Sensors for Smartphone and Tablet
Since the emergence of Apple’s iPhone and iPad, the smartphone and tablet computer market has shown an unprecedented prosperity, and attracted many leading manufacturers into this profitable area. It is reported that until the third quarter of 2011, Apple’s iOS-based smartphone and tablet series have gained 15% of global market share, while the Android-based smartphones and tablets account for an astonishing share of 52.5%. The booming market has in turn spurred a variety of related technologies to develop further, especially the wide variety of sensors used in these handheld devices, which are constantly improving the user experience.
Today, a smartphone or a tablet might integrate a MEMS microphone, an image sensor, a 3-axis accelerometer, a gyroscope, an atmosphere pressure sensor, a digital compass, an optical proximity sensor, an ambient light sensor, a humidity sensor and touch sensors. MEMS microphones have a smaller size and lower power consumption than traditional ones, making them an ideal choice for voice input on highly integrated devices. The image sensor, as the key part of camera on smartphones and tablets, is used to capture images and record videos. Using a 3-axis accelerometer makes it possible for smartphones and tablets to detect users’ gestures and therefore accomplish specific function based on predefined configuration. The gyroscope, atmospheric pressure sensor and digital compass work together to take over the job of providing navigation data for users when a GPS signal is not available. The optical proximity sensor detects the distance between the device and another object which could be user’s ear or a protection cover, so that CPU can disable touch screen when the distance is found lower than a preset value, hence avoid mis-operations and save battery power. An ambient light sensor enables smartphones and tablets to automatically adjust the brightness of the screen backlight depending on ambient light intensity. This function further saves battery power, but more importantly, makes users feel comfortable by applying appropriate screen brightness level under different ambient light condition. Touch sensors are used to take the place of traditional keys with advantages of longer life, water-proof capability and higher design flexibility. The temperature sensor, humidity sensor and atmospheric pressure sensor detect real-time environmental conditions such as temperature, humidity and atmosphere pressure, making smartphones or tablets miniaturised meteorological stations.