A Ronchi ruling, Ronchi grating, or Ronchi mask, named after the Italian physicist
Vasco Ronchi, is a constant-interval bar and space
square-wave optical target or mask. The design produces a precisely patterned light source by reflection or illumination, or a stop pattern by transmission, with precise uniformity, spatial frequency, sharp edge definition, and high contrast ratio.
Manufacturing
Ronchi rulings are typically manufactured through
photolithographic
Photolithography (also known as optical lithography) is a process used in the manufacturing of integrated circuits. It involves using light to transfer a pattern onto a substrate, typically a silicon wafer.
The process begins with a photosensit ...
deposition of metallic
chromium
Chromium is a chemical element; it has Symbol (chemistry), symbol Cr and atomic number 24. It is the first element in Group 6 element, group 6. It is a steely-grey, Luster (mineralogy), lustrous, hard, and brittle transition metal.
Chromium ...
on a substrate, which yields a precise, nearly 100% contrast pattern. For a reflective or illuminated type, dark stripes are printed on a diffusely reflecting or translucent substrate, such as a square of white ceramic material or
opal glass. For a transmissive type, opaque stripes are printed on a transparent glass substrate. A transmissive type may be readily modified to act as an illuminated type by stacking a reflective object behind it.
Applications
A test target in the Ronchi pattern provides a precise signal for testing resolution, contrast, distortion, aberrations, and diffraction in optical imaging systems.
In constructing telescope mirrors, the
Ronchi test In Optics, optical testing a Ronchi test is a method of determining the surface shape (Figuring, figure) of a mirror used in Optical telescope, telescopes and other Optics, optical devices.
Description
In 1923 Italian people, Italian physicist Vasc ...
procedure evaluates the quality of the surface figure and provides guidance on refining the figure. The ruled divisions in a
linear encoder are in the form of Ronchi ruling, which provides the basic precision of the measurements.
A single Ronchi device provides a pattern that is periodic in one dimension. Stacking a pair of Ronchi transmission elements produces a two-dimensional array of periodic rectangular or rhomboidal apertures. By varying the translation, rotation, and chosen frequency of one element against the other, a wide assortment of laboratory test patterns can be generated with the paired arrangement.
Telescopic focusing aids such as the
Bahtinov mask consist of multiple adjacent Ronchi transmission stop patterns. Inserting a Ronchi mask in the entrance aperture produces diffraction effects in the image, which visibly change with the focusing condition.
See also
*
1951 USAF resolution test chart
References
{{Reflist
Optical components