3D shape reconstruction of optical element using polarization

We present a novel polarization based metrological method of 3D shape measurement for in-line control of optical surfaces and control of highly aspheric optical surfaces. This technique is fast, non contact, high resolution, alignment free and with unprecedented dynamic. It has the potential to reach tens of nanometers accuracy. In this paper we show that a polarization imaging camera combined with an un-polarized illumination and 3D reconstruction algorithm lead to the 3D reconstruction of optical element (regular lens and aspheric lens) and the measurement of their parameters. The optical element to be measured is placed in a diffusive integrating sphere and illuminated by unpolarized light. The reflection of the un-polarized light by the optical element gets partially polarized. A polarization camera captures the image of the optical element and measures the polarization state of each pixel in real time. The Degree Of Light Polarized and the Angle Of Polarization parameters are related to the geometry of the optical element. The 3D shape of the optical element is reconstructed using dedicated software. The architecture of the hardware, calibration results and sensitivity measurements is presented and experimental results and observations as well as possible further steps and new applications are discussed.