Determination of e/h ratio by optical measurements

A follow-up initiative of development in the field of optical radiometry undertaken in the frame of European Metrology Research Programme (EMRP) is described. Amongst the other tasks, the new project NEWSTAR aims at accurate determination of ratio e/h of fundamental constants - elementary charge e and Planck's constant h. This is envisaged to achieve by using improved version of Predictable Quantum Efficiency Detector with carefully pre-examined physical properties of inversion-layer Silicon-photodiodes and advanced measurement techniques. The principal approach towards reaching the goal is presented and discussed.