Is it possible to model the objective lens using either fourier transform formula or geometrical optics calculation derived for thin lens. If it cannot be modeled in this way, what is the focal length reported in the information provided on the companies' websites? (e.g. http://www.newport.com/Microscope-Objective-Lenses/141071/1033/info.aspx )
Dear Parinaz, I modeled total thin lens system including the microscope objective lens (f1) and the eyepiece (f2) instead of objective lens itself. Please see file attached, where other important parameters are tube length D=160mm for Newport M series objective lens and range of clear vision D0=250mm for eyepiece. Using these, magnification of the objective lens and eyepiece are given by beta1=D/f1 and beta2=D0/f2. If beta1=50x and beta2=10x, total magnification is 500x. From the calculated f1=3.2mm and f2=25mm for this example, total focal length is calculated as f= DD0/f1f2 = 0.5mm, which is much smaller than original f1. Therefore, understanding thin lens system of the microscope is very informative. Shigeo
Dear Parinaz, If you are familiar with Newton's lens formula x x'=f^2, where x and x' are the distance between object and the first focal point and distance between the image and the second focal point of lens with focal length f. From the formula, m=-f/x and m=-x'/f hold. Coming back to the definition of Newport microcope objetive lens, m=D/f, where D is tube length, which is distance between the second focal point of objective lens and the first focal point of eyepiece. Combined them, we know D=x', implying the image by the objective lens locates at the first focal point of eyepiece. Therefore, the image by eye piece locates at infinity and to see it, eye should locates at the second focal point of eyepiece. Shigeo
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