Within this thesis we upgraded the measurement system for measuring the spectral responsivity and quantum efficiency of optoelectronic elements. In the first part we focused on theory, which enables a deeper understanding of the system functioning. The dominant physical models of light, light diffraction and the basic principles of the operation of the monochromator are all described. The second part of the paper describes the course of measurement before and after the double beam upgrade, the lock-in method is presented, and more detailed descriptions of the measuring instruments used and the upgrade of the LabVIEW control program are given. The last part contains an evaluation of the effectiveness of the upgrade, supported by the interpretation and analysis of the results obtained. The operation of the system was also tested by performing practical measurements.