[seminar] Podsjetnik: nastupno predavanje dr. sc. Hrvoje Skenderović u UTORAK 16.05.2023. u 11:00h

[Damir Dominko]

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-------- Original message --------From: Damir Dominko <ddominko at ifs.hr> Date: 16/05/2023  10:49  (GMT+01:00) To: seminar <seminar at phy.hr> Subject: Podsjetnik: nastupno predavanje dr. sc. Hrvoje Skenderović u UTORAK 16.05.2023. u 11:00h 
    
      
        
          utorak, 16.
                  svibnja 2023., u 11:00 sati
            
              
                
                  
                  
                  Holography and
                          coherent optics 
                  Dr. 
                              sc. Hrvoje
                          Skenderović
                  Institute of
                          Physics 
                  
                    
                      
                        The topic of the
                              talk is research in the field of Digital
                              Holography and connected themes.
                              Especially, implementation of holographic
                              measurements with scanning single photon
                              avalanche detector (SPAD), as well as
                              time-averaged digital holography (TADH) is
                              presented. In TADH measurements, holograms
                              of a vibrating object are recorded,
                              usually in such a way that the exposure
                              period of the camera recording the
                              hologram is many times greater than the
                              period of vibrations. We examined the
                              error in the reconstruction if the
                              exposure time is only a few times greater
                              than the oscillation period and if it is a
                              non-integer ratio of the two times. In the
                              following, we have shown that it is
                              possible to obtain an accurate hologram
                              even when the exposure is only half the
                              oscillation period with a known phase.
                              Finally, we have given a procedure for
                              determining the unknown oscillation period
                              and phase with several short exposures.
                              All these numerical calculations were
                              confirmed by experimental measurements
                              with real objects. 
                          
                        We also investigated
                            the differences in sampling and
                            nonlinearities in holography using a SPAD
                            detector and a camera. We have shown how it
                            is possible to determine the optimal
                            sampling using a scanning detector. Also,
                            the standard camera mainly works with an
                            8-bit image, that is, it has 256 gray
                            levels, which easily leads to saturation in
                            the recording, or to the appearance of
                            non-linear members in the reconstruction of
                            the hologram. In contrast, SPAD as a
                            detector has an infinite dynamic range.
                        
                        An experiment dealing
                            with application of quantum light in
                            holography is also discussed. The objective
                            is to use individual photons in a classic
                            holographic setup and see if they can be
                            used to obtain a hologram and if visibility
                            improves compared to classic source of the
                            same (very low) intensity. Since holography
                            is based on the interference of two light
                            beams, and in the case of individual photons
                            we a photon can not be split at the BS, the
                            possibility of interference is not clear a
                            priori. Also, there is a problem with the
                            phase, which is indeterminate for individual
                            photons. It is shown that a hologram can be
                            recorded, amplitude and phase reconstruction
                            can be obtained, and the SNR is better
                            compared to classical light of the same
                            intensity.
                        
                        
                        
                        
                        
                          Predsjednik Znanstvenog vijeća Instituta
                            za fiziku
                          dr. sc. Damir Starešinić
                            
                            
                            
                            https://us06web.zoom.us/j/89856158536?pwd=b2l4bG5reDQ5Tk1wMU1MTG1MeExBdz09
                            Meeting ID: 898 5615 8536
                            Passcode: 332504
                            
                            
                            
                          
                        
                      
                    
                  
                
              
            
          
        
      
    
  

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