In order to realize miniaturization of absolute optical encoder with the character of greater accuracy and more reliability

a new coding mode and structure of reading head are investigated. The eight-matrix coding used in absolute optical encoder

is different from custom four-matrix coding. Eight-matrix coding which reduce dimension of encoder greatly is a bran-new coding technique. It can realize the function of 10-bit binary coding through only two grating tracks. With the optimizing coding

we reduce the position errors which are brought by signals getting from two grating tracks. The grating tracks are more the position error is bigger. Single reading-head is also good for reducing dimension of encoder

so the number of LED is smaller. Moiré fringe obtained by phase compensation is another new technique in this paper. Experimental results indicate that eight-matrix encoder has smaller size (Φ25mm×16mm)

lighter weight while higher resolution (resolution of 16-bit)and higher accuracy(30″). Also it can normally work in very hard condition for long time with more reliability. It can be widely applied to the field of modern military and aerospace.