Flow meter using a dynamic background image

Patent metadata

Field	Value
Publication number	US-9759343-B2
Application number	US-201514938083-A
Country	US
Kind code	B2
Filing date	Nov 11, 2015
Priority date	Dec 21, 2012
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

A flow meter includes a coupler, a support member, an image sensor, and one or more processors. The coupler is adapted to couple to a drip chamber. The support member is coupled to the coupler. The image sensor has a field of view and is operatively coupled to the support member. The image sensor is positioned to view the drip chamber within the field of view. The processor is operatively coupled to the image sensor to receive image data from the image sensor and is configured to: capture an image of a drip chamber using an image sensor; compare the image of a drip chamber with a dynamic background image; and adjust a flow rate of fluid flowing through the fluid line in accordance with the comparison between the image of the drip chamber and the dynamic background image.

First claim

What is claimed is:

1. A method for adjusting a flow rate of a fluid line, the method comprising:
capturing an image of a drip chamber using an image sensor;
comparing the image of a drip chamber with a dynamic background image wherein the dynamic background image contains a pattern having a plurality of lines; and
adjusting a flow rate of fluid flowing through the fluid line in accordance with the comparison between the image of the drip chamber and the dynamic background image.

2. The method according to claim 1 , wherein the dynamic background image is generated using another image captured by the image sensor.

3. The method according to claim 1 , further comprising the act of estimating a volume of the drop using the comparison between the image of the drip chamber and the dynamic background image.

4. The method according to claim 1 , further comprising the act of identifying a plurality of pixels of interest within the image.

5. The method according to claim 4 , wherein the plurality of pixels of interest are identified by comparing the image to the dynamic background image.

6. The method according to claim 4 , further comprising the act of determining a subset of pixels within the plurality of pixels of interest, wherein each pixel of the plurality of pixels is determined to be within the subset of pixels when there is a path to a baseline corresponding to the drip chamber.

7. The method according to claim 4 , further comprising the act of determining a volume of the drop based upon the plurality of pixels of interest.

8. The method according to claim 1 , further comprising the act of initializing the dynamic background image.

9. The method according to claim 1 , further comprising the act of updating the dynamic background image using the image captured by the image sensor.

10. The method according to claim 9 , wherein the dynamic background image is updated in accordance with:
P background,i,j =P background,i,j (1−α background )+α background P input,i,j .

11. The method as in claim 1 , further comprising the act of updating an array of variances using the image captured by the image sensor.

12. The method according to claim 11 , wherein the array of variances is updated in accordance with:
σ temp 2 =( P background,i,j −P input,i,j ) 2

σ background,i,j 2 =σ background,i,j 2 (1−β background )+β background σ temp 2 .

13. The method according to claim 1 , further comprising the act of updating an array of integers in accordance with the image captured by the image sensor.

14. The method according to claim 13 , wherein each integer of the array of integers corresponds to a number of updates of a pixel of the dynamic background image.

15. The method according to claim 14 , wherein the comparison of the image to the dynamic background image only compares pixels within the image to pixels within the dynamic background image if a respective integer of the array of integers indicates a respective pixel within the dynamic background image has been updated at least a predetermined number of times.

16. The method according to claim 1 , further comprising the acts of:
identifying a drop in the image and a predetermined band near an edge of the drop; and
initializing the dynamic background image by setting each pixel of the dynamic background image to the image unless it is within the identified drop or the predetermined band near the edge of the drop.

17. The method according to claim 16 , further comprising the act of setting a pixel of the dynamic background image to a predetermined value if a corresponding pixel of the image is within the identified drop or the predetermined band near the edge of the drop.

18. The method according to claim 17 , wherein the corresponding pixel of the image has a location corresponding to a location of the pixel of the dynamic background image.

19. The method according to claim 1 , further comprising the act of determining the baseline corresponding to an opening of the drip chamber.

20. The method according to claim 1 , wherein the act of determining a subset of pixels within the plurality of pixels of interest that corresponds to a drop includes determining each of the plurality of pixels of interest is within the subset of pixels if the respective pixel of the plurality of pixels has a contiguous path back to the baseline of the drop forming at an opening of the drip chamber.

21. The method according to claim 1 , further comprising the acts of:
identifying the drop within the image and a predetermined band near an edge of the drop;
initializing the dynamic background image by setting each pixel to the image unless it is within the identified drop or the predetermined band near the edge of the drop;
setting pixels within the region of the drop or within the predetermined band to a predetermined value;
initializing an array of integers; and
initializing an array of variances.

22. The method according to claim 21 , further comprising the act of updating the dynamic background image, the array of integers, and the array of variances using the image.

23. The method according to claim 1 , further comprising the act of adjusting a valve to control the flow rate.

24. The method according to claim 1 , wherein the dynamic background image is configured to filter out low frequency artifacts.

25. The method according to claim 1 , further comprising the acts of:
subtracting the image from the dynamic background image to thereby generate a difference image;
converting each pixel of the difference image to a true value if an absolute value of a respective pixel is beyond a predetermined threshold or to a false value if the absolute value of the respective pixel is less than the predetermined threshold;
summing each row of the converted difference image to generate a plurality of summation values, wherein each summation value of the plurality of summation values corresponds to a respective row of the converted difference image; and
examining the plurality of summation values.

26. The method according to claim 25 , wherein the act of examining the plurality of summation values includes determining if a free flow condition exists within the drip chamber.

27. The method according to claim 25 , wherein the act of examining the plurality of summation values includes determining if the free flow condition by determining if the plurality of summation values includes a plurality of contiguous summation values above another predetermined threshold.

28. The method according to claim 25 , wherein act of examining the plurality of summation values includes determining if a drop has been formed within the drip chamber.

29. The method according to claim 28 , wherein the act of determining if the drop has been formed within the drip chamber includes determining if the plurality of summation values includes a plurality of contiguous summation values within a predetermined range greater than a minimum value and less than a maximum value.

30. The method according to claim 25 , further comprising the act of converting each pixel of the difference image to a squared value of each pixel after the subtracting act and prior to the converting act.

31. The method according to claim 1 , further comprising the acts of:
creating a first thresholded ima

Assignees

• Deka Products Lp

Inventors

• Peret Bob D
• Kane Derek G
• Kamen Dean
• Murphy Colin H
• Kerwin John M

Classifications

• F16K27/00 Primary

  Construction of housing (methods for welding housings B23K); Use of materials therefor · CPC title

• A61M5/1689 Primary

  Drip counters · CPC title

• G06V10/761

  Proximity, similarity or dissimilarity measures · CPC title

• G06V10/75

  Organisation of the matching processes, e.g. simultaneous or sequential comparisons of image or video features; Coarse-fine approaches, e.g. multi-scale approaches; using context analysis; Selection of dictionaries · CPC title

• G06F18/22

  Matching criteria, e.g. proximity measures · CPC title