Lensmaker’s Equation
The focal length of a lens in air can be calculated from the lensmaker’s equation.
Let
f is the focal length of the lens,
n is the refractive index of the lens material,
R1 is the radius of curvature of the lens surface closest to the light source,
R2 is the radius of curvature of the lens surface farthest […]

Chromatic aberration is caused by the scattering of the microscope objective lens material. Chromatic aberration of a microscope objective lens is seen as fringes of color around the image. It can be lessened by using an achromatic doublet or achromat, in which two materials with different dispersions are bonded together to form a single […]

Another type of aberration is coma. The term derives its name from the comet-like appearance of the deviated image. Coma occurs when an object off the optical axis of the microscope objective lens is reflected. Rays pass through the lens at an angle to the axis ?.

Spherical aberration happens because spherical surfaces are not the ideally shaped. Spheres are the simplest shape to which glass can be ground and polished. Spherical aberration causes light beams to become parallel to each other but at the same time causes them to move away from the lens axis. Moving the light beams away […]

Lens construction
Microscope objective lens may be spherical. Such lens surfaces have spherical curvature. The front and back surfaces of the microscope objective lens can each be imagined to be part of the surface of a sphere.
Each surface can be:
1. convex or bulging outwards from the lens
2. concave […]