Method and apparatus for analyzing a body having a marker located thereon

• US 5,072,294 A
• Filed: 02/05/1991
• Issued: 12/10/1991
• Est. Priority Date: 06/07/1989
• Status: Expired due to Fees

• Current Assignee: Loredan Biomedical, Inc.
• Original Assignee: Loredan Biomedical, Inc.
• Inventors: Engle, Gary L.
• Primary Examiner(s): Kostak, Victor R.
• Application Number:
  US07/652,296
• Time in Patent Office: 308 Days
• Field of Search: 358/105, 358/125, 358/108, 358/107, 358/126, 358/93, 364/516
• US Class Current: 348/172
• CPC Class Codes: A61B 5/1127 using markers
• CPC Class Codes: A61B 5/7232 involving compression of the physiological signal, e.g. to extend the signal recording period
• CPC Class Codes: G06T 7/246 using feature-based methods, e.g. the tracking of corners or segments
• CPC Class Codes: G06V 10/245 by locating a pattern; Special marks for positioning

Abstract

A video motion analysis system wherein a camera converts an image of a body having illuminated markers placed thereon into a plurality of image frames. Each image frame comprises a plurality of image lines, and each image line comprises a plurality of pixels. An image preprocessor receives the plurality of image lines and detects the occurrence of each marker in each image line. This is done by comparing each pixel amplitude value to a threshold value and indicating when the pixel amplitude value exceeds the threshold value. When a pixel amplitude value exceeds the threshold value, an offset value representing the difference between the pixel amplitude value and the threshold value is added to a running total of amplitude values for the detected marker. Similarly, the offset value is used to calculate the moment value for each pixel in each marker based on the position of the pixel in the scan line. The calculated moment value is added to a running total of moment values for the detected marker. The amplitude and moment sums for each series of pixels for each marker in each image line are passed to a signal processor which groups the amplitude and moment sums for each marker together. The grouped values are used to calculate a centroid value for each marker. Centroid calculation is performed in real time and the resulting values are provided to a master CPU for further processing.

Claims

1. An apparatus for analyzing a body having a marker that is distinguishable from the body located thereon comprising:

image line receiving means for receiving a plurality of image lines which form an image frame of the body, each image line comprising a plurality of pixels, each pixel having an amplitude value associated therewith;

marker detecting means, coupled to the image line receiving means, for detecting the occurrence of the marker in each image line, said marker detecting means including threshold detecting means for detecting when an amplitude threshold value is exceeded by the pixel amplitude value, and marker indicating means, coupled to the threshold detecting means, for providing a marker indicating signal as long as the amplitude threshold value is exceeded by the pixel amplitude value; and

position calculating means, coupled o the marker detecting means, for calculating a position of the marker in the frame in real time, said position calculating means including amplitude summing means, coupled to the marker indicating means, for summing a pixel amplitude value in response to the marker indicating signal to produce an amplitude sum associated with the detected marker in each image line.

2. The apparatus according to claim 1 further comprising display means, coupled to the position calculating means, for displaying the image, the display means including marker display means for displaying the marker on the image.

3. The apparatus according to claim 1 wherein the marker detecting means further comprises marker discriminating means for detecting the marker only if the marker lies within a selected subset of the image frame.

4. The apparatus according to claim 1 wherein the threshold detecting means further comprises amplitude offset means for calculating the difference in value between the amplitude threshold value and the pixel amplitude value, the difference being termed an amplitude offset value.

5. The apparatus according to claim 4 wherein the position calculating means is coupled to the amplitude offset means, and wherein the amplitude values summed by the position calculating means comprise the amplitude offset values for the detected marker.

6. The apparatus according to claim 5 wherein the position calculating means further comprises:

horizontal location means for providing a horizontal location for each pixel in each line; and

horizontal moment summing means, coupled to the marker indicating means, for summing the product of the horizontal location and the amplitude offset value of each pixel in response to the marker indicating signal to produce a horizontal moment sum associated with the detected marker in each image line.

7. The apparatus according to claim 6 wherein the position calculating means further comprises:

vertical location means for providing a vertical location for the detected marker in each image line; and

vertical moment summing means, coupled to the vertical location means, for summing the product of the vertical location and the amplitude sum associated with the detected marker in each image line to produce a vertical moment sum associated with the detected marker.

8. The apparatus according to claim 1 wherein the position calculating means calculates a centroid of the region of the image occupied by the marker.

9. The apparatus according to claim 8 wherein the position calculating means further comprises:

an X-coordinate calculating means, coupled to the horizontal moment summing means and to the amplitude summing means, for calculating an X-coordinate for the marker according to the algorithm;

##EQU2## wherein the summations are performed over each image line for which the marker is detected, wherein SXMy is the horizontal moment sum of the marker in each image line, and wherein SMy is the amplitude sum of the marker in each image line.

10. The apparatus according to claim 9 wherein the position calculating means further comprises a Y-coordinate calculating means, coupled to the vertical moment summing means and to the amplitude summing means, for calculating a Y-coordinate for the marker according to the algorithm:

##EQU3## wherein the summations are performed over each image line for which the marker is detected, and wherein Y*SMy is the vertical moment of the marker in the yth image line.

11. An apparatus for analyzing a body having a plurality of markers that are distinguishable from the body located thereon comprising:

image line receiving means for receiving a plurality of image lines which form an image frame of the body, each image line comprising a plurality of pixels, each pixel having an amplitude value associated therewith;

marker detecting means, coupled to the image line receiving means, for detecting the occurrence of the plurality of markers in the plurality of image lines, said marker detecting means including threshold detecting means for detecting when an amplitude threshold value is exceeded by the pixel amplitude value, and marker indicating means, coupled to the threshold detecting means, for indicating the occurrence of each marker in each image line as long as the amplitude threshold value is exceeded by the pixel amplitude value; and

position calculating means, coupled to the marker detecting means, for calculating the centroids of the plurality of markers in the image frame in real time, said position calculating means including amplitude summing means, coupled to the marker indicating means, for summing a pixel amplitude value in response to the marker indicating signal to produce an amplitude sum associated with each detected marker in each image line.

12. The apparatus according to claim 11 wherein the threshold detecting means further comprises amplitude offset means for calculating the difference in value between the amplitude threshold value and the pixel amplitude value, the difference being termed an amplitude offset value.

13. The apparatus according to claim 12 wherein the position calculating means is coupled to the amplitude offset means, and wherein the amplitude values summed by the position calculating means comprise the amplitude offset values for each detected marker.

14. The apparatus according to claim 13 wherein the position calculating means further comprises:

horizontal location means for providing a horizontal location for each pixel in each line; and

horizontal moment summing means, coupled to the marker indicating means, for summing the product of the horizontal location and the amplitude offset value of each pixel in response to the marker indicating signal to produce a horizontal moment sum associated with each detected marker in each image line;

vertical location means for providing a vertical location for each detected marker in each image line; and

vertical moment summing means, coupled to the vertical location means, for summing the product of the vertical location and the amplitude sum associated with each detected marker in each image line to produce a vertical moment sum associated with the detected marker.

15. The apparatus according to claim 14 wherein the position calculating means further comprises:

an X-coordinate calculating means, coupled to the horizontal moment summing means and to the amplitude summing means, for calculating an X-coordinate for each marker according to the algorithm;

##EQU4## wherein the summations are performed over each image line for which each marker is detected, wherein SXMy is the horizontal moment sum of each marker in each image line, and wherein SMy is the amplitude sum of each marker in each image line; and

a Y-coordinate calculating means, coupled to the vertical moment summing means and to the amplitude summing means, for calculating a Y-coordinate for each marker according to the algorithm;

##EQU5## wherein the summations are performed over each image line for which each marker is detected, and wherein Y*SMy is the vertical moment of the marker in the yth image line.

16. The apparatus according to claim 15 further comprising display means, coupled to the position calculating means, for displaying the image, the display means including marker display means for displaying the marker on the image.

17. The apparatus according to claim 16 wherein the marker detecting means further comprises marker discriminating means for detecting the marker only if the marker lies within a selected subset of the image frame.

18. A method for analyzing a body having a marker that is distinguishable from the body located thereon comprising the steps of:

receiving a plurality of image lines which form an image frame of the body, each image line comprises a plurality of pixels, each pixel having an amplitude value associated therewith;

detecting the occurrence of the marker in each image line including the sub-steps of detecting when an amplitude threshold value is exceeded by the pixel amplitude value, and providing a marker indicating signal as long as the amplitude threshold value is exceeded by the pixel amplitude value; and

calculating a position of the marker in the frame in real time including the sub-step of summing a pixel amplitude value in response to the marker indicating signal to produce an amplitude sum associated with the detected marker in each image line.

19. The method according to claim 18 further comprising the steps of:

displaying the image; and

displaying the marker on the image.

20. The method according to claim 19 wherein the marker detecting step further comprises the step of detecting the marker only if the marker lies within a selected subset of the image frame.

21. The method according to claim 18 wherein the threshold detecting step further comprises the step of calculating the difference in value between the amplitude threshold value and the pixel amplitude value, the difference being termed an amplitude offset value.

22. The method according to claim 21 wherein the summed amplitude values comprise the amplitude offset values for the detected marker.

23. The method according to claim 22 wherein the position calculating step further comprises the steps of:

providing a horizontal location for each pixel in each line; and

summing the product of the horizontal location and the amplitude offset value of each pixel in response to the marker indicating signal to produce a horizontal moment sum associated with the detected marker in each image line.

24. The method according to claim 23 wherein the coordinate calculating step further comprises the steps of:

providing a vertical location for the detected marker in each image line; and

summing the product of the vertical location and the amplitude sum associated with the detected marker in each image line to produce a vertical moment sum associated with the detected marker.

25. The method according to claim 24 wherein the position calculating step further comprises the step of calculating a centroid of the region of the image occupied by the marker.

26. The method according to claim 25 wherein the position calculating step further comprises the step of:

calculating an X-coordinate for the marker according to the algorithm;

##EQU6## wherein the summations are performed over each image line for which the marker is detected, wherein SXMy is the horizontal moment sum of the marker in each image line, and wherein SMy is the amplitude sum of the marker in each image line.

27. The method according to claim 26 wherein the position calculating step further comprises the steps of:

calculating a Y-coordinate for the marker according to the algorithm;

##EQU7## wherein the summations are performed over each image line for which the marker is detected, and wherein Y*SMy is the vertical moment of the marker in the yth image line.

28. A method of analyzing a body having a plurality of markers that are distinguishable from the body located thereon comprising the steps of:

receiving a plurality of image lines which form an image frame of the body, each image line comprising a plurality of pixels, each pixel having an amplitude value associated therewith;

detecting the occurrence of the plurality of markers in the plurality of image lines including the sub-steps of detecting when an amplitude threshold value is exceeded by the pixel amplitude value, and indicating the occurrence of each marker in each image line by providing a marker indicating signal as long as the amplitude threshold value is exceeded by the pixel amplitude value; and

calculating the centroids of the plurality of markers in the image frame in real time including the sub-step of summing a pixel amplitude value in response to the marker indicating signal to produce an amplitude sum associated with each detected marker in each image line.

29. The method according to claim 28 further comprising the steps of:

displaying the image; and

displaying the plurality of markers on the image.

30. The method according to claim 28 wherein the marker detecting step further comprises the step of detecting a marker only if the marker lies within a selected subset of the image frame.

31. The method according to claim 28 wherein the threshold detecting step further comprises the step of calculating the difference in value between the amplitude threshold value and the pixel amplitude value, the difference being termed an amplitude offset value.

32. The method according to claim 31 wherein the summed amplitude values comprise the amplitude offset values for the detected marker.

33. The method according to claim 32 wherein the position calculating step further comprises the steps of:

providing a horizontal location for each pixel in each line;

summing the product of the horizontal location and the amplitude offset value of each pixel in response to the marker indicating signal to produce a horizontal moment sum associated with each detected marker in each image line;

providing a vertical location for the detected marker in each image line; and

summing the product of the vertical location and the amplitude sum associated with the detected marker in each image line to produce a vertical moment sum associated with each detected marker.

34. The method according to claim 33 wherein the position calculating step further comprises the steps of:

calculating an X-coordinate for each marker according to the algorithm;

##EQU8## wherein the summations are performed over each image line for which each marker is detected, wherein SXMy is the horizontal moment sum of each marker in each image line, and wherein SMy is the amplitude sum of each marker in each image line; and

calculating a Y-coordinate for each marker according to the algorithm;

##EQU9## wherein the summations are performed over each image line for which each marker is detected, and wherein Y*SMy is the vertical moment of each marker in the yth image line.