Holographic reconstruction device and method

Abstract

The present disclosure relates to improved holographic reconstruction device and a method. In one aspect, the present disclosure relates to improved holographic reconstruction device and method that can measure a digital hologram regardless of optical characteristics of an object to be measured, by an all-in-one type system integrating a transmissive system that measures an object transmitting light and a reflective system that measures an object reflecting light.

What is claimed is: 
     
         1 . A holographic reconstruction method comprising:
 a) selecting two types of measurement modes of an object hologram of an object to be measured (S 1 );   b) measuring the object hologram according the selected mode (S 2 );   c) removing direct current, imaginary image, curvature information of the measured object hologram (S 3 );   d) extracting phase information of the object hologram (S 4 ); and   e) reconstructing three-dimensional shape information and quantitative thickness information of the object to be measured (S 5 ).   
     
     
         2 . The holographic reconstruction method of  claim 1 , wherein operation b) comprises measuring the object hologram in a transmissive mode (S 21 ) or measuring the object hologram in a reflective mode (S 22 ). 
     
     
         3 . The holographic reconstruction method of  claim 2 , wherein a beam transmitting object hologram acquired in operation S 21  is expressed as a complex conjugated hologram corresponding to an interference pattern for a beam transmitting part of the object to be measured as in Equation 1 below:
   | U   T ( x,y, 0)| 2   =|O   T ( x,y )| 2   +|R   T ( x,y )| 2   +O*   T ( x,y ) R   T ( x,y )+ O   T ( x,y ) R*   T ( x,y )  (1)
 
 wherein x and y denote spatial coordinates, U T (x,y,0) denotes the acquired beam transmitting object hologram, O T (x,y), R T (x,y) denote an object beam and a reference beam of the beam transmitting object hologram, and O T *(x,y), R T *(x,y) denote complex conjugates of the object beam and the reference beam of the beam transmitting object hologram. 
 
     
     
         4 . The holographic reconstruction method of  claim 2 , wherein a beam reflecting object hologram acquired in operation S 22  is expressed as a complex conjugated hologram corresponding to an interference pattern for a beam reflecting part of the object to be measured as in Equation 2 below:
   | U   R ( x,y, 0)| 2   =|O   R ( x,y )| 2   +|R   R ( x,y )| 2   +O*   R ( x,y ) R   R ( x,y )+ O   R ( x,y ) R*   R ( x,y )  (2)
 
 wherein x and y denote spatial coordinates, U R (x,y,0) denotes the acquired beam reflecting object hologram, O R (x,y), R R (x,y) denote an object beam and a reference beam of the beam reflecting object hologram, and O R *(x,y), R R *(x,y) denote complex conjugates of the object beam and the reference beam of the beam reflecting object hologram. 
 
     
     
         5 . The holographic reconstruction method of  claim 1 , wherein:
 operation c), for each case wherein the measured object hologram is the beam transmitting object hologram or the beam reflecting object hologram,   comprises: c1) dividing a frequency spectrum of the beam transmitting object hologram or the beam reflecting object hologram, which acquired by performing 2D Fourier Transform, into real image, imaginary image, and direct current information of the beam transmitting object hologram or the beam reflecting object hologram to remove the direct current and imaginary image information from the beam transmitting object hologram or the beam reflecting object hologram (S 31 );   c2) extracting a real image spot-position by applying an automatic real image spot-position extraction algorithm to remove the divided imaginary image and direct current (DC) information of the beam transmitting object hologram or the beam reflecting object hologram (S 32 );   c3) extracting reference beam information of the beam transmitting object hologram or the beam reflecting object hologram by using a frequency filtering algorithm (S 33 );   c4) calculating a wavenumber vector constant of the extracted reference beam information (S 34 );   c5) calculating a compensation term of the extracted reference beam information by using the calculated wavenumber vector constant (S 35 );   c6) extracting curvature information from the beam transmitting object hologram or the beam reflecting object hologram to compensate for a curvature aberration of an object beam objective lens used when measuring the object hologram (S 36 ); and   c7) converting the beam transmitting object hologram or the beam reflecting object hologram having the compensated compensation term and the compensated curvature information into information of a reconstruction image plane by using an angular spectrum propagation algorithm (S 37 ).   
     
     
         6 . The holographic reconstruction method of  claim 5 , wherein operation c6) comprises: generating a curvature information compensation term by using an automatic frequency curvature compensation algorithm; and acquiring a compensated beam transmitting object hologram or a compensated beam reflecting object hologram by multiplying the beam transmitting object hologram or the beam reflecting object hologram by the compensation term of the extracted reference beam information and the curvature information compensation term. 
     
     
         7 . The holographic reconstruction method of  claim 6 , wherein the compensated beam transmitting object hologram or the compensated beam reflecting object hologram is expressed as in Equation 3 or 4 below:
   | U   CT ( f   x   ,f   y ,0)| 2   =F{O   T ( x,y ) R*   T ( x,y ) R   CT ( x,y ) R   CAT ( x,y )}  (3)
     | U   CR ( f   x   ,f   y ,0)| 2   =F{O   R ( x,y ) R*   R ( x,y ) R   CR ( x,y ) R   CAR ( x,y )}  (4)
   wherein U CT (f x ,f y ,0) denote the compensated beam transmitting object hologram, U CR (f x , f y ,0) denotes the compensated beam reflecting object hologram, O T (x,y), R T *(x,y) denote an object beam and a reference beam of the beam transmitting object hologram, O R (x,y), R R *(x,y) denote an object beam and a reference beam of the beam reflecting hologram, R CT (x,y) denotes the compensation term of the reference beam information of the beam transmitting object hologram, R CAT (x,y) denotes the curvature information compensation term of the beam transmitting object hologram, R CR (x,y) denotes the compensation term of the reference beam information of the beam reflecting object hologram, and R CAR (x,y) denotes the curvature information compensation term of the beam reflecting object hologram.   
     
     
         8 . The holographic reconstruction method of  claim 1 , wherein operation d) comprises extracting phase information from a converted compensated object hologram through inverse 2D Fourier Transform,
 wherein the acquired phase information comprises only phase information of the beam transmitting or reflecting part of the object to be measured, from which remaining information is removed except for the phase information of the beam transmitting or reflecting part of the object to be measured that the acquired beam transmitting object hologram or the acquired beam reflecting object hologram has.   
     
     
         9 . The holographic reconstruction method of  claim 1 , wherein:
 operation e) comprises: respectively compensating the extracted phase information of the beam transmitting part of the object to be measured or the extracted phase information of the beam reflecting part of the object to be measured for distorted phase information, by using a 2D phase unwrapping algorithm;   calculating the quantitative thickness information of the object to be measured, by using the compensated phase information; and   reconstructing the three-dimensional shape information of the object to be measured, by using the calculated quantitative thickness information of the object to be measured.   
     
     
         10 . The holographic reconstruction method of  claim 9 , wherein the calculated thickness information of the object to be measured is expressed as in Equation 5 below: 
       
         
           
             
               
                 
                   
                     
                       Δ 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       L 
                     
                     = 
                     
                       
                         λ 
                         ⁡ 
                         
                           ( 
                           
                             
                               
                                 Δ∅ 
                                 T 
                               
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               
                                 ( 
                                 
                                   x 
                                   , 
                                   y 
                                 
                                 ) 
                               
                             
                             + 
                             
                               
                                 Δ∅ 
                                 T 
                               
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               
                                 ( 
                                 
                                   x 
                                   , 
                                   y 
                                 
                                 ) 
                               
                             
                           
                           ) 
                         
                       
                       
                         2 
                         ⁢ 
                         π 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         Δ 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           n 
                           ⁡ 
                           
                             ( 
                             
                               x 
                               , 
                               y 
                             
                             ) 
                           
                         
                       
                     
                   
                 
                 
                   
                     ( 
                     5 
                     ) 
                   
                 
               
             
           
         
         wherein ΔL denotes the quantitative thickness information of the object to be measured, λ denotes a wavelength of a light source used when acquiring the object hologram, ΔΦ T (x,y) denotes the phase information of the beam transmitting part of the object to be measured, ΔΦ R (x,y) denotes the phase information of the beam reflecting part of the object to be measured, and Δn(x,y) denotes a difference between refractive indexes of the object to be measured and air.