Radial Gratings Research Articles

A novel application of parallel strip hinges

An instrument has been designed using radial diffraction gratings to measure the transmission errors in gear hobbing machine table drives. Potential errors of measurement, due to eccentricity of the grating unit with respect to the table axis, and axis wander effects are avoided by the use of the linkage described.

A radial grating dividing engine of high accuracy

A dividing engine for the production of radial gratings by photographic means has been constructed according to the principles described by Burch. A moiré fringe signal derived from an existing pair of radial gratings is used to control the manufacture of a similar but improved grating. Repetition of this process has led to the production of a second generation of gratings with a peak-to-peak error less than 0.2 second of arc.

An optical shaft resolver using coupled light-modulators

An experimental, optical shaft resolver is described which uses continuously rotating radial gratings to form two light modulators. Angular position is determined as the phase difference between the signals from the fixed reference modulator and the variable position modulator. 360 line gratings are used, each line interval being divided into 200 parts by conventional equipment. The method is able to average centring and manufacturing errors, thus reducing production tolerances.

An optical incremental shaft resolver using plastic radial gratings

An optical incremental shaft resolver using inexpensive plastic radial gratings, capable of resolving 6000 parts in one shaft revolution at velocities from 0 to 2500 revolutions per minute is described. The performance of the gratings produced from master radial patterns formed without the use of a ruling machine is described. Electronic circuits are given to produce counting pulses and direction information.

Production of radial line gratings using a mechanical-photographic apparatus

An electromechanical method is described for producing primary radial line patterns on photosensitized materials. Up to 6000 lines per circle can be produced in a matter of minutes. Considerable variations in length and shape of lines are possible. The method has greater precision than hand drawing methods and should find application as an intermediate process between hand drafting and ruling machines.

Measurement of ground speed with a radial grating

This paper describes a device capable of measuring, with very high accuracy, the ground speed of a moving carriage. The device employs a 6000-line radial grating combined with a simple optical system and a photoelectric circuit. The electrical output is fed to a frequency and time measuring instrument, which compares the pulses with a crystal controlled time base and displays speed as feet per second with five-digit accuracy.

Widening the applications of diffraction gratings for measurement and control

The paper describes the construction of radial gratings having between 90 and 32,400 lines photographed on to plate glass disks of 12 in. dia. or less. Errors less than ±3 seconds of arc are obtained. Applications of radial and linear gratings to various machine tools are described. In a gear hobbing machine errors have been reduced to 1/20 for worm/table rotation and 1 4 in actual cut gears of 20 in. dia. Circuits for phasemeters for servo and for measuring purposes are contrasted, and new techniques for using batching counters with gratings described; typical applications to gear measurement and a gearboxless lathe are mentioned.

Use of radial gratings in a small inclinometer

Some of the factors involved in the choice of gratings for use in the digital measurement of angles are discussed. This problem is accentuated in the case of the instrument described by its small size and the decision, therefore, to use two complete circles for the gratings, instead of the less critical method using one circle and adjustable grating cursors. The tolerances which have to be achieved for satisfactory performance are considered and the instrument itself, a pendulous inclinometer intended to measure the pitch angle of wind tunnel models, is described.