Light tracing method and apparatus thereof

A light tracing method, comprising:

• a sensor chip, disposed in an optical indexer, receiving a reflected light by a surface, wherein the sensor chip includes a plurality of sensor pixels arranged in an array;
• wherein the reflected light is made by a coherent light with good spatial coherence generated by a light source emitted to the surface;
• calculating an energy of light received by every sensor pixel within a period of a sampling time;
• calculating a statistical average by averaging the energies received by all or part of the sensor pixels;
• calculating a difference between the energy received by the every sensor pixel and the statistical average, further an energy state of the sensor pixel is defined according to the energy difference and there are two types of energy states represented by binary characteristic values, in which change of the energy states for the sensor pixels in the array within the period of the sampling time shows a transition of a movement of the optical indexer;
• obtaining the energy states of all or part of the sensor pixels within the period of the sampling time;
• and
• determining a moving vector for the optical indexer according to the change of the energy states of at least two adjacent sensor pixels of the sensor chip within the period of the sampling time.