define posts 616 618 620 and 622 the posts 616 618 620 and 622 have supports 6161 6181 6201 and 6221 disposed in the openings 606 608 610 and 612 respectively the posts 616 618 620 and 622 also have the first supporting layers 6162 6182 6183 6202 6203 and 6222 the first supporting layers 6162 6182 6183 6202 6203 and 6222 are the same in length subsequently a second material layer 624 is formed on the sacrificial layer 604 and the first supporting layers 6162 6182 6183 6202 6203 and 6222 reference is made to fig7 c a photolithographic process patterns the second material layer 624 for keeping the second material layer 624 on the first supporting layers 6162 6182 6183 6202 6203 and 6222 so as to form the second supporting layers 6241 6242 6243 and 6244 further a third material layer 626 is formed on the sacrificial layer 604 and the second supporting layers 6241 6242 6243 and 6244 reference is made to fig7 d a photolithographic process patterns the third material layer 626 for keeping the third material layer 626 on the second supporting layers 6241 6242 6243 and 6244 so as to form the third supporting layers 6261 and 6262 the first supporting layers 6162 and 6182 form the arms 646 and 648 of the optical interference display unit 630 the first supporting layers 6183 and 6202 and the second supporting layers 6241 and.