Omni directional cameras¶
Omnidirectional cameras refer to cameras that have a larger field of view than the normal cameras (more than 180 ° and ideally 360 °). This includes cameras with horizontal 360 ° field of view(FOV) and cameras with FOV spanning a 360 ° horizontal and more than 90 (ideally 180) vertical field of view(FOV).[1] Ever imagined how we can get a 360 ° field of view?
An omnidirectional camera (from Omni, meaning all) is a camera with a 360 ° field of view in the horizontal plane, or with a visual field that covers a hemisphere or (approximately) the entire sphere. There are designs proposed to achieve a 360 ° degree field of view.
1. Dioptric cameras with a single lens¶
Cameras which use an only special lens to refract light such that the field of view is more than 90 ° vertically and 360 ° horizontally. One common example of such type of camera is a fisheye camera.
Figure 1 - Image of a fisheye camera. (source - wikipedia) [3]¶
2. Catadioptric cameras¶
Cameras that use a combination of the lens (to refract light) and mirrors (to reflect light) with a normal camera to generate 360 ° horizontal and more than 90 ° vertical field of view.[1] Figure 2 is an example of a catadioptric camera.
Figure2 - Example of an omni directional camera using mirrors. (souce-wikipedia ) [2]. 1. Camera 2. Lower mirror 3. Aperture 4. Glass housing 5. Cover and upper mirro¶
3. Camera with two lens¶
Cameras that consist of two fisheye cameras placed facing away from each other and each one has a FOV that can span more than a hemisphere. Images from both cameras are stitched to get the full 360 ° image. This configuration is commonly used in the 360 ° cameras available in the market.
Figure 3 - Image of a 360 ° camera with two lenses. (source - wikipedia) [4]¶
4. Polydioptric cameras¶
Cameras which consist of more than two cameras with overlapping field of view.[1] One example of such type of camera is the throwing camera “panono”[5]. Image from all the cameras is captured at the same time and then stitched to get the full 360 ° image.
Figure 4 - Image of panono polydioptric camera. (source - wikipedia) [6]¶
Read this paper. [1] on Omnidirectional cameras to know more about different ommni directional cameras
References¶
[1] Scaramuzza, Davide. (2014).Omnidirectional Camera. Computer Vision: A Reference Guide, Editors: Katsushi Ikeuchi, ISBN: 978-0-387-30771-8 (Print) 978-0-387-31439-6 (Online), Springer, April, 2014
[2] https://en.wikipedia.org/wiki/Omnidirectional_camera
[3] Figure 1 - https://commons.wikimedia.org/wiki/File:Nikon_1_V1_%2B_Fisheye_FC-E9_01.jpg
[4] Figure 3 - https://upload.wikimedia.org/wikipedia/commons/thumb/d/d5/Ricoh_Theta_S_camera.jpg/220px-Ricoh_Theta_S_camera.jpg
[5] Omnidirectional cameras - https://en.wikipedia.org/wiki/Omnidirectional_camera