Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Patent
1991-10-15
1993-06-29
Turner, Samuel A.
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
356238, 356384, G01B 902
Patent
active
052239128
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a method for measuring at least one transverse dimension of a textile yarn, in which the yarn is lit up by means of at least one beam of light emitted by a coherent light source, the interference pattern obtained in the focal plane of an optical system is examined and the said transverse dimension is deduced from the distance separating the interference bands.
It also concerns a device for measuring at least one transverse dimension of a textile yarn, in which the yarn is lit up by means of at least one beam of light emitted by a coherent light source, the interference pattern obtained in the focal plane of an optical system is examined and the said transverse dimension is deduced from the distance separating the interference bands, for the application of the method outlined above.
The known methods which carry out an analysis of the diffraction spectrum in the focal plane of an optical system have several drawbacks. Depending on the dimensions of the yarns measured, the interference bands are further apart or closer together, so that depending on the type of yarn analysed the sensitivity varies. Consequently, if the device is not designed for a very specific type of yarn, the precision of the measurement will be affected. Moreover, the known devices do not provide any information about the shape of the yarn, i.e. about the geometry of its cross-section which can be circular, more or less oval, or even almost rectangular, if the yarn is shaped like a flat or twisted ribbon.
The present invention proposes to offset these various drawbacks by creating a method and a device which are adapted for measuring the transverse dimensions of a yarn, whatever the type of yarn examined, and which enable information to be deduced about the geometrical shape of the cross-section of this yarn.
With this aim, the method according to the invention is characterized in that at least two slots are made, one on either side of the yarn, symmetrical in relation to the yarn, to form two secondary sources arranged to interfere, and in that the said transverse dimension is deduced from the spacing between the bands of the resulting interference pattern.
According to a preferred method, the width of the said symmetrical slots is regulated according to the proportions of the said transverse dimension of the yarn.
According to a particularly advantageous variant, two pairs of slots are made, one pair on either side of the yarn, symmetrical in relation to this yarn and perpendicular two by two, the first pair of slots is lit up by means of a first coherent light beam and the second pair of slots by means of a second coherent light beam, these two beams being perpendicular one to the other, and the transverse dimensions of the yarn in two perpendicular directions are deduced from the interference patterns formed respectively by the slots of the first pair of slots and by those of the second pair of slots.
With this same aim, the device according to the invention is characterized in that it comprises means for making at least two slots, symmetrical in relation to this yarn to form two secondary sources arranged to interfere, means for analysing the resulting interference pattern and means for deducing the said transverse dimension of the yarn from the spacing between the bands of the interference pattern.
The width of the slots is preferably adjustable so that the device can be adapted for analysing different types of yarns.
According to a preferred embodiment, the device comprises two pairs of slots symmetrical in relation to the yarn and perpendicular two by two, means for generating two coherent light beams perpendicular one to the other and respectively perpendicular to the two pairs of slots, means for analysing the resulting interference patterns and means for deducing from these patterns the transverse dimensions of the yarn according to two directions perpendicular to the axis of this yarn and perpendicular to each other.
The present invention can be better understood by referring to the description
REFERENCES:
patent: 3518007 (1970-06-01), Ito
patent: 3709610 (1973-01-01), Kruegle
patent: 3937580 (1976-02-01), Kasdan
Passap Knitting Machines Inc.
Turner Samuel A.
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