Distortion reduced signal detection

• US 9,480,434 B2
• Filed: 08/24/2012
• Issued: 11/01/2016
• Est. Priority Date: 08/26/2011
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips N.V.
• Inventors: De Haan, Gerard, Kirenko, Ihor Olehovych
• Primary Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US14/239,371
• Publication Number:
  US 20140206965A1
• Time in Patent Office: 1,530 Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/0077 Devices for viewing the surface of the body, e.g. camera, magnifying lens
• CPC Class Codes: A61B 5/0082 adapted for particular medical purposes
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/02405 Determining heart rate variability
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7232 involving compression of the physiological signal, e.g. to extend the signal recording period
• CPC Class Codes: A61B 5/7246 using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: G06F 2218/02 Preprocessing
• CPC Class Codes: G06F 2218/04 Denoising
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 2207/30076 Plethysmography
• CPC Class Codes: G06T 5/70 Denoising; Smoothing
• CPC Class Codes: G06T 7/0014 using an image reference approach
• CPC Class Codes: G06T 7/0016 involving temporal comparison
• CPC Class Codes: G06V 10/32 Normalisation of the pattern dimensions
• CPC Class Codes: G06V 2201/03 Recognition of patterns in medical or anatomical images
• CPC Class Codes: G06V 40/15 : Biometric patterns based on physiological signals, e.g. heartbeat, blood flow

Abstract

The present invention relates to a device and a method for extracting information from detected characteristic signals. A data stream (26; 124a, 124b, 124c) derivable from electromagnetic radiation (14) emitted or reflected by an object (12) is received. The data stream (26) comprises a continuous or discrete characteristic signal (76; 32a, 132b, 132c) including physiological information (100) and a disturbing signal portion 5 (94). The physiological information (100) is representative of at least one at least partially periodic vital signal (20; 156). The disturbing signal portion (94) is representative of at least one of an object motion portion and/or a non-indicative reflection portion. The characteristic signal (76; 132a, 132b, 132c) is transferred by converting at least three absolute components (92a, 92b, 92c) of the characteristic signal (76; 132a, 132b, 132c) related to respective 10 additive channels (74a, 74b, 74c) to at least two difference components (102; 142a, 142b) of the characteristic signal (76; 132a, 132b, 132c), wherein each of the at least two difference components (102; 142a, 142b) can be derived through a respective arithmetic transformation considering at least two of the at least three absolute components (92a, 92b, 92c), wherein the arithmetic transformation comprises additive and subtractive coefficients. Consequently, the 1 disturbing signal portion (94) can beat least partially suppressed in the transferred signal (32; 50).

Claims

1. Device for extracting information from detected characteristic signals, comprising:

an interface for receiving a data stream derivable from electromagnetic radiation reflected by an object, wherein the data stream comprises a characteristic signal including (i) physiological information and (ii) a disturbing signal portion, the physiological information being representative of at least one at least partially periodic vital signal, the disturbing signal portion being representative of at least one selected from the group consisting of an object motion portion and a non-indicative reflection portion, wherein the characteristic signal is associated with an additive signal space, wherein the signal space comprises additive channels for representing the characteristic signal;

a converter means for transferring the characteristic signal into a transferred signal by converting (i) at least three absolute components of the characteristic signal related to respective additive channels to (ii) at least two difference components of the characteristic signal, wherein each of the at least two difference components is derived through a respective arithmetic transformation that comprises an at least partial subtraction of at least one of the at least three absolute components from the remaining absolute components, wherein the arithmetic transformation for each of the at least two difference components further comprises coefficients that at least substantially sum to zero, and further wherein the at least two difference components enable the disturbing signal portion to be at least partially suppressed in the transferred signal; and

an extractor means for extracting the at least partially periodic vital signal from the at least two difference components in the transferred signal.

2. Device as claimed in claim 1, wherein the signal space is an additive color signal space, wherein the at least three absolute components represent three distinct color components indicated by the additive channels, wherein the additive channels are related to defined spectral portions.

3. Device of claim 2, wherein the signal space is further indicative of luminance information and chrominance information, the chrominance information being representable by the at least two difference components.

4. Device of claim 3, wherein the luminance information is substantially aligned with a luminance index element in the signal space, the luminance index element being substantially indicative of a selected source of electromagnetic radiation.

5. Device of claim 4, wherein the at least two difference components are substantially orthogonal to the luminance index element.

6. Device of claim 5, further wherein the at least two difference components are substantially orthogonal to each other.

7. Device as claimed in claim 1, wherein the at least one at least partially periodic vital signal is selected from the group consisting of heart rate, heart beat, respiration rate, heart rate variability, Traube-Hering-Mayer waves, and oxygen saturation.

8. Device of claim 1, further comprising a weighting means for weighting the at least two difference components so as to derive a weighted transferred signal from the transferred signal under consideration of at least two weighted difference components.

9. Device of claim 8, wherein the weighting comprises a determination of a deviation value of each of the at least two difference components, and wherein the deviation value of each of the at least two difference components is determined under consideration of temporal variations thereof over a moving window applied to a sequence of each of the at least two difference components.

10. Device of claim 9, wherein the deviation value is a standard deviation.

11. Device of claim 8, wherein the weighting is directed to minimize a spread of the weighted transferred signal.

12. Device of claim 1, wherein at least one of the converter means and the extractor means is further adapted to normalize the transferred signal under consideration of a deviation value thereof, preferably a standard deviation, over a moving window applied to a sequence of the transferred signal.

13. Device of claim 12, wherein the deviation value is a standard deviation.

14. Device as claimed in claim 1, further comprising an analyzing means, the analyzing means being comprised in the extractor means or coupled thereto, wherein the analyzing means is adapted for a frequency analysis of the at least one at least partially periodic vital signal.

15. Device as claimed in claim 14, further comprising a processing unit that comprises the converter means, the extractor means and the analyzing means.

16. Device as claimed in claim 15, wherein at least one of the converter means, the extractor means and the analyzing means is further adapted for delivering a compressed output signal, wherein the compressed output signal comprises the luminance information represented by a luminance signal and the chrominance information represented by the at least two difference components, wherein selective compression rates are applied to the luminance information and the chrominance information, and wherein the chrominance information is compressed to a lower compression factor than the luminance information.

17. Device of claim 14, wherein the analyzing means is further adapted for filtering the processed transferred signal and for enhancing a signal component at a bandwidth between 0.2 Hz and 10 Hz.

18. Device of claim 17, wherein the bandwidth further comprises between 0.5 Hz and 3.5 Hz.

19. Method for extracting information from detected characteristic signals, comprising the steps:

receiving a data stream derivable from electromagnetic radiation reflected by an object, wherein the data stream comprises a characteristic signal including (i) physiological information and (ii) a disturbing signal portion, the physiological information being representative of at least one at least partially periodic vital signal, the disturbing signal portion being representative of at least one selected from the group consisting of an object motion portion and a non-indicative reflection portion, wherein the characteristic signal is associated with an additive signal space, wherein the signal space comprises additive channels for representing the characteristic signal;

transferring the characteristic signal into a transferred signal by converting (i) at least three absolute components of the characteristic signal related to respective additive channels to (ii) at least two difference components of the characteristic signal, wherein each of the at least two difference components is derived through a respective arithmetic transformation that comprises an at least partial subtraction of at least one of the at least three absolute components from the remaining absolute components, wherein the arithmetic transformation for each of the at least two difference components further comprises coefficients that at least substantially sum to zero, and further wherein the at least two difference components enable the disturbing signal portion to be at least partially suppressed in the transferred signal; and

extracting the at least partially periodic vital signal from the at least two difference components in the transferred signal.

20. A non-transitory computer-readable medium embodied with a computer program comprising program code for causing a computer to carry out the steps of the method as claimed in claim 19 when said computer program is carried out on the computer.