1. A three-dimensional depth perception method with an adjustable working range, characterized in that: the method being applied to a three-dimensional depth perception apparatus, the apparatus comprising: a laser pattern projector driving circuit, a laser pattern projector, a receiving camera, a depth perception module, a control module, and a memory; the method comprising steps of: presetting or re-setting a working range mode of the apparatus by disposing the control module on the apparatus, parameters of the working range mode being stored by disposing the register in the apparatus; and transmitting, by the control module, control commands to a laser pattern projector driving circuit, the receiving camera, and the depth perception module, respectively, based on the parameters of the preset or re-set working range mode; wherein a control command transmitted to the laser pattern projector driving circuit is for adjusting a driving current and an output power of the laser pattern projector driving circuit, projecting an encoded pattern to a target object or space through a laser pattern projector, the target object or space being within a working range corresponding to the parameters of the working range mode; a control command transmitted to the receiving camera being for adjusting a focal length and a baseline distance of the receiving camera, collecting encoded images generated by the laser pattern projector at a certain frame frequency so as to generate an input encoded image sequence that is fed into the depth perception module; the receiving camera is for receiving encoded patterns projected by the laser pattern projector within a specific wavelength range, comprising an image sensing device including an optical focusing imaging lens unit and a filtering unit; the baseline distance referring to a horizontal distance between the laser pattern projector and the receiving camera, central optical axes of the laser pattern projector and the receiving camera being parallel; a control command transmitted to the depth perception module being for adjusting control parameters for pre-processing images, such that the input encoded image sequence being subjected to consistent processing after being pre-processed; and for selecting to output one group of reference encoded images in coincidence with the working range mode from among multiple groups of reference encoded images that have been solidified in the memory, the pre-processed input encoded image sequence being subjected to block-matching-based disparity computation and depth computation, thereby outputting a depth image sequence; the multiple groups of reference encoded images refer to encoded images, in conjunction with different work range modes, each of which is projected onto a vertical plane vertical to a projector optical axis at a different distance, pre-collected, and subjected to a same image pre-processing as the input encoded images, the encoded images being pre-solidified in the memory as standard reference encoded images; the parameter M i for each working range mode corresponding to a group of reference encoded images with a distance d i ; wherein one group of reference encoded images may consist of one or more images, where i denotes the i th group; The block-matching-based disparity computation resolving a displacement amount between an image block and an optimal matching block in the inputted encoded image by performing block matching similarity comparison between respective input encoded images in the pre-processed input encoded image sequence and the reference encoded images; the depth computation: assume a focal length f of the receiving camera, a physical pixel pitch μ of the receiving camera image sensor, a baseline distance S between the laser pattern projector and the receiving camera, a displacement amount Δm resulting from the block-matching-based disparity computation, the Δm being Δx or Δy, a known distance d i corresponding to the reference encoded image, the corresponding depth value d′ may be derived through an equation below for depth computation: d ′ = d i - Δ ⁢ ⁢ m ⁢ ⁢ μ ⁢ ⁢ d i ⁢ 2 f ⁢ ⁢ S + Δ ⁢ ⁢ m ⁢ ⁢ μ ⁢ ⁢ d i = f ⁢ ⁢ S ⁢ ⁢ d i f ⁢ ⁢ S + Δ ⁢ ⁢ m ⁢ ⁢ μ ⁢ ⁢ d i .