Pointing device and displacement estimation method

• US 7,417,623 B2
• Filed: 06/24/2004
• Issued: 08/26/2008
• Est. Priority Date: 12/29/2003
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: PixArt Imaging Incorporated
• Inventors: Lan, Jeng-Feng, Lin, Chun-Huang
• Primary Examiner(s): Hjerpe; Richard
• Assistant Examiner(s): Shapiro; Leonid
• Application Number:
  US10/875,346
• Publication Number:
  US 20050151724A1
• Time in Patent Office: 1,524 Days
• Field of Search: 345/166, 345157-158, 345/163
• US Class Current: 345/166
• 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
• CPC Class Codes: G06T 7/238 using non-full search, e.g. three-step search

Abstract

A method of estimating image displacement by block matching for a pointing device used in a computer system. The method provided in the present invention comprises capturing digital images sequentially using a photo capture device, obtaining a template frame and a current frame, estimating a predicted velocity vector, and computing the displacement of the image. The efficiency and reliability of block match searching are improved by reducing the search range according to the calculated displacement. The template block can be defined anywhere on the template frame according to the predicted velocity to extend the lifetime of the template frame, and the displacement vector between the template block and the center of the template frame is proportional to the predicted velocity.

Claims

1. A pointing device for a computer system, comprising:

a photo capture device, capturing images sequentially to produce a first frame and a second frame; and

a displacement detection circuit, predicting a velocity of the pointing device, and comparing the first frame and the second frame according to the predicted velocity to obtain a displacement of the pointing device, wherein the predicted velocity is estimated as;

$\stackrel{\to <br><br>}{V}<br><br>p=\frac{<br><br>\stackrel{\rightharpoonup <br><br>}{V}<br><br><br><br>m<br><br>+<br><br>\stackrel{\rightharpoonup <br><br>}{V}<br><br>n}{<br><br>2}+\left(\stackrel{\rightharpoonup <br><br>}{V}<br><br>m-\stackrel{\rightharpoonup <br><br>}{V}<br><br>n\right)$

where Vm and Vn comprise average velocities by accumulating m and n instantaneous velocities respectively and m>

n.

2. A pointing device for a computer system, comprising:

a photo capture device, capturing images sequentially to produce a first frame and a second frame; and

a displacement detection circuit, predicting a velocity of the pointing device, and comparing the first frame and the second frame according to the predicted velocity to obtain a displacement of the pointing device,

wherein the step of comparing the first frame and the second frame further comprises;

defining a template block in the first frame;

defining a search range in the second frame according to the predicted velocity; and

searching a matched block in the searching range in order to output the displacement, wherein the matched block is the block with the greatest correlation to the template block;

wherein the step of defining the searching range further comprises the following steps;

computing an predicted block according to the predicted velocity, wherein the predicted block is the same size as the template block, and is the most probable location in the second frame for the template block according to the predicted velocity of the pointing device; and

extending the predicted block to set the search range;

and wherein each frame comprises X pixels*Y pixels, and the predicted block is extended symmetrically by at least one pixel to form search range.

3. A pointing device for a computer system, comprising:

a photo capture device, capturing images sequentially to produce a first frame and a second frame; and

a displacement detection circuit, predicting a velocity of the pointing device, and comparing the first frame and the second frame according to the predicted velocity to obtain a displacement of the pointing device,

wherein the step of comparing the first frame and the second frame further comprises;

defining a template block in the first frame;

defining a search range in the second frame according to the predicted velocity; and

searching a matched block in the searching range in order to output the displacement, wherein the matched block is the block with the greatest correlation to the template block;

wherein the step of defining the searching range further comprises the following steps;

computing an predicted block according to the predicted velocity, wherein the predicted block is the same size as the template block, and is the most probable location in the second frame for the template block according to the predicted velocity of the pointing device; and

extending the predicted block to set the search range;

and wherein the predicted block is extended asymmetrically to form the search range.