Optic sensors
Diffiuse optical sensors
These sensors operate based on the transmission of modulated infrared waves and the reception of their reflections from various surfaces.
Some applications of these sensors are shown in the figure below.
Used to detect the presence or absence of objects by sensing the reflection of infrared waves from the object's surface.
Used to identify tears or breaks in sheets (such as paper, metal, or fabric) by detecting changes in the reflected infrared waves.
Used to monitor and control the alignment or deviation of sheets during processing by detecting shifts in the reflected infrared waves.
In these sensors, modulated infrared waves are emitted directly into the environment by the transmitter. When these waves encounter an obstacle, they are reflected, with the amount of reflection depending on the color and material of the surface, and the reflection is not in a straight line. Bright and polished surfaces reflect more than dark and non-polished surfaces, and the switching distance of these sensors depends on the amount of reflected light. When an obstacle is placed in front of the sensor and the reflected waves are received by the sensor’s receiver, the sensor’s output changes state.
In general, these sensors are divided into two types:
Normally Open:
In the normal state, when there is no obstacle in front of the sensor and the transmitted light does not reach the receiver, the sensor output is inactive (light on). When an obstacle causes the infrared waves to reach the receiver, the output changes from inactive to active.
Normally Closed:
In the normal state, when there is no obstacle in front of the sensor and the transmitted light does not reach the receiver, the sensor output is active (dark on). When an obstacle causes the infrared waves to reach the receiver, the output changes from active to inactive.