resetting said step of counting to minimum values after said step of producing.

9. The method of claim 8, wherein said step of inputting frames of video further comprises the steps of:

removing synchronization data from said frames of video;

producing, by said step of removing synchronization data, a signal of video-only data from said frames of video; and

adding a clamp signal, gain, and offset to said video-only data.

10. The method of claim 9 further comprising the steps of:

removing video data from said frames of video;

producing, by said step of removing video data, a signal of timing-only data from said frames of video; and

producing delineation signals, comprising said timing-only data, to delineate a start of each line of said frames of video.

11. The method of claim 10 further comprising the steps of:

comparing said video-only data with an external, stable DC voltage; and

producing a detect signal said step of comparing.

12. The method of claim 8 further comprising the step of producing an oscillating signal for performing said step of counting.

13. The method of claim 12 further comprising the steps of:

setting a number of lines and a number of pixels based on delineation signals; and

repeating said step of counting when said pointer'"'"'s image is not detected.

14. The method of claim 8, further comprising the step of packaging said position in a digital data format.

15. Apparatus for tracking a user-operated light pointer on a passive or active single display or passive or active multiple displays, said apparatus comprising:

means for simultaneously inputting frames of video to a tracking device, said frames of video comprising interleaved fields;

means for detecting said light pointer'"'"'s image on said display;

means for counting lines and pixels in said frames of video until said pointer'"'"'s image is detected,

wherein said means for counting further comprises;

means for prescaling said means for counting, said means for prescaling further comprising;

means for producing an oscillating signal to enable said means for prescaling said means for counting, and

means for dividing said oscillating signal by a number not less than four;

means for determining and storing a value of a current one of said interleaved fields, said value being odd or even, until said pointer'"'"'s image is detected;

means for stopping counting said lines and said pixels when said pointer'"'"'s image is detected;

means for producing a position of said pointer'"'"'s image, said position comprising absolute x and y coordinates of said position and a synchronization bit; and

means for resetting said means for counting to minimum values after said means for producing has produced said position.

16. Apparatus as in claim 15, wherein said means for simultaneously inputting frames of video further comprises:

means for removing synchronization data from said frames of video;

means for producing, by said means for removing, a signal of video-only data from said frames of video; and

means for adding a clamp signal, gain, and offset to said video-only data.

17. Apparatus as in claim 16, further comprising means for removing video data from said frames of video;

means for producing, by said means for removing video data, a signal of timing-only data from said frames of video; and

means for producing delineation signals, comprising said timing-only data, to delineate a start of each line of said frames of video.