Prototype of Directional Observation Camera Considering Coaxial Constraint of Short Baselines

  Objectives  Considering the insufficient resolution of interested targets in a large field of view camera, a coaxial constraint model of short baselines is proposed, and a master-slave camera prototype is designed. A large field of view camera is used to monitor the entire field of view, and the directional high-definition observation is carried out by an active camera.

  Methods  The yaw angle and pitch angle of the active camera are solved by using the image point of the target center point in the large field of view camera image. Firstly, the mapping relationship between the large field of view camera and the active camera is constructed, and the external parameter matrix of the camera is simplified by using the coaxial constraint model of short baselines. The initial control parameters of the active camera are solved through trigonom‍et‍ric functions. Secondly, the pitch-angle compensation values of close-range scenes are calculated according to the installation position of the prototype.

  Results  Experimental results show that(1) The compensation for the control parameters of the active camera in close-range scenes can improve the control accuracy to a certain extent, and the compensation effect in the central area is better. (2) In close-range scenes where the distance between the observation target and the large field of view camera is 3‍-‍10 m, the prototype can actively observe the details of the target. The actual and ideal position error of the target in the active camera image is less than 30 pixels, and the horizontal direction error can be ignored. (3) In the outdoor long-distance scenes, the prototype can actively and accurately observe the target details within the effective distance. As the depth of the observed target increases, the error decreases gradually. In the range of 40‍-‍50 m, the system error caused by steering engine control accuracy and baseline length becomes the main error, and the overall error is maintained at about 6 pixels. (4) The time for prototype to calculate the control parameters of the active camera of a single target point is within 0.2 ms, which can meet the real-time requirement. (5) The algorithm solves the control parameters of the active camera without scene dependence. It can control the rotation of the active cam‍era with high precision and strong adaptability in different scenes. (6) When the large field of view cam‍era is used to observe the far target at low resolution, the target cannot be located accurately in the im‍age. Improving the resolution of the large field camera is helpful to improve the accuracy of active camera control parameters and effective observation distance.

  Conclusions  The directional high-definition observation of interested regions in the large field of view can be realized through the prototype. The camera part is modularized, and only one offline calibration is needed to adapt to different scenes and target depth. The accurate and fast target observation is realized. Compared with oth‍er methods, it has higher accuracy and timeliness with better applicability. Additionally, the accuracy and the observation distance can be increased by properly improving the resolution of the large field of view cam‍era.