Micro-bar code reader system

Abstract: A bar code reader system is adapted to read a micro-bar code (5). The bar code reader system comprises a light emitting body for irradiating a light beam onto a bar code surface, on which the micro-bar code to be read is provided, a focusing lens (2) for focusing a reflected light from the bar code surface, an image pick-up (1) means for receiving the focused reflected light and forming an image of the micro-bar code to be read, and a cylindrical lens body (4) arranged to pass both of the light beam from the light emitting body (3) and the reflected light beam reflected from the bar code surface therethrough, the cylindrical lens body being arranged orienting the axis thereof substantially consistent with a bar code reading direction.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a bar code reader system for reading information from a micro-bar code which has reduced in size in comparison with known and currently available bar codes. More specifically, the invention relates to a bar code reader which can assure reading information from the micro-bar code. Description of the Related Art As is well known, a bar code is designed to encode information, such as various characters, such as letters, figures, signs by combination of a plurality of solid bars arranged in mutually parallel relationship to one another and blank intervals between the bars (which will be hereafter referred to as white bars). The following four types of bar codes are typically put into the field use. (1) JAN (Japanese Article Number) Code This coding system has been used for identification of consumer goods produced in Japan. The JAN coding system is compatible with UPC (Universal Product Code) used in the United States and EAN (European Article Number) used in Europe and Asia. In the JAN coding system, 13 digits of standard code and 8 digits of compressed code are available. The standard JAN code is consisted of 2 digits of a country code, 5 digits of a product maker code, 5 digits of a product item code and 1 check digit. The compressed code has essentially the same code format to the standard code but has 4 digits of the product maker code and 1 digit of the product item code. In JAN coding system, only figures of 0 ∼ 9 can be expressed by the combination of the solid bars and white bars. This coding system is convenient for reading operation since it is not sensitive for scanning directions of a bar code reader. (2) ITF (Interleaved Two of Five) Code ITF coding system is a standard coding system adapted to physical distribution, which is established by adding a physical distribution identification code of 1 or 3 (including 1 leading digit which is normally held 0) to the foregoing JAN code. Therefore, this ITF code may express only figures of 0 ∼ 9. This coding system is successfully spread in the field of transportation. In addition, this coding system is employed as data for timed recording of a video tape recorder (VTR). The ITF coding system features in high recording density and in stable information reading precision level even when the bar code is printed on a printing medium having bad printing condition. (3) CODE 39 In this coding system, one character is expressed by 9 bars (4 white bars between 5 solid bars). Among 9 bars, 3 bars are thick solid or white bars having greater width. As start and stop code, asterisk (*) is employed. This coding system permits to express figures of 0 ∼ 9, alphabetic letters of A ∼ Z, various signs (e.g., +, -, blank space, /, $, %, ·). This coding system has been employed as standard in industrial fields for factory automation. AIAG in the United States automobile manufactures, HIBC in the United States hospitals and pharmaceutical industries are well known examples of this type of coding system. (4) NW-7 (CODABAR) In this coding system, one character is expressed by 7 bars (3 white bars between 4 solid bars). Among seven bars, 2 or 3 bars are thicker bars. As start and stop codes, one of A, B, C and D is used. This coding system is capable to express figures of 0 ∼ 9 and various signs (e.g., +, -, blank space, /, $, %, :, ·). As bar code readers for reading information recorded on the bar codes, there are CCD type bar code readers which read information employing charge-coupled devices (CCDs), as disclosed, for example, in WO-A-8603605, and laser scanners which are adapted to scan the bar code with laser beams. For a hand-held type bar code reader, electronic scanning type readers are frequently used, as disclosed in, for example, EP-A-0238067 for capability of reduction of size and weight and being less expensive. CCD devices are commonly used for such electronic scanning. Both these documents reflect the preamble of independent claim 1. Discussion will be given for one example of the conventional CCD type bar code reader with reference to Figs. 10 to 12. Fig.10 shows the conventional bar code reader system 20 in operation. Fig. 11 is a diagrammatic illustration of an arrangement of components of an optical system employed in the conventional bar code reader of Fig.10 , as viewed from the front side. Fig.12 is a diagrammatic illustration of the optical system of Fig.11 as viewed from the side. As can be seen from Fig. 12, the bar code reader system comprises a CCD sensor 1, a focusing lens 2 and a pair of light emitting elements 3, 3 (which are aligned in the transverse direction relative to the plane of Fig.12 ). The bar code reader 20 shown in Fig.10 is designed to be gripped by a hand and the tip end placed onto a bar code 5a in an attitude perpendicular to a plane, on which the bar code 5a is printed. By this, an image of the bar code 5a irradiated by the light beam from the light emitting elements 3, 3 is received by the CCD sensor 1 through the focusing lens 2 as a reflected light. The image of the bar code 5a formed on the CCD sensor 1 is converted into electric signals. Then, the information contained in the bar code is decoded by a decoder (not shown). The shown bar code reader 20 is particularly adapted to read information from a compressed size of bar code (hereafter referred to as "micro-bar code") which has a bar width in the extent of approximately 100 µm in the thinnest solid bar, and length of the bars is in a range of approximately 1 ∼ 10 mm. In order to facilitate aligning of the beam axis 7 of the CCD sensor 1 in the bar code reader system 20 to the bar code 5a , a cut out 10 is formed at the tip end of the system 20. However, when the micro-bar code is read by the bar code reader system 20 constructed as set forth above, the following problems are to be encountered. Fig.13(a) is a diagrammatic illustration showing part of the bar code in the enlarged form. Upon printing the bar codes, very high attention is paid. However, there is inherently caused defects in the solid bar, spots in the white bars, blurs or distortion of the solid bars. When such defective bar code is scanned along 3 lines (1), (2) and (3) as shown, Fig.13(b) illustrates timing chart showing the result of scan through the lines (1), (2) and (3), in which an output signal becomes HIGH level when the solid bar is detected and LOW level when the white bar is detected. As can be apparent from Fig. 13(b) , the results are differentiated for containing the reading error α due to the defect of void V in the solid bar, the reading error β due to blur and the reading error γ due to spot S in the white bar. In addition, due to the presence of the cut out 10 at the tip end of the bar code reader system 20 in order to facilitate positioning thereof relative to the bar code 5a , the external light may penetrate through the cut out 10 to cause variation of the received light intensity at the CCD sensor 1 . Therefore, it requires adjustment of the exposure period of the CCD sensor 1 . This extends the period required for decoding the information recorded on the bar code 5a and thus lowers efficiency in reading the information. Furthermore, it is possible that dust and dirt penetrate through the cut out 10 to adhere on the optical parts, such as the light receiving surface of the CCD sensor 1 to make reading of information impossible. SUMMARY OF THE INVENTION The present invention is to solve the problems as set forth above. Therefore, the present invention aims to provide a bar code reader system which can certainly read information from a micro-bar code which is smaller than the conventional bar code. In order to accomplish the above-mentioned and other objects, the present invention provides a bar code reader for reading a bar code provided on a bar code surface, the reader comprising means for illuminating the bar code; image detection means; and focusing means for focusing light from the illuminated bar code onto the image detection means to enable said image detection means to read information included in the bar code; characterised by a cylindrical lens means arranged in the path of said light from the illuminated bar code with its axis extending in a direction substantially along the bar code reading direction of the image detection means. The bar code reader of the present invention can thus be adapted for reading information contained in a micro-bar code. Further features of the described embodiments are defined in claims 2 to 11. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be understood more fully from the detailed description given herebelow and from the accompanying drawings of the preferred embodiments of the invention, which, however, should not be taken to be limitative to the invention but are for explanation and understanding only. In the drawings: Fig. 1 is a front elevation diagrammatically illustrating the internal arrangement of components forming the preferred embodiment of a bar code reader system according to the present invention; Fig. 2 is a side elevation of the bar code reader system of Fig. 1 ; Fig. 3 is an illustration of a primary light flux in the first embodiment of the present invention; Fig. 4 is an illustration showing a distribution of a light amount on a irradiated surface as viewed from the transverse side in Fig. 3 ; Fig. 5 is an illustration of the primary light flux in the second embodiment of the present invention; Fig. 6 is an illustration of the primary light flux in the third embodiment of the present invention; Figs. 7 to 9 are illustrations of the primary light flux in the fourth embodiment of the present invention; Fig.10 is a perspective view of the conventional bar code reader system; Fig.11 is a front elevation diagrammatically showing the arrangement of the internal components of the conventional bar code reader system; Fig. 12 is a side elevation of the arrangement of Fig. 11 ; Figs. 13(a) and 13(b) are an enlarged illustration of a bar code and a timing chart showing a result of reading the shown bar code; Fig. 14 is an illustration showing one example of the bar code; Fig. 15 is an illustration showing the primary light flux in the bar code reader system only employing a focusing lens; and Fig. 16 is an illustration showing the primary light flux of the bar code reader system according to the present invention, in which a cylindrical lens body is disposed between the focusing lens and the bar code. DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiments of the present invention will be discussed herebelow with reference to the accompanying drawings. It should be noted that the like reference numerals to those of the prior art represent like components. At first, the principle of the present invention will be discussed briefly with reference to Figs. 14 to 16. Considering reading information from a bar code as illustrated in Fig. 14, the bar code information is read by reading respective individual bar information in a direction perpendicular to the direction of the longer edges of the bars. The direction to read the bar code information will be hereafter referred to as "reading direction". Also, the direction along which the longer edges of the bars, i.e., solid bars and white bars, are oriented will be hereafter referred to as "bar direction". As viewed in the direction perpendicular to the surface carrying the bar code, when only focusing lens L x is provided as in the prior art, the images at points A 1 and A 2 on the surface are formed at points F 1 and F 2 on a light receiving surface of an image pick-up means, as shown in Fig.15. Conversely to this, according to the present invention, a cylindrical lens body L f is disposed between the surface carrying the bar code and the focusing lens L x . The cylindrical lens body L f is oriented so that the axis thereof is in parallel relationship to the surface along the reading direction. Therefore, reflected light beam reflected from points B 1 and B 2 is deflected in the axial direction of the cylindrical lens body L f in few magnitude so that no substantial scattering of the reflected light beam is caused, as shown in Fig.16(a). On the other hand, in the direction perpendicular to the axis of the cylindrical lens body L f , the reflected light beams reflected from points C 1 and C 2 are refracted to disperse to establish dispersed light beams as illustrated by H 1 and H 2 , as shown in Fig.16(b) . Considering single solid bar, the image of the point on the solid bar is thus projected on the light receiving surface as a line. As set forth above, the void, blur, distortion and other defects in the solid bar potentially become a cause of reading error. However, in case of the present invention, the images of respective individual points on the solid bar are projected on the light receiving surface of the image pick-up device a line in overlapping manner. Therefore, defect on the image due to presence of void can be compensated by the solid image of the adjacent points. On the other hand, the distortion of the projected image due to presence of the blur or distortion on the bar code can be faded by the contrast with the surrounding region. Also, the spot in the white bar, which can also be the cause of reading error, can be faded by the white image established with respect to adjacent blank points. Therefore, since the micro-bar code reader system according to the present invention irradiates the light beam from a light source to the surface carrying the bar code and receives the reflected light therefrom, through the cylindrical lens body, the image of the bar code is formed on the image pick-up means in the form dispersed in the bar direction. As a result, the defects of the bar code caused in printing can be compensated in the bar direction to facilitate formation of the image data which can be decoded. Also, since the external light penetrating through a cut-out formed in a housing can be scattered and cannot reach the image pick-up means, the influence of the external light which otherwise causes reading error or makes reading information impossible, can be successfully avoided. Furthermore, since the cut-out portion of the housing is closed by the cylindrical lens body, the external dust, dirt or so forth may hardly penetrate into the interior space of the bar code reader system, contamination of the internal components by such dust, dirt or so forth, which otherwise causes failure of components or the entire system, can be successfully avoided. <Embodiment 1> Fig. 1 diagrammatically illustrates internal components of the preferred embodiment of a bar code reader system according to the present invention. Fig.2 illustrates a side elevation of the components of Fig.1. The bar code reader system generally comprises an image pick-up means 1 , such as a CCD sensor, a focusing lens 2 , light emitting bodies 3, 3 , such as LEDs which are arranged in a spaced apart relation in a lateral direction (a longitudinal direction of the CCD sensor array 1 ) for a given distance s 1 (e.g., 10 mm in the shown embodiment), and a cylindrical lens body 4 arranged transversely to the bar code 5a and having substantially circular cross-section. In the practical manner of picking-up the image of the bar code, image pick-up elements forming an array of the CCD sensor are scanned in the reading direction (which may correspond to the longitudinal direction of the CCD sensor) by a non-shown control circuit for obtaining image information in order. In the concrete embodiment, but not being limitative, the lens body 4 is provided with an external diameter of 5.0 mm and a refraction index of 1.488. The lens body 4 may be formed of either a synthetic resin or a glass. The lens body 4 is so positioned as to have a distance s 4 (e.g., 2 mm in the shown embodiment) from the irradiating surface, on which the bar code 5a is provided and to have a distance s 6 (e.g., 3 mm in the shown embodiment) from the light emitting bodies 3, 3 . The surface, on which the bar code is provided by way of printing, sticking a bar code label or any other appropriate means, will be hereafter referred to as "bar code surface". In addition, the lens body 4 is arranged with orienting the axial center in consistent direction to a bar code reading direction, in which the bar code reader system is scanned and therefore substantially perpendicular to a direction of the longer edge of the bars of the bar code. The direction of the longer edge of the bars of the bar code will be hereafter referred to as "bar direction". On the other hand, the focusing lens 2 is so arranged as to have a given distance s 3 (e.g., 27 mm in the shown embodiment) from the bar code 5a and to have a given distance s 2 (e.g., 21 mm in the shown embodiment) from the CCD sensor 1 . These components are arranged on a common light beam axis 7. In the bar code reader system constructed as set forth above, the light beams emitted from the LEDs 3 and 3, as the light emitting body, passes the lens body 4 and reaches the bar code 5a . The primary light flux of the emitted light beam is fragmentarily illustrated by hatched area in Fig. 3. It should be noted that Fig. 3 illustrates the primary light flux in the condition where the bar code reader system illustrated in Fig. 1 is employed and the bar code reader system is situated to place the lens body 4 to have a distance of approximately 2 mm between the bar code surface and the lower portion of the lens body. Most of the external light 9 is reflected by the incident surface of the lens body 4. Even when a part of the external light penetrates through the lens body 4, it may not be focused on the bar code surface 5. Therefore, the external light will never affect for irradiation on the bar code surface 5. The light beams emitted from the LEDs 3 and 3 are irradiated on the bar code surface 5 and reflected and received on a light receiving surface of the CCD sensor 1 through the lens body 4 and the focusing lens 2 . Therefore, an image of the bar code 5a is picked up by the CCD sensor 1. The image thus formed in the CCD sensor 1 is output as an electric analog signal. The analog signal is then processed by not shown analog-to-digital (A/D) converter and decoder to attain an information contained in the bar code 5a . It should be noted that the light beams in the angular range β about the light beam axis 7 irradiated onto the lens body 4 from the LEDs 3 and 3 is focused on the bar code surface 5 , as shown in Fig.3. This can be compared with the angular range α of the light beam from the LEDs 3,3 as in the prior art. As can be clear, by the effect of the lens body 4 , wider angular range of light beam can be focused on the bar code surface 5 in comparison with that in the prior art. Fig.4 is an illustration as viewed from the side in Fig.3 and showing the distribution of the light amount 13 on the bar code surface 5 irradiated by the light beams from the LEDs 3, 3 arranged with a 10 mm of distance from one another through the lens body 4. The light amount distribution on the bar code surface 5, as illustrated in Fig.4 , is substantially equal to that in the case where no lens body 4 is provided at a width s 10 (e.g., approximately 14 mm in the shown embodiment). Also, even when the bar code is read at a skewed attitude of the bar code reader system, the shown embodiment can reduce influence of the external light 9 penetrating through the cut-out portion 10 of the bar code reader system (see Fig. 10 which shows the prior art). Furthermore, since the lens body 4 is oriented substantially transverse to the light beam axis and thus parallel to the end opening of the housing of the bar code reader system, it may serve to block penetration of the dust and dirt into the interior of the bar code reader system. <Embodiment 2> The second embodiment is a modification of the foregoing first embodiment. In case of the bar code reader system having a construction of the optical system illustrated in the first embodiment, it is possible to form images with the reflected lights from intersections 8a and 8b between the surface of the lens body 4 and the light beam axis 7 to cause reading error or to make reading impossible. In the shown embodiment, in order to reduce influence of the reflected lights from the intersections 8a and 8b , the lens body 4 is offset from the light beam axis 7 in a direction transverse to the longitudinal direction of the CCD sensor 1 (i.e., lateral direction in Fig.5 ) for a given offset magnitude s 7 (e.g., 0.5 mm in the shown embodiment), as illustrated in Fig.5 corresponding to Fig.3. The primary light flux in this case is shown by the hatched area in Fig.5 . In the shown embodiment, since the incident angle of the light beam at the intersections 8a and 8b is not right angle relative to the surface on the lens body 4 , the reflected lights from the intersections 8a and 8b will never return to the CCD sensor 1. Therefore, the problem held in the former embodiment can be solved to provide performance in reading the bar code 5a . <Embodiment 3> As shown in Fig.6 , in the shown embodiment, the lens body 4 is offset from the light beam axis 7 in a direction transverse to the longitudinal direction of the CCD sensor 1 (i.e., lateral direction in Fig.6) in a given offset magnitude s 7 (e.g., 0.5 mm in the shown embodiment), as in the second embodiment. In addition, the LEDs 3, 3 are also offset from the light beam axis 7 in a direction transverse to the longitudinal direction of the CCD sensor 1 in a given magnitude s 8 (e.g., 0.2 mm in the shown embodiment). The arrangement in the shown embodiment is intended to avoid displacement of the focusing center on the bar code surface 5 and the light beam axis 7 due to the influence of tolerance in assembling components. Namely, as shown in Fig. 5 , the arrangement of the LEDs 3, 3 is intended to compensate difference of distances s 11 and s 12 from the light beam axis 7 to the outer edges of the focused light beam due to offset of the lens body 4. The primary light flux to be established in the shown embodiment is illustrated by the hatched area of Fig. 6 . As shown in Fig. 6 , according to the shown embodiment, the distances s 11 and s 12 between the light beam axis 7 and the outer edges of the focused light beam become substantially equal to each other. Therefore, a fine image can be established on the CCD sensor 1. <Embodiment 4> As shown in Figs. 7 to 9, the fourth embodiment employs lens bodies 4 of hollow construction. The LEDs 3, 3 and the lens body 4 are arranged at offset position as those proposed in the foregoing third embodiment. Namely, in the shown embodiment, the lens body 4 is offset in the transverse direction to the longitudinal direction of the CCD sensor 1 in the magnitude of 0.5 mm, and the LEDs 3, 3 are offset in the transverse direction in the magnitude of 0.2 mm. The primary light fluxes in the shown embodiment are shown in the hatched areas of Figs. 7 to 9 . It should be noted that Fig. 7 shows the case where a hollow cylindrical lens body having 5.0 mm of external diameter and 0.6 mm of internal diameter is employed, Fig. 8 shows the case where a hollow cylindrical lens body having 5.0 mm of external diameter and 2.0 mm of internal diameter is employed, and Fig. 9 shows the case where a hollow cylindrical lens body having 5.0 mm of external diameter and 4.4 mm of internal diameter is employed. Under the influence of the refraction index of the lens body 4 , the focusing performance is decreased according to increasing of the internal diameter. Therefore, depending upon application of the bar code reader system, optimal configuration of the lens body can be selected. It should be noted that the offset magnitudes s 7 and s 8 of the LEDs 3 , 3 and the lens body 4 are not limited to those discussed above. Also, it is possible to employ various light emitting elements in place of LEDs. Furthermore, as the material for forming the lens body, any appropriate material other than glass, synthetic resin can be used. Also, the refraction index of the lens body is not limited to the above-mentioned value (i.e., 1.488). In addition, as the image pick-up means, any other solid state image pick-up elements, conventional imaging tube and other image pick-up means can be employed in place of the CCD sensor.

Claims: A bar code reader for reading a micro-bar code (5a) provided on a bar code surface (5), the reader comprising: means (3) for illuminating the bar code; image detection means (1); and focusing means (2) for focusing light from the illuminated bar code onto the image detection means to enable said image detection means to read information included in the bar code; characterised by a cylindrical lens means (4) arranged in the path of said light from the illuminated bar code (5a) with its axis extending in a direction substantially along the bar code reading direction of the image detection means (1). A micro-bar code reader as set forth in claim 2, wherein the cylindrical lens means (4) is arranged to pass both the light beam from the illuminating means (3) and the light beam reflected from the bar code surface (5) therethrough. A micro-bar code reader as set forth in claim 1 or claim 2, wherein the illuminating means (3) comprises a light emitting body. A micro-bar code reader as set forth in claim 3, wherein the light emitting body is a pair of light emitting diodes (3). A micro-bar code reader as set forth in any of claims 1 to 4, wherein the image detection means (1) includes an image pick-up element comprising a charge coupled device. A micro-bar code reader as set forth in any of claims 1 to 5, wherein the focusing means is a focusing lens (2), and the focusing lens and the image detection means (1) are arranged along a common light beam axis (7). A micro-bar code reader as set forth in claim 6, wherein the cylindrical lens means (4) is arranged on said common light beam axis (7). A micro-bar code reader as set forth in claim 6, wherein the cylindrical lens means (4) is offset from said common light beam axis (7) in a direction transverse to the axial direction of the cylindrical lens means. A micro-bar code reader as set forth in claim 6, wherein the illuminating means (3) is arranged on said common light beam axis. A micro-bar code reader as set forth in claim 6, wherein the illuminating means (3) is offset from said common light beam axis in a direction transverse to the axial direction of the cylindrical lens means (4). A micro-bar code reader as set forth in any of claims 1 to 8, or claim 10, wherein said cylindrical lens means (4) is of a hollow cylindrical configuration.

Inventors: KOMAI TOSHIYUKI, NAKAMURA YUUKI, KOMAI, TOSHIYUKI, NAKAMURA, YUUKI
Applicants: NEOREX CO LTD, NEOREX CO., LTD.
Application year: 1992
Main classification: G06K7
IPC codes: G06K7