CN109124614B - Non-contact heart rate detection method based on optical lever - Google Patents
Non-contact heart rate detection method based on optical lever Download PDFInfo
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- CN109124614B CN109124614B CN201810992085.4A CN201810992085A CN109124614B CN 109124614 B CN109124614 B CN 109124614B CN 201810992085 A CN201810992085 A CN 201810992085A CN 109124614 B CN109124614 B CN 109124614B
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- 238000001514 detection method Methods 0.000 title claims abstract description 29
- 230000003287 optical effect Effects 0.000 title claims abstract description 14
- 238000000034 method Methods 0.000 claims abstract description 9
- 238000003384 imaging method Methods 0.000 claims description 14
- 238000001914 filtration Methods 0.000 claims description 6
- 239000008280 blood Substances 0.000 abstract description 5
- 210000004369 blood Anatomy 0.000 abstract description 5
- 230000004886 head movement Effects 0.000 abstract description 4
- 210000003128 head Anatomy 0.000 description 14
- 238000009610 ballistocardiography Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000012544 monitoring process Methods 0.000 description 3
- 230000000284 resting effect Effects 0.000 description 3
- 230000008859 change Effects 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 230000007774 longterm Effects 0.000 description 2
- 230000003321 amplification Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 210000001061 forehead Anatomy 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000007794 irritation Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 238000013186 photoplethysmography Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 208000020016 psychiatric disease Diseases 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 230000011218 segmentation Effects 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
- A61B5/024—Detecting, measuring or recording pulse rate or heart rate
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
- A61B5/7203—Signal processing specially adapted for physiological signals or for diagnostic purposes for noise prevention, reduction or removal
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
- A61B5/7225—Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
- A61B5/7235—Details of waveform analysis
- A61B5/7253—Details of waveform analysis characterised by using transforms
- A61B5/7257—Details of waveform analysis characterised by using transforms using Fourier transforms
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Abstract
The invention discloses a non-contact heart rate measuring device based on an optical lever, which is used for amplifying a head movement signal in a ballistocardiographic technique, and the movement state of the head is represented by a facula signal with amplified movement amplitude, and the movement signal of the focal spot is processed, so that the problems of small amplitude and low signal-to-noise ratio of an original signal of movement generated by the head subjected to blood impact can be solved, the signal-to-noise ratio of an acquired movement track signal can be effectively improved in a complex background environment, and accurate non-contact heart rate detection is realized.
Description
Technical Field
The invention belongs to the technical field of human health monitoring, and relates to a non-contact heart rate detection method based on an optical lever.
Background
Heart rate is the number of beats per minute of a normal person's heart in a resting state, called resting heart rate or resting heart rate, and can be classified into contact type and non-contact type according to the difference in detection technique and method, however, contact type detection causes discomfort of the patient's body, causes irritation or pain, and even causes physiological changes to affect the accuracy of the detection result. Moreover, these methods are not suitable for long-term human contact, long-term detection and daily monitoring at any time. Especially for patients with large-area burn, patients with mental diseases, infants and the like which cannot cooperate autonomously, and are not suitable for contacting the body by using electrodes or sensors, the contact type heart rate detection has obvious limitation. The non-contact detection method has the advantages of real-time convenience, high cost performance, good repeatability, suitability for large-scale detection and the like, and has wide application prospect.
Currently, imaging non-contact heart rate detection methods can be divided into photoplethysmography (IPPG) and Ballistocardiography (BCG). Compared with the heart rate detection method based on the IPPG principle, the heart rate detection method based on the BCG principle has obvious advantages for realizing non-contact heart rate detection in a complex environment, and is not influenced by light variation. However, the heart rate detection by the BCG method is realized by extracting tiny impact generated by the impact of pumping blood by the heart from the head in the image, and the accuracy of the extracted head movement signal is difficult to be ensured if the signal is directly applied to heart rate detection due to the low signal-to-noise ratio of the extracted head movement signal.
Disclosure of Invention
In order to solve the problems, the invention provides a non-contact heart rate detection method based on an optical lever, and the movement state of the head is represented by a facula signal with amplified movement amplitude, so that the signal to noise ratio can be effectively improved, and the accuracy of heart rate detection is improved.
Besides heart rate detection objects, the device required by the invention further comprises a light source, a plane mirror, imaging equipment and a receiving screen, and the heart rate detection method comprises the following steps.
Firstly, placing a plane mirror in a head area of a heart rate detection object, adjusting the posture of the plane mirror, enabling a light beam emitted by a light source to reach a receiving screen after being reflected by the plane mirror, and forming bright light spots on the surface of the light beam; the imaging device is placed in front of the receiving screen, the position of the imaging device is adjusted, the complete image of the receiving screen can be obtained in the field of view, and after adjustment, the positions of all elements are fixed.
And secondly, starting the imaging equipment to acquire and receive video of the spot movement on the screen.
And thirdly, converting each frame of image of the video into a binary image.
And fourthly, calculating and tracking the barycenter coordinates of the light spots in the binary image, and obtaining a time sequence signal.
And fifthly, performing Fourier transform on the time sequence signals of the positions of the optical spots to obtain a spectrogram.
And sixthly, carrying out band-pass filtering on the spectrogram.
And seventh, extracting the frequency corresponding to the position with the maximum amplitude in the spectrogram, and multiplying the frequency by 60.
Preferably, the band-pass filtering mode is to reserve data in the frequency range of 0.5-3 Hz.
Preferably, the spot movement tracking adopts a centroid tracking algorithm.
The beneficial effects of the invention are as follows.
The invention builds the optical lever by using the light reflection principle, realizes the amplification of the head movement signal in the ballistocardiographic technology, characterizes the movement state of the head by the facula signal with amplified movement amplitude, processes the light spot movement signal, can solve the problems of small amplitude and low signal-to-noise ratio of the original signal of the movement generated by the head subjected to the blood impact, can effectively improve the signal-to-noise ratio of the acquired movement track signal under the complex background environment, and realizes accurate non-contact heart rate detection.
Drawings
Fig. 1 is a schematic diagram of the method according to the invention.
Fig. 2 is an optical lever diagram according to the present invention.
Fig. 3 is a flowchart of a non-contact heart rate detection method according to the present invention.
The device comprises a 1-light source, a 2-plane mirror, a 3-imaging device, a 4-receiving screen and a 5-tested object.
Detailed Description
In order to clearly illustrate the technical scheme provided by the invention, the invention will be described in detail below with reference to the accompanying drawings and the embodiments.
The schematic diagram of the experimental method is shown in fig. 1, the experimental method comprises a light source 1, a plane mirror 2, an imaging device 3 and a receiving screen 4, wherein a light beam emitted by the light source is reflected by the plane mirror 3, and forms a light spot on the surface of the receiving screen 4 after reaching the receiving screen 4, the imaging device 3 is placed in front of a heart rate monitoring object 5, and a video of the light spot movement at the receiving screen 4 is obtained.
The optical lever principle is shown in the attached drawing2, the working principle is that the light beam emitted by the light source 1 is reflected to the receiving screen through the plane mirror 2 at the forehead position, and a light spot S is formed on the receiving screen. Due to the heart beat of the subject 5, the pump emits blood to exert a force on the head, resulting in regular weak mechanical movements of the head and thus in a movement of the plane mirror 2 fixed in the head region. Alpha is the angle between the light beam emitted by the light source 1 and the normal of the plane mirror 2 and the plane mirror 2. Beta is the angle at which the plane mirror 2 moves. M is the distance between the normal lines of the two plane mirrors 2, H and H 'are the incident light spots from the light beam emitted by the light source 1 to the end positions A and A' of the plane mirrors 2, respectively, and x 1 And x 2 Representing the distance between a and a' to the receiving screen 4, respectively. When the point a moves to the point a 'position, the spot on the receiving screen will move from the S position to the S' point.
From the geometrical relationship shown in fig. 2, the distance SS' traveled by the spot can be expressed by the following formula.
SS’＝tan(α+2β)(x 1 +x 2 )-tan(x 2 -x 1 )
The amplitude of the head motion is defined as HH' and its expression can be solved by the geometric relationship.
HH’＝x 1 /cosα
After the expression of the spot moving distance and the head moving amplitude is obtained, the magnification of the optical lever can be expressed by the following formula.
g＝SS’/HH'＝[tan(α+2β)(x 1 +x 2 )-tan(x 2 -x 1 )]cosα/x 1
According to the above formula, after the light beam is reflected by the plane mirror 2, a tiny movement displacement HH 'is generated for the head, and the light beam appears as a larger spot displacement SS' on the receiving screen 4, thereby realizing the amplifying function. In addition, the spatial relative position and the gesture of the plane mirror 2 and the receiving screen 4 in the adjusting method can be used for adjusting the magnification of the optical lever so as to meet the actual use requirement.
The non-contact heart rate detection method of the invention has an execution flow shown in figure 3, and the specific contents are as follows.
Firstly, placing a plane mirror 2 in a head area of a heart rate detection object, and adjusting the posture of the plane mirror 2 to enable a light beam emitted by a light source 1 to reach a receiving screen 4 after being reflected by the plane mirror 2 and form a bright light spot on the surface of the light beam; after the imaging device 3 is placed, the position of the imaging device is adjusted, so that the complete image of the receiving screen 4 can be obtained in the field of view, and after the adjustment is finished, the positions of all elements are fixed.
And secondly, starting the imaging device 3, and collecting video of the light spot movement on the receiving screen 4.
And thirdly, converting each frame of image of the video into a binary image to realize the segmentation of the facula area and the background area of the receiving screen 4.
And fourthly, calculating and tracking the centroid coordinates of the light spots in the binary image, obtaining a time sequence change signal, wherein the tracking method adopts a centroid tracking algorithm, and a formula for calculating the centroid coordinates of the light spots is shown as follows.
x＝(∑ j＝1:n ∑ i＝1:m g(i,j)×i)/(∑ j＝1:n ∑ i＝1:m g(i,j))
y＝(∑ j＝1:n ∑ i＝1:m g(i,j)×j)/(∑ j＝1:n ∑ i＝1:m g(i,j))
In the spot centroid calculation formula, m and n respectively represent the total number of pixels in two coordinate directions in an image, and g (i, j) represents a gray value of a pixel with coordinates (i, j).
And fifthly, performing Fourier transformation on the time sequence change signal of the light spot position to obtain a spectrogram of the time sequence signal.
And sixthly, carrying out band-pass filtering on the spectrogram, only retaining the data in the frequency range of 0.5-3 Hz, and filtering out background environment motion noise which obviously does not belong to the heart rate range.
And seventh, extracting the frequency corresponding to the position with the maximum amplitude in the spectrogram, wherein the frequency is the frequency of the movement generated by the impact of blood on the head per second, and multiplying the frequency by 60 to obtain the frequency of the movement of the head per minute, and the frequency is the heart rate.
In summary, the above embodiments are only provided to the present invention, and are not intended to limit the scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (2)
1. A non-contact heart rate detection method based on an optical lever, characterized in that the method comprises the following steps:
firstly, placing a plane mirror in a head area of a tested object, adjusting the posture of the plane mirror, enabling a light beam emitted by a laser to reach a receiving screen after being reflected by the plane mirror, and forming a bright light spot on the surface of the light beam; after the imaging equipment is placed, the position of the imaging equipment is adjusted, so that a complete receiving screen image can be obtained in a view field, and after the adjustment is finished, the positions of all elements are fixed;
secondly, starting imaging equipment, and collecting video of spot movement on a receiving screen;
thirdly, converting each frame of image of the video into a binary image;
fourthly, calculating and tracking the barycenter coordinates of the light spots in the binary image, and obtaining a time sequence signal;
fifthly, performing Fourier transform on the time sequence signals of the positions of the optical spots to obtain a spectrogram;
sixthly, carrying out band-pass filtering on the spectrogram;
and seventh, extracting the frequency corresponding to the position with the maximum amplitude in the spectrogram, and multiplying the frequency corresponding to the maximum amplitude by 60.
2. The method for non-contact heart rate detection based on an optical lever as claimed in claim 1, wherein the band-pass filtering range is 0.5Hz-3Hz.
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| CN111880397A (en) * | 2020-08-10 | 2020-11-03 | 广东众科智能科技股份有限公司 | A intelligent wrist-watch that is used for medical treatment block chain to provide health information |
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