JP2667393B2 - Barcode reader - Google Patents

Description

TECHNICAL FIELD The present invention relates to a bar code reading device,
In particular, it reads a barcode at an arbitrary distance from the barcode reader. [Prior Art] A conventional device of this type irradiates optical information with light, forms a reflected image of this light through a lens system to form an information image on the surface of a reading sensor, and then forms the image on the electronic image of the sensor. It is converted to an electric signal by a reading operation by scanning. For example, handheld bar code readers and stationary bar code readers are generally known, and the distance to the bar code is designed in advance, and the magnification of the lens system is also set to these distances. Designed accordingly. [Problems to be Solved by the Invention] However, the present situation is that the setting distances of the bar code and the information reading sensor are determined by the selection of the lens, and the degree of freedom for use by the user is ignored. For example, in the case of a stationary bar code scanner, even if some error occurs in the position of the bar code, the focal depth of the lens system is deepened to read the bar code correctly,
In some cases, the focus is adjusted so that the output of the reading sensor is equal to or higher than a predetermined value. Conventional stationary bar code scanners read bar codes within a predetermined distance range. However, if the range of the distance is widened, the image of the barcode at a long distance becomes small, and reading becomes difficult, even if the focusing function is provided. In view of this, the present invention provides a bar code reading device that is provided with a magnification adjusting mechanism for changing the magnification in a lens system of the bar code reading device and can form a readable bar code image on a reading sensor regardless of the distance. It is done for the purpose of. [Means for Solving the Problems] In order to achieve the above-described object, the present invention, as shown in FIG. 1, includes a start code (2a) and an end code (2b) indicating the beginning and end of information. An image forming lens system (11) including a focus adjusting mechanism (16) and a magnification adjusting mechanism (18) for forming an image of a bar code (2) recorded at both ends on a predetermined reading position. A reading sensor (13) arranged at the reading position for converting the image of the bar code into an electric signal, and a focus control circuit (15) for controlling the focus adjusting mechanism so that the focus of the image coincides with the reading position. And a microcomputer (17) that controls the magnification adjusting mechanism so that the image of the barcode is detected by the reading sensor at a predetermined magnification, and the microcomputer includes, as shown in FIG. The reading section Based on an electric signal from the controller, it is determined whether or not the width of the bar included in the barcode exceeds a predetermined value, and the first step of enlarging the magnification adjusting mechanism until it is determined that the width exceeds a predetermined value. (103, 104, 201, 20
2) and, based on the electric signal from the reading sensor, it is determined whether or not there is a signal corresponding to the predetermined start code, and the magnification adjusting mechanism is reduced until it is determined that there is a signal. Two steps (105, 106, 201, 203)
And a third step of reducing the magnification adjusting mechanism until it is determined that there is a signal corresponding to the predetermined end code based on the electrical signal from the reading sensor (108, 109, 201, 203). [Operation] In the above configuration, the barcode reading device of the present invention
An imaging optical system including an issue adjustment mechanism and a magnification adjustment mechanism is provided. That is, the imaging optical system is variably rehabilitated for both the focal point and the magnification. The focus adjustment mechanism is controlled by the focus control means and forms an image of the barcode on the reading sensor. On the other hand, the magnification adjusting mechanism is controlled by the microcomputer and adjusts the magnification so that the image of the barcode is detected by the reading sensor at a predetermined magnification. At this time, the microcomputer controls the magnification adjusting mechanism by the following processing. The first step is to judge whether the width of the bar included in the bar code exceeds a predetermined value based on the electric signal from the reading sensor, and expand the magnification adjusting mechanism until it is judged that the width of the bar exceeds the predetermined value. Let it. As a result, even if the magnification of the magnification adjusting mechanism is not appropriate and the barcode is not sufficiently enlarged, this state is determined and the bar width is enlarged until it reaches a predetermined value. As a result, the magnification of the magnification adjustment mechanism becomes an appropriate value, and it is possible to prevent a problem that the bar code image is small and the bar width is recognized in a narrow state. In the second step and the third step, it is determined whether or not there is a signal corresponding to a predetermined start code, or whether or not a signal corresponding to encoding is present. Reduce the adjustment mechanism. As a result, even if the image of the barcode is enlarged too much and the image does not fit within the reading range of the reading sensor, it is determined that the start code and the encode existing at the end of the barcode exist. Since the size of the bar code is reduced until the information is read, it is possible to prevent a problem that information existing at both ends of the bar code is recognized outside the reading range. [Advantages of the Invention] As described above, even if the magnification of the magnification adjusting mechanism is not appropriate and the barcode is not sufficiently enlarged, or even if the barcode is sufficiently enlarged. The bar code image is formed on the reading sensor at an appropriate magnification based on the determination. Therefore, even if the bar card is located at a long distance and the image formed on the reading sensor becomes small, and vice versa, the bar code is always read at the correct magnification. Therefore,
A barcode at an arbitrary distance can be read. [Embodiments] Hereinafter, embodiments of the present invention shown in the drawings will be described. First, the configuration of the present embodiment will be described. FIG. 1 is a block diagram of a bar code reader to which the present invention is applied. Reference numeral 1 is a bar code reading device, which reads a generally known bar code and uses a predetermined character code, for example,
Convert to ASCII code and output. This Barco reader 1 has the following configuration. 11 is a lens having a cooled focus adjusting mechanism and a magnification adjusting mechanism, 12 is a diaphragm member having a slit having a longitudinal direction parallel to each bar constituting a bar code to be read, 13 is a large number of photoelectric conversion elements in a straight line. It is an electronic scanning type image sensor arranged. The image sensor 13 is sequentially scanned by the exposure control circuit 14 for controlling the exposure time of the photoelectric conversion elements from a photoelectric conversion element at the end at predetermined time intervals, and produces an output according to the exposure amount of each photoelectric conversion control element. The exposure control circuit 14 obtains an optimum exposure time so that this output satisfies a predetermined condition. Similarly, the focus control circuit 15 drives the focus adjustment motor 16 based on the output of the image sensor 13. The focus control circuit 15 adjusts the focus so that the output waveform of the image sensor 13 rises to a value having a certain value with a sharpness of a predetermined value or more. The output of the image sensor 13 is input to a microcomputer 17, which outputs an ASCII code according to the output of the image sensor 13 and drives a magnification adjusting motor 18. This magnification adjustment is performed so that the start code 2a and the end code 2b of the bar code 2 are detected. Generally, a bar code encodes and records information in a predetermined format, and is determined to include a start code and an end code to indicate the start and end of the information. The bar code 2 in FIG. 1 records four characters "a12a" in a bar code system of NW-7. Of these four characters, the front and rear "a" indicate a start code and an end code, respectively. Various bar code systems have been proposed, and different start codes and end codes are defined for each system, but the start code and end code according to these bar code systems are processed by a microcomputer. It is easy to recognize this, and the following description will be made based on the barcode 2 of the NW-7 system shown in FIG. FIG. 2 is a conceptual diagram of a system that manages trucks entering and leaving a factory using the barcode reader shown in FIG. A bar code label 3 on which a bar code 2 encoding information on cargo is printed is affixed to a predetermined position on trucks entering and leaving the factory. Track 4
Stops at a predetermined position at the entrance of the structure. At this time, the barcode reader 1 reads the barcode 2, converts it into a predetermined code, and outputs it to the entry / exit management computer 5. This data is also sent out to a data network constituting the factory management system. Next, the operation of the magnification adjustment which is a main part of the present invention will be described in more detail. In the case of a bar code, there is a convention that bar characters defined by each bar code system exist at both ends of the bar code. By utilizing this, zoom control can be performed. Conventionally, for recognition of a barcode, a start character is recognized after cutting out margins (blanks) at both ends, and if this does not exist, it is processed as a reading error. Also, if there is no end character at the end of decoding, this has also been processed as an error. The two causes of these errors are that the bar width is too narrow to make reading impossible, and that the start character and the end character are outside the reading range and make reading impossible. FIGS. 3A and 3B are flowcharts showing a part of the operation of the microcomputer 17. FIG. When the program of the microcomputer 17 arrives at the reading start processing, the processing of FIG. 3 (a) is executed. In step 101, the output of the image sensor 3 is input as digital data. The output of the image sensor 13 is an output at an arbitrary magnification, and the exposure and the focus have already been adjusted by the exposure control circuit 14 and the focus control circuit 15. The microcomputer 13 recognizes the width of each bar of the bar code 2 from the output of the image sensor 13. In step 102, the part corresponding to the start code of the data input from the image sensor 13 is decoded. In step 103, it is judged whether or not the width of the bar indicated by the data processed in step 102 is smaller than a predetermined value. If it is narrow, the enlargement mode is set in step 104 and the motor drive routine shown in FIG. 3 (b) is set. Move to In step 201, it is determined whether the setting mode is enlargement. Steps if enlargement
In 202, the motor is driven in the expansion direction by a predetermined amount, and if it is reduced, the motor is driven in the reduction direction by a predetermined amount. Upon completion of any of the processes, the process returns to step 101. If it is determined in step 103 that the bar width is equal to or larger than the predetermined value, step 10
Proceed to 5. In step 105, it is determined whether or not the data corresponding to the start code decoded in step 102 is the start code. If it is not the start god, the reduction mode is set by the stab 106, and the process proceeds to the motor drive routine. If a start code is detected in step 105, all data following the start code is decoded in step 107. In step 108, it is determined whether or not there is an end code in the decoding in step 107. If there is no end code, set the reduction mode in step 109,
Move to motor drive routine. If there is an end code, the reading is terminated assuming that the reading was successful, and the ACCII code obtained by decoding the barcode is output. Although one embodiment of the present invention has been described above, the method described below may be applied to the magnification adjustment. The reference value of the width of the bar of the bar code to be read is stored in advance, and the magnification is adjusted so that the width of the bar code indicated by the output of the image sensor 13 becomes the reference value. Start code and end code correspond to the image sensor
The magnification is adjusted so that an image is formed in a predetermined range on 13. As described above, the present invention is not appropriate for the magnification adjustment mechanism, and is not appropriate even if the barcode is not sufficiently enlarged or the barcode is enlarged too much. Is determined, and a barcode image is formed on the reading sensor at an appropriate magnification based on the determination. Therefore, even if the bar code is located at a long distance and the image formed on the reading sensor becomes small, and vice versa, the bar code is always read at the correct magnification.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a bar code reading apparatus according to an embodiment of the present invention, and FIG. 2 is a conceptual diagram of a system using the bar code reading apparatus according to an embodiment. 3 (a),
(B) is a flowchart showing the operation of the microcomputer of one embodiment. 1 ... Barcode reader, 2 ... Barcode, 11 ...
Lens, 13 image sensor, 15 focus control circuit,
16: Focus adjustment motor, 17: microcomputer,
18 …… Magnification adjustment motor

Claims (1)

(57) [Claims] An image forming optical system including a focus adjusting mechanism and a magnification adjusting mechanism for forming an image of a bar code in which a start code and an end code indicating the start and end of information are recorded on both ends, at a predetermined reading position, A reading sensor which is arranged at the reading position and which converts the image of the barcode into an electric signal; a focus control circuit which controls the focus adjusting mechanism to match the focus of the image with the reading position; And a microcomputer which controls the magnification adjusting mechanism so that the image is detected by the reading sensor at a predetermined magnification, the microcomputer is included in the barcode based on an electric signal from the reading sensor. Determining whether the width of the bar exceeds a predetermined value, and expanding the magnification adjustment mechanism until it is determined that the width exceeds the predetermined value. A second step of determining whether or not there is a signal corresponding to the predetermined start code based on an electric signal from the reading sensor, and reducing the magnification adjusting mechanism until it is determined that the signal exists. A third step of determining whether or not there is a signal corresponding to the predetermined end code on the basis of an electric signal from the reading sensor, and reducing the magnification adjusting mechanism until it is determined that the signal exists. A bar code reader, comprising: