1. A video monitor device, comprising: a storage system; at least one processor; and an image processing unit stored in the storage system and executable by the at least one processor, the power management unit comprising: an image obtaining module operable to control a video camera to capture a series of left images and right images of a target area at predetermined intervals; an image analysis module operable to select a left image and a corresponding right image captured at the same time from the series of left images and right images, and to compare the left image with the right image to analyze identical image data and different image data of the left image and the right image; an image compression module operable to combine the identical image data and the different image data of each of the left images and right images to form a combined image, to compress all of the combined images to generate compressed images correspondingly, and to store the compressed images into the storage system; and an image output module operable to determine the time of an event that has occurred in the target area, to obtain a compressed image corresponding to the time from the storage system, to decompress the compressed image to generate a 3D image of the target area, and to display the 3D image on a display device to for monitoring of the target area.