Patent Publication Number: US-4060306-A

Title: Achromatic aplanatic condenser

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to microscope condensers and in particular to an achromatic aplanatic condenser having a numerical aperture of 1.30 which uniformaly fills a field of 2.4mm diameter at the object plane of the microscope. 
     It is an object of the present invention to provide a 3 component achromatic condenser having a numerical aperture of 1.30 which is well corrected for spherical and chromatic aberrations. 
     It is another object of the present invention to provide a microscope condenser having a front focal plane external to the condenser unit. 
     It is still further an object of the present invention to provide illumination at the object plane of the microscope with substantially parallel rays or pencils of light. 
    
    
     DRAWING 
     The drawing is an optical diagram of a microscope condenser. 
    
    
     DESCRIPTION 
     Referring now to the drawing, pupil plane P is shown in the illumination system (not shown) of the microscope (not shown) with aperture diagram D lying in the same plane as the pupil plane of the condenser. The condenser comprises 3 components. A double convex positive doublet I; a meniscus singlet II and a convex plano doublet III provide in combination a greatly simplified condenser system having the advantages of much more complex prior art condensers. Lens parameters as shown in the drawing, have been given the following identifications: axial air spaces have been designated S 1  to S 3  ; axial thickness are designated T 1  to T 6  ; lens radii are designated R 1  to R 8 , with a minus sign (-) applies to surfaces whose center of curvature lie on the side of their vertices toward the pupil plane, refractive indices are designated ND(1) to ND(6) and Abbe numbers are designated γ (1) to γ (6) and So is the axial thickness of the immersion oil. 
     The values of radius, thickness, air space and oil thickness are in mm and the values for indices of refractions and Abbe numbers are absolute values. 
     The Table presents the preferred embodiment of the present invention. 
     
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                               Refractive                                 
                                       Abbe                               
Lens Radius     Thickness                                                 
                       Space   Index   No.                                
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                      S.sub.1 = 1.526                                     
    R.sub.1 = 38.54                                                       
               T.sub.1 = 8.73 ND.sub.1 = 1.6203                           
                                      γ.sub.1 = 60.3                
I   R.sub.2 = -24.33                                                      
               T.sub.2 = 1.50 ND.sub.2 = 1.786                            
                                      γ.sub.2 = 25.5                
    R.sub.3 = -169.084                                                    
                      S.sub.2 = 0.10                                      
    R.sub.4 = 13.48                                                       
II             T.sub.3 = 4.77 ND.sub.3 = 1.6203                           
                                      γ.sub.3 = 60.3                
    R.sub.5 = 32.96                                                       
                      S.sub.3 = 0.10                                      
    R.sub.6 = 7.77                                                        
               T.sub.4 = 6.13 ND.sub.4 = 1.651                            
                                      γ.sub.4 = 55.8                
III R.sub.7 = 00                                                          
               T.sub.5 =  4.12                                            
                              ND.sub.5 = 1.786                            
                                      γ.sub.5 = 25.5                
    R.sub.8 =00                                                           
    IMMERSION OIL     So = 0.4177                                         
                              ND.sub.0 = 1.515                            
                                      γ.sub.0 = 43.6                
    OBJECT                                                                
    SUPPORT A  T.sub.6 = 1.25 ND.sub.6 = 1.524                            
                                      γ.sub.6 = 58.3                
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     In the above Table the preferred values for the immersion oil thickness, refractive index and Abbe number as well as the object support glass thickness, refractive index and Abbe number have been given. These values do not form a part of the present invention but have been provided as a part of the best mode of practicing the same.