Short Answer:

An optical encoder measures displacement by detecting the motion of a rotating or moving object using a light source, a code disk, and a light sensor. As the object moves, the code disk with transparent and opaque sections rotates or shifts, interrupting the light beam in a specific pattern.

This interruption is converted into electrical pulses by the sensor. By counting these pulses, the system calculates the amount and direction of displacement. Optical encoders are widely used in robotics, CNC machines, and automation systems for accurate position and speed feedback.

Detailed Explanation:

Working of optical encoder

An optical encoder is an electromechanical sensor that measures displacement, position, or speed by converting mechanical motion into electrical signals. It works based on the interruption or modulation of light, which is detected and converted into readable digital signals. Optical encoders are commonly used in machines where precise motion control and feedback are required.

Optical encoders can be of two main types:

• Incremental encoders
• Absolute encoders

Both types use the same basic components but provide different kinds of output.

Basic Components:

1. Light Source: Usually an LED that emits a steady light beam.
2. Code Disk or Scale: A circular or linear disk with alternating transparent and opaque sections or lines. This disk is fixed to the moving shaft or object.
3. Photodetector or Light Sensor: Placed on the opposite side of the disk to detect light passing through.
4. Signal Processing Circuit: Converts the light pulses into electrical signals (digital pulses).

Working Principle:

1. Motion Initiation:
   When the shaft or object connected to the encoder moves, it rotates or shifts the code disk along with it.
2. Light Modulation:
   As the disk rotates, the transparent and opaque sections alternatively block or allow the light from the LED to reach the photodetector.
3. Signal Generation:
   Every time the light beam is interrupted or passed, a pulse is generated. These pulses are counted by the circuit.
4. Displacement Calculation:
   • In incremental encoders, the number of pulses tells how far the object has moved.
   • In absolute encoders, each position on the disk has a unique pattern, so the exact position is known at all times.
5. Direction Detection (Optional):
   Many encoders use two light sensors slightly apart (known as quadrature output). The phase difference between the two signals helps determine the direction of movement.

Advantages:

• High Accuracy and Resolution: Ideal for precision control systems.
• Digital Output: Easy to interface with microcontrollers and PLCs.
• Reliable for Speed and Position Measurement
• Non-contact Measurement: Reduces mechanical wear.
• Compact Design: Fits in small machine spaces.

Limitations:

• Sensitive to Dust and Vibration: Optical parts may get dirty, affecting accuracy.
• Power Dependency: Requires continuous power to operate.
• Fragility: Optical components are delicate and need careful handling.
• Limited Operation in Harsh Environments: Moisture, oil, or light interference can cause false readings.

Applications:

• CNC machines and lathes
• Industrial automation systems
• Robotics and motion control
• Servo motor position feedback
• Elevator and conveyor systems

Conclusion:

An optical encoder measures displacement by detecting the interruption of light through a coded disk as the connected object moves. The resulting light signals are converted into electrical pulses, which are counted to determine position, direction, or speed. Optical encoders offer high precision and are widely used in advanced automation and control systems for accurate motion tracking.