Electro - total internal reflection ellipsometry has been reported as a phase sensitive ellipsometry technique to observe the redox reactions on the surface of the electrode. In this work, with the imaging ellipsometry, we have used Electro-total internal reflection imaging ellipsometry (Electro-TIRIE) to measure the dissolved oxygen concentration on the surface tethered weak polyelectrolyte brush, carboxylated poly(oligo(ethylene glycol) methacrylate-random-2-hydroxyethylmethacrylate), modified electrode. The cyclic voltammetry has shown despite the covering of the weak polyelectrolyte brush, the electrode could still reduce the dissolved oxygen and Electro-TIRIE technique could unveil the different swelling behavior of the brushes during the reduction. The difference may be attributed to the electro-active probe permeability of the brushes. With the imaging ellipsometry, we proposed a parallel dissolved oxygen measurement. Compared with our previous results, the optical signal noise ratio has been enhanced 10 times and the measurement time has reduced from 30 minutes to 10 minutes. (C) 2016 The Electrochemical Society. All rights reserved.