enabling the scanner controller 6 to produce the reference position signal p based on the voltage signal d and the reference level ref 0049 fig2 and 3 show programs or sequences of logical steps performed in the optical scanner 2 the program of fig2 is an initialization program executed one time upon turning on of the optical scanner 2 the program of fig3 is an updating program executed in response to each input of the updating signal k from the microcomputer 8 after entering the program of fig2 the routine proceeds to step 110 wherein the coil driver 14 starts to energize the driver coils 10 and an initializing operation is carried out to output the reset signals rsa and rsb to reset the reference level holding circuit 28 and the digital filter 24 the routine proceeds to step 120 wherein an initial value is set to the reference level ref in the reference level holding circuit 28 through a data loading circuit not shown the routine proceeds to step 130 wherein the selection signal sla of the inactive level is provided for producing the reference position signal p the routine proceeds to step 140 wherein the operating clocks ck are produced to initiate the operations of the a d converter 20 the reference level holding circuit 28 and the digital filter 24 and terminates subsequently the scanner controller 6 outputs the reference position signal p each time the output hav of the digital filter 24 is reversed from positive to negative that is the scan angle u03b8 of the mirror support 4 becomes 0 u00b0 the microcomputer 8 outputs the updating signal k to the scanner controller 6 each time it detects the reference position signal p two times the control circuit 34 of the.