Abstract: A preparation method for a diffractive optical waveguide, and an imprinting master. The method comprises: providing a waveguide substrate; forming a graphical imprinting adhesive layer on one surface of the waveguide substrate; and performing first-stage etching on the waveguide substrate by using the graphical imprinting adhesive layer as a first mask, so as to form a coupling-in structure in a first region, forming a remaining graphical imprinting adhesive layer in a second region into a second mask, and etching the waveguide substrate by using the second mask as a mask, so as to form a coupling-out structure, wherein the depth of the coupling-out structure is greater than the depth of the coupling-in structure. In this way, the requirement of there being no obvious deviation in the relative positions between the coupling-in structure and the coupling-out structure is met while solving the problem of how to ensure the formation.

Abstract: Techniques for estimating speed for an object in a video (either stream or file) are described. In particular, once an object has been recognized, additional data (such as size) for that recognized object is used in a determination of a 3D position of that object in a plurality of frames. An estimated speed may be found using a difference between 3D positions of the object in different frames over the time between the frames.