Non-contact method for detecting physiological signal and motion in real time

• US 10,413,248 B2
• Filed: 06/27/2016
• Issued: 09/17/2019
• Est. Priority Date: 07/09/2015
• Status: Active Grant

• Current Assignee: National Taiwan University of Science and Technology
• Original Assignee: National Taiwan University of Science and Technology
• Inventors: Lin, Yuan-Hsiang, Lin, Yu-Chen, Lin, Guan-You, Li, Meng-Han
• Primary Examiner(s): Thirugnanam, Gandhi
• Application Number:
  US15/193,196
• Publication Number:
  US 20170007185A1
• Time in Patent Office: 1,177 Days
• CPC Class Codes: A61B 2562/0233 Special features of optical sensors or probes classified in A61B5/00
• CPC Class Codes: A61B 5/02433 for infrared radiation
• CPC Class Codes: A61B 5/1032 Determining colour for diagnostic purposes measuring colour in general G01J3/46
• CPC Class Codes: A61B 5/1121 Determining geometric values, e.g. centre of rotation or angular range of movement
• CPC Class Codes: A61B 5/1128 using image analysis A61B5/1127 takes precedence
• CPC Class Codes: A61B 5/721 using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured
• 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: A61B 5/746 Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms alarms per se G08B

Abstract

A method includes: sensing a portion of a human body to generate a series of image frames by an optical sensing element; determining a complexion region from each of the image frames; then calculating a central coordinate of the complexion region; determining a sample block by expanding a surrounding range from the central coordinate, for getting a complexion fluctuation waveform; comparing the central coordinate with a central coordinate of a later image frame, to calculate a displacement in a unit time for determining whether the portion of the human body is in a static state. In the static state, an operating unit performs noise filter and peak detecting for complexion fluctuation waveform, and calculates a physiological signal. The method can reduce the amount of data required to be processed in physiological signal detection, and improve the accuracy of the detection.

Claims

1. A non-contact method for detecting physiological signal and motion in real time, comprising steps of:

sensing a portion of a human body to generate a first image frame and a second image frame by an optical sensing element, wherein the second image frame is generated later than the first image frame;

providing a complexion judging mechanism by an operating unit for determining a first complexion region from the first image frame, and calculating a first central coordinate of the first complexion region;

the operating unit determining a first sampling block by acquiring a specific surrounding range expanded with the first central coordinate as an expanding center;

the operating unit determining a second complexion region from the second image frame by executing the complexion judging mechanism, and calculating a second central coordinate of the second complexion region;

determining a second sampling block by acquiring another specific surrounding range expanded with the second central coordinate as another expanding center;

the operating unit comparing the first central coordinate with the second central coordinate, to calculate a displacement in a unit time;

the operating unit discriminating whether a motion state of the portion of the human body is in a static state according to the displacement;

the operating unit calculating a physiological signal formed as a complexion fluctuation waveform in accordance with a complexion fluctuation between the first sampling block and the second sampling block if the motion state of the portion of the human body is in the static state; and

transmitting the physiological signal to a relevant receiving device.

2. The non-contact method for detecting physiological signal and motion in real time as claimed in the claim 1, further comprising:

the operating unit calculating an area of the first complexion region;

judging whether the area of the first complexion region is larger than a preset area or not;

displaying the first sampling block in a succeeding image frame following the first image frame on a display unit, and the operating unit determining the portion of the human body is really sensed by the optical sensing element if the area of the first complexion region is larger than a preset area threshold; and

the operating unit generating and sending a warning signal to the relevant receiving device to alert a user if the area of the first complexion region is smaller than the preset area threshold.

3. The non-contact method for detecting physiological signal and motion in real time as claimed in the claim 2, further comprising:

determining the portion of the human body is not really sensed by the optical sensing element, and generating an alerting signal by an alarm unit if the area of the first complexion region is less than the preset area threshold.

4. The non-contact method for detecting physiological signal and motion in real time as claimed in the claim 1, further comprising:

the operating unit executing a motion detecting mechanism comprising steps of;

receiving a first displacement critical value and a second displacement critical value preset by the user, wherein the first displacement critical value is less than the second displacement critical value;

the operating unit retrieving the first displacement critical value and the second displacement critical value to respectively compare with the displacement;

if the displacement is not greater than the first displacement critical value, then the operating unit defining the portion of the human body is in a static state;

if the displacement is greater than the first displacement critical value and not greater than the second displacement critical value, then defining the portion of the human body is in a slightly motion state;

if the displacement is greater than the second displacement critical value, then defining the portion of the human body is in a violent motion state; and

changing the first displacement critical value and the second displacement critical value by the operating unit, to adjust a sensitivity of the motion detecting mechanism.

5. The non-contact method for detecting physiological signal and motion in real time as claimed in the claim 1, wherein each of the first image frame and the second image frame includes a plurality of pixels, the operating unit executes the complexion judging mechanism to judge that each of the pixels is a skin-color pixel or a nonskin-color pixel, wherein the complexion judging mechanism comprises steps of:

selecting one of the pixels to be a central pixel, and defining a judging block by outspreading from the central pixel to the surrounding thereof;

calculate an area ratio of a skin-color area located in the judging block to an entire area of the judging block, wherein the skin-color area is formed by the skin-color pixels in the judging block and located around the central pixel;

the operating unit receiving a reference ratio preset by the user, and comparing the area ratio with the reference ratio; and

determining the central pixel is a nonskin-color pixel if the area ratio is less than the reference ratio.

6. The non-contact method for detecting physiological signal and motion in real time as claimed in the claim 1, further comprising:

the operating unit calculating one of an average of red channel signals, an average of green channel signals and an average of blue channel signals for each of the first sampling block and the second sampling block, to create the complexion fluctuation waveform.

7. The non-contact method for detecting physiological signal and motion in real time as claimed in the claim 6, further comprising:

obtaining a real ambient illuminance via the optical sensing element;

the operating unit receiving an illuminance threshold preset by the user, and comparing the real ambient illuminance with the illuminance threshold by the operating unit, so as to obtain a comparing result;

preparing a light source of infra-red, and selecting one of a switch-on mode and a switch-off mode for the light source of infra-red in accordance with the comparing result;

switching the light source of infra-red into the switch-off mode and using the average of green channel signals for creating the complexion fluctuation waveform if the real ambient illuminance is greater than the illuminance threshold as the comparing result; and

switching the light source of infra-red into the switch-on mode and using the average of red channel signals for creating the complexion fluctuation waveform if the real ambient illuminance is less than the illuminance threshold as the comparing result.

8. The non-contact method for detecting physiological signal and motion in real time as claimed in the claim 1, further comprising:

inputting the physiological signal into an infinite impulse response filter to perform filtering process for generating an output signal.

9. The non-contact method for detecting physiological signal and motion in real time as claimed in the claim 8, further comprising:

providing a moving average algorithm for the operating unit;

the operating unit executing the moving average algorithm to smooth a waveform of the output signal generated from the infinite impulse response filter.

10. The non-contact method for detecting physiological signal and motion in real time as claimed in the claim 1, wherein the operating unit is a field-programmable gate array with an internal microprocessor, the field-programmable gate array executes the complexion judging mechanism, and the internal microprocessor calculates the physiological signal.