LIDAR
Uses laser light and a receiver to measure distance. In a pulsed time-of-flight design, the travel time to a target and back determines range. Wavelength, detector technology, range and accuracy depend on the selected system.
A pulsed lidar emits laser light and detects a return. For a round-trip time t, distance is c × t / 2, using the appropriate propagation speed c. The factor of two accounts for travel out and back. Surface reflectivity, geometry and the receiver's sensitivity influence whether a usable return is detected. Detector technology and pulse duration are design choices, not fixed properties of all lidar.
In plain terms
Like a stopwatch on a thrown stone — the stone (a photon) leaves the hand, hits the wall, returns, and the chip multiplies the round-trip time by the speed of light to find the wall.
Why designers use it
- Measuring distances from returned light to build a spatial view of a scene.
- Combining range samples with scanning or multiple viewing directions for mapping.
- Choosing a documented sensor where its optical safety, target response and environmental performance meet the application; not every LiDAR is inherently eye-safe or equally effective on every surface.
Best for
- Autonomy
- Drones
- Robot vacuums
Key specifications
- Operating limits: Check the exact manufacturer's datasheet (A family name does not establish voltage, current, temperature or timing limits.)
- Pin assignment: Match the complete part and package code (A similar name or function does not guarantee the same wiring.)
- Mechanical fit: Use the exact package drawing (Check pad layout, dimensions and viewing direction before building.)
When not to use it
- When target geometry, optical transmission, weather or contamination prevent a reliable return in the selected system.
- As a safety-rated protective device unless the complete product and installation meet the applicable safety requirements.
Common mistakes
- Forgetting the divide-by-two when converting round-trip time to distance.
- Treating the quoted maximum range as guaranteed for every surface and ambient-light condition.
- Assuming a general-purpose ranging module is an eye-safe or safety-certified system without checking its documentation.
Where you will find it
- A Roomba j7+ robot vacuum's Hokuyo URG-04LX-UG01 LiDAR scans a 240° field at 4 cm to 5.6 m range: the SPAD's 100 ms full-scan rate gives the SLAM mapper enough updates to navigate around a sleeping cat without grazing it.
- A Tesla Cybertruck rear-bumper park-assist module includes a TI OPT3101 short-range LiDAR-on-chip ToF sensor that reads bumper-to-curb distance during low-speed maneuvering: the chip's 2 cm resolution at 4 m range works through dirty cameras when the vision pipeline can't.
- A DJI Matrice 350 RTK drone's Livox Mid-360 LiDAR module produces a 360° × 59° point cloud at 200,000 points/sec: the sensor's 70 m range on 905 nm lets the drone autonomously avoid power-line trees during a beyond-visual-line-of-sight pipeline inspection.
A short history
NASA's account of the EAARL mapping instrument describes laser ranging over hurricane-affected beaches, vegetation and shallow water. Different surfaces return different amounts of light, so the laser, receiver and processing are designed for particular measurement conditions. This is a concrete application example, not a claim about the first-ever lidar or the capabilities of every small sensor.