Optical tracking system, and method for calculating posture of marker part in optical tracking system

Patent metadata

Field	Value
Publication number	US-2017193670-A1
Application number	US-201515314669-A
Country	US
Kind code	A1
Filing date	May 29, 2015
Priority date	May 29, 2014
Publication date	Jul 6, 2017
Grant date	—

Abstract

An optical tracking system comprises a marker part, an image forming part, and a processing part. The marker part includes a pattern having particular information and a first lens which is spaced apart from the pattern and has a first focal length. The image forming part includes a second lens having a second focal length and an image forming unit which is spaced apart from the second lens and forms an image of the pattern by the first lens and the second lens. The processing part determines the posture of the marker part from a coordinate conversion formula between a coordinate on the pattern surface of the pattern and a pixel coordinate on the image of the pattern, and tracks the marker part by using the determined posture of the marker part. Therefore, the present invention can accurately track a marker part by a simpler and easier method.

First claim

What is claimed is:

1 . An optical tracking system comprising:
a marker part configured to include a pattern that has particular information and a first lens that is spaced apart from the pattern and has a first focal length; an image forming part configured to include a second lens that has a second focal length and an image forming unit that is spaced apart from the second lens and on which an image of the pattern is formed by the first lens and the second lens; and a processing part configured to determine a posture of the marker part from a coordinate conversion formula between a coordinate on the pattern surface of the pattern and a pixel coordinate on the image of the pattern and configured to track the marker part by using the determined posture of the marker part.

2 . The optical tracking system according to claim 1 , wherein the processing part acquires: a first conversion matrix that converts a first coordinate corresponding to the coordinate on the pattern surface of the pattern to a second coordinate corresponding to a three-dimensional coordinate for the first lens of the marker part; and a second conversion matrix that converts a third coordinate corresponding to a three-dimensional coordinate of the second coordinate for the second lens to a fourth coordinate corresponding to the pixel coordinate on the image of the pattern of the image forming part,
wherein the coordinate conversion formula is defined to convert the first coordinate to the fourth coordinate while including the first conversion matrix and the second conversion matrix, and wherein the processing part acquires, from the coordinate conversion formula, a posture definition matrix that defines the posture of the marker part.

3 . The optical tracking system according to claim 2 , wherein the coordinate conversion formula is defined by the following equation,

s


[

u
′

v
′

1

]

=



[
A
]



[
R
]



[
C
]



[

u

v

1

]

{(u,v) denotes the first coordinate, (u′,v′) denotes the fourth coordinate, [C] denotes the first conversion matrix, [A] denotes the second conversion matrix, [R] denotes the posture definition matrix, and s denotes a proportional constant}.

4 . The optical tracking system according to claim 3 , wherein the first conversion matrix is defined by the following equation,

[
C
]

=

[

1

0

-

u
c

0

1

-

v
c

0

0

f
b

]

{(u c ,v c ) denotes a coordinate of a center of the pattern and f b denotes the first focal length}.

5 . The optical tracking system according to claim 4 , wherein the processing part acquires the first conversion matrix by acquiring calibration values of u c , v c , and f b from three or more photographed images.

6 . The optical tracking system according to claim 3 , wherein the second conversion matrix is defined by the following equation,

[
A
]

=

[

-

f
c

pw

0

u
c
′

0

-

f
c

ph

v
c
′

0

0

1

]

{(u′ c ,v′ c ) denotes the pixel coordinate o

Assignees

• Koh Young Tech Inc
• Kyungpook Nat Univ Industry-Academic Coop Found

Inventors

• Lee Hyun Ki
• Chae You Seong
• Kim Min Young

Classifications

• G06T7/246 Primary

  using feature-based methods, e.g. the tracking of corners or segments · CPC title

• G06T2207/30204

  Marker · CPC title

• G06T7/70 Primary

  Determining position or orientation of objects or cameras (camera calibration G06T7/80) · CPC title

• G06T7/20 Primary

  Analysis of motion (motion estimation for coding, decoding, compressing or decompressing digital video signals H04N19/43, H04N19/51) · CPC title

• G06T7/73

  using feature-based methods · CPC title