What Is an Area Sensor?
An area sensor is a sensor that detects people or objects within a predefined area.
It detects objects by emitting light or sound waves and detecting their reflection or transmission. Safety light curtains are one type of area sensor.
In recent years, sensors that detect not only two-dimensional surfaces but also three-dimensional spaces have become available.
Uses of Area Sensors
Area sensors are used for industrial or security purposes. The following are examples of applications of area sensors:
1. Intrusion Detection in Factory Equipment
Industrial equipment includes many facilities that operate under pressure and torque that can easily destroy the human body. Presses for industrial waste disposal and conveyor belts for transporting coal fuel are examples. If workers or passersby inadvertently come into proximity to such equipment, there is a risk of personal injury.
It is common practice to surround these facilities with perforated metal or handrails to prevent easy contact, but it is inconvenient to cover areas completely where people frequently enter and leave the facility or where periodic maintenance is required. In such locations, area sensors are installed so that equipment will be shut down when a person enters. Area sensors used for such safety purposes are also called safety light curtains.
2. For Object Detection in Unmanned Vehicles
In factories and automated warehouses, AGVs (Automated Guided Vehicles) are used to transport goods automatically in order to save labor and reduce costs, and area sensors are often used to detect objects in the direction the AGV is traveling and in the surrounding area. area sensors, such as those used in AGVs are also called Safety Light Scanners.
3. Human Detection
Sensors are sometimes used to detect people in order to open and close automatic doors or to turn on gate lights. Sensors that detect people are specifically called human detection sensors.
They may also be used to detect unauthorized intruders at night for security purposes. Attached to a security camera, it zooms in or triggers an alarm when it detects a person. Often sold as a security sensor light in combination with lighting fixtures.
Principle of Area Sensors
Area sensors use infrared, ultrasonic, or visible light as the detection medium.
1. Infrared Light
Infrared light is light with a longer wavelength than visible light. Since it is invisible and does not damage the landscape, it is a widely used detection medium in applications ranging from general security equipment to industrial applications. Generally, detection is performed using light with wavelengths of 1 to 1,000 μm.
Infrared rays have the characteristic of being emitted spontaneously from objects that are warmer than the outside air. This characteristic makes it ideal for detecting human bodies with body heat, and it is used for gate lights and security lighting. In addition, a detection method based on the difference in sensed temperature may be used to open and close faucets, and a mechanism that converts the temperature difference into an electrical signal after detecting the temperature difference within the detection area is used.
2. Ultrasonic Waves
Sound waves with wavelengths shorter than the human audible range are called ultrasonic waves. Ultrasonic waves are sometimes used in area sensors because they are inaudible to the human ear and can detect surrounding objects by their reflected velocity. A sensor that uses ultrasonic waves to detect objects is also called an ultrasonic sensor.
After measuring the time it takes for sound to be reflected back, it is converted into an electrical signal to detect the distance to the object.
3. Visible Light
Sensors that detect objects by visible light are called photoelectric sensors. Area sensors using the same principle as photoelectric sensors are also available. They consist of a light emitting part and a light receiving part. The light receiving part detects when the light emitted is intercepted or reflected, thereby detecting an object.
Types of Area Sensors
The following types of area sensors exist due to differences in the above-mentioned principles.
1. Light Curtains and Safety Light Curtains
Products that use multiple photoelectric sensors side-by-side to detect flat surfaces are called light curtains, while products that are specifically designed for safety measures are called safety light curtains. In general, this type of product is often referred to as an Area Sensor.
2. Infrared Sensor / Human Detection Sensor
These sensors detect infrared rays and are often used to detect people. They are intended for crime prevention and safety.
3. Laser Scanner
A laser scanner is a sensor that detects surrounding objects by transmitting light rays in a fan shape. A wide area centered on the sensor can be detected in three dimensions. Laser scanners used especially for safety applications are called safety laser scanners.
In recent years, due to its wide detection range, it has been actively developed as an in-vehicle sensor.