A circuit and method are provided for reducing power consumption in an optical navigation system for use in an input device to sense displacement of the device relative to a surface. Generally, the system includes: (i) an optical sensor having at least first and second arrays of photosensitive elements; (ii) imaging optics to map an illuminated portion of the surface to the optical sensor; (iii) a signal processor including a first and second sensor circuits coupled to the respective first and second arrays to generate from each array a set of signals in response to motion of light received thereon; and (iv) a control circuit capable of independently switching power to the sensor circuits. In one embodiment, the control circuit powers down one sensor circuit when the strength of the set of signals from the other is greater than a predetermined minimum thereby maintaining device performance. Other embodiments are also disclosed.