The method and apparatus that is used for the external fiber of optical detection longitudinally moving fiber strand
Technical field
The present invention relates to the method for the external fiber of a kind of fibrous bundle for the optical detection lengthwise movement (being in particular yarn), the method comprises: the direction along fibrous bundle sends light, determine the brightness value of yarn by the light that is reflected by yarn, and in order to obtain this brightness value of continuous review with the deviation of average brightness value.The invention still further relates to a kind of device for carrying out the method.
Background technology
In the manufacturing of fiber or yarn or processing, mishmash (such as external fiber) be unfavorable for subsequently processing procedure and the quality of final products.Therefore, it is essential, detect external fiber, to obtain the quality information about fibrous bundle, perhaps can take immediate steps after external fiber being detected and remove external fiber.
In order to detect external fiber, in practice, main employing is optical means, and these optical meanss are based on the different reflecting properties of different colours or brightness fiber.A kind of like this method has for example been described in patent families WO 93/19359.Wherein, light action on the textile testing material of yarn, rove or strip-type, and is measured light by the test material reflection, thus according to catoptrical variation draw about whether there being the conclusion of mishmash.For this reason, at two some place's illumination test materials, except reflecting, also measure the variation of diameter or its diameter of test material, and obtain the business from reflected signal and diameter signal at least, and the deviation of continuous review and mean value.In this case, can determine adaptively mean value by forming continuously mean value for the suitable test material of length.Described business is the brightness value of test material in this case.
In order to determine brightness value, there are a large amount of other methods in prior art.For example as described in DE 100 09131 A1, can according to the diameter adjustment along the light that fiber bundle direction sends, make the light by the fibrous bundle reflection directly produce brightness value.
In the case, can determine with the form of absolute deviation the deviation of the current brightness value that is detected and average brightness value, that is to say poor between measured value and mean value.Usually, utilize relative deviation to obtain in other words, to utilize the business of absolute deviation and average brightness value to estimate on being subjected to the better evaluation of the fibrous bundle that external fiber affects.
EP 0 877 108 A1 have described a kind of method and apparatus for the cleaning yarn, wherein the character of yarn are detected, and are limited the yarn defect that will be eliminated by adjustable cleaning limit value.In this case, described yarn property can be thickness and quality, the length of yarn defect and color and the structure of yarn of yarn.Therefore can form the cleaning limit value for the yarn defect, for example thick knot or thin knot, external fiber, foreign matter or filoplume (hairiness).Form mean value for corresponding measured value, and thereby definite relative deviation with respect to this mean value.With this relative deviation and threshold, thereby to yarn fault grading, perhaps start clear operation.
Above-mentioned WO 93/19359 has described the corresponding activation threshold value corresponding to reference value, and it obtains by continuous formation average brightness, and measuring-signal exceeds described triggering reference value and has external fiber or other mishmash with regard to corresponding expression.
DE 100 57 170 A1 have described a kind of for determining fabric, specifically determine the method for flaw from fiber.In order to determine that whether particular luminance value increases with respect to the normal brightness value of fabric, needs to determine the mean value of fabric brightness.Set up threshold value according to this mean value.If determined brightness is positioned on this threshold value, be indicated as flaw.Determined mean value can be multiply by a factor and come definite threshold.This factor can be different along with the difference of fabric type.Nowadays for detection of the device of external fiber, major part is that signal is carried out digitized processing.That is to say, at first the simulating signal that detects by the sensor of the light of fibrous bundle reflection is converted into digital signal, then further digitized processing in addition in suitable control module.
During the digitizing of simulating signal, quantize not only aspect the time but also carrying out aspect value.The quantization step that is quantified as limited quantity causes decrease resolution, and causes quantization error, that is to say, has difference between original signal and digital signal.The discrete value that obtains is fewer, and the quantizing noise of generation is just larger; Signal to noise ratio (S/N ratio) reduces.
When utilization checks the brightness value of fibrous bundle of lengthwise movement with respect to the above-mentioned relative deviation of mean value, in the situation that dark yarn that is to say can cause large relative deviation in the situation that average brightness value is less.On the contrary, in the situation that light yarn, relative deviation is on the contrary less, and this is because divisor is larger.As mentioned above, in the situation that digitized processing, only the discrete value of limited quantity can be used, and the relative deviation of generation must be mapped on these discrete values.The resolution of the relative deviation after these higher values under dark yarn situation cause digitizing is less, therefore, according to the above description, produces the quantizing noise of not expecting.
Summary of the invention
The object of the invention is to be reduced in digitizing and determine quantizing noise in luminance deviation, and make estimate reliable.
Characteristic features by the device of the method for first aspect present invention and fourth aspect present invention realizes according to purpose of the present invention.
In order to realize this purpose, form absolute deviation and business specific to the predetermined fixed value of fibrous bundle, this commercialization is in estimating described deviation.
By ground calculates described luminance deviation according to the present invention, can come brightness adjusting deviate scope for various yarn colors.So, can utilize best the discrete value of quantity available in the numeral evaluation, thereby reduce quantizing noise.Simultaneously, can with in the situation that absolute deviation differently, is investigated the relation with the brightness of flawless yarn.
On dark yarn, observer is difficult to find the external fiber of the external fiber of other colors, particularly light colour, and result is possible accept difference larger aspect amount.In deviation according to the present invention is calculated, carried out corresponding weighting by the fixed value specific to fibrous bundle, therefore needn't adjust threshold value (surpass or lower than this threshold value place thinking yarn defect), or not regulate threshold value in order to such degree of the prior art at least.Therefore, not only regulated go out the scope of present worth, but also regulated the acceptable value scope of the calculation deviation of various fibers.Thereby, also regulate the resolution in the acceptable value scope, thereby totally reduced quantization error.
In the preferred implementation according to the inventive method, change described fixed value (H along with the variation of yarn color
0).
In other preferred implementation, specific fixed value is not less than predetermined value.
Also realize this purpose by a kind of device for the optical detection external fiber, this device comprises: light source, this configurations of light sources become towards the direction of described fibrous bundle to send light; Sensor, this sensor arrangement becomes to detect the light by described yarn reflection; And control device, described control device is configured to determine from sensor signal the brightness value of described yarn, and in order to obtain the described brightness value of continuous review with the deviation of average brightness value.According to the present invention, described control device further is set as determines described absolute deviation and business specific to the predetermined fixed value of fibrous bundle, and utilizes this business to estimate described deviation.
Description of drawings
The below will describe the present invention in detail by means of the embodiment shown in figure.In accompanying drawing:
Fig. 1 represents the device for the optical detection external fiber;
Fig. 2 represents to calculate according to the present invention the schematic diagram of luminance deviation;
Fig. 3 represents to determine the process flow diagram of fixed value.
Embodiment
Fig. 1 represents theory structure for the device of the external fiber of optical detection longitudinally moving fiber strand in very simple mode.Fibrous bundle 1 moves along the direction of arrow 7.Light source 2 sends light towards the direction of fibrous bundle 1.This light is reflected by fibrous bundle 1, and is detected by sensor 3.Light source 2 is connected to digital control unit 4 by operation circuit 6, sensor 3 by operation circuit 5.Control module 4 adopts a kind of known method to determine continuously the brightness value of fibrous bundle.Light source or the sensor that may also need other, this depends on for the method for determining brightness.
At each scanning step k, control module 4 the method according to this invention are determined luminance deviation Δ H (k).Fig. 2 illustrates this calculating.By
totalizer 10, the brightness value H (k) that determines from current scanning step k deducts the average brightness value H that determines continuously
m(k).Acquired results is offered computing unit 11.This difference multiply by factor
Should differ from other words divided by value H
oH
oBe here the fixed value specific to fibrous bundle, therefore do not rely on current scanning.According to the present invention, obtain the deviation of brightness value and average brightness value by following formula (i) value of calculating Δ H (k).
Fig. 3 shows the fixed value H that forms specific to fibrous bundle
0A kind of may mode.The process flow diagram of Fig. 3 originates in initiating terminal 21.At first set up brightness value H by operating 22
1 Operation 23 is determined to have processed the average brightness value H of fibrous bundle by formula (ii) from the scanning of j brightness value
m(j).
In branch 24, with average yarn value H
m(j) with predetermined value H
1Compare.If mean value H
m(j) less than predetermined value H
1, executable operations 25.Operation 25 is with predetermined value H
1Give and be the fixed value H specific to fiber
0If average brightness value H
m(j) be not less than predetermined value H
1, then operate 26 after branch 24.Thereby, with predetermined average brightness value H
m(j) give fixed value H
0Finishing the fixed value H of end 27 end specific to fibrous bundle
0Foundation.If average brightness value H
m(j) greater than predetermined value H
1, fixed value H
0Can also be again by consecutive mean brightness value H
m(k) substitute.That is to say, in the situation that light yarn can keep known relative deviation, and this fixed value only is used for its brightness value less than predetermined value H
1Dark yarn.