With technological advancements, mobile phones are no longer simple communication tools, but rather portable electronic devices with comprehensive functions. Virtual functions, such as interaction and games, are achieved through the powerful computing capabilities of the processor, while functions that integrate with reality are realized through sensors. Below is a summary of common mobile phone sensors to help you understand their principles and uses.
I. Light Sensor:
Principle: When a phototransistor receives external light, it generates currents of varying strengths, thereby sensing the ambient light level.
Uses: Typically used to adjust the screen's automatic backlight brightness, increasing screen brightness during the day and decreasing it at night for clearer, less glaring visibility. It can also be used for automatic white balance when taking photos. Furthermore, it can be used in conjunction with the proximity sensor below to detect if the phone is in a pocket, preventing accidental touches.
II. Distance Sensor:
Principle: Infrared LED lights emit infrared rays, which are reflected by nearby objects. The infrared detector measures the distance by receiving the intensity of the infrared rays, typically within 10cm. Distance sensors have both transmitting and receiving devices and are generally quite large.
Purpose: To detect if the phone is being used while it's held to the ear during a call, automatically turning off the screen to save power. It can also be used to automatically unlock and lock the screen in cases or pocket modes.
Additionally: the positions of the light sensor and the proximity sensor
Light and proximity sensors are usually placed together, around the earpiece on the front of the phone. This presents a problem: too many holes or a long black strip on the top of the phone doesn't look good. Therefore, Apple has been trying to reduce or hide these openings. Black-panel phones can easily hide these two sensors, but white-panel phones face a bit more difficulty.
Starting with the iPhone 5, Apple made the light sensor white, effectively hiding it. Many domestic phone manufacturers haven't been able to achieve this yet; they can only use smaller sensors, combining the light and proximity sensors into a smaller, elongated shape, or a large circle like the camera lens, which looks relatively better. Smartisan's sensor is also elongated, but it's placed directly inside the earpiece, which is also considered hidden.
III. Gravity Sensor:
Principle: It utilizes the piezoelectric effect. Inside the sensor, a weight and a piezoelectric element are integrated together. The horizontal direction is calculated by measuring the magnitude of the voltage generated in two orthogonal directions.
Applications: Intelligent switching between portrait and landscape modes on mobile phones, photo orientation during photography, and gravity-sensing games (such as rolling steel balls).
IV. Accelerometer
Principle: Similar to gravity sensors, it also uses the piezoelectric effect to determine the direction of acceleration through three dimensions, but it consumes less power and has lower accuracy.
Applications: Pedometer, phone placement and orientation.
V. Magnetic field sensor:
Principle: Anisotropic magnetoresistive materials change their resistance when they sense a slight change in magnetic field, which is why a phone can accurately indicate direction only after being rotated or shaken a few times.
Applications: Compass, map navigation, metal detector app.
VI. Gyroscope:
Principle: Conservation of angular momentum. When an object (gyroscope) is rotating at high speed, its axis of rotation will not change direction unless affected by an external force. Gyroscopes are based on this principle to maintain a certain orientation. A three-axis gyroscope can replace three single-axis gyroscopes, simultaneously measuring position, trajectory, and acceleration in six directions.
Applications: motion sensing, shake (using the phone to perform certain functions), panning, rotation, moving the phone to control the viewpoint in games, VR virtual reality, and conventional navigation based on the movement of objects when there is no GPS signal (such as in a tunnel).
VII. GPS
Principle: Twenty-four GPS satellites orbit the Earth, each constantly broadcasting its current position coordinates and timestamp information to the world. The mobile phone's GPS module receives this information via its antenna. The chip in the GPS module uses the instantaneous position of the rapidly moving satellite as known starting data, calculates the distance between the satellite and the phone based on the time difference between the satellite's transmission timestamp and the reception timestamp, and determines the position coordinates of the point to be measured using a spatial distance resection method.
Applications: Maps, navigation, speed measurement, distance measurement.
8. Fingerprint sensor
Currently, capacitive fingerprint recognition is the mainstream technology, but starting in 2016, ultrasonic fingerprint recognition, which has a faster recognition speed and higher recognition rate, will gradually become more widespread.
The principle of capacitive fingerprint sensors: The finger forms one stage of a capacitor, and the other stage is a silicon chip array. A micro-current is formed between the micro-electric field of the human body and the capacitive sensor. The peaks and troughs of the fingerprint and the distance between the sensors form the capacitance difference, thus depicting the fingerprint image.
The principle of ultrasonic fingerprint sensors: Ultrasonic waves are often used for distance measurement, such as sonar systems used for seabed topographic mapping. The principle of ultrasonic fingerprint recognition is the same: it directly scans and maps the fingerprint texture, even detecting pores. Therefore, ultrasonic fingerprints are 3D, while capacitive fingerprints are 2D. Ultrasonic sensors are not only faster, but also unaffected by sweat or oil, and provide richer fingerprint details, making them more difficult to crack.
Uses: encryption, unlocking, payment.
IX. Hall Sensor
Principle: Hall effect. When an electric current passes through a conductor located in a magnetic field, the magnetic field exerts a force on the electrons in the conductor perpendicular to the direction of electron motion, thereby creating a potential difference across the conductor.
Applications: Automatic unlocking when flipping the phone, automatic screen locking when closing the phone.
10. Barometric Pressure Sensor:
Principle: Barometric pressure sensors are divided into capacitive and resistive types. A thin film is connected to a rheostat or capacitor. Changes in air pressure cause changes in the resistance or capacitance, thereby obtaining air pressure data.
Applications: GPS altitude calculations can have an error of about ten meters. Barometric pressure sensors are mainly used to correct altitude errors (reducing them to about one meter). Of course, they can also be used to assist GPS in locating overpasses or building positions.
11. Heart Rate Sensor
Principle: When a finger is illuminated by a high-brightness LED light source, the brightness (depth of red) changes periodically like a wave when the heart pumps fresh blood into the capillaries. The interval of this regular change is quickly captured by a camera and then converted by an application in the mobile phone to determine the heart's contraction frequency.
Uses: Sports, Health
12. Blood Oxygen Sensor
Principle: The photoelectric emission effect of certain semiconductors, metals or metal compounds releases a large number of electrons under ultraviolet irradiation. The intensity of ultraviolet radiation can be calculated by detecting this discharge effect.
Uses: Sports, Health
13. Ultraviolet Sensor
Principle: Utilizing the photoelectric emission effect of certain semiconductors, metals, or metal compounds, a large number of electrons are released under ultraviolet radiation. Detecting this discharge effect allows for the calculation of the ultraviolet radiation intensity.
Uses: Sports, Health
Summarize:
The first eight sensors are considered standard features in mobile phones. The last five are less common, mainly used in medical and health applications, but are still relatively common in higher-end mobile phones.
Mobile phones are no longer just communication tools; they are practically all-in-one personal assistants. They integrate commonly used and practical functions, as well as less frequently used but occasionally useful ones. It's easy to imagine that future mobile phones will integrate more and more sensors and become increasingly intelligent.
