Popular Types of Consumer-Level Cameras ======================================= Monocular Vision cameras ------------------------ A `monocular vision `_ camera is a camera used for a single eye. The optical route of such cameras may have a series of lenses, but it has only one vision. Most of the cameras on the market are monocular vision cameras, including various types of `webcams `_, `single-lens reflex (SLR) cameras `_, and `industrial cameras `_, etc. Monocular cameras have limited `depth perception `_. The following picture shows a typical monocular vision SLR camera ( cited from `Wikipedia SLR `_ ). .. figure:: ../resource/chapter2/images/3DSensors/Exa_camera.jpg :align: center :target: https://en.wikipedia.org/wiki/Single-lens_reflex_camera :alt: Original Ihagee Exakta Exa Single lens reflex Original Ihagee Exakta Exa Single lens reflex Binocular Vision cameras ------------------------ A `binocular vision `_ camera (stereo camera) is a camera used for two eyes that a lot of animals have. It helps to build up the `depth perception `_ by calculating `binocular disparity `_. All state-of-the-art cellphones now come with dual back cameras, such as Xiaomi Pocophone F1 (cited from `Wikipedia Stereo_camera `_). .. figure:: ../resource/chapter2/images/3DSensors/800px-Xiaomi_Pocophone_F1.jpg :width: 240 :align: center :target: https://en.wikipedia.org/wiki/Stereo_camera :alt: Dual Back Cameras on Xiaomi Pocophone F1 Dual Back Cameras on Xiaomi Pocophone F1 RGB-D Cameras ------------- As one of the most popular RGB-D sensors, `Kinect `_ was firstly launched by Microsoft in November 2010. Just as its name implies, RGB-D sensors are particular sensors which - **not only** sense the `RGB colors `_ - **but also** have `depth perception `_ RGB-D sensors have active light source (therefore, a stereo camera is not regarded as a RGB-D camera), and are normally categoried in three types according to three different technologies: - Structured light sensors based on dense `gray code `_, etc. -- normally for industrial applications, such as `3D scanners `_ - Structured light sensors based on sparse `speckle pattern `_ -- normally for consumer-level applications, such as `Intel Realsense `_, etc. - `Time of flight (TOF) sensors `_ No matter which technology in the above is utilized, a RGB-D sensor share similar components: - An RGB sensor - A depth sensor composed of a pair of IR emitter and receiver - Both RGB sensor and depth sensor need to be well-calibrated for the alignment of both RGB image and depth image Some popular structured light RGB-D sensors based on sparse `speckle patterns `_ are enumerated as follows (**all** pictured are cited from their respective official websites): .. list-table:: * - .. image:: ../resource/chapter2/images/3DSensors/structureio.jpg :align: center :target: https://structure.io/ :alt: structure sensor - .. image:: ../resource/chapter2/images/3DSensors/kinect1.jpg :align: center :target: https://www.researchgate.net/figure/Comparison-between-Kinect-v1-and-Kinect-v2_tbl1_299132365 :alt: Kinect 1 * - .. image:: ../resource/chapter2/images/3DSensors/xtionprolive.jpg :align: center :target: https://www.asus.com/ca-en/3D-Sensor/Xtion_PRO_LIVE/ :alt: Xtion Pro Live - .. image:: ../resource/chapter2/images/3DSensors/depth_camera_t265_dimensions-1.jpg :align: center :target: https://www.intelrealsense.com/ :alt: Intel Realsense What's more, `Kinect 2 `_ changes its core technology from `structured light `_ to `TOF `_, and the parameters and its price/performance ratio stands out among all `TOF `_ sensors. `Kinect 2 `_ sensor looks as (cited from `SlideShare: Programming with kinect v2 `_): .. figure:: ../resource/chapter2/images/3DSensors/Kinect-V2-RGB-D-camera_W640.jpg :width: 100% :align: center :target: https://developer.microsoft.com/en-us/windows/kinect/ :alt: Kinect 2 Kinect 2 In the following sections, we're going to discuss how to calibrate: - monocular vision cameras with narrow-angle lens - monocular vision cameras with fisheye lens - binocular vision Cameras - RGB-D cameras step by step.