What Is a Rod Lens?
A rod lens is a lens that is cylindrical and whose outer surface is polished to a high degree of precision. The cross-section is a cut surface, but some of them have a polished finish.
As an optical function, it can convert light irradiated on the periphery into a line and diffuse it in a fan shape. They are often used to collect light for devices that require light on a line, such as line sensors.
The wavelength and focal length of light that can be handled vary depending on the lens material.
Uses of Rod Lenses
This section describes the uses of rod lenses.
Rod lenses have the effect of diffusing light along a line and are used as lenses for architectural markers and non-contact 3D shape measuring instruments. Rod lenses are also used in manufacturing lines in factories, where they are placed just in front of line sensors to let in light to make it easier for the sensors to respond.
Rod lenses are also used in barcode readers and scanners at supermarket checkout counters.
Principles of Rod Lenses
Lenses have the effect of focusing or diffusing light.
For example, light incident on a convex lens is refracted by the lens and redirected toward the thicker center. Since the thickness of a convex lens increases toward the center, light passing through the lens converges at a single point. This point is called the focal point, and the distance from the center of the lens to the focal point is called the focal length.
Lenses come in a variety of shapes, and each shape has a different effect on light. Rod lenses are classified as a special shape among lenses. Since only one directional component of the incident light acts as a lens, the light after passing through becomes on a slit line and spreads out in a fan shape. Using this characteristic, it is possible to focus laser light into a thin beam or form a sheet of light.
Cylinder lenses (cylindrical lenses) are classified as the same special shape lenses as rod lenses. The action of light is the same as that of rod lenses, but the cylinder lens has a cylindrical shape.