Answer

1. What is Optical Encoder?

Device that converts rotary/linear position to digital pulses via light interruption. Resolution $=360°/2^n$ where $n$ tracks.

2. How It Works

LED → Code disk (opaque/transparent sectors) → Photodetector. Rotation interrupts beam → pulses count = angle, quadrature phase → direction.

• Incremental: Tracks A/B 90° shifted → pulses, index Z. Count pulses $\Delta N$ → angle $\theta = \Delta N \times$ resolution.
• Absolute: $n$ concentric tracks Gray code → unique $n$-bit word per position, no homing.

3. Types

Type	Principle	Output
Incremental (quadrature)	Two tracks A/B	Pulses + direction
Absolute	$n$-track Gray	Absolute $n$-bit code
Linear	Strip scale	Linear position
Rotary	Disk	Angle

4. Advantages

• High resolution ($0.1°$), accuracy.
• Non-contact (no wear vs potentiometer).
• Digital output directly to controller.
• Fast response.

5. Disadvantages

• Incremental loses position on power-off (needs homing).
• Dust/light contamination sensitive.
• Costlier than potentiometer for low resolution.

6. Applications

• Robot joint feedback, servo motors.
• CNC, 3D printer, conveyor positioning.
• Mobile odometry.

Final Answer

Optical encoder = light-interruption position sensor; counts pulses (incremental) or reads Gray code (absolute); high-resolution non-contact feedback for robot joints/CNC, needs homing for incremental.