This paper proposes a specular reflection-based normal estimation method that employs polarization imaging to separate surface reflections into specular and diffuse components, achieving high-precision normal imaging. The imaging transition model is explored, an optimal strategy to determine the normal angle is discussed, and based on this, an active normal field imaging system employing a polarized LED light source is built and calibrated. Experimental results show that our method can measure surface normals with an MSE<0.7 (°)² in a range from -25° to 25°. This imaging system is applied to investigate 14 different types of art paper. The results reveal that this method can effectively capture the normal variation of surfaces with low sensitivity to paper color. It also offers insights for the identification and restoration of calligraphy, paintings, and cultural relics.