Conventional camera systems provide an image from a limited viewing angle. In many applications such as security, surveillance, automotive, robotics, autonomous navigation or domotics it is desirable to “see” in all directions simultaneously. Omnidirectional cameras offer a horizontal field of view of 360°. Catadioptric sensors , which are consisting of a camera, a camera lens and rotationally symmetrical mirror above the lens, capture panoramic images instantaneously in one frame. However, conventional catadioptric system designs require mirror diameters and optical path lengths of several centimeters, since the mirror is not integrated into the lens system of the camera. For robotics and space applications, for example, such systems can be too heavy or bulky.
CSEMs novel design combines the mirror and the lens functionality: For packaging reasons and to ensure a high scale of miniaturization, it has been of advantage to integrate the mirror into the first lens of the optics, fig.1.
Fig.1: (a) Schematic of the miniaturized catadioptrical design, (b) omniview camera with mirror lens on the sensor.
In the European project muFly [1], the rigorous miniaturization resulted in a catadioptrical system that has been so small and lightweight that it could be used as a key navigation aid for an autonomous flying micro-robot, fig.2. The camera is used for active laser triangulation in multiple directions. The optical design has distorted the beam path to increase the distance resolution by a factor of 2. Further, the omniview camera has been equipped with a custom CMOS image sensor with a polar pixel field. Due to the pixel geometry a simple transfer has been used to reconstruct an undistorted panorama.
In the European project ProVisG [2], the omniview design has been adapted to a stereovision omniview camera for space applications. Here, the lens design has focused on a low distortion design to be smaller than 2 % along the complete image radius.
Fig.3: (a) Top-down mounted omniview cameras for stereovision, (b) test rover with mounted omniview stereovision camera.
[1] http://www.mufly.ethz.ch/index: 6th Framework Programme of the European Commission contract number FP6-IST-034120.
[2] http://www.ProVisG.eu: 7th Framework Programme of the European Commission contract number FP7-SPACE- 218814