Color measurement of angularly color variant textiles

#Cross-reference and incorporation by reference is made to the following additional copending, commonly assigned, and commonly owned at the time of their Invention U.S. patent applications and patents: appln. Ser. No. 09/862,247 filed May 22, 2001 by Jagdish C. Tandon and Lalit (then Lingappa) K. Mestha appln. Ser. No. 09/867,042 filed May 22, 2001 by Jagdish C. Tandon, Lalit K. Mestha and Fred F. Hubble, III, now allowed appln. Ser. No. 09/535,007, filed Mar. 23, 2000, by Fred F. Hubble, III, and Joel A. Kubby, now U.S. Pat. No. 6,384,918 issued May 7, 2002 and U.S. Pat. No. 6,351,308 issued Feb. 26, 2002 from allowed appin. Ser. No. 09/448,987 filed Nov. 24, 1999 by Lalit K. Mestha.

#There is provided an improvement in the color measurements of irregular surfaces, especially textiles, especially including, but not limited to, the testing and/or on-line control of color dying or other manufacturing operations for textiles. The disclosed method is especially suitable for improved yet low cost color measurements for any textiles which can change their apparent or observed color depending on the viewing or illumination angle of the area of the textile being tested. The disclosed improved color measurement system may thus be used with woven silk, polyester or other woven textiles with particular color measurement difficulties, but may also be used for color measurement of other textiles, such as carpeting and other non-woven textiles, and even threads or yarns of or for textiles.

#Specifically, a desirable system for color measurements of textiles is provided that can be used easily, quickly, and uncritically in terms of the handling, positioning and orientation of the material to be tested, yet provide accurate and consistent color measurements, at relatively low cost.

#Various of the above-mentioned and further features and advantages will be more apparent from the specific exemplary apparatus and its operation described in the examples below. The following is a description of a specific embodiment, including the drawing figures (approximately to scale, except for schematics) wherein:

#FIG. 1 is a top view of one example or embodiment of a spectrophotometer which may be used with one example of the subject method;

#FIG. 2 is a cross-sectional view taken along the line 2—2 of the spectrophotometer of FIG. 1 shown measuring the color of a test patch of an irregular surface color textile web segment, moving in this example in an exemplary path relative to the spectrophotometer;

#We will now refer in further detail to the specific exemplary embodiment of a color sensing system 10 with a spectrophotometer embodiment 12 as shown in the above-described Figures, for testing color test areas. The azmuthal insensitivity features of this spectrophotometer 12 embodiment are shown and described herein combined with displacement insensitivity features thereof which are also the subject of said above cross-referenced copending commonly owned U.S. appln. Ser. No. 09/535,007 filed Mar. 23, 2000, by the same Fred F. Hubble, III and Joel A. Kubby, now U.S. Pat. No. 6,384,918 issued May 7, 2002. The principles of those displacement insensitivity features will be re-explained below in relation with the different spectrophotometer 12 here.

#As noted in said copending application, it is desirable to reduce variations in the spectrophotometer output with variations in the target displacement distance. However, achieving improvement in either or both displacement insensitivity and azmuthal insensitivity is complicated when it is desired to measure reflectivity from a test area illuminated at 45 degrees relative thereto.

#Although not essential, it is normally desirable to be compatible with industry standards set forth by the CIE, ASTM, and others, in which the test patch illumination for color measurement should be at 45 degrees to the surface of the media on which the color test patch is printed. Also for these standards the color test patch measurement should be performed using flux diffusely scattered from the (so-illuminated) test patch at 90 degrees (perpendicular) to that color test patch surface. A significant challenge in implementing a spectrophotometer to that standard is the repeatable collection of the reflected flux, as the amount of flux collected is proportional to the solid angle subtended by the entrance pupil of the flux collection optics. However, it has been found that these standards can be met by the different architecture spectrophotometer 12 here, which instead illuminates the test surface at 90 degrees, and makes the color measurements of reflected light at 45 degrees to that illuminated test surface.