< > [Scanning Processes](..) > Laser Scanning
## Laser Scanning
<div style="margin-left:2.5%">
Multiple laser scanning techniques exist.
They differ in the measurement they make to infer geometry.
They include measuring
* The deflection of a laser beam (from a receiver at a fixed angle)
* The round-trip time (or *time-of-flight*) of a laser beam
### Deflection-based / Line Laser Scaning
**Keywords**: laser line scanning, laser triangulation, laser deflection
* [The Digital Michelangelo Project: 3D Scanning of Large Statues](http://graphics.stanford.edu/projects/mich/)
* [Paper](https://dl.acm.org/citation.cfm?id=344849)
* [Cyberware's system](http://cyberware.com/products/scanners/px.html)
* Issues with sub-surface scattering in marble
* Color registration on geometry
* [Makerscanner](http://makerscanner.com/docs/1-makerscanner.html) (opensource 3d scanning)
* [Micro-epsilon](https://www.micro-epsilon.com/2D_3D/laser-scanner/)
* [3D reconstruction for underwater laser line scanning](https://ieeexplore.ieee.org/document/6607973/) as a brief example
* [Low-Cost 3D Scanner](http://www.instructables.com/id/3D-Laser-Scanning-DIY/) on Instructables
* [FabScan](http://hci.rwth-aachen.de/FabScan) from RWTH
* [Keyence](https://www.keyence.com/products/measure/laser-2d/lj-v/index.jsp)
* [Eora3D](https://eora3d.com/)
* [Matter and Form](https://matterandform.net/)
* [Ciclop 3D Scanner](https://www.thingiverse.com/thing:740357) on Thingiverse
* [NextEngine](https://www.nextengine.com)
### LIght Detection And Ranging (LIDAR)
Also known as **time-of-flight** since it consists of measuring the round-trip time of a laser pulse to measure distance.
Different receiver types exist:
* Point-by-point scanning LIDAR systems that use mechanical systems to scan full environments
* Time-of-flight cameras that acquire a whole depth image at once
* [101 LIDAR](https://coast.noaa.gov/data/digitalcoast/pdf/lidar-101.pdf) from National Oceanic and Atmospheric Administration
* Extensively used from airplanes for large-scale scanning
* More and more common on cars (because autonomous cars)
* For medium to large-range scanning (light goes fast)
#### LIDAR Systems
* [FAROS](https://www.spar3d.com/news/lidar/faros-focus-m-70-lidar-cost-25k/)
* [Leica Geosystems](https://leica-geosystems.com/en-us/products/laser-scanners/scanners/blk360)
* [LeddarTech](https://leddartech.com/modules/leddarvu/)
* [Velodyne](velodynelidar.com) including [HDL](http://velodynelidar.com/hdl-32e.html) and [Puck](http://www.velodynelidar.com/vlp-16-lite.html)
* [Paracosm](https://paracosm.io/), acquired by Occipital (structured light)
#### Vision datasets using LIDAR (on cars):
* [Vision meets robotics: The KITTI dataset](http://journals.sagepub.com/doi/pdf/10.1177/0278364913491297) using a [Velodyne](http://velodynelidar.com/) HDL-64E rotating 3D laser scanner
* [Cityscape Dataset](https://www.cityscapes-dataset.com/)
* [Semantic Instance Annotation of Street Scenes by 3D to 2D Label Transfer](https://arxiv.org/abs/1511.03240): Velodyne + [SICK LMS200](https://www.sick.com/us/en/detection-and-ranging-solutions/2d-lidar-sensors/lms2xx/lms200-30106/p/p109843)
#### LIDAR on UAVs:
* [senseFly](https://www.sensefly.com/) from Parrot
* [Phoenix LiDAR Systems](https://www.phoenixlidar.com/)
#### Mini LIDAR:
* [TF Mini LiDAR](https://www.seeedstudio.com/Seeedstudio-Grove-TF-Mini-LiDAR-p-2996.html) at Seeed studio
* [TFMini](https://www.sparkfun.com/products/14588) at Sparkfun
* [Sweep](https://www.kickstarter.com/projects/scanse/sweep-scanning-lidar) on Kickstarter
#### LADAR (LAser Detection And Ranging):
* [Single-Photon-Sensitive Imagers](https://www.ll.mit.edu/mission/electronics/ait/single-photon-sensitive-imagers/single-photon-sensitive-imagers.html) from Lincoln Labs
#### Time-of-flight cameras:
* [Kinect](https://www.xbox.com/en-US/xbox-one/accessories/kinect) (for Xbox One)
* See [comparison](https://arxiv.org/abs/1505.05459) paper with previous [structured-light](../structured) kinect
* Continuous Wave Intensity Modulation: get timing from phase shift in periodic signal
* [DepthSense](https://www.sony-depthsensing.com/) now at Sony
* Pulsed vs Continuous Wave
* Pulsed: `d=c t/2 q2/(q1+q2)`, q1 when light is emitted, q2 when off
* Continuous: `d=c t/(2pi) arctan( (q3-q4) / (q1-q2) )`, measuring phase offset of periodic signal
]]>