【Technical Principles】Emitters and Receivers

Types：

    - VCSEL (Vertical-Cavity Surface-Emitting Laser): Low cost and easy to integrate, suitable for short-range scenarios (e.g., robotic vacuum cleaners)。  

    - EEL (Edge-Emitting Laser): High power and long detection range, ideal for automotive LiDAR。  

Wavelength Selection： 

905nm：Mature manufacturing processes and relatively low material costs, compatible with silicon-based photodetectors (e.g., APD, SPAD) that are low-cost and highly integrated.

Limited by eye-safe power, with an effective detection range of tens to 100 meters. Narrow pulse width enables high distance resolution, suitable for close-range, high-precision detection.

Applications: Consumer electronics (robot vacuums, smart home devices), low-speed autonomous driving (campus logistics vehicles), short-range industrial scanning.   

1550nm：Belongs to the near-infrared band, with low corneal penetration and a high safety threshold (no retinal damage even at high power). Lower atmospheric attenuation enables longer detection ranges. 

Requires more expensive InGaAs detectors (silicon-based detectors have low responsivity at 1550nm), increasing overall costs.

Applications: Automotive LiDAR, terrain mapping 

Collimating Lens：Converts divergent beams from lasers (e.g., EEL/VCSEL) into parallel light, reducing energy diffusion and improving beam quality over long distances (similar to focusing a flashlight).  

Diffractive Optical Element (DOE)：

Beam Splitting: Divides a single laser beam into a regular array of multiple beams (e.g., 128-channel array) for non-scanning area projection in solid-state LiDAR.

Beam Expanding: Adjusts the energy distribution of the beam cross-section or expands the beam coverage angle to match FOV (field of view) requirements.  

Transmit Optical Lens：Integrates components like collimating lenses and DOE to form a complete emission optical path for final beam shaping.

Receive Optical Lens：Collects reflected light from targets, converging weak scattered signals (as low as nanowatt-level power) onto the photosensitive surface of the detector to improve reception efficiency.

Filter：Only allows light of the target wavelength (e.g., 905nm±10nm or 1550nm±20nm) to pass through, blocking interference from ambient light such as sunlight and artificial lighting.  

Polarizer：Controls the polarization state of the emitted laser (e.g., linear polarization). The receiver only allows light of the same polarization state to pass through, suppressing non-target reflected light.。

Convert optical signals into electrical signals (photocurrent or voltage)

APD (Avalanche Photodiode): Utilizes the "avalanche effect" to amplify signals, suitable for 905nm wavelength (sensitive to silicon-based materials).  

SPAD (Single-Photon Avalanche Diode): Detects single photons with extremely high sensitivity.   

SiPM (Silicon Photomultiplier): Parallel connection of multiple SPADs, balancing sensitivity and resolution.  

TIA (Transimpedance Amplifier): Converts picoamp-level current signals into voltage signals. 

ADC (Analog-to-Digital Converter): Converts analog signals into digital signals for subsequent algorithmic processing.

1. Time-Space Synchronization:

   - Ensures strict synchronization between laser emission and signal reception via hardware triggering or PTP (Precision Time Protocol).  

2. Signal Matching:  

   - Matches the emitter’s pulse width with the receiver’s response time to avoid signal distortion.   

3. Environmental Adaptation:

   - In rainy or foggy weather, 1550nm laser offers stronger penetrability, paired with SPAD to enhance the signal-to-noise ratio.