JP2003004535A - Measurement of change in color according to viewing angle in textile and other surfaces - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of measuring color of a material having an irregular surface which exhibits different color intensity depending on the viewing angle. SOLUTION: A sampling area of the irregular surface material is illuminated approximately perpendicularly thereto, and the color reflected from the area is measured at a predetermined angle, preferably 45 deg.. The measurement is conducted with a plurality of individual photodetectors 14 arranged spaced apart circularly around the illuminated sampling area of the material 30 having an irregular surface to receive reflected illumination from substantially opposite directions and at a predetermined angle to the illuminated area. A more accurate and low-cost color measuring system is thereby provided for textiles. This system can be used easily, quickly, and handling, positioning, and orientation of the textiles to be tested has no significance.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION Testing and / or testing of irregular surfaces, especially textiles, especially dyeing or other manufacturing processes of textiles.
Or there are (but not limited to) improvements in online control. The disclosed method is particularly suitable for improved, low cost color measurements on fabrics where the appearance or observed color of the region of the fabric under test may change depending on the angle of observation or illumination. Accordingly, the improved color measurement system disclosed is not limited to woven silk, polyester, or other wovens that are particularly difficult to measure color, as well as fabrics such as carpets and other non-woven fabrics, and sutures and yarns for fabrics. May also be used for color measurement.

In particular, the desired system for making color measurements on textiles is easy and fast to use, the handling, position and orientation of the material under test are not important, and at a relatively low cost. Accurate and uniform color measurement can be performed.

[0003]

The principles of operation of the improved spectrophotometer color sensing arrangement of the embodiments disclosed herein provide an unexpectedly improved method of accurately measuring fabric color. Here, the woven fabric includes a dense woven fabric, a carpet, and the like, and particularly includes a product having a surface sensitive to an angle of irradiation or reflection. The color of these cloths and the surface that reflects light unevenly can be measured more accurately if the insensitivity to the color target direction angle and displacement is broader. This is due to, for example, the greatly improved color measurement reproducibility and the (t
(extended) textile sample, or reduction of azimuthal variation with respect to the textile sample that rotates during the test.

[0004]

In the actual testing of rough-textured textile samples, 0-45 degree illumination and displacement-insensitive optics and six light-averaging reflected lights are arranged. By using a spectrophotometer detector having a detection arrangement with a detector, color reflection measurements can be reproduced in less than 1 delta E in measurements made while rotating the fabric sample.

The output reproducibility of the exemplary color measuring system was high even in the testing of colored yarns. Therefore,
The exemplary system is also beneficial for knit and woven fabric designs made of different colors of yarn. When it is desired or necessary to use a specific color of thread for a design, the textile designer can more accurately measure the actual thread color in advance and determine what color the cloth will look like when woven. You can predict exactly what will happen. According to such an improved work flow, a high quality product can be produced even if the production time is reduced.

Further, the color signal measured for the weaving yarn and / or the woven fabric can be input to the computer and displayed on the display. This would be particularly useful when designing on a computer by incorporating the measured color of a textile sample. Also, existing software can be used to move and align color areas on the screen (adjacent colors affect human color perception, as is well known).

The disclosed method of color measurement can make cost-effective improvements in a wide variety of other textile / fashion retail markets and / or graphic arts as well as textile manufacturing processes. Other possibilities include dyeing carpets, dyeing fashion accessories (such as knitwear and yarns), leather dyeing, color matching and color adjustment of plastic coatings.

The disclosed method can be used online in the manufacture of textiles as part of a direct feedback color control and color correction system. Alternatively, it may be used on a fabric sample off-line to perform a quality control test, either normal or optional. The disclosed low cost textile color measurement system can be used in many different color calibration or correction systems. It can also be used and integrated in color calibration or correction of various online color controls or color processing systems.

As an example of a particularly long-term commercial need, it is desirable to provide fabric dyers with a color-matching solution, in order to maintain a uniform color, especially in different "dye lots" or batches. is there. Maintaining color uniformity is still difficult for current dyers. The properties of the materials and dyes supplied and the processing conditions of the environment continue to change slightly. Also, the mixing of dyes is becoming more complex. Because of these factors of change,
Dyeers face great difficulties in producing accurate and reproducible colors and need better color measurement systems.

Controlling metamerism such that samples that look the same under one illumination appear different under another is another important element in the dye and textile industry. This exemplary system can quickly measure the color of the same test target area at different wavelengths,
From this, spectra of different reflectivities can be generated and detected that can provide accurate and extensive spectrum reconstruction algorithms.

In particular, the disclosed system provides a variety of colors that are tilted, curved, non-planar, or have varying angular orientations with respect to the optical measurement system device (the improved spectrophotometer in this example). Provides improved measurement accuracy in color measurement of test surfaces. This is particularly desirable to improve the accuracy of non-contact spectrophotometers. A non-contact type spectrophotometer can measure the color or color density of a test surface away from the photometer, or a moving colored object, a thin metal plate, a substance, or the like. There is no need to hold it against the reference plane or spectrophotometer. Thus, the ability of the test material to freely move in and out of the spectrophotometer at various intervals is desirable in a variety of color measurement applications.

Furthermore, a color measuring system which allows freedom of angular or rotational movement of the test substance or medium is further provided
It also allows the color test surface to change the angular alignment to the spectrophotometer. The disclosed spectrophotometer embodiments and measurement systems can significantly reduce the measurement and output signal errors caused by such changes in the angular alignment, as desired. This involves significantly reducing measurement variations caused by differences in the reflectivity of the media due to differences in the orientation angle or rotational orientation of the media (such as caused by differences in the orientation of the yarns or fibers relative to the measuring device).

In the particular embodiment of the spectrophotometer described below, a plurality of differently colored LEDs are used to sequentially illuminate a color test target surface vertically (without elevation) in a generally parallel fashion, and the test surface ( Form a generally circular common irradiation area (rather than an ellipse). In other words, since all LEDs are arranged in the center, the irradiation pattern on the test surface is about 9
It is formed by light that strikes at 0 degrees, that is, vertically. Thus, if the test surface is 90 degrees with respect to this light, a circular or substantially circular irradiation pattern is formed in the selected area on the test surface. Further, the photosensor may be optically oriented with respect to the test target at an elevation angle of 45 degrees to receive reflected light from the illuminated test surface. As will be explained further below, the circular LED illumination pattern is slightly elliptical even if the color test surface deviates from 90 degrees, and the area does not change much. Therefore, the reflected illuminance on the test surface does not fluctuate much, and the output signal of the optical sensor also fluctuates little. This can provide an improved spectrophotometer that is less sensitive to angles.

As a further feature of the improved spectrophotometer in the disclosed embodiment, the target is obtained by averaging the outputs of a plurality of photodetectors that obliquely observe the target irradiation area from different positions on the opposite side. Averaging the variation in the angle and / or azimuthal reflectivity of the area further reduces the sensitivity of the spectrophotometer to changes in the placement of the test surface.

The exemplary spectrophotometer of this embodiment described herein may be (but is not limited to) be part of an automatic online continuous color correction system of a color printer. This is because such spectrophotometers can be provided at a reasonable price, for a variety of dyeing or printing processes that make non-contact (spaced) color measurements without interfering with the normal movement of the medium. It can be attached to a mass transfer or motion path. Examples of such a variety of color control systems or "colorimetry" functional systems are further disclosed in the above-referenced co-pending applications and patents and other techniques cited therein. This is expensive (and unsuitable for online use)
In contrast to a typical laboratory spectrophotometer.

Making color measurements and / or making color measurements for a variety of quality or consistency control functions has many other technologies and applications (textiles, wallpaper, plastics, paints, inks). Etc.) is also important. Therefore, the color detection system disclosed herein may be applied in various fields other than those described above for color testing these substances and objects.

As an example of a variety of other color spectrophotometer configurations or designs, Xerox US Pat. No. 5,748,2
In addition to No. 21, U.S. Pat. Nos. 5,671,059 (issued September 23, 1997) and 5,272,518 (issued December 21, 1993) by Hewlett-Packard, Accuracy Microsensor,
Inc. US Pat. Nos. 5,838,451 (issued November 17, 1998) and 5,137,364 (1).
Published August 11, 992 (both Cornelius)
J. (For McCarthy), Color S
avvy US Pat. Nos. 6,147,761 and 6,0
20,583, 5,963,333, BYK-G
Ardner US Pat. No. 5,844,680, Co
There is US Patent No. 6,157,454 to Lorimeter.

In particular, with regard to the non-contact measurement of the light reflection absorption and / or transmission of a test object, including a biological specimen, by means of a plurality of LEDs of different wavelengths arranged in a circle at a predetermined angle, US Pat. 910, 701 (October 7, 1975, GW Henderson)
Etc.)

The patents relating to the densitometer are:
53,033, 4,989,985, 5,07
Including No.8,497. Homogeneous surface emission (surface irradianc
Patents relating to providing e) are: 5,526,19
Including No. 0.

As used in the examples herein, unless specified otherwise, the term "spectrophotometer" refers to spectrophotometers, colorimeters and densitometers. Broadly included. That is, in the present specification, the term “spectrophotometer” includes
Broad definition and scope are given. Definitions and uses of such technical terms differ among various scientists and engineers, but include all of them.

"Spectrophotometer", "Colorimeter", "Densitometer"
The following is a brief classification to distinguish the term. A narrower definition may be used in the technical context, but not as a limitation of the claims.

A typical "spectrophotometer" is a reflectan of an illuminated object over a number of wavelengths of light in order to cover the human-visible color spectrum or wavelength range.
ce) is measured. A typical spectrophotometer provides color information in the form of reflectance or transmission of light from a test surface at different light wavelengths (which is a composite image of a wide range of white light spectral image reflections to the human eye). While attempting to measure closer to what is visible, the spectrophotometer desirably provides distinct electronic signals corresponding to different levels of reflected light from each different illumination wavelength range or channel).

A "colorimeter" usually has three irradiation channels (red, green, blue). That is, in general, "colorimeter"
Provides these three (red, green, blue or RGB) values. This value receives the reflected light from the color test surface that is sequentially illuminated by the red, green, and blue illuminators (such as three differently colored LEDs or three lamps with three different color filters). It is read by a photosensor or photodetector. Therefore, this may be considered to be different from the “spectrophotometer” in that color information is output as a trichromatic quantity known as RGB, or a limited special case thereof.

Some kind of conversion is performed using the three primary color amounts to obtain 3
It may represent a color in the dimensional coordinate space. "Device-dependent color space" (that is, RG converted to conventional L * a * b *
Other RGB conversions to B) usually use color conversion formulas or "look-up table" systems in a known manner (reference example cited here and others, this example is given).

A "densitometer" usually has only one channel to measure the amplitude of light reflected from a test surface, such as a developed toner test patch, on a photoreceptor over a wavelength range (wide or narrow). Simply measure at a selected angle over. IR
You may use one irradiation source, such as an LED, a visible LED, or an incandescent lamp. The output of the densitometer is programmed to provide the optical density of the sample. This type of densitometer is basically "color blind". For example, a cyan test patch and a magenta test patch can, of course, exhibit different colors but have the same light density when measured with a densitometer.

A multiple LED reflectance spectrophotometer as a particular example of the disclosed embodiment may be considered a special type of spectrophotometer, which typically illuminates the target with narrow band or monochromatic light. As a type having a broadband irradiation source, there is a flash xenon lamp spectrophotometer, that is, an incandescent lamp spectrophotometer. A spectrophotometer is typically programmed with a conversion algorithm to obtain more detailed reflectance values using four or more channel measurements (eg, four or more channel measurements). This is in contrast to a standard 3-channel colorimeter (colorimeter). Standard colorimeter (colorimeter) measurements are not sufficient (only 3 measurements),
Inaccurate spectral measurements of reflectance related to the human eye cannot be made.

The preferred embodiments and features of the disclosed system may vary according to circumstances. Also, some of the disclosed features and components may be used to perform functions such as gray scale balancing and turning on two or more illumination sources at once.

This patent application describes various algorithms and mathematical techniques (eg, references) that process electronic signals from a spectrophotometer to create or update color correction tables, tone reproduction curves, or other color controls. (See some of the above), and need not be further described here, as they are not intended to be limited to or by any particular one of them.

A wide variety of possible color correction systems can use the output signal of the spectrophotometer with a variety of improved feedback, correction and configuration systems. These specific concepts and embodiments have been described in many other patents (including the patents disclosed herein) and publications, and need not be discussed at length here.

[0030]

A particular feature of certain embodiments disclosed herein is that it more accurately determines the color of materials with irregular surfaces, including fabrics that appear to be different colors depending on the viewing angle. Provide a way to measure. In this method, a sample region of the substance having an irregular surface is irradiated substantially vertically, and the irradiation reflected from the sample region irradiated with the sample regions arranged at intervals around the sample region is substantially opposite to each other. A plurality of separate photodetectors that receive from the sample area of the substance at a predetermined angle measure the color reflected by the sample area of the substance at a predetermined angle to the sample area of the substance.

Further features disclosed singly or in combination disclosed herein include: The predetermined angle is about 45 degrees. And / or the irradiation of the sample area of the material having the irregular surface comprises a plurality of rapid and continuous irradiations with different spectral irradiations.
And the material is a textile material that moves relative to the plurality of individual photodetectors. And / or the plurality of individual photodetectors are arranged relatively uniformly in a circle around the illuminated sample area of the substance. And / or each of the plurality of individual photodetectors,
It has a plurality of light sites with different spectral sensitivities. And / or the material is a textile material and the textile material is a carpet. And / or the material having irregular surfaces is a textile material and the textile material is a woven material. And / or irradiating a material having an irregular surface to it in a substantially perpendicular region, spaced apart around the sample region and reflecting the reflected light to the sample region from substantially opposite directions More accurate color of a substance by measuring the color reflected by the sample region of the substance at a predetermined angle with respect to the sample region of the substance by a plurality of separate photodetectors receiving at a predetermined angle to the sample region It is a method of measuring.
And / or a method of accurately detecting the color of a substance exhibiting different degrees of color depending on the viewing angle, which comprises irradiating a sample area of the surface substance and reflecting the irradiation from the substance to be irradiated. A color of light reflected from the irradiated substance is detected by a photodetector arranged around the irradiated substance so as to receive light at an angle with respect to the sample region of the substance from opposite directions. Is a method of measuring.

[0032]

DETAILED DESCRIPTION OF THE INVENTION A spectrophotometer 12 as shown in the drawings.
And color detection system 10 for testing a color test area
Specific exemplary embodiments of the will be described in detail. First figure
Please refer to FIGS. The directional angle insensitive feature of this embodiment of the spectrophotometer 12 is shown and will be described in combination with the displacement insensitive feature of this photometer. Displacement-insensitive characteristics are also attributed to U.S. patent application Ser. No. 09 / 535,007 (filed Mar. 23, 2000;
Fred F. Hubble III, Joel A .;
Kubby) is also the subject. The principle of these displacement-insensitive features is related to different spectrophotometers 12,
It will be described below again.

As explained in the above-mentioned co-pending application, it is desirable to reduce variations in the output of the spectrophotometer, including variations in the displacement distance of the target. However, where it is desired to measure the reflected light from a test area illuminated at 45 degrees, the improvement to make it insensitive to displacement and / or azimuth is complicated.

It is not necessary, but usually preferred, to comply with industry standards set by CIE, ASTM, etc.
According to these criteria, test patch irradiation for color measurement must be done at 45 degrees to the surface of the medium on which the color test patch is printed. The color test patch is measured at 90 degrees (perpendicular) to the plane of the color test patch using the diffusely scattered light flux from the test patch (illuminated so that the light is diffusely scattered). Must be done.
However, when a spectrophotometer is realized so as to satisfy this standard, repeated collection of reflected light is a major obstacle. The amount of this converged light is proportional to the solid angle facing the entrance pupil of the converging optical system. However, such a standard can also be satisfied by a spectrophotometer 12 having a structure different from the above, such that the test surface is illuminated at 90 degrees and the reflected light is color-measured at 45 degrees with respect to the illuminated test surface. I understood.

As described above, the conventional spectrophotometer, colorimeter, and densitometer must hold the target to be measured at a predetermined fixed position during measurement. This is usually done by pressing the target material physically flat against a reference surface that is mounted on or held adjacent to the sensing head of the device.
This limits or limits many of the desired color measurement opportunities. This does not require the system disclosed herein.

When the displacement between the color sensor and the medium to be detected changes, the amount of light that converges changes correspondingly according to the following equation.

[Equation 1] Where Ω = solid angle facing the projection optics, A = area of projection entrance pupil, r = displacement between test patch and entrance pupil,
Is.

When the displacement changes, the amount of light that converges also changes.
However, this variation is indistinguishable from the variation in patch density in the electrical signal output, and if this variation remains uncompensated, an error occurs in the measured density.

One way to solve this is to provide an additional device in the paper path to mechanically restrain the medium in the measuring groove. However, as mentioned above, this is highly undesirable. This is because the costs associated with the additional elements increase and paper jams are more likely to occur due to the narrowing of some of the paper path.

The solution disclosed herein, in lieu of providing an additional device, is a new spectrophotometer 1 that is relatively insensitive to relative displacements with respect to the color target medium being measured.
2 is to be provided. This method is much more desirable. This is because if interference with the medium is minimized, structural variability is allowed in the arrangement of the sensors, and if done accurately, the sensor UMC (unit manufacturing cost) should be slightly increased. The spectrophotometer 12 provided here delivers an output that is relatively insensitive to displacement from the surface of the medium to be inspected, yet is compact and relatively inexpensive.

In other words, the spectrophotometer 1 shown in FIG.
2 the selected series of light sources D1, D2, D3, D4
The light flux from (the light source being irradiated at that time) is collimated by the common condenser lens 13 (with the IR filter 13A), and the print medium 30 (here, nonuniform (relative to position or angle) is relatively unconstrained). The test patch 31 on the fabric piece) is irradiated. An inverted image of the illuminated area is detected by the projection (target) optical system 18 and the detector 12
It is formed on the plane (14 in FIG. 2). The reverse image is then maximally exposed in the area of the detector. When the magnification of the target optical systems 18 and 19 is set to about 1: 1, the energy density in the image detected by the detector is primarily the object-sensor displacement smaller than the total conjugate. It was found that it does not change even if the distance between the medium and the sensor head changes. This will be explained below.

That is, the light energy reflected by the test patch 31 and converged by the lenses 18, 19 is proportional to the solid angle facing the projection lens. Mathematically speaking, when the displacement r (not shown) between the medium and the optical system changes, the total energy in the image changes with the solid angle. This is proportional to r ^ (-2). Further, even if the distance between the medium and the sensor is changed, the size of the image is influenced so as to compensate for the change. In an image processing optical system with a magnification of 1: 1 the magnification changes as the reciprocal of the object displacement r ^ (-1), which causes a change in the image area proportional to r ^ (-2). Therefore, the image energy density, that is, the energy per unit area, does not change even if the displacement changes. Also, because the detector samples a fixed area in the image, its output remains unchanged over distance.

In other words, if a condenser lens for a photosensitive detector with a 1: 1 magnification is used, the fixed exposure area of the photosensitive detector will not change even if the target area changes ± 3 mm or more in the distance from the fixed exposure area. Almost the same microwattage of energy per mm ^{2 is} effectively obtained from the target area. In this example, the displacement of the color printer test sheet relative to the spectrophotometer, ie, the freedom for the color printer test sheet to move within the printer paper path, without affecting the system's ability to accurately read the color of the test, is at least about ±. About 3 mm is acceptable.

Mathematically speaking, the image-object conjugate is 2f, the system magnification is 1: 1 and the image area is ~ (2f + d) for a small variation "d" in the displacement of the medium. ) ^-2, the target reflected illuminance is kept constant by the collimating action of the condenser lens, and the total energy in the image is ~ (2F + d) ^-2, the image energy density (image energy / image area) Does not depend on "d" for a magnification of 1: 1.
Therefore, a magnification of 1: 1 is the optimum operating point in the detector optics.

However, even though 1: 1 is preferable, 0.
It is believed that the range 9: 1 to 1.1: 1, or approximately 1: 1 (although somewhat less accurate) may be used in some situations. The magnification of the lens 13 (the lens with respect to the fixed area of the light receiving portion of the optical sensor D12) is “substantially” 1: 1 means here that the optical intensity of the optical sensor, and thus the output signal thereof, is about 1: 1. This means that for a finite range, primary accuracy is obtained. Within this range, the accuracy of the above-described primary color reflectance measurement still allows a variation of ± about 2.5-3 mm with respect to the distance between the target and the spectrophotometer 12. Therefore, a normal distance at that point between the defined or restricted baffles disposed opposite the paper path is about 6 mm or more.

Therefore, in this lens system that transmits the reflection from the test patch to the photodetector, the electrical signal output from the photodetection sensor is not affected by a variation of at least 6 mm in the displacement between the test patch and the spectrophotometer. You can effectively be less sensitive. This allows a corresponding amount of freedom for lateral displacement (and spacing between opposing baffles). Additionally / or, winding or wrinkling of the test area surface may be acceptable. Therefore, pressing the test substance against the reference surface or the spectrophotometer,
There is no need to restrain in this vicinity.

A suitable exemplary focal length for the photosensor lens systems 18, 19 may be about 11 mm. This appears to be a good balance between the amount of light energy desired to be collected at the sensor and the insensitivity to displacement in a moderately sized spectrophotometer package.
Lenses of different focal lengths may be used, but to be similarly insensitive to displacement, the overall conjugation (distance between test patch and its image) will change accordingly.

This concept can be implemented using a variety of technologies, including hybrid chip-on-board or conventional components. This is particularly suitable when providing a single on-board chip or board for a multiple LED spectrophotometer as shown. In this configuration, LED dies with different wavelengths that cover the visible spectrum may be appropriately selected and mounted on the PWB. Also, each LED may sequentially emit light, as further described with reference to the example circuit of FIG.

The luminous flux from each LED is collimated and directed toward the center to irradiate the same test patch area under the central portion of the spectrophotometer 12. As shown in FIG. 1, this position is on the optical axis of the lens 13, and the lens 13 is located at the center of the LED ring or ring. Recording the continuous output of the detector while continuously illuminating the test patch with each LED allows the reflectance of the test patch as a function of different wavelengths to be detected. A sufficient number of different LEDs
The output wavelength can be used to extrapolate or interpolate the reflectance of the same test patch as a function of different wavelengths throughout the visible spectrum.

An exemplary test measurement time for spectrophotometer 12 is only about 2-5 seconds or less. At this speed, the test medium can be measured in real time as it passes across the sensing area of the spectrophotometer 12 and interference with normal medium fabrication and output can be prevented.

Referring now to the subject azimuth insensitive feature, in the configuration of the conventional spectrophotometer embodiment shown in the above-referenced cross-referenced application, the optical sensor (detector) is a spectrophotometer. It is installed on the central axis or zero axis of the
45 degrees relative to the test target by a plurality of LEDs spaced apart around the central axis.
In degrees, you receive this reflection.

On the other hand, the spectrophotometer 1 shown in FIG. 1 and FIG.
In the second configuration, a plurality of light emitting LEDs of different colors are combined into one central unit, board or chip, and the test target (for example, on a moving sheet) is parallel to the central axis or the optical axis of the spectrophotometer. 9 color patch)
Irradiate at 0 degrees to form a substantially circular (rather than elliptical) irradiation area on the test target. The optical sensor is optically oriented at 45 degrees with respect to the test target and receives the reflected light from the test target. 45-
It was found that by changing from the 0 degree system to the 0-45 degree system, the measurement error due to the alignment error of the test target with respect to the spectrophotometer can be greatly reduced. That is, it addresses large variations in the angle of the test surface with respect to the central axis of the spectrophotometer, which can vary for a variety of reasons.

By placing all the LEDs in the center, the test target is approximately 90 degrees (perpendicular to the target).
The irradiation area on the test target may be formed by the light irradiated in step (1). Thereby, if the target surface is 90 degrees as intended, a circular or substantially circular irradiation pattern is formed in the selected region on the target. Even if the target surface deviates from 90 degrees due to winding, twisting, sensor mounting error, etc., this LED irradiation pattern is only slightly elliptical, and its area is 1 / cos (theta).
It becomes larger than the circle by the coefficient of. In this case theta is the deviation from 90 degrees. For example, if the incident angle is 93 degrees, theta is 3 degrees, and the irradiation area is A / cos (3) = 1.
It will be 001A. Here, A is the selected irradiation area. The luminous flux reflected by the target and collected by the detector is proportional to the reflected illuminance. In this example of 3 degrees, the irradiance (energy per unit area) does not change much (only a change of 0.001), and similarly, the signal from the detector does not change much either.

In FIG. 2, the luminous flux from each LED is condensed by the same condenser lens 13 and the test patch surface is irradiated at 90 degrees, that is, at a right angle, to form an irradiation area. An inverted image of this illuminated area is formed in the focal plane of each of the projection lenses 18, 19 (providing the desired 1: 1 image optics). Here, this inverted image is maximally exposed to the respective optical detector.

Other than the above effect of the above-described configuration in which the LEDs are arranged in the center, all the LEDs (not one per one)
One condensing lens can be used for each; the temperature and / or output of all LEDs can be easily and accurately measured with one integrated circuit located in the vicinity; configuration is realized at low cost You can, etc.

An important disclosed feature in improving the measurement accuracy of a spectrophotometer for various angles of the target, or for various relative rotations of the target, such as a fabric, which has different apparent reflections at different angles, is the important feature disclosed in FIG. As shown in, by averaging the outputs of multiple photodetectors that observe it from different positions around the irradiation area, by averaging the various directional angle reflectivities of the target area (azimuthal reflectivity),
It is to further increase the insensitivity to the angular alignment error of the target area. In the example of the target surface inclined by 3 degrees described above, the photodetector on one side of the central axis of the spectrophotometer observes the irradiation target area at (45-3) degrees, and the other photodetector (45+). 3) Degree observations (or vice versa),
As shown in FIG. 3, by summing these output signals, the output signals may be averaged to cancel the effect.

In the embodiment of FIGS. 1 and 2, an example of four equally spaced photosensor 14 sites is arranged at 90 degrees around the central axis of the LED, eg at 60 degree intervals. The six LEDs may be arranged apart from each other. Also,
Even with a configuration in which only three spectrophotometers are arranged at intervals of 120 degrees around the central axis (thus, only four lenses are required for the spectrophotometer), such azimuth variation The measurement error due to can be reduced to less than 1%.

As shown in FIG. 4, as an alternative to the conventional single-cell photodetector, each of the plurality of photodetectors provided at intervals is a low-cost single-chip photodetector as described below. It may be a pixel multi-color photodetector. This spectrophotometer may have a reduced number of LEDs, but this is not critical, and even with only three conventional individual cell photodetectors, the spectrophotometer disclosed herein may be used. By L
The number of EDs is from 10, 12, or 24,
Full color measurement can be performed by reducing the number to only eight. However, as will be explained next, by using a multi-color multi-optical site detector optically, only three or four different L
The ED may be used to increase measurement speed and / or spectral coverage.

According to this additional optional feature, the spectrophotometer 12 embodiment provides a reduced number (up to only three or four) LEs that output spectra of suitable different colors.
D can sequentially illuminate the exemplary color test target. Further, in this spectrophotometer 12, the detection of the reflected irradiation level is not performed by one light cell or individual light cells, but the multi-spectrum which constitutes the low-cost color image sensor array chip 14 as shown in the example of FIG. Simultaneous detection by reaction photo site. This includes a plurality of adjacently arranged color sensor rows (optical sites D12F, D12E, D12) comprising a plurality of different integrated color filters (none, blue, green, red).
C, D12D), exhibiting different spectral responsiveness and outputting multiple output signals in parallel from the LED illumination reflected on the test target area, rather than outputting one output signal from each individual photosensor. Output to. The LEDs D1, D2, D3, D4 of different color outputs are turned on in a predetermined order (shown in FIG. 3, etc.) to provide a number of specific different spectral measurements within the visible wavelength as shown in FIGS. You may. It is preferred that one LED provides white illumination, which allows normal color detection to be performed quickly and at low cost.

If desired, these spectral measurements in the test target area may be transformed to provide a true broad reflectance spectrum. This can be done with well-known or other reconstruction and extrapolation algorithms. The number and spectrum of LED illuminators and photosensor sites may be varied as appropriate and need not be limited to the particular numbers and wavelengths shown in this particular embodiment.

In the present specification, the terms "photosensor site", "photosite", "photosensitive cell", "cell", "detector" (D) or "sensor" are variably interchangeable unless otherwise stated. Used interchangeably. This is the same as the conventional example.

A commercial mass-produced low-cost document image bar is usually formed by combining a plurality of individual image chips and arranging them closely. Each chip has a large number of small light sites closely spaced. An example of such a chip 14 is enlarged and a part thereof is schematically shown in FIG. Typically, such a chip 14 would have three rows of optical sites (D12) manufactured to each have a red, green, and blue integrated filter.
D, D12C, D12E) and integrated sample and hold circuits and the like. The spectrophotometer 12 optionally utilizes at least one (one or more depending on spectrophotometer design) of such low cost image chips 14. Here, it is recommended that the chip 14 be obtained as a single unit from the manufacturer before the chips are integrated and integrated as a document image forming bar.

As an example of a well-known document image bar, this may be made using 20 image chips 14 each 16 mm long. Each chip can read 400x660 pixels,
248 photosensitive cells are provided with an intercell pitch of 63.5 micrometers. These cells form three parallel rows with red, green and blue filters in each row. An example of this is shown in FIG. These chips are formed with integrated electrical leads to connect already installed electrical equipment to all 248 optical sites.

If desired, as shown in the example of FIG.
In addition to these, such an optical site D12F may be added to these chips to detect white (broad spectrum). This can be achieved by changing the manufacturing process relatively easily. That is, in the same silicon semiconductor manufacturing step (or other), another parallel cell row is simply added, and the same cell row as the other cell rows except that the color filter layer is not provided on the cell. Or provide a similar optical site. Alternatively, a different filter may be overlaid on the thus added fourth optical site row, and such a chip 14 may be made from the existing three rows of cells. That is, no filter may be provided for every four cells in each column, or different filters may be provided. Further, if desired, the cell without a filter may be provided with a diaphragm (the exposure area is reduced by partially masking).

Such a suitable image sensor chip or a modification such as the one described above would be of low cost compared to non-commercial photosensors and would allow a very high level of circuit integration. Therefore, rather than using individual photosensors,
When such an image sensor chip is used, a more cost-effective spectrophotometer can be manufactured, and a large number of parallel detection outputs can be output from each.

As mentioned above, the exemplary color image sensor chip 14 has a color image sensor array optical site (D12).
F) is somewhat different from conventional document color image sensor arrays or bars in that it has no cover and no color filter layer. In this way, the chip makes a fourth broadband spectral measurement from these unfiltered optical sites, in addition to the three different spectral measurements provided by the colored filter optical sites D12E, D12C, D12D of the three different colors. be able to. As mentioned above, commercially available color image sensor array chips typically have three rows of photosites covered with different three color (red, green, blue) color filter layers, thus providing a spectrum of three colors. Because of its measurable performance, these same sensor array chips are simply modified at low cost to add an additional 4
The performance of making the second spectrum measurement can be realized. That is, some of the light sites are modified so that no color filter is provided. A broad spectrum illumination source such as a white light LED may be used with it in a spectrophotometer configuration.
This will be explained further below.

As shown, a relatively small number of LEDs and multiple light sites that are exposed at the same time and these LEDs are
The spectrophotometer 12 used in combination with an appropriate LED switch to turn on and off in sequence allows for rapid measurement of multiple test target colors. The greater the number of measurements, the more accurate the color measurement performance.

Different numbers of LEDs may be used depending on the needs of a particular color correction or color calibration system. But,
Due to the small number of LEDs with spectral output covering the sensing areas of only two or more different types of light sites and the white LED or other light source, the overall component count is low and therefore the cost is relatively low. It has been found that a spectrophotometer can be realized that can measure a large number of spectra.

This can be further understood by reference to the exemplary spectral curves shown in FIGS. 5-10 and the above description in connection with these figures. 5-10, an exemplary LED is shown.
For each of the curves corresponding to
2, the same reference number as D4 or D5.

As mentioned above, FIG. 4 is a schematic, enlarged view of a portion of an exemplary color image sensor array chip 14 that may be used in an exemplary spectrophotometer. The figure shows an exemplary illuminated area 34 of this tip 14. This area 34 is illuminated by the LED illumination through the lens 13. This illumination is reflected at the test target area and passes through the lens system 18, 19 to simultaneously illuminate multiple optical sites in three or four rows of each sensor chip 14. These simultaneously illuminated light sites include red, green, and blue light sites D12D, D12C, D12E and, if the unfiltered light site D12F is provided on the chip 14.

The table below shows the number of spectral measurements that can be performed with different example combinations of different numbers of specific LEDs and image sensor chips 14 with different optical site filters.

[Table 1]

As can be seen from the last example of this table, using four color image sensor chips 14 (red, green, and blue filtered light sites plus unfiltered light sites) yields only four LEDs ( White, 595 nm peak, 505 nm peak, 430 nm peak) color test target 31
By detecting the irradiation of 4, 3, 3, 2 (total 12)
A set of spectral measurements can be made. In other words, only 4 LEDs and 1 low-cost multi-pixel (multi-light site)
A spectrophotometer with an image sensor array (chip) 14 can be used to interrogate 12 spectral combinations.

The integration times used for the various rows of the chip 14 of the image sensor array are individually controlled and L
An appropriate output signal can be obtained from the sensor array by matching the power levels of the EDs.

As described above, some of the optical sites of one or more rows among these plural rows are left uncovered (no color filter), and the others are conventional.
It is desired to obtain four spectral outputs from the image sensor array of the array. To compensate for this, optical sites that are not covered by color filters typically output much larger signals, so to compensate for this, some of the sensing area of these uncovered (unfiltered) optical sites is manufactured. Optically covered with multiple layers of opaque material or tri-color filter layers to slow down photoreaction.

Of course, any or all outputs of sensor chip 14 may be calibrated / reconfigured to obtain a true reflectance value.

As a result, a spectrophotometer that combines the spectral discrimination performance of the low-cost multispectral image sensor 14 with the spectral output from a relatively small number of different LEDs is a cost-effective and high-performance spectrophotometer. Would look like Such a spectrophotometer may have the effects described below and / or other effects. That is, multiple measurements can be made in response to three or four different parallel outputs from the color image sensor and the outputs can be sent in parallel. Costs can be reduced by reducing the number of LEDs and reducing the cost of detectors and detection electronics. The integration time of 3 or 4 rows of a 3 or 4 row image sensor can be individually adjusted to match the power levels of different LEDs.

With reference to the first row of the above table, the alternative application, function, option is to turn on only the white illumination source for all color test patches currently being read and keep that state. And to implement the "colorimeter" function of the RGN value from the output of the chip 14.

Next, as described above, see above, while describing the exemplary operation of the exemplary color detection system 10 using the exemplary spectrophotometer 12 (with or without chip 14). Certain embodiments are described in the examples and in the cross-reference application above.

In the illustrated example, the spectrophotometer 12 is used in conjunction with the circuit shown in FIG. 3 etc. to provide one or more moving or stationary color test materials such as the moving knitted fabric 30 shown in FIG. The reflected light from different color test areas (31, etc.) may be accurately read.

As described, the disclosed spectrophotometer 12
The color of the test patch 31 can be accurately read even if the test medium 30 moves while changing the distance or angle from the spectrophotometer 12 during color measurement. Therefore,
This color measurement is not affected by normal variations in surface position. Therefore, the spectrophotometer 12 is provided with a normal printed sheet output path 40 (such as 40 in FIG. 2) for various color reproduction systems.
Can be simply attached to one side.

The spectrophotometer output signal may be input to the online color detection and color correction system 10. Here, the system 10 is a microprocessor controller 10
0 and / or interaction circuits and / or software. When the controller 100 supplies a control signal or an actuation signal to the spectrophotometer 12, the spectrophotometer 12
Can sequentially test or read each color of each selected test patch 31 of the test medium 30 as it passes through the spectrophotometer 12 provided in the output path 40.

This alternative requires removal of the test cloth or patch, holding it stationary, or moving a standard contrast colorimeter or spectrophotometer over the test cloth or patch. This is in contrast to the traditional system, which must be done.

A calibration target area for the spectrophotometer may further be provided. This area is a standard test tile or test surface of white, gray, black and / or any other color (such as the facing surface 47 of FIG. 2) and is used by the spectrophotometer 12
, Can be manually (or automatically by a solenoid) inserted into the effective field of view in the absence of test media. An individual calibration for each of the spectral energy outputs of the spectrophotometer's LEDs is provided by a standard white (or other) whose reflectance is known so that the spectrophotometer converts each LED's measurement into an absolute reflectance value. ) You may use a tile test target. This calibration can be done automatically without removing the spectrophotometer. Integrated PRM IC shipped with spectrophotometer initial calibration data
May be stored in. Alternatively, the LED output initial calibration data can be loaded into software used for spectrophotometer output analysis in other known ways, such as loading it into the disk storage or programmable memory of the printer controller 100 or system print server, May be programmed.

When the test target is illuminated by any one LED, various levels of light are obtained as reflected light from the test target depending on the color of the test patch and the selected irradiation source. The dotted line in FIG. 2 indicates the irradiation of the target area by the LED and the light rays in which a part of the light reflected from this irradiation portion is focused through the lenses 18 and 19 (in this example, a simple two-element optical system). Show.

The spectrophotometer 12 of FIGS. 1 and 2 shows a conventional glass or plastic lens, but it will be understood that an optical fiber or a selfoc lens can be used. For example, you may perform irradiation from LED using an optical fiber. Also, if desired, a collection optical fiber may be used to position the detection light sensor away from the focal plane of the lens.

As utilized in the embodiments of the online color detection system 10 disclosed herein, this low cost spectrophotometer 12 is mounted on a colored media reproduction travel path 40 to be part of a color correction system, Well known mathematical techniques for color error correction may be used to automatically control and drive to maintain the desired color producing color accuracy. In other words, while continuously illuminating the test patch with each LED,
By recording a number of different outputs from the detector array, the reflectivity of the test patch as a function of different wavelengths can be detected, and the reflectivity of the test patch as a function of different wavelengths across the visible spectrum. Can be extrapolated or interpolated.

Thus, the accurate color control system disclosed herein can test and store current color reproductions on a regular or near constant basis for on-line color control or operation.

The photosensor of FIG. 4 provides maximum exposure as desired and is connected to avoid the effect of increasing the exposure area on the image chip 14 by increasing the distance between the target and the spectrophotometer. The circuit may be configured to ignore or limit cells that are only partially exposed (light sites). In addition, and / or the signal from the outer cells may be ignored, even if illuminated by reflected light from the target, and only the fixed minimum number of cells exposed in the center may be examined.

Due to the large number of cells of the chip 14 shown in FIG. 4 with different color filters, the connecting circuit knows which cells are exposed to which color transmitted from the illuminated test area. However, this is not essential here, and as shown in the cross-reference application and the cited document, the conventional single-cell photosensor (D12A or D12
12B) may expose (detect) only one color test patch at a time.

FIG. 3 is a schematic block diagram of an exemplary LED driving device and signal processing circuit of the spectrophotometer 12 shown in FIGS. 1 and 2. For convenience here it is part of the controller 100, but this whole or part may be a separate circuit, preferably having one driver chip or die for all the LEDs of the spectrophotometer itself.
In response to normal timing signals from the circuit 110 marked "LED drive, signal acquisition and data valid logic", each LED has its own transistor driver Q1-Q.
Pulses are sequentially given by turning on 4 for a short time. As a result, LEDs D1 to have different spectra, respectively.
D4 causes resistors R1 to R4 to be driven by the current from the common voltage source.
Is turned on via. In Figure 3, these four LEDs
Four different exemplary light outputs from are noted next to these LEDs. This sequentially drives one LED at a time, sequentially transmitting light through the condenser lens 13 shown in FIGS. 1 and 2.

It will be appreciated that although the LEDs in this example are sequentially turned on one at a time, the system is not so limited. In some measurement modes it may be desirable to turn on more than one LED or other illumination source at the same time for the same target area.

As shown on the right side of the example circuit of FIG. 3, the relative reflectance of the turned-on LEDs of each color or wavelength was measured by conventional circuitry or software (in FIG. 3, generically D12A and D12B). Amplify each signal output of the photodiode detector array of optical site 14 (shown by 11)
2) and integrate (114) and route the integrated signal information to the sample and hold stage 116. This stage 116, when opened by the enable signal input from the circuit 110, produces an output signal (here Vou
can be output). Stage 116 also outputs an accompanying "data valid" signal.

As mentioned above, the pulse rate of the corresponding LED and the sampling rate of the detector are not critical for sampling each of a number of moving appropriately sized color test patches by the spectrophotometer. , Fast enough. This is fast enough even when measuring high speed media. However, if a short pulse is given to the voltage source of the common LED driver to give a short LED drive current at a level higher than the level that can be maintained in the continuous current mode, a higher luminous flux detection signal can be obtained and the test can be performed in a shorter time. Can measure patches. In any case, the S / N ratio can be improved by integrating the signal here by the integrator 114 or the like. Those skilled in the art will appreciate that the circuit shown in FIG. 3 is merely a relatively simple and straightforward example. This circuit and its various alternative circuits can be easily realized by an onboard hybrid chip and other configurations. Since the chip 14 of FIG. 4 has built-in electronics, the circuit shown on the right side of FIG. 3 for its output may not be needed.

In addition, conventional LED emitters and detectors may be integrated or additionally mounted separately to provide black reference or timing marks printed along one side or margin of medium 30, if desired. It may detect and provide enable signals for illumination and reading within each color test patch area. These fiducial marks can be used to indicate that the adjacent or juxtaposed desired test patch 31 is then in view of the spectrophotometer 12. However, it will be appreciated that such fiducial marks may not be necessary or desirable in some media.

It is well known to use conventional different colored optical fibers for each of the target illumination sources of different colored LED spectrophotometers. In particular, such color filters may be used to eliminate secondary illumination from the LED and / or LE.
It is well known to narrow the output spectrum of D radiation sources. Such color filters can be used for this purpose, for example, in Precision Microsensors® LED-based products. However, those skilled in the art will recognize that such a color filter is unnecessary for LEDs with a sufficiently narrow bandwidth or for LEDs without secondary illumination that must be suppressed. Thus, filters may be used in the subject spectrophotometer, but are not required.

Spectrophotometers have heretofore been made using irradiation sources other than LEDs. For example, US Pat. No. 5,671,059 of Hewlett-Packard Company (September 1997)
A multi-electroluminescent (EL) emitter having a filter and an active layer, published in March 23), incandescent lamps and xenon flash lamps. Also, as mentioned in the introduction, white L (not narrow spectrum)
An ED irradiation unit, a plurality of sensors having different color filters, and the like are disclosed in EP0921381A2 (issued on Sep. 6, 1999, color sensor for inspecting colors printed on newspapers and other printed materials).

While the embodiments disclosed herein are preferred, those skilled in the art will appreciate that various alternatives, modifications, variations or improvements can be made. These are included in the claims.

[Brief description of drawings]

FIG. 1 is a top view of an example of a spectrophotometer that may be used with an example of the subject method.

2 is a cross-sectional view of the spectrophotometer of FIG. 1 taken along line 2-2, in this example of a portion of a colored fabric having irregular faces that travels an exemplary path for the spectrophotometer. It is sectional drawing which shows a mode that the color of a test patch is measured.

FIG. 3 LE of the exemplary spectrophotometer of FIGS. 1 and 2.
It is a schematic diagram of an example of the circuit which D operates.

FIG. 4 may be used in place of the conventional single optical site detector of the exemplary spectrophotometer shown in FIGS. 1 and 2,
An exemplary silicon color imaging sensor array chip having three rows of photosensor sites optically transparently filtered by red, green, and blue, respectively, in a known manner (typically available from commercially available document imaging bars). FIG. 3 is an enlarged schematic plan view showing an optical multi-photosite photodetector for detecting the spectra of these three colors, respectively;
4th of unfiltered optical sensor site for white light detection
FIG. 3 is an enlarged schematic plan view showing (selective) rows of with a circularly defined area representing an exemplary area of this sensor row chip illuminated by an LED light source and reflected at a test target.

5 illustrates four examples of the exemplary image sensor array chip of FIG. 4 for each of a no-filter sensor (solid line), a blue filter sensor (dashed line), a green filter sensor (dashed line), and a red filter sensor (dotted line). It is a figure which shows the dynamic spectral response by the graph which took the wavelength on the horizontal axis and the relative reaction on the vertical axis.

FIG. 6 is similar to FIG. 5, but with the spectral output of four different exemplary LED illumination sources (described in the table below) that may be integrally formed with the exemplary spectrophotometers of FIGS. 1 and 2.
(White LED (long dash line), 430 nm LED (thin line), 505 nm LED (square line), 595 nm LED
(Dashed-dotted line)) is a graph shown by superimposing it on the curve of FIG. 7.

7 is a white LED among four different LEDs shown in FIG.
FIG. 5 is a diagram showing a combination of reactions of all four different photosites of the photosensor chip of FIG. 4, when only the light is irradiated and sequentially exposed.

FIG. 8 shows 430 nm of four different LEDs shown in FIG.
It is a figure which shows the combination of reaction of all four different optical sites of the optical sensor chip of FIG. 4 when only LED is irradiated and it exposes sequentially.

FIG. 9 shows 505 nm of four different LEDs shown in FIG.
It is a figure which shows the combination of reaction of all four different optical sites of the optical sensor chip of FIG. 4 when only LED is irradiated and it exposes sequentially.

FIG. 10 shows 595n among four different LEDs shown in FIG.
FIG. 5 is a diagram showing a combination of reactions of all four different photo sites of the photo sensor chip of FIG. 4 when only mLEDs are irradiated and sequentially exposed.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tonya L Love             Roche, New York, United States             Star Chartwell Court 113 (72) Inventor Daniel E Robins             Willi, New York, USA             Amson Takaho Road 7120 (72) Inventor Gary W Skyiner             Roche, New York, United States             Star Menlo Place 21 F term (reference) 2G020 AA08 DA13 DA22 DA24 DA31                       DA32 DA44

Claims (13)

[Claims] 1. A method for more accurately measuring a color of a substance having an irregular surface, including a fabric which looks different in color depending on a viewing angle, comprising irradiating a sample region of the substance substantially vertically, A plurality of discrete photodetections spaced around the illuminated sample area of the substance for receiving the illumination reflected at the sample area from substantially opposite directions at an angle to the sample area. A method of measuring the color reflected by the sample area at a predetermined angle with respect to the sample area by a measuring instrument. 2. The method of claim 1, wherein the predetermined angle is about 45 degrees. 3. A method according to claim 1 or 2, wherein the irradiation of the sample area of the material with irregular surfaces comprises a plurality of irradiations in rapid succession with different spectral irradiations. 4. The method according to claim 1, wherein the irregular surfaced material is a textile material that moves relative to a plurality of individual photodetectors. 5. The plurality of individual photodetectors are arranged in a relatively uniform circular pattern around an illuminated sample area of the material having the irregular surface. The method according to any one of 1. 6. The method of claim 1, wherein each of the plurality of individual photodetectors has a plurality of photosites having a plurality of different spectral sensitivities. 7. The method according to claim 1, wherein the irregular surfaced material is a textile material and the textile material is carpet. 8. The method according to claim 1, wherein the irregular surfaced material is a woven material, and the woven material is a woven material. 9. The method according to claim 1, wherein the irregular surfaced material passes through a plurality of individual photodetectors. 10. The method according to claim 1, wherein the substance having an irregular surface is a colored thread. 11. The material having an irregular surface is a weaving yarn.
The method of claim 1, which is (yarn). 12. Irradiation in which a substance having an irregular surface is irradiated in a substantially perpendicular region to the substance, and the substance is reflected by the sample region arranged at intervals around the irradiated sample region. An irregular surface for measuring the color reflected by the sample area at a predetermined angle with respect to the sample area by a plurality of separate photodetectors receiving the light at a predetermined angle with respect to the sample area from substantially opposite directions. A method for more accurately measuring the color of a substance having. 13. A method for accurately detecting the color of a substance exhibiting different degrees of color depending on the viewing angle, comprising irradiating a sample area of the surface substance, and reflecting the irradiation from the substance to be irradiated. The color reflected from the irradiated substance is detected by the photodetector arranged around the irradiated substance so as to receive light at an angle with respect to the sample region irradiated from the opposite direction. How to measure with an angle.