1. An image depth perception device, comprising: an image adaptive pre-processing sub-module configured: to receive a standard speckle image having known depth and range information and an inputted speckle image sequence comprising inputted speckle images captured by an image sensor in a digital video format and having different characteristics of brightness, signal to noise ratio and size, wherein the standard speckle image is an image projected onto a plane perpendicular to the center axis of a speckle projector (z-axis) and having a known position distance, and to perform adaptive and uniform pre-processing on the standard speckle image and the inputted speckle image sequence, wherein the adaptive and uniform pre-processing comprises (a) converting format of the standard speckle image and the inputted speckle images from a Bayer format to a RGB format, (b) converting the RGB format to a YUV format by color space conversion, (c) processing adaptive de-noising on the YUV format, and (d) processing adaptive enhancing on the YUV format, so as to improve brightness uniformity of the inputted speckle images and the signal-to-noise ratio of both the standard speckle image and the inputted speckle images; a memory for storing the pre-processed standard speckle image; a block-matching motion estimation sub-module configured to compare each of the inputted speckle images in the pre-processed, inputted speckle image sequence with the pre-processed standard speckle image to calculate displacement of image blocks in the pre-processed inputted speckle image, wherein the block-matching motion estimation sub-module is configured to perform the comparison and the calculation by: extracting an image block block m×n with a size of m×n from the pre-processed inputted speckle image, and seeking, in the pre-processed standard speckle image, an optimum matching block of the image block block m×n within a search block search_block M×N having a size of M×N and centered on a corresponding position of the image block block m×n , according to a search strategy and a similarity measurement indicator, such that the displacement of the image block block m×n is obtained, wherein M, N, m and n are integers, wherein M>m and N>n; a depth calculating sub-module configured to calculate depth values of the image blocks in the pre-processed inputted speckle images, using a lookup table established according to different displacement values of the standard speckle image and corresponding depth values thereof, based on the displacement of the image blocks, to obtain a calculated depth image sequence, wherein one of the depth values of the image blocks is obtained from the lookup table when one of a horizontal displacement value and a vertical displacement value serves as an input value of the lookup table; and a depth image post-processing sub-module configured to reduce noises of the calculated depth image sequence by noise-reducing filtering.