What Is a Cylindrical Lens?
A cylinder lens is a lens in the shape of a cylinder (cylindrical). It has a mantle shape with a portion of the side surface of the cylinder cut out.
The incident plane of the lens is divided into two components, the x-axis, and the y-axis. Only one axis has a curvature that acts as a lens, while the other has no curvature and acts merely as a window. Therefore, only one direction of the image is enlarged or reduced.
This is used to change the magnification of the image in only one direction.
Uses of Cylindrical Lenses
Cylinder lenses convert a laser beam into a line (laser line generator) to focus light on a slit aperture or line sensor. They can also collimate an elliptical beam of a semiconductor laser with different spread angles in two orthogonal directions into a circular beam to obtain a parallel beam (collimating).
For image processing applications, it is used to correct astigmatism and to enlarge or reduce the height of an image in only one axis direction.
Specifically, they have significant roles in laser printers, photocopiers, barcode scanning, laser projectors, holography equipment, laser markers, etc.
Principles of Cylindrical Lenses
Cylindrical lenses can have a variety of shapes, including rectangular, square, circular, and elliptical. Plano-convex shapes diverge light, while plano-convex shapes focus light. Extending the total length of a cylindrical lens along a non-curvature axis does not affect the optical power of the lens.
For example, when a narrow laser beam is injected into a cylindrical lens, a flat laser beam is emitted because the beam is diffused in the direction with curvature (direction perpendicular to the matrix). In contrast, in the direction without curvature (along the matrix), the beam is the thickness of the original laser beam.
When looking at the laser surface spread like a sheet with a camera, objects crossing the sheet will shine through, and the position, size, and speed of these objects can be examined. A typical example is the Particle Image Velocimetry (PIV) method.
Also, when a sheet of light is shone on a wall, a straight line is drawn, which can be combined with a level to project a highly accurate horizontal line. This is called a laser marker and is utilized on construction sites.