Optical detecting device capable of determining relative position of a reference object or a light source

An optical detecting device capable of determining a relative position of a reference object or a light source according to an optical reflecting signal generated from the reference object, the reference object reflecting an optical detecting signal emitted by the light source to generate the optical reflecting signal, the optical detecting device comprising:

• a light penetrating component, a focal length of the light penetrating component being greater than a predetermined distance;
• at least one light tight structure located on a region correlative to the light penetrating component;
• and
• an optical detecting component disposed by the light penetrating component and spaced from the light penetrating component in the predetermined distance, the optical reflecting signal being projected onto a detective surface of the optical detecting component through the light penetrating component at a projecting direction, a part of the optical reflecting signal blocked by the light tight structure being applied to form a characteristic image on the detective surface, and the optical detecting component determining the relative position of the reference object or the light source according to a parameter of the characteristic image, wherein the projecting direction is not parallel to a normal vector of the detective surface.