Speed sensor, device for measuring speed and method thereof

A method for measuring a speed, applied to a speed sensor, wherein the speed sensor comprises an imaging device and a liquid crystal lens, the liquid crystal lens is on a side of the imaging device, and the method comprises:

• applying different voltages to the liquid crystal lens, and obtaining, via the imaging device, images of a reference object formed through the liquid crystal lens under the different voltages;
• controlling, based on information of the images, the liquid crystal lens to realize focus for a plurality of times for the reference object;
• and
• obtaining a voltage that is correspondingly applied to the liquid crystal lens when each of the plurality of times of focus is realized, and calculating a speed based on the voltages.

A computer readable storage medium, having a program stored thereon, wherein, when the program is executed by a processor, the following steps are implemented:

• applying different voltages to a liquid crystal lens, and obtaining, via an imaging device, images of a reference object formed through the liquid crystal lens under the different voltages;
• controlling, based on information of the images, the liquid crystal lens to realize focus for a plurality of times for the reference object;
• and
• obtaining a voltage that is correspondingly applied to the liquid crystal lens when each of the plurality of times of focus is realized, and calculating a speed based on the voltages.