Resolving power d of the image passing through the optical system of the lens and reaching the CCD of the digital camera is expressed in the formula d=1/(2*f)and.f=2*NA/ λ
f: lens cut-off frequency
From the above formulae, d= λ /(4*NA).Here, λ :is 550nm(the wavelength at the center area of the visible light).
NA is the NA of the lens closest to the CCD of the microscope optical system divided by the magnification, and this resolving power controls the overall resolving power. In the optical system of the microscope, this NA is greatest in a low-magnification lens. At present, the maximum value of NA is perhaps about 0.04. If this value is used to calculate resolving power, d = 0.55/(4*0.04) = 3.43 λ. Therefore, resolving power required by the CCD = 3.4 λ.
d = 0.55/(4*0.04) = 3.43 λ. Therefore, resolving power required by the CCD = 3.4 λ m.
If the pixel pitch of the CCD used in the camera is on the order of 3.4 λm or less, the image of the subject is sufficiently resolved.
BTW, 1 cm = 10,000 microns. Nikon D90 pixel pitch is at 5.5 µm. Nikon D700 and D3 has it at 8.4 µm. Nikon D300 is at 5.4 µm.