Perancangan sistem generator medan magnet berotasi dan pengamatan gerak brown untuk pengukuran konstanta difusi microbead 1um, 3um, 5um berbasis surf (speeded-up robust feature) dan rlof (robust local optical flow) = System design rotating magnetic field generator and brownian motion observation for measuring diffusion constant on 1μm, 3μm, 5μm microbeads using surf (speeded-up robust feature) and rlof (robust local optical flow)