1. A system for three dimensional motion estimation, the system comprising: a light source configured to emit light toward a scene, wherein the light is substantially temporally coherent around a center frequency); an image sensor; and a hardware processor that is programmed to: cause the light source to emit light toward the scene; cause the image sensor to capture a first defocused image of the scene at a first time, wherein the first defocused image includes a first speckle pattern generated by an object in the scene reflecting the light emitted by the light source; cause the image sensor to capture a second defocused image of the scene at a second time, wherein the second defocused image includes a second speckle pattern generated by the object in the scene reflecting the light emitted by the light source; generate a first scaled version of the first defocused image by expanding the first defocused image by a predetermined amount; generate a second scaled version of the first defocused image by contracting the first defocused image by the predetermined amount; compare the first defocused image to the second defocused image; compare the first scaled version of the first defocused image to the second defocused image; compare the second scaled version of the first defocused image to the second defocused image; determine axial motion of the object between the first time and the second time based on the comparisons; and determine lateral motion of the object between the first time and second time based on the comparisons.