Detector system for optical mouse

Abstract

An improved detector system for an optical mouse including an optical mouse housing for supporting a four-by-four array of detector elements, a light source, and a light directing mirror. The light source may be visual, ultraviolet or infrared. The optical detector elements of the array are labeled A through P starting with row 1, column 1 and going left to right. Each element is about one-quarter of a grid period square and capable of producing an electrical output signal corresponding to the amount of light it receives. The elements are grouped into pairs of elements which are located so as to image areas on the grid pattern a distance of an odd multiple of grid periods apart in a direction which is orthogonal to the direction of motion which they detect. Pairs A+C, E+G, I+K, and M+O detect vertical motion and pairs A+I, B+J, C+K, and D+L detect horizontal motion. Paired output signals measuring motion along the same axis are 90 degrees out of phase if adjacent to one another, and 180 degrees out-of-phase if an odd multiple of grid periods apart. Detector movement and position is determined by comparting output signals measuring motion in the same direction which are 180 degrees out-of-phase with one another. At points where the compared output signals cross, a grid line or space is detected. Each crossing point indicates a state change. By combining and comparing output signals from each of the eight pairs of elements, four square wave quadrature signals indicating motion in either the x or y-axis direction can be produced. The quadrature signal for a particular direction of movement that leads in time the other quadrature signal representing motion along the axis is indicative of the direction of movement of the optical mouse.