Contactless Heart Rate Estimation from Facial Video Signals
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Solution Overview
Problem
Existing heart rate estimation methods require contact with the body, limiting their use scenarios and requiring expensive and cumbersome equipment.
Innovation Solution
A method utilizing face video analysis, including face detection, weighted averaging of pixel values, time-frequency domain conversion, and peak value detection to estimate heart rate without contact, using devices with camera units and processing units for accurate heart rate estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contact-based measurement methods (electrocardiogram or PPG) are used, then measurement precision is improved, but device complexity and ease of operation deteriorate due to requiring expensive equipment, professional operation, or close contact with sensors
Solution Approach 1:
The patent uses a camera to capture optical images of the face, creating a visual copy of the physiological state. Instead of direct electrical or optical contact measurement, the system captures reflected light patterns from facial skin that correlate with blood flow changes, thereby measuring heart rate through an indirect visual representation
Solution Approach 2:
The patent replaces mechanical/contact-based measurement systems (electrodes, optical sensors requiring skin contact) with an optical imaging system using a camera. The mechanical contact requirement is substituted by capturing reflected light from the facial surface, eliminating the need for physical attachment while maintaining measurement capability
2Measurement precision
If contact-based PPG method is used, then measurement precision is improved, but ease of operation deteriorates due to requiring close contact between sensor and fixed human body part
Solution Approach 1:
The system creates an optical copy of the facial surface through camera imaging, capturing blood flow-induced color changes without requiring physical sensor contact. This visual copying approach allows measurement while the user maintains natural facial expressions and movements
Solution Approach 2:
Instead of placing a sensor on the user's body (user-adapted-to-sensor), the patent inverts the approach by bringing the measurement capability to the user through facial imaging. The camera captures images of the face in natural settings, reversing the traditional sensor-to-body attachment paradigm
3Measurement precision
If electrocardiogram method is used, then measurement precision is improved, but ease of operation deteriorates due to requiring professional operation
Solution Approach 1:
The patent uses optical imaging to create a visual record of facial blood flow changes, replacing the need for electrical signal acquisition and interpretation. This visual copying approach simplifies the measurement process to basic image capture and analysis, eliminating complex electrical measurement procedures
Solution Approach 2:
The patent replaces expensive, specialized medical equipment with a standard camera and simple image processing algorithms. This substitution with readily available, low-cost technology makes the system accessible to general users without requiring professional medical equipment or expertise
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables non-contact, accurate, and robust heart rate estimation suitable for various scenarios, including mobile platforms, with improved accuracy and reduced hardware complexity, allowing continuous monitoring without harm to the user.
Implementation Method 1
Photo plethysmo graphy (PPG) is a non-invasive measurement method for monitoring blood volume changes in living body tissues by means of photoelectric means. When light of a certain wavelength is irradiated on a skin surface such as between fingers, the light will be captured by a photoelectric receiver in a transmission or reflection manner.
Implementation Method 2
During the whole process, the light is weakened due to the absorption by skin, muscles, blood and the like, and thus the light intensity reaching the photoelectric receiver will be reduced. The weakening effect of the skin, the muscles and the like on the light intensity is constant, while the weakening effect of blood in blood vessels on the light will show a pulsatile change with the beating of the heart.
Data Source
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AI summary
A heart rate estimation method and apparatus, and an electronic device applying same. The heart rate estimation method comprises: obtaining a face video (S100); performing face detection on the face video, and extracting a face local area which is set to be used for heart rate estimation (S102); performing first processing on values of pixel points in the face local area to obtain an initial heart rate signal (S104); performing time-frequency domain conversion on the initial heart rate signal to obtain a frequency domain signal (S106); and performing second processing on the frequency domain signal within a heart rate estimation range to obtain a heart rate estimation value (S110).