WO2001015063A1

WO2001015063A1 - System and method for identification using symbols with varying color densities

Info

Publication number: WO2001015063A1
Application number: PCT/US2000/022490
Authority: WO
Inventors: William G. Reed
Original assignee: Digital Now, Inc.
Priority date: 1999-08-20
Filing date: 2000-08-17
Publication date: 2001-03-01
Also published as: AU7060400A

Abstract

The present invention provides a method and system for labeling and identifying objects that utilize different reflectance densities of color or grayscale symbols to represent encoded information. The encoded symbols (105) comprise a background surface (100) with a minimum reflectance density, a first symbol (120) printed on the background (100) with another reflectance density, and a second symbol (130) printed on the background (105) with still another reflectance density. The encoded symbols (105) can be created in grayscale or multiple colors, and may be printed on or affixed to the background surface (100).

Description

SYSTEM AND METHOD FOR IDENTIFICATION USING SYMBOLS WITH VARYING COLOR DENSITIES

Field of Invention The present invention relates to object labeling and identification. More particularly, the present invention relates to the use of symbols with varying reflectance density levels for labeling and identification.

Related Art

Barcodes are well known in the retail, packaging, and shipping industries. Barcodes are machine-readable symbols comprising patterns of black and white bars and stripes of different widths and/or lengths. Some bardcodes are made of two different black and white bar patterns overlaid to form checkerboard-like grids. Just as unique combinations of letters and/or numbers can represent information and data, unique barcode symbols can also encode information. The data encoded by barcodes can be read by scanners and is often used in conjunction with databases containing the encoded data and corresponding information. Barcodes are often used for labeling items sold in the retail channel that are destined to be scanned at a checkout counter. They are also used for, among other things, shipping forms, labels, identification cards, direct mail pieces, and invoices .

The Universal Product Code (UPC) symbol found on packaged retail grocery items in the United States and Canada is an example of a barcode system. Numerical characters are represented by unique bar patterns made up of a combination of four possible space widths and four possible bar widths which are of integer proportions. Each numerical character is represented by a bar pattern with a fixed total width. Combinations of numbers can therefore be represented by a combination of bar patterns.

Each unique UPC symbol is usually separated into two parts by a center divider and has distinct bar patterns for the numerical characters of each of the two parts. The first five data values on a 10 -digit UPC barcode are assigned to and identify a manufacturer code, and the last five data values are assigned to and identify a product code . Some products use a compressed UPC symbol, containing only six digits. On these symbols, only the left side codes are used, and there is no center divider.

Scanners programmed to interpret the patterns of light and dark bars of UPC symbols can decipher the data string represented by these barcodes. Often the data string is a look-up into a database of information assigned to the data string. For example, the UPC barcode represents a string of numbers that matches a record in a store's database. The database may contain the price and name of the item assigned the UPC barcode as well as the amount of inventory available. The barcode itself is just a record that references information that is stored in the database.

UPC symbols on retail grocery items will typically have the encoded numerical data string printed beneath the bar patterns. Usually, a scanner operator can alternatively access a store's UPC symbol database by manually entering the numerical digits into a computer in communication with the database .

Additional examples of commonly used barcode systems include EAN and JAN symbols that are used in Europe and Japan respectively. Bookland symbols, based on ISBN numbers, are used in books, and ISSN barcodes are used to label non-U.S. periodicals. Code 39 (Code 3 of 9) is the most popular barcode system used for personnel identification, inventory, and tracking purposes . The bars of this system have variable length, supports alphanumeric strings, and can be printed in a variety of sizes and aspect ratios. This barcode system is typically used by video stores, on ID badges, and anywhere a simple barcode is needed. It is sometimes used with an optional check digit.

POSTNET barcodes use a binary system to encode ZIP codes on U.S. mail. Unlike other barcodes, POSTNET symbols consist of bars that vary in height, not width. A check digit is appended to the barcode, which can be used for 5- digit ZIP codes, 9-digit ZIP + 4 codes, or the newer 11- digit delivery point barcodes. Code 128 is a denser, more compact system used whenever space is at a premium. It has variable length strings with a mandatory check digit . It is widely used in the shipping industry. There are several industry-specific subsets of Code 128. Codebar is a numeric-only barcode system used by Federal Express, libraries, and blood banks.

Two-dimensional barcodes are extremely dense and look like crossword puzzles or honeycomb matrices. PD 417 has emerged as the two-dimensional barcode of choice. The other popular two-dimensional barcode system is Maxicode that is used by the United Parcel Service.

Optical character recognition (OCR) is another technology that is analogous to bar codes and can be used to identify objects. OCR technology uses a more complex scanner than simple barcodes for reading alphanumeric characters. OCR scanners read characters and recognize them by comparing them to pre-stored templates or by training artificial neural networks to recognize the characters. Compared to barcode systems, however, OCR systems require a lot more computing power to operate and read characters at a slower rate. For these reasons, OCR technology is a more expensive and less efficient system for labeling objects compared to barcodes .

One drawback of barcode technology is that barcodes must be scanned or read in a certain way. A scanner cannot read barcodes scanned in the wrong direction. In addition, the barcodes themselves must be large enough to permit a scanner to clearly read them. These facts combined with the unattractive appearance of barcodes make it unappealing to place barcodes in more than one location on a retail item. As a result, the process of locating and scanning barcodes at a retail checkout counter is often cumbersome and time consuming. Furthermore, barcode symbols cannot be properly scanned whenever part of a symbol is destroyed, deformed, or covered.

Barcodes are also easily duplicated by, for instance, electrostatic copiers. While this characteristic may be an advantage in some cases, this means that barcodes cannot be used in applications in which security is a concern.

For the foregoing reasons, there is a need for an improved system for labeling and identifying objects that is economical and unobtrusive and can effectively replace barcoding in certain situations. The improved system should be durable, multi-directional , and, for security applications, not easily reproduced.

Summary of the Invention The present invention is directed to a method and system for labeling and identifying objects that utilize different reflectance densities of color or grayscale symbols to represent encoded information. In one aspect of the invention, a symbol, comprising a background with a minimum reflectance density, a first symbol printed on the background with another reflectance density, and a second symbol printed on the background with still another reflectance density, is provided. The symbol according to the present invention can further comprise additional symbols each with its own reflectance density values .

In another aspect of the invention, the symbols are created in grayscale. In a further aspect of the invention, the symbols are created in color.

In still another aspect of the invention, the each symbol is created using multiple colors.

In yet another aspect of the invention, the symbols are affixed to the background.

It is another aspect of the invention to provide a system for identifying objects that has a white light to illuminate an image, a lens to focus a view of the image, a video camera chip with a color mosaic filter to detect the view of the focused image, an interface between the video camera chip and a computer, and a software program run by the computer to interpret the reflectance densities of the image .

The present invention advantageously provides an improved method for labeling and identifying objects and is an analogue replacement for conventional barcoding systems.

A further advantage of the present invention is to provide an improved method for industrial tagging and tracking of packages and containers. Another advantage of the present invention is that it can label and identify objects in a proprietary manner that is not decodable by conventional decoders. It is yet another advantage of the invention to provide a method for labeling and identifying objects that is scalable .

It is a further advantage of the invention to provide an alternative system for barcoding that is compact in size.

These and other features and advantages of the invention will be more fully understood from the following detailed description of preferred embodiments of the invention that should be read in light of the accompanying drawings.

Brief Description of the Drawings

The accompanying drawings, which are incorporated in and form a part of the specification, illustrate a preferred embodiment of the present invention and, together with the description, serve to explain the principles of the invention.

FIG. 1 illustrates a preferred embodiment of a symbol of the present invention; FIG. 2 illustrates a plot of the reflectance densities of the symbol in FIG. 1 produced in grayscale;

FIG. 3 illustrates a plot of the reflectance densities of the symbol in FIG. 1 produced in three colors;

FIG. 4 illustrates a plot of the reflectance densities of the three colors illustrated in FIG. 3.

FIG. 5 illustrates a second preferred embodiment of a symbol of the present invention; and

FIG. 6 illustrates another preferred embodiment of the present invention comprising a hybrid symbol; and FIG. 7 illustrates a block diagram of a device of the present invention.

Detailed Description of the Invention In describing the invention, specific terminology will be used for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all equivalents.

The present invention creates a system of symbols with different color shades having known discrete reflectance density values. Each shade of a color has a unique reflectance density value that can be used as a unique identifier. Thus, the infinite number of different shades of one color, the color blue for example, can be used to mark and identify objects. This is limited, of course, by the sensitivity and accuracy of a reader that can identify the difference in color shades. In this manner, color symbols can be used to replace conventional bar code technologies. One system of symbols, barcoding, can be replaced with, as will be shown below, a more advantageous system of color symbols.

Reflectance density is a measurement of the ratio of the light incident upon a surface and the light reflected from the surface. A darker shade of one color will have a higher reflectance density than a lighter shade of the same color. Although reflectance density is usually expressed as units on a logarithmic scale, in a preferred embodiment of the present invention, the invention measures reflectance density in unit values that are not converted to or are not measured on a base-ten logarithmic scale.

The method of the invention includes printing a symbol at the maximum possible reflectance density, i.e. at full color for a given method of printing, on a given background surface. A second symbol of the same color is printed near the first symbol. The unprinted surface thus has the minimum possible reflectance density relative to the two symbols because no color has been added to the unprinted surface. The second symbol has a reflectance density greater than or equal to the minimum and less than or equal to the maximum. Because measuring reflectance densities is well known in the art, a unique reflectance density of a symbol by itself can be used to encode information. Nevertheless, the method of the invention also includes calculating the ratio of the reflectance density of the second symbol to the reflectance density of the first symbol. This method solves the problem of reflectance densities changing over time as the printed symbols fade with age or exposure to sunlight. The invention accounts for the fact that fading of the first and second symbols would occur in the same proportion as their reflectance density ratio thus maintaining a constant ratio value.

In a preferred embodiment of the invention, the reflectance density of the background surface is subtracted from the reflectance densities of the first and second symbols before computing the density ratio. In this way the reflectance density ratio of the first and second symbols remains constant regardless of the surface they are printed on. This is useful in some situations in which the packaging of an item changes, but it remains desirable to retain the same identification symbol . Thus method also accounts for changes in the reflectance density of the background surface over time.

Color symbols can be printed using many possible printing technologies. For example, Cycolor™ micro- encapsulated printing media can be used to produce a printer for less than $100 that could print symbols as small as one millimeter on polyester stock. Color symbols can also be created using an exposure system that utilizes photographic paper to produce the symbols. Low-cost ink-jet printers can also be used to produce low-cost symbols.

A low-cost reader can be built to scan small color symbols with high reliability. As is known in the art, red, green, and blue LEDs and a low cost photodiode, or lasers, or filtered incandescent light can be used to read the color symbols .

In a preferred embodiment of the invention, a reader device comprises an illumination system of substantially white light from a solid state source, such as a white LED. The illumination system has an inherent constant spectral output which preserves the long-term stability of the reader. The reader device further comprises a lens for focusing an image lit by the illumination system. A miniature solid-state video camera chip with a color mosaic filter detects the image focused by a lens. The image data is transmitted to a computer, preferably by a USB or wireless interface. Software on the computer is used to identify the location of any color symbols within the detected image and to measure the reflectance densities of the image colors, the maximum and minimum reflectance in each color.

Furthermore, as is well known in the art, scanners, such as color video cameras for connection to personal computers, can be built to detect overlapping colors of different wavelengths. Therefore, the color symbols of the invention can be created using a combination of multiple colors, and a scanner can be used to detect the presence of the reflectance densities of each color. The use of more than one color introduces additional variables and increases the amount of information that can be encoded by the color symbols of the invention. Unlike barcode symbols, the color symbols of the present invention do not have to be a certain size. The color symbols can be small enough as to be innocuous. The color symbols can also be incorporated into the packaging designs or logos of retail products. Thus, it is possible that the color symbols can be printed all over the surface of an item without being noticed by a consumer.

With reference to the drawings, in general, and FIGS. 1 through 7 in particular, some of the preferred embodiments of the present invention are described.

FIG. 1 illustrates a preferred embodiment of the present invention. In FIG. 1, symbol 105, comprising dot 110, surrounding circle 120, and surrounding circle 130, is printed on surface 100 in order to label an object for subsequent identification. The invention, however, is not limited to circular symbols. The symbols of the invention may be oval, square, rectangular, or any other shape, including specific designs that are incorporated into the packaging of items. In one embodiment of the invention, surface 100 is a portion of the surface of the labeled object. In such an embodiment, surrounding circle 120 is part of the original surface of the object not covered by printed ink.

In another preferred embodiment of the present invention, surface 100 is not a portion of the surface of the object to be labeled. In this embodiment, surrounding circle 120 is part of the different surface that is not covered by printed ink. In such an embodiment, surface 100, with dot 110 and surrounding circle 130 printed thereon, is subsequently affixed to an object in order to label the object for subsequent identification.

In one embodiment of the present invention, surrounding circle 130 and dot 110 are printed in grayscale. In this embodiment, surrounding circle 130 is printed at the maximum reflectance density of the grayscale, i.e. it is printed in black, and represents the maximum reflectance density value. Surrounding circle 120 has no ink printed in its surface and represents the minimum reflectance density. Dot 110 is printed in a grayscale color and has a reflectance density value greater than or equal to the minimum reflectance density value and less than or equal to the maximum reflectance density value. In another preferred embodiment of the present invention, dot 110 and surrounding circle 130 are printed using a combination of different colors. In a more preferred embodiment, dot 100 and surrounding circle 130 are printed using the colors cyan, magenta and yellow. In this embodiment, surrounding circle 130 is printed at the maximum color reflectance densities for each color used, i.e. it is printed in full color. For the colors cyan, magenta and yellow, surrounding circle 130 would appear to be black in color. Surrounding circle 130 thus represents the maximum color reflectance density value for each color used.

Surrounding circle 120 has no ink printed in its surface and represents the minimum reflectance density. Dot 110 can be printed with any combination of reflectance densities of the colors used. Therefore, for each color used, dot 110 has a color reflectance density greater than or equal to the minimum reflectance density value for that color and less than or equal to the maximum color reflectance density value for that color.

In another preferred embodiment of the invention, dot 110 and surrounding circle 130 are printed using ultraviolet or infrared ink. In this embodiment, surrounding circle 130 is printed at the maximum reflectance density of the ink used and represents the maximum reflectance density value. Surrounding circle 120 has no ink printed in its surface and represents the minimum reflectance density. Dot 110 is printed such that it has a reflectance density value greater than or equal to the minimum reflectance density value and less than or equal to the maximum reflectance density value. In another embodiment of the invention, dot 110 and surrounding circle 130 are created by exposing photographic paper to various lights. In still another preferred embodiment, dot 110 and surrounding circle 130 are created by exposing cycolor micro-encapsulated photopaper to LED light controlled by pulse width modulation or analog power control. In other embodiments of the invention, color xerography, color dye-sublimation, or color ink-jet printing can be used to create dot 110 and surrounding circle 130. FIG. 2 is a sample plot of the possible reflectance densities of dot 110 (Dl) , surrounding circle 120 (D2) , and surrounding circle 130 (D3) when dot 110 and surrounding circle 130 are created in grayscale. The Y-axis measures the reflectance density, D, and the X-axis measures the distance from the center of dot 100. From FIG. 2, it is clear that the reflectance density of surrounding circle 130 is the maximum reflectance density of symbol 105, and the reflectance density of surrounding circle 120 is the minimum reflectance density of symbol 105. The reflectance density of dot 110 can be used to compute a unique value that is related to a look-up table in communication with a database. In a preferred embodiment of the invention, the unique value is derived by calculating the ratio of the reflectance density of dot 110 to the reflectance density of surrounding circle 130. In another preferred embodiment of the invention, before the ratio is computed, the reflectance densities of dot 110 and surrounding circle 130 are first normalized by subtracting the reflectance density of surrounding circle 120 from each. Although, the individual reflectance densities of dot 110 and surrounding circle 130 may change over time due to fading or exposure to sunlight, the ratio of the reflectance densities will remain constant. Surrounding circle 130 serves as a reference that reduces the effects of aging of the printing dyes.

Surrounding circle 130, representing the maximum reflective density value, also helps to calibrate the scanning sensor. The distinctive visible characteristic of dot 110 and surrounding circle 130 also helps a scanner distinguish symbol 105 from other patterns on surface 100 and physically locate dot 110 in the symbol space.

In another preferred embodiment of the invention, the reflective density of surrounding circle 130 is ninety percent of the maximum possible reflectance density of the ink used, i.e. surrounding circle 130 is printed in dark gray. This facilitates better ratiometric accuracy when calculating the unique value. FIG. 3 is a sample plot of the possible color reflectance densities of dot 110, surrounding circle 120, and surrounding circle 130 when dot 110 and surrounding circle 130 are created with three colors. Similar to FIG. 2, FIG. 3 illustrates the reflectance densities of symbol 105 as a function of the distance from the center of dot 110. In FIG. 3, however, there is a reflectance density plot for each color used to create dot 110 and surrounding circle 130. A scanner calibrated to the light wavelength for each color used can determine the color reflectance density for each color.

In a preferred embodiment of the invention, the data string encoded by a color symbol 105 can be derived by calculating, for each color used, the ratio of the color reflectance density of dot 110 to the color reflectance density of surrounding circle 130. In another preferred embodiment of the invention, the color reflectance densities of dot 110 and surrounding circle 130 are first normalized by subtracting the color reflectance density of surrounding circle 120 from each.

In a preferred embodiment of the invention, the ratio for each color used represents one component of the data string encoded by color symbol 105. For example, in one preferred embodiment, the color reflectance density for each color used can be accurately measured to within plus or minus five percent (+/- 5%) of the maximum color reflectance density value. In this case, each color used can represent up to ten different values. If three colors are used and each color represents a different successive numerical digit, a three-colored symbol can encode a value from 000 to 999. If the color reflectance density for each color used can be accurately measured to within plus or minus one-half percent (+/- 0.5%) of the maximum color reflectance density value, then each color used can represent up to 100 different values, and a three-colored symbol can encode a value from 000000 to 999999. In this example, two color- encoded symbols of the present invention can represent a twelve-digit data string. Thus, the invention can easily be used as a substitute for ten-digit UPC barcode symbols. FIG. 4 illustrates a sample plot of the reflectance densities of three colors that can be used in combination to create the color symbols of the invention. The Y-axis measures the reflectance densities for each of the three colors used. The X-axis measures the electromagnetic wavelength of the three colors in nanometers (nm) . Each color occupies a distinct range within the electromagnetic wavelength spectrum. Because each color can encompass a distinct range on the electromagnetic spectrum, scanners can be easily built to read the reflectance densities of each color from a symbol composed of a combination of different colors . As is known in the art, dot 110 and surrounding circle 130 can be created with two or three or more different colors. The only limitations to the number of colors that can be used are the accuracy of the methods used for printing the symbols within specified ranges of the electromagnetic wavelength spectrum and the accuracy of scanners used for reading the symbols.

FIG. 5 illustrates another preferred embodiment of the present invention in which two dots are printed proximate to each other on the same surface. In this embodiment, dot 510 serves the same function as dot 110. However, dot 520 is printed at the maximum reflectance density possible and replaces surrounding circle 130 as representing the maximum reflectance density value of symbol 505. Furthermore, the unprinted areas of surface 500 replaces surrounding circle 120 as representing the minimum reflectance density value. FIG. 6 illustrates another embodiment of the present invention that combines the symbol of FIG. 1 with conventional barcode technology. In one embodiment of the invention, guard bars 610, 630, and 650 determine the place values of the data strings encoded by symbols 620 and 640. Symbols 620 and 640 could be implemented in like manner to symbols 105 and/or 505 described above, either in color or grayscale. For example, in one embodiment, guard bars 610, 630, and 650 are successively wider bars that orient symbols 620 and 640 such that, when scanned, the data string of symbol 620 is placed before the data string of symbol 640. This is one method of increasing the length of the data string encoded by the invention. FIG. 7 illustrates a block diagram of one embodiment of a device for reading and interpreting the color density symbols of the present invention. The device comprises illumination system 720 that can be used to illuminate variable color density symbols. In a preferred embodiment, illumination system 720 is a substantially white light from a solid state source, such as a white LED. Lens 710 can focus the image of the color density symbols as lit by illumination system 720. The focused image is captured by video camera chip 730. In a preferred embodiment, video camera chip 730 is a miniature solid-state video camera chip with a color mosaic filter. Video camera chip 730 then transfers the data extracted from the captured image to computer 740. The computer runs software that can interpret the image data to identify the location of any color density symbols within the captured image and to measure the reflectance densities of the image colors .

While there have been shown and described specific embodiments of the present invention, it is obvious to those skilled in the art that various changes and modifications may be made without departing from the scope of the invention or its equivalents. The invention is intended to be broadly protected consistent with the spirit and scope of the appended claims.

Claims

What is claimed is:

1. A method of identifying objects comprising the steps Of: providing a background wherein a reflectance density of the background represents a minimum value; printing a first symbol on the background wherein a reflectance density of the first symbol represents a reference value; printing a second symbol on the background, proximate to the first symbol, wherein a reflectance density of the second symbol represents a third value, wherein the third value is less than or equal to the reference value and greater than or equal to the minimum value; determining the reflectance densities of the background, the first symbol, and the second symbol; calculating the third value based on a relationship between the reflectance densities of the background the first symbol, and the second symbol; and identifying an object with the third value.

2. The method of claim 1 wherein the reference value is determined by subtracting the reflectance density of the background from the reflectance density of the first symbol .

3. The method of claim 1 wherein the third value is determined by subtracting the reflectance density of the background from the reflectance density of the second symbol .

4. The method of claim 1 wherein the identifying step comprises determining a ratio of the third value to the reference value.

5. The method of claim 1, further comprising the steps of: printing a third symbol in a different color on the background, proximate to the first and second symbols, wherein a reflectance density of the third symbol represents a fourth value, wherein the fourth value is less than or equal to the reference value and greater than or equal to the minimum value; determining the reflectance density of the third symbol ; calculating the fourth value based on a relationship between the reflectance densities of the background, the first symbol, and the third symbol; and identifying an object with the third and fourth values.

6. A method of identifying objects comprising the steps of: determining the reflectance densities of a background, a first symbol, and a second symbol; calculating a value based on a relationship between the reflectance densities of the background, the first symbol, and the second symbol ; and identifying an object with the value.

7. A method of marking objects to be identified comprising the steps of : providing an object surface wherein the reflectance density of the object surface represents a minimum value; printing a circle on the object surface, wherein the reflectance density of the circle represents a reference value; and printing a symbol on the object surface inside the circle, wherein a reflectance density of the symbol represents a third value, wherein the third value is less than or equal to the reference value and greater than or equal to the minimum value .

8. A method of identifying objects comprising the steps of: providing a background wherein a reflectance density of the background represents a minimum value; printing a first symbol on the background using a first color; printing said first symbol again using a second color on top of said first color, wherein a reflectance density of the first symbol printed with the first and second colors represents a reference value; printing a second symbol on the background using said first color, proximate to the first symbol; printing said second symbol again using said second color on top of said first color, wherein a reflectance density of the second symbol printed with the first and second colors represents a third value, wherein the third value is less than or equal to the reference value and greater than or equal to the minimum value; determining the reflectance density of the background, the first symbol, and the second symbol; calculating the third value based on a relationship between the reflectance density of the background, the first symbol , and the second symbol ; and identifying an object with the third value.

9. The method of clam 8 further comprising the step of printing the first and second symbols with a third color on top of said first and second colors.

10. A method of identifying objects comprising the steps of: providing a background wherein a reflectance density of the background represents a minimum value; affixing a first symbol on to the background wherein a reflectance density of the first symbol represents a reference value; affixing a second symbol on to the background, proximate to the first symbol, wherein a reflectance density of the second symbol represents a third value, wherein the third value is less than or equal to the reference value and greater than or equal to the minimum value; determining the reflectance densities of the background, the first symbol, and the second symbol; calculating the third value based on a relationship between the reflectance densities of the background, the first symbol, and the second symbol; and identifying an object with the third value.

11. A system of identifying objects comprising: a white light to illuminate an image; a lens to focus a view of the image; a video camera chip with a color mosaic filter to detect the view of the focused image; an interface between the video camera chip and a computer; and a software program run by the computer to interpret the reflectance densities of the image.