## 2 Related Work
### Camera Arrays  
[PERSON] et al. presented a study on camera arrays and their applications [21]. They described using arrays both for depth recovery and for other applications such panoramic imaging. [PERSON] presented a survey on preparing 3D videos on the basis of multiple cameras [22]. The usage of camera arrays for providing 3D vision in robotic applications was discussed by [PERSON] and [PERSON] [23]. Camera arrays are widely used in astronomy for space observations. [PERSON] et al. wrote a survey on this subject [24].  
[PERSON] et al. performed a study at Stanford University on constructing arrays from a large number of cameras. They built an array of 100 cameras in the \(10\times 10\) configuration and they applied it for making high quality images and videos [20]. Another significant camera array called PiCam was constructed by [PERSON] et al [25]. It was an ultra-thin array consisting of 16 cameras distributed uniformly over a square grid. The size of the array was similar to a size of a coin. The paper describing PiCam contains also an in-depth review on camera arrays usage. [PERSON] and [PERSON] are the authors of a very influential research paper concerning arrays in which cameras are placed along a straight line [19]. [PERSON] et al. proposed the usage of a sliding camera resembling a linear camera array [26].  
A construction with a moving camera was also proposed by [PERSON], [PERSON] and [PERSON] [27]. They constructed a synthetic aperture integral imaging (SAII) by using a camera moving in two dimensions, making it possible to acquire images as if a camera array was used. Such a technique cannot be used for even slowly moving objects because the scene would be changing while subsequent images are taken. Authors applied their method for detecting and removing occlusions of objects in images.  
Arrays containing only a few cameras are also constructed and used. Such arrays can be used for 3D imaging instead of stereo cameras without a substantial increase in the size of data which need to be processed due to the increase in the number of images. [PERSON] and [PERSON] proposed the usage of a five-camera array [1]. The array contained a central camera and side cameras. This kind of an array is also considered in this paper, and it is further described in Section 3. [PERSON] described a similar kind of an array which was constructed from four cameras with three side cameras placed on vertices of an isosceles triangle and a central camera located in the middle [28].  
[PERSON] and [PERSON] wrote in 1991 a highly influential paper regarding trinocular vision [29]. They used the array for identifying contours visible in images and building a three-dimensional description of the environment. The performance of trinocular vision systems were also researched by [PERSON], [PERSON] and [PERSON] [30,31]. [PERSON] et al. also used a trinocular stereo vision for navigating a robot [32]. [PERSON] and [PERSON] applied trinocular vision to detect obstacles on highways [33].  
[PERSON] and [PERSON] performed research on using an array with unknown poses of cameras placed on a flexible surface [34]. The major advantage of this solution is the ease of construction. However, in case of such an array, there is also a necessity to identify locations of cameras. This process is performed on the basis of images for which a disparity map is obtained. When an array with predefined poses of cameras is used, then the step of resolving cameras locations is completed before using the array in the target environment. It speeds up the process of acquiring 3D data. Moreover, predefining locations makes it possible to place cameras in the most advantageous positions providing the highest quality of data.