Bar code with optical reading device

4,323,772 4/1982 Serge ................................. .. 235/463

Primary Examiner—Harold I. Pitts
Attorney, Agent, or Firm—-James B. Raden; William J.
Michals

[57] ABSTRACT

The novel bar code, in the spaces (4) between neighboring code bars (1) which have a width greater than one modular_width, with the modular width always being larger than the diameter of the scanning spot (55) of a reading device, contains counting-line marks (5, 6) or counting bars (7). The thickness of the counting line marks is substantially smaller than the diameter of the scanning spot, for example one third of the width of the code bars. The counting bars have a reflectance lying between that of the spaces and that of the code bars. As a result of these measures, at the output of a photoreceiver (9) of a reading device, pulses (31) of a smaller amplitude than that of the pulses (30) formed by the code bar, are generated. By these pulses there is formed a counting clock by which the decoding is rendered independent of the scanning speed.

12 Claims, 6 Drawing Figures

01
',_'~1 E/u1

BAR CODE WITH OPTICAL READING DEVICE

BACKGROUND OF THE INVENTION

The invention relates to a bar code of the type set forth in the preamble of claims 1 and 3, capable of being read with the aid of a reading device, and to an associated reading device of the type set forth in the preamble of claim 6.

There are known various types of bar codes. They consist of a number of lines or bars of different widths which are arranged in parallel with their longitudinal sides and are separated from one another by spaces of different widths. They enjoy great increasing acceptance because of requiring little investment for the scanning process and the character recognition.

From the DIN 66 236 standard there is known a bar code having machine-optically recognizable characters, with each character consisting of a group of bars and spaces, and with the widths of both the bars and the spaces of each character amounting to an integer multiple of one module. Moreover, the length of one intelligencecharacter of this code corresponds to a certain, predetermined number of modules. This code, however, is only machine-readable, i.e., with the aid of a mechanically guided scanner, in order to adhere to the modular spacing which is necessary for safeguarding a faultless reading during the scanning.

SUMMARY OF THE INVENTION

The well known CODABAR code, however, is also suitable for being scanned with the aid of a portable or hand-held bar code reader. In this code, each character consists of four bars and three spaces. For both the bars and the spaces two widths are available of which the larger width amounts to almost three times that of the smaller width. During the scanning, in this conventional code there is only distinguished between narrow and wide widths. Yet, when scanning this conventional bar code with a hand-held bar-code reader there often occur reading errors when the scanning is not carried out at an approximately constant guiding speed of the bar code reader.

It is the object of the invention to design a bar code of the type mentioned hereinbefore,'in such a way that also in the case of greatly varying scanning speeds, a correct reading is carried out by the bar-code reader at a high reliability and, in addition thereto, to provide a reading device suitable for reading such a bar code.

According to the invention, this object is achieved in an advantageous manner by the technical features set forth in the characterizing part of claim 1 as well as by the technical features set forth in the characterizing part of claim 3.

By the invention there is introduced a further reflectance value for the optical scanning, which ranges between the reflectance value of the bars and the reflectance value of the spaces. With the aid of these counting bars lying within the spaces, it is possible in an advantageous manner to measure (count) the space widths and to utilize in this way the different space widths for serving as a different information.

Preferred embodiments of the bar codes according to the invention are set forth in the subclaims 2, 4 and 5.

The technical features set forth in the characterizing part of claim 6 solve in an advantageous manner the problem underlying the invention, i.e., of designing a reading device permitting the optical scanning of a bar

code as set forth in the preamble of claim 6, in such a way as to be suitable for reading (scanning) a bar code according to the invention.

Advantageous developments and further embodiments of a reading device according to the invention are set forth in the subclaims 7 to 11.

BRIEF DESCRIPTION OF THE DRAWING

In the following, the invention will now be explained in greater detail with reference to some examples of embodiment schematically shown in FIGS. 1 to 4 of the accompanying drawings, in which:

FIG. 1 shows a bar code with counting line marks arranged in the individual spaces,

FIG. 2 shows a bar code with counting bars arranged in the individual spaces, '

FIG. 3 shows a block diagram relating to an optical reading device suitable for reading the bar codes shown in FIGS. 1 and 2, and

FIGS. 4a, 4b and 4c show diagrams of an electric scanning signal as produced by the photo-receiver of an optical reading device as shown in FIG. 3, during the scanning of one of the bar codes as shown in FIGS. 1 or 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The bar code as shown in FIG. 1 contains one initial character A and several subsequently following intelligence characters Z1 to Z8. The information content of each character can be recognized from the number of code bars 1 of the character and from the position of the code bars within the character. The position of the code bars is determined by their spacing from the character start 2 or the character end 3. When a space 4 is provided between the character start or the character end and a code bar of the character, then a counting line mark 5 is arranged at this particular character start or character and. If the space between a code bar 1 and the code start or the code end, or between a further neighbouring code bar of the character is substantially greater than one modular width L, then a counting line mark 6 is arranged in this space for each further modular width L. One modular width L is identical to the minimum width of a space or code bar, which is required for scanning the space without being affected by adjoining code bars, or which is necessary for scanning a code bar without being affected by the adjoining spaces. The distance between the counting line marks 5 or 6 and from the neighbouring code bars 1 is at least as large as one modular width L. The thickness of the counting line marks 5 and 6 is substantially smaller than one modular width L, and amounts preferably to one third of this modular width. The code bars at least have a width corresponding to one modular width. One intelligence-bearing character Z1, Z2 through Z8 contains, in the given example of embodiment, altogether always four counting line marks and/ or code bars, with characters (Z7) without code bars also being likely to occur.

The bar code as shown in FIG. 2 differs from the code as shown in FIG. 1 in that it, instead of the counting line marks 5 and 6 of the bar code as shown in FIG. 1, contains counting bars 7, with the reflectance thereof ranging between the reflectance of the spaces 4 and the reflectance of the code bars 1, and with the bar width thereof being at least as large as one modular width L. In the given example of embodiment, the counting bars