Cylindrical lens

A toric lens combines the effect of a cylindrical lens with that of an ordinary spherical lens.

If a thin cylindrical rod is placed on a ruled white paper with the axis of the rod making an angle θ with the ruled lines, the lines will appear broken and tilted at some angle α as shown in the figure, the Refractive Index of the rod can be given as:

Uses

Uses in optometry

• Cylindrical lenses are prescribed to correct astigmatism.
• Cross cylinder, which is a combination of two cylindrical lenses with equal strength and opposite power, is used in subjective refraction to diagnose astigmatism, and assess the strength and axis of the astigmatic power etc.
• Maddox rods, made up of cylindrical lenses arranged in parallel, are used to detect strabismus and diplopia.

Other uses

• In a light sheet microscope, a cylindrical lens is placed in front of the illumination objective to create the light sheet used for imaging.
• Cylindrical lenses are used in optical spectrometers.
• Cylindrical lenses are used in holography.
• Doublet cylinder lens system is used in optical coherence tomography.
• Cylinder lenses are also used in many laser applications. A cylindrical lens can be used to create a laser line. A doublet cylinder lens is used to make laser sheets and circularize elliptical beams from laser diodes.
• Cylindrical lenses are key to make anamorphic lenses, useful in photography and cinematography to create a widescreen image without needing to crop the frame by horizontally squeezing the image. (see Cinemascope and Techniscope)