A Ronchi ruling, Ronchi grating, or Ronchi mask, named after the Italian physicist

Vasco Ronchi Vasco Ronchi (; December 19, 1897 – October 31, 1988) was an Italian people, Italian physicist known for his work in optics. He was born on 19 December 1897 in Florence, Italy. Along with Enrico Fermi, he was a student of Luigi Puccianti. He s ...

, 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 In integrated circuit manufacturing, photolithography or optical lithography is a general term used for techniques that use light to produce minutely patterned thin films of suitable materials over a substrate, such as a silicon wafer, to protect ...

deposition of metallic

chromium Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal. Chromium metal is valued for its high corrosion resistance and hardne ...

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 Milk glass is an opaque or translucent, milk white or colored glass that can be blown or pressed into a wide variety of shapes. First made in Venice in the 16th century, colors include blue, pink, yellow, brown, black, and white. Principle Mi ...

. 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 optical testing a Ronchi test is a method of determining the surface shape (figure) of a mirror used in telescopes and other optical devices. Description In 1923 Italian physicist Vasco Ronchi published a description of the eponymous Ronchi tes ...

procedure evaluates the quality of the surface figure and provides guidance on refining the figure. The ruled divisions in a

linear encoder A linear encoder is a sensor, transducer or readhead paired with a scale that encodes position. The sensor reads the scale in order to convert the encoded position into an analog or digital signal, which can then be decoded into position by a di ...

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 The Bahtinov mask is a device used to focus small astronomical telescopes accurately. Although masks have long been used as focusing aids, the distinctive pattern was invented by Russian amateur astrophotographer Pavel Bahtinov (russian: Пав ...

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.

References

{{Reflist Optical components

Manufacturing

Applications

See also

References