Dual mode optical navigation device and mode switching method thereof

A mode switching method of a dual mode optical navigation device, the dual mode optical navigation device being operated on a working surface and having a first bottom surface and a second bottom surface, the first bottom surface having a first flat surface which has an included angle with a second flat surface of the second bottom surface, the mode switching method comprising:

• capturing an image frame of a working surface by an image sensor;
• determining, using a process unit, whether the first bottom surface or the second bottom surface contacts with the working surface according to a ratio of a bright area and a dark area of the image frame;
• switching to a first mode when identifying that the ratio of the bright area and the dark area is larger than a ratio threshold, and capturing, using the image sensor, image frames of the working surface through the first bottom surface;
• and
• switching to a second mode when identifying that the ratio of the bright area and the dark area is within a ratio threshold range, and capturing, using the same image sensor, image frames of the working surface through the first bottom surface, wherein
• the ratio threshold range is smaller than the ratio threshold,
• in the first mode, the first flat surface of the first bottom surface is fully contacted with the working surface, and
• in the second mode, the second flat surface of the second bottom surface is fully contacted with the working surface.