Motion analysis system

• US 6,437,820 B1
• Filed: 07/09/1999
• Issued: 08/20/2002
• Est. Priority Date: 01/13/1997
• Status: Expired due to Fees

• Current Assignee: Qualisys Medical AB
• Original Assignee: Qualisys AB (Qualisys Holding AB)
• Inventors: Josefsson, Thorleif
• Primary Examiner(s): Kelley, Chris
• Assistant Examiner(s): PHILIPPE, GIMS S
• Application Number:
  US09/350,853
• Time in Patent Office: 1,138 Days
• Field of Search: 348/169, 348/170, 348/154, 348/152, 348/155, 348/149, 348/148, 348/420, 348/158, 382/236, 382/168, 382/103, 340/572, 340/825.31, 340/5.8, 340/572.4, 600/595, 600/592, 356/620, 345/156, 345/158
• US Class Current: 348/169
• CPC Class Codes: A61B 5/1127 using markers
• CPC Class Codes: G01S 17/74 Systems using reradiation of electromagnetic waves other than radio waves, e.g. IFF, i.e. identification of friend or foe
• CPC Class Codes: G01S 3/7864 T.V. type tracking systems
• CPC Class Codes: G06T 7/246 using feature-based methods, e.g. the tracking of corners or segments

Abstract

A motion analysis system for tracking the motion of one or more light-emitting markers attached to an object includes at least one camera for recording a series of image frames, and at least one light source in communication with said at least one camera for generating optical trigger signals. Each of the light-emitting markers includes a sensor for detecting the optical trigger signals generated by the at least one light source. Each light-emitting marker also includes one or more light-emitting elements for generating optical response signals after the sensor detects the optical trigger signals, the optical response signals having a first state and a second state being recordable by the camera as a series of image frames. The system also includes a detector for detecting the positions of the optical response signals in each recorded image frame, an arrangement mechanism for arranging the detected positions of the optical response signals in a sorted list, a processor for processing the sorted list and a generator for generating a unique identification code for each light-emitting marker based upon the optical response signals and the state of the response signals in the sorted list.

Claims

1. A motion analysis system for tracking the motion of one or more light-emitting markers attached to an object, said system comprising:

at least one camera for recording a series of image frames;

at least one light source in communication with said at least one camera for generating optical trigger signals;

each said light-emitting marker including a sensor for detecting the optical trigger signals generated by said at least one light source, each said marker further including one or more light-emitting elements for generating optical response signals after the sensor detects the optical trigger signals, said optical response signals having a first state and a second state and being recordable by said camera as the series of image frames;

said system further comprising means for detecting the positions of said optical response signals in each said recorded image frame, means for arranging the detected positions of said optical response signals in a sorted list, means for processing the sorted list and means for generating a unique identification code for each said light-emitting marker based upon the optical response signals and the state of the response signals in said sorted list.

2. A system according to claim 1,

characterized in,

that said markers are arranged to generate the response signal substantially simultaneously.

3. A system according to claim 1,

characterized in,

that each marker is arranged to generate a unique pattern of response signals, substantially repeated after a period.

4. A system according to claim 3,

characterized in,

that said period is between two synchronisation signal (24).

5. The system according to claim 1, wherein said trigger signal is a light burst generated by at least one light source according to a control signal.

6. The system according to claim 1, wherein said detecting means comprises a light sensor.

7. The system according to claim 1, wherein said means for radiating said response signal comprises a LED.

8. The system according to claim 1, wherein said system operates within an infrared region.

9. A system according to any of claims 1,

characterized in,

that said trigger signal and said response signals are electromagnetic waves.

10. An arrangement for tracking and identifying light-emitting markers comprising:

at least one camera arranged to record a series of image frames;

one or more light sources in communication with said at least one camera for selectively generating electromagnetic trigger signals;

each said light emitting marker having a sensor for detecting the electromagnetic trigger signals generated by the one or more light sources and light-emitting elements for generating one or more light signals in response to the electromagnetic trigger signals; and

a processing unit for processing the recorded series of image frames, said processing unit including means for utilizing the recorded image frames to calculate position data of said light-emitting markers, means for arranging the position data in a sorted order and sequentially outputting the sorted position data, means for generating a matrix including sequentially outputted sorted position data and an identification unit for processing each row of said matrix for generating a data sequence identifying each said light-emitting marker.

11. An arrangement according to claim 10,

characterized in,

that said markers are arranged with a control unit (20) to count number of trigger signals and avoid to generate a response signal in accordance with instructions of the control unit (20).

12. An arrangement according to claim 11,

characterized in,

that said response signals and said avoided response signals are represented by different data states (1;

0) which constitute the identifying code.

13. An arrangement according to claim 11,

characterized in,

that said identification unit (28) includes means for transferring the identity codes to another processing unit.

14. An arrangement according to one of claims 11,

characterized in,

that said response signals are generated during entire exposure time of the camera unit.

15. An arrangement according to one of claims 10,

characterized in,

the arrangement further includes means for calculating the roundness of a marker.

16. An arrangement according to one of claims 10,

characterized in,

the markers are arranged to be programmed by means of electromagnetic waves.

17. A method for tracking the motion of a light-emitting marker comprising:

providing said light-emitting marker including a sensor for detecting optical trigger signals and one or more light-emitting elements for generating optical response signals;

generating one or more of said optical trigger signals;

detecting said one or more optical trigger signals;

after detecting said optical trigger signals, activating the one or more light-emitting elements of said marker to generate said optical response signals;

recording said optical response signals;

generating one or more lists for the recorded optical response signals; and

utilizing the lists for the recorded optical response signals to generate a sequential code for said marker, wherein said sequential code identifies said marker.

18. A method according to claim 17,

characterized in,

that said response signal is an ON or OFF state for said marker.

19. A method according to claim 17,

characterized in,

that said OFF states determines a unique code useable to identify a marker.

20. A method according to claim 17,

characterized in,

that for increased code identification reliability parity control and/or zero-enclosing are used.

21. A method according to claim 20,

characterized in,

that a set of codes are generated using the maximum number of markers, a grade of zero-enclosure and a maximum data loss grade.

22. A method according to claim 17,

characterized in,

that said sequence code is tested according to the following principle, applied on the sequence code:

only one zero (0) or one (1) in series,

odd number of zero or one,

selection of code for a certain degree of data disappearance (percentage of number of zeros or ones.).

23. A method according to a claims 17,

characterized in,

that all markers respond, substantially simultaneously.