Mirrored surface optical symbol scanner

#This invention is directed to the scanning devices, such as bar code scanners, and is more particularly concerned with an arrangement for reading optical symbols, e.g., small linear or two-dimensional bar code symbols that are directly marked on parts or components. Such bar code symbols may be used to identify the part number and serial number of an electronic microcircuit devices, communications cables and connectors, diesel engine ignitors, as well as many other products. The invention is more particularly concerned with a device that is combined with an illuminator for shining light on the bar code symbol or other symbol which is marked onto a specularly reflective, i.e., mirrored surface.

#Within the past several years, two dimension bar code systems have begun to be employed on small articles so that the article can be tracked thought a manufacturing process. For example, two-dimensional bar code symbols are inscribed onto electronic parts, e.g. as miniature etched or printed part numbers and serial numbers on microprocessors, other integrated circuits, and printed circuit boards. Because of the high information density of the 2D symbols, these can carry the part number, part serial number, and manufacturing history of the part, such as the place and date of manufacture, and all in a square that may typically be only three millimeters on a side. The symbols can be screen printed, ink jet printed, or laser-etched directly onto the top surface or the case of the device or part. However, in order to read the bar code easily on the first attempt, the conventional wisdom is that the illumination should impinge on the bar code symbol in a way that fully illuminates it but avoids flare from specular reflection.

#Because of the small size of 2-D bar code symbols, the symbols can be difficult for the scanner to interpret where the lighting is weak or if the contrast is too low. For example, Datamatrix TM bar code, which has been selected as the EIA (Electronics Industry Association) standard for small parts marking, is in the form of a matrix of bars about three millimeters on a side. These are inscribed by laser etching onto the plastic or ceramic housing or package for the electronic module, or can be printed by an ink jet technique. In either case, if the lighting is such that the scanner picks up specular reflection, the bar code symbol typically produces a wash out, and may take several attempts to obtain a valid reading. Consequently, current bar code scanners have had some difficulty in obtaining bar code data in industrial processes where the small parts are to be identified from these very small bar code symbols.

#FIG. 1 is a perspective view of a bar code scanner with a diffuse illuminator, according to on embodiment of this invention.

#FIG. 2A is a perspective view of a bar code symbol having mirror finish elements and diffuse elements.

#FIG. 2B is a perspective view of a two-dimensional bar code symbol having mirror finish elements and diffuse elements.

#With reference to the Drawing, and initially to FIG. 1, a hand-held data inputting scanner 20, i.e., a hand-held two-dimensional bar code scanner, and an illumination attachment 22 according to an embodiment of this invention is mounted on the front or distal end of the scanner 20. The combination scanner and illumination attachment of this embodiment is designed to read a bar code symbol that is printed, etched, or otherwise formed on a highly reflective mirror surface. The illuminator attachment 22 is in the form of a block or slab of a clear acrylic, with a distal side that receives light from light generating elements on the scanner 20, and a diffuse surface 24, i.e., “frosted”, that scatters or diffuses the light that exits the illuminator attachment. A clear or open passageway 26 is provided in the center of the illuminator attachment 22 along the optic axis of the scanner 20 to provide a path or passageway for viewing and imaging bar code symbols.

#As shown in FIG. 2A, a linear or one-dimensional symbol 10 may be formed as a pattern of parallel alternating dark and light bars of different widths. In this case, the symbol 10 is formed on a mirror-finish surface 12, and light that lands on this surface 12 is reflected specularly, i.e., so that the light remains in a reflected beam 13, as illustrated here. The symbol 10 is printed with an ink that is diffusely reflective, e.g., flat with white or colored pigments, forming diffusive (i.e., non-mirror-finish) bars 14. The light 15 that lands on these bars 14 is diffused or scattered, and much less of this light continues in the same direction as the specularly reflected light 13. A two-dimensional bar code symbol 10′ is shown in FIG. 2B, with a base surface 12′ that is mirror-finish, and a pattern of areas 14′ of diffusive ink or surface treatment. As with the FIG. 2A symbol 12, any light 13′ landing on the mirror-finish surface 12′ will be specularly reflected, and any light 15′ landing on the areas 14′ will be scattered or diffusely reflected.

#As illustrated in FIG. 3, the scanner 20 with its illuminator attachment 22 can be positioned at an angle to a bar-coded article to view and read the symbol or symbols printed on it, where the symbols are formed directly on a mirror-finish surface of the article. In this example, an electronics module 30 can have one or more microcircuit chips 32 mounted on it, each with a small, two-dimensional bar code symbol 34 carried on an upper surface. In other examples, the bar-coded articles may be automotive or aviation parts, or articles for any of a wide variety of commercial or industrial uses. The bar code symbol 34 can be a matrix symbology, such as DataMatrix, or alternatively, Maxicode, PDF41 7, Aztec, or another protocol. Alternatively, a linear bar code, full-size to ultra-small, can be used, such as Codabar, UPC, or another symbology. The bar code symbol makes it possible to read automatically the part number, part serial number, manufacturing history, and other important data about the microcircuit 32 or of the module 30 during various manufacturing stages, or later on during the product life, e.g., for warranty purposes. However, because of the small size of the bar code symbol 12, the same is often applied directly onto the surface of the module 10 for example by an ink jet printing technique. Low contrast and specular reflection of the illumination has previously made it very difficult to read the symbol. However, if the optical axis of the scanner 20 is held at an angle to the bar code symbol 34, the diffuse light from the diffusion surface 24 forms a bar of diffuse light that is seen as a reflected image in the mirror-finish surface. The diffuse areas (of ink, paint, etching, etc) which scatter the light appear as dark areas of the bar code symbol, and the pattern of alternate light and dark areas is easily seen by the scanner to produce a good read.