Micro lens captures less light than normal lens dose, which makes low quality noise image, and current image sensor cannot preserve whole dynamic range in real world. HDR image with multi-exposure image overcomes the problems mentioned above. Choosing good exposure time is a seldom-discussed but important issue in HDR imaging technology. In this paper we propose a Histogram Based Exposure Time Selection (HBETS) method to automatically adjust proper exposure time of each lens for different scenes. Adopting the proposed weighting function restrains random distributed noise caused by micro-lens and produces a high quality HDR image. An integrated tone mapping methodology, which keeps all details in bright and dark parts when compressing the HDR image to LDR image for being displayed on monitors, is proposed. The result image has extended the dynamic range, that is, comprehensive information is provided. Eventually, we have implemented the proposed 4-CAM HDR system on Adlink MXC-6300 platform that can reach VGA video@10 fps.