Abstract:
In one embodiment, apparatus for characterizing a target is provided with a plurality of light sources that are positioned to illuminate a target. The light sources emit different wavelengths of light. A color sensor is positioned to receive and sense different wavelengths of light reflected from the target. A control system is operably associated with the plurality of light sources and the color sensor to A) in a calibration mode, operate the light sources and separately regulate drive signals of light sources emitting different wavelengths of light, in response to outputs of the color sensor, and B) in an operational mode, i) operate the light sources using the regulated drive signals, and ii) characterize the target in response to data output from the color sensor. A textile characterization system is also disclosed.

Description:
BACKGROUND  
       [0001]     Automated optical inspection systems for detecting contaminated textiles are becoming increasingly prevalent in the textile industry. This is because automated optical inspection is typically cheaper, more efficient, and more reliable than human inspection of textiles. However, automated optical inspection systems are not without their limitations. For example, with respect to certain types of contaminants, automated optical inspection systems may not be as sensitive as the human eye. Automated systems may also be subject to drifts in their configuration, which can lead to  1 ) a failure to properly identify contaminants, or  2 ) a misidentification of contaminants.  
       SUMMARY OF THE INVENTION  
       [0002]     In one embodiment, apparatus for characterizing a target comprises a plurality of light sources, a color sensor and a control system. The plurality of light sources is positioned to illuminate a target and emits different wavelengths of light. The color sensor is positioned to receive and sense different wavelengths of light reflected from the target. The control system is operably associated with the plurality of light sources and the color sensor to A) in a calibration mode, operate the light sources and separately regulate drive signals of light sources emitting different wavelengths of light, in response to outputs of the color sensor, and B) in an operational mode, i) operate the light sources using the regulated drive signals, and ii) characterize the target in response to data output from the color sensor.  
         [0003]     In another embodiment, a system for characterizing a textile comprises a plurality of light sources, a color sensor, a control system and a feed system. The plurality of light sources is positioned to illuminate the textile and emits different wavelengths of light. The color sensor is positioned to receive and sense different wavelengths of light reflected from the textile. The control system is operably associated with the plurality of light sources and the color sensor to A) in a calibration mode, operate the light sources and separately regulate drive signals of light sources emitting different wavelengths of light, in response to outputs of the color sensor, and B) in an operational mode, i) operate the light sources using the regulated drive signals, and ii) characterize the textile in response to data output from the color sensor. The feed system moves the textile in relation to the color sensor, to thereby cause the color sensor to receive light reflected from different portions of the textile.  
         [0004]     Other embodiments are also disclosed.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]     Illustrative and presently preferred embodiments of the invention are illustrated in the drawings, in which:  
         [0006]      FIG. 1  illustrates an exemplary method for characterizing a target in response to data obtained from a color sensor;  
         [0007]      FIG. 2  illustrates a first exemplary system for characterizing a target in response to data obtained from a color sensor;  
         [0008]      FIG. 3  illustrates an exemplary method for, in an operational mode, characterizing a target in response to data obtained from a photodetector and, in a calibration mode, regulating drive signals of a number of light sources; and  
         [0009]      FIG. 4  illustrates a second exemplary system for characterizing a target in response to data obtained from a color sensor, which apparatus also provides a calibration mode in which drive signals of a number of light sources are regulated.  
     
    
     DETAILED DESCRIPTION  
       [0010]     Contaminant detection is especially important in the textile industry, where textiles must be continually monitored during manufacture to ensure proper color, quality and density. Contaminant or anomaly detection is also important in other industries, such as the food &amp; beverage industry, liquid processing industries, and others.  
         [0011]     Current automated optical inspection systems for detecting contaminated textiles utilize a single-color light source such as a solid-state light source (e.g., a light emitting diode (LED)), together with a photodiode that converts light reflected from a textile into a photocurrent. This photocurrent can then be used to characterize the textile and determine whether it is contaminated. However, one problem with such a system is that its contamination detection capabilities are limited, as the system can only detect a single light intensity, and different contaminants or textile properties may cause the same intensity of light to be reflected.  FIGS. 1 &amp; 2  therefore illustrate a method  100  and system  200  that are capable of detecting a wider range of contaminants and/or textile properties.  
         [0012]     Referring to  FIG. 1 , the method  100  commences with the illumination  102  of a target with light of at least two different wavelengths. Light reflected from the target is then received  104  by a color sensor (which may take the form of a CCD, or one or more filtered photosensors, phototransistors or photodiodes), and data output by the color sensor is used to characterize  106  the target.  
         [0013]      FIG. 2  illustrates an exemplary apparatus  200  for implementing the method  100 . The apparatus  200  comprises a number of light sources  204 ,  206 ,  208 ,  212 ,  214 ,  216  that are positioned to illuminate a target  202  with at least two different wavelengths of light (λ). In one embodiment, the light sources may comprise solid-state light sources such as LEDs or laser diodes. By way of example, the apparatus  200  is shown to comprise two groups  210 ,  218  of light sources, each comprising red (R)  204 ,  212 , green (G)  206 ,  214  and blue (B)  208 ,  216  LEDs. However, the number, groups and colors of light sources included in the apparatus  200  can vary depending on the application.  
         [0014]     The light projected by the light sources  204 - 208 ,  212 - 216  is reflected from the target  202  (e.g., a textile such as a strand of yarn) onto a color sensor  224 . Upon receiving the reflected light, the color sensor  224  senses the light and outputs one or more data signals  228  to a control system  226 .  
         [0015]     In one embodiment, the color sensor  224  may take the form of a charge coupled device (CCD) that senses red, green and blue wavelengths of light. In another embodiment, the color sensor  224  may take the form of a plurality of photodiodes, each of which is filtered so that it only senses a certain wavelength or wavelengths of light. In some cases, the filters may be deposited directly on the photodiodes, or incorporated into encapsulants that protect the photodiodes. In other cases, the filters may be positioned adjacent the photodiodes. In yet another embodiment, the color sensor  224  may take the form of a photodiode having a color wheel positioned between it and the target  202 . In this manner, the photodiode could be operated to detect different colors of light sequentially.  
         [0016]     As shown in  FIG. 2 , the light sources  204 - 208 ,  212 - 216  and color sensor  224  may be mounted on a substrate or frame  222  which holds the light sources  204 - 208 ,  212 - 216  and color sensor  224  in fixed relation to one another. Depending upon the type, size and location of a target  202  to be characterized, as well as the number of light sources  204 - 208 ,  212 - 216 , the frame  222  may take on a variety of configurations. In one embodiment, it comprises a printed circuit board  238  to which generally triangular bases  240 ,  242  are mounted for positioning the groups  210 ,  218  of light sources at a desired angle. Alternately (not shown), the light sources  204 - 208 ,  212 - 216  can take the form of through-hole lamps having leads that can be bent to position them at any desired angle.  
         [0017]     In one embodiment, a number of optic elements  232 ,  234 ,  236  are included with the apparatus  200 . As shown, the optic elements  232 - 236  may take the form of plano-convex lenses that are 1) positioned between each group  210 ,  218  of light sources and the target  202  so as to mix emitted light and broadly illuminate the target  202  with mixed light, and 2) positioned between the target  202  and the color sensor  224  so as to collimate the light received by the color sensor  224 . Although not shown, the optic elements  232 - 236  may be mounted to, and suspended over, the frame  222 .  
         [0018]     Data  228  output from the color sensor  224  is provided to a control system  226  for analysis. In one embodiment, the control system  226  compares the data  228  received from the color sensor  224  (which is indicative of the intensities of different wavelengths of reflected light) to expected light intensity values. Then, based on these comparisons, the control system  226  may variously characterize the target  202  as 1) being within or outside of predetermined tolerances, 2) having or not having a certain kind of contaminant thereon or therein, or 3) being of an incorrect density.  
         [0019]     The light intensity values to which the control system  226  compares the data  228  may be fixed or programmable, and may be internally stored by the control system  226 , or obtained via an interface  230 . Regardless, the control system  226  may provide a signal of any perceived problems with the target  202  to an equipment operator or machine control system.  
         [0020]     In one embodiment, the apparatus  200  is incorporated into a system (or alternately controls a system) that comprises a feed system  220  for moving the target  202  in relation to the light sources  204 - 208 ,  212 - 216  and color sensor  224 . In this manner, different portions of a target such as a yarn strand may be assessed and characterized. Optionally, the control system  226  may halt the feed system  220  upon detecting a target irregularity.  
         [0021]     Another problem with conventional automated optical inspection systems (i.e., those comprising a single-color light source and a photodiode) is that the light emitted by a solid-state light source is subject to change as a result of changes in its temperature and aging. The light-emitting characteristics of solid-state light sources can also vary from batch to batch. As a result, in systems where the integrity of light emitted by a light source needs to be maintained (e.g., in textile contamination detection systems), it would be beneficial to provide a means for calibrating the light that is emitted by the system&#39;s light source(s).  FIGS. 3 &amp; 4  therefore illustrate a method  300  and system  400  that are capable of regulating the light sources of an automated optical inspection system.  
         [0022]     Referring to  FIG. 3 , the method  300  commences with the illumination  302  of a target (possibly with different wavelengths of light). Light reflected from the target is then received  304  by a photodetector (which in some cases may be a color sensor, including one or more photosensors, phototransistors or photodiodes), and data output by the photodetector is provided to a control system. In a calibration mode, the control system regulates  306  the drive signals of the light sources that illuminate the target; and in an operational mode, the control system characterizes  308  the target in response to the data output by the photodetector.  
         [0023]      FIG. 4  illustrates an exemplary apparatus  400  for implementing the method  300 . In general, the apparatus  400  may be configured similarly to the apparatus  200 . Thus, similar elements are provided similar reference numbers in  FIGS. 2 &amp; 4 . Of note, however, the apparatus  400  need not comprise light sources for emitting different wavelengths of light. That is, the apparatus  400  could be provided with one or more light sources that all emit the same wavelength of light.  
         [0024]     Of note in the apparatus  400  is the alternate control system  402 , which not only characterizes the target  202 , but also regulates the light sources  204 - 208 ,  212 - 216 . That is, during an “operational mode”, the control system  402  receives data from the color sensor  224  and characterizes the target  202  as already described with respect to the apparatus  200 . However, the control system  402  is also capable of entering a “calibration mode”. In its calibration mode, a target having known characteristics is illuminated by the light sources  204 - 208 ,  212 - 216 , and the data  228  received from the color sensor  224  is analyzed by the control system  402  to determine whether it 1) corresponds to defined calibration values, or 2) is within defined calibration ranges. If not, the control system  402  adjusts the drive signals of the light sources  204 - 208 ,  212 - 216  so as to regulate the light emitted thereby. As shown, the control system  402  may provide control signals to separate driver circuits  404 ,  406 . Alternately, the driver circuits may be included within the control system  402 . By way of example, the drive signals may be pulse width modulated, and regulation of the drive signals may comprise changing their pulse width modulation.  
         [0025]     If the apparatus  400  comprises light sources  204 - 208 ,  212 - 216  of different colors, as well as a color sensor  224 , the control system  402  may regulate the drive signals of each differently-colored light source individually, thereby regulating both the intensity and color of light that is emitted by the light sources  204 - 208 ,  212 - 216 . However, if the apparatus  400  were alternately provided with only a single light source, or a plurality of light sources of one color, the control system  402  would still be useful, but only to regulate the intensity of the light emitted by the light source(s).  
         [0026]     Similarly to the control values used to characterize a target, the desired calibration values used by the control system  402  may be fixed or programmable, and may be internally stored by the control system  402 , or obtained via an interface  230 .  
         [0027]     In one embodiment, the calibration mode is entered upon action by a machine operator. In another embodiment, the calibration may be automatically initiated by a machine (including, for example, the control system  402 ). In either case, a target having known characteristics should be illuminated during the calibration mode. Referring to  FIG. 4 , and by way of example, the target having known characteristics may take the form of a “yarn standard”, or a surface of the feed system from which light can be reflected in a known manner (e.g., a reflective calibration target).  
         [0028]     Preferably, the calibration mode of the control system  402  is entered before first use of the apparatus  400 , and then periodically thereafter.