Double Convex Lenses are suitable for cases where one conjugate distance is 0.2 to 5 times that of the other. The performance of the lens shape is suitable for the same object distance and image distance.
There is also an external lens in the double convex lens, which has a smaller spherical aberration.
Contour lenses are designed to minimize spherical aberrations and comets (aberrations introduced by light not on the optical axis) while still using the sphere to form the lens. The spherical design makes the shape lens easier to manufacture than the aspheric lens and reduces the cost. Each side of the contour lens is polished so that it has different radius of curvature, providing better performance for spherical single lens. For small diameter input beams, the shape lens even has diffraction properties. These lenses are typically used in high-power applications where achromatic adhesive lenses cannot be used. Contour lenses are designed to minimize aberrations while still using a sphere to form the lens. These lenses are optimized for infinitely large conjugate ratios and are ideal for focusing collimating beams or collimating point sources.