Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1986-12-03
1988-08-09
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
356371, 356376, G01N 2186, G01B 1130, G01B 1124
Patent
active
047630060
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Background
The invention relates to a device for the detection of form deviations of a low order and, in particular, of form deviations of the first or second order.
Form deviations of the first to third orders are described as roughness, waves or grooves. (Form deviations of the second order are sometimes also described as "chatter marks). This type of form deviations and, in particular, form deviations of the second order result, for example, in the low frequency range in noise development such as whistling in bearing surfaces of transmission shafts. The occurrence of whistling necessitates the disassembly of the transmission to remove the shaft. To avoid this time-consuming effort, it would be desirable, for example during the assembly of the transmission, to check all shafts for the occurrence of form deviations and/or form errors of a low order and, in particular, for the occurrence of chatter marks which cause noise, prior to assembly.
2. State of the Art
Up until now, form deviations of a low order have been measured industrially only with mechanical form testing instruments such as, for example, the "Perthen-Formtester" of Messrs. Mahr. However, a mechanical form testing does not only have the disadvantage that it requires a relatively great deal of time but also that it requires a great deal of effort to perform the form testing: For example, the test stand must be free of low-frequency building vibrations.
It has nevertheless been found that even when a great deal of effort is invested in the instruments, the results of mechanical form testing cannot always be used as a reliable assessment of whether, for example, a transmission shaft will "whistle" once installed. For this reason, it has already been suggested that form deviations of a lower order be assessed optically (Annals of the CIRP Vol. 33/1/1984, Page 407 f.). With this known device for an optical detection of surface defects, the angle of reflection or the change in this angle of reflection of the reflected beam which results from form deviations is measured using "light scales" consisting of two photodiodes.
However, this known device has several disadvantages: A measurement using light scales consisting of two photoreceivers does not permit a free choice in the spot size of the examining light beam on the surface to be examined for a certain, desired angular resolution. In addition, a relatively large electronic and optical effort is required for a control of the intensity of the examining light beam.
Above all, however, form deviations of a higher order, for example, the roughness of the surface, have a comparatively great influence on the measuring results due to the "splitting up" of the light beam caused by the roughness.
Representation of the Invention
The object of this invention is to present a device for the optical detection of form deviations and/or surface errors of a low order with which form deviations of a low order can be assessed with high precision with a comparatively low optical and electronic effort.
This object is solved according to the invention by having a device such as is known from "Annals of the +IRP, Vol. 33/1/1984, Page 407 f.", as a base device and then further developing this device with the features of the characterising part.
In accordance with this invention it has been recognised that a high-precision angular resolution is possible when the light-receiving device consists of a number of light-receiving elements arranged in a line and when the output signals of all light-receiving elements are evaluated in the determination of the angle of inclination. In this way, it is surprisingly possible to resolve shifts in the core of the reflected light beam which are considerably below the width of a light-receiving element. The process in accordance with the invention also has the further surprising advantage that the measuring results obtained remain practically uninfluenced by form deviations of a higher order such as roughness, etc. Nevertheless, the device in accordance with
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Brodmann et al., "Optical Roughness Measuring Instrument for Fine-Machined Surfaces," Optical Engineering vol. 24, No. 3, 6/85, pp. 408-419.
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Brodmann Rainer
Gerstorfer Oskar
Hubner Gerd
Rau Norbert
Staiger Wolfgang
Kalish & Gilster
Messinger Michael
Nelms David C.
Optische Werke G. Rodenstock
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