Importance

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Abstract

Apparatus, such as a compass, for determining the positional relationship between two structures having limited motion therebetween is disclosed. The apparatus includes a photoelectric array spaced from an illuminating or light source. The array and light source are mounted to a first structure or member, such as for example, a compass housing. A second member suitable for limited motion such as a rotating disc having a mask mounted thereon is located between the array and the light source so as to substantially block light transmitted from the source being received by the array. The mask, however, includes light transmission areas of selected shapes, such as for example, a spiral, or three lines. These light transmissive areas result in the illumination of unique, random patterns of individual elements of the array for each specific relative position between the first member and the second member. Also included are means such as a read only memory (ROM) which has stored therein information correlating the individual unique patterns with each specific relative position. In operation the specific pattern of illumination on the array is compared to the stored information and the specific relative position is then provided to a display.

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First Claim