JPH05225374A - Bar code reader - Google Patents

Abstract

PURPOSE:To provide a bar code reader capable of accurately reading out any bar code only by the reader itself independently of a distance up to a bar code to be read out. CONSTITUTION:A distance from the set position of the reader up to a bar code to be read out is detected by a range finder 11. Respective reading time width data of a margin, a thin bar and a thick bar corresponding to the distance detection signal are computed by an operation means and automatically set up. An electric signal obtained by photoelectrically converting reflected light from the bar code by a photodetecting element is converted into a digital signal by a binarizing circuit 18. The bar code is decoded from the digital signal by a decoding means 27 correspondingly to the computed reading time width data. Thereby the single reader is arranged, and even if a reading distance from the reader up to the bar code is changed, margins and thin and thick bars can be accurately read out without requiring any adjusting work.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a machining setup change system for accurately sending product number information to a transfer machine for automatic setup change, and for grasping production results in real time by reading a bar code. The present invention relates to a stationary fixed bar code reader used for process control systems and the like.

[0002]

2. Description of the Related Art Such a stationary fixed bar code reader is capable of reading remote bar codes, unlike other bar code readers which can be read only by applying them to bar codes such as pen scanners and touch switches. Since it has the advantage that it can read a bar code attached to a product moved on a conveyor, for example, it is mainly used in the above-mentioned physical distribution field and production control field. Laser light is generally used as the light source of this type of bar code reader, and when used for the above-mentioned applications, the positional relationship between the bar code and the bar code reader for projecting light and receiving reflected light is Since it is constant in the same process, a laser beam obtained by focusing laser light by a collimator lens is used.

By the way, a bar code is a bar code symbol that represents data and the like in a combination of a thick bar and a thin bar of different thickness written in black and a white space between these bars, and a bar code symbol of this bar code symbol. Each of the margins is composed of a pair of white margins provided as margins on the left and right sides.
The left margin is a start character that represents the start of data, and the right margin is a stop character that represents the end of data. Then, when the barcode is read and decoded by the barcode reader, it is determined that the margin is detected when the black bar signal is read after the margin is read for a certain period of time or more, and the process is performed as the barcode read signal. A method is generally adopted in which the signal processing is started at the same time as the black-and-white bar signal is read and then the margin is read for a certain period of time or more to determine the margin detection.

[0004]

By the way, FIG. 4 (a)
When the barcode (B) is placed opposite to the barcode reader (BR) at a distance of L1 as shown by the solid line, and when the barcode L (L) is longer than the distance L1 at the barcode reader (BR) as shown by the chain line. Comparing with the case where the barcode (B) is placed at the distance of, the time for scanning the distance D1 when the barcode (B) at the solid line position is read by the laser beam reflected by the rotating mirror, and the one-dot chain line position Since the time for scanning the distance D2 when reading the barcode (B) is the same, the reading time of the margin (M) of the barcode (B) at each reading is different.
That is, the bar code (B) at the alternate long and short dash line position shown by MS2 in FIG. 4 (b) corresponds to the read signal of the margin (M) of the bar code (B) at the solid line position shown by MS1 in FIG. 4 (b).
The margin (M) read signal has a very small pulse width. In this way, since the reading time of the margin and the reading time of the thick bar and the thin bar are different according to the distance between the bar code reader (BR) and the bar code (B), the read signals have different pulse widths. There is naturally a limit to the range of distance that can be read by the same stationary fixed barcode reader. Therefore, conventionally, many models are produced according to the distance to the reading barcode in each process, which is very uneconomical. In addition, for users of this barcode reader, it is necessary to install many models in parallel and use them differently, or to perform troublesome work such as replacement and adjustment of models each time the reading distance to the barcode changes. However, when only a single model is installed, there is a drawback that it is necessary to change the transfer route of the object attached with the barcode to be read so as to match the reading distance of the barcode reader.

Further, as shown in FIG. 5A, when a laser beam from a laser diode (LD) is scanned from a point S to a point E by a polygon mirror (PM) rotating at a constant speed in the arrow direction, The scanning speed of the laser beam is S
It gradually becomes slower from the point toward the E point. Therefore, when a bar group in which bars having a constant width (t) are arranged at constant intervals (T) is read as shown in FIG. 5A, the read signal is gradually pulsed as shown in FIG. 5B. The pulse train signal changes so that the width becomes larger. That is, although the bars have the same width, a polygon mirror (PM) is used.
Since the read signals with different pulse widths are generated according to the change of the rotation angle, the thick bar and the thin bar cannot be accurately discriminated when the bar code is read, and an erroneous detection may occur.

Therefore, the present invention is to provide a bar code reader capable of accurately reading a bar code with a single model regardless of the difference in the distance to the bar code to be read and the rotation angle of the rotating mirror. It is what

[0007]

According to the present invention, a bar code reader is constructed as follows as a technical means for achieving the above-mentioned object. That is, a rotating mirror that reflects the projected laser beam to scan the bar code to be read, a light receiving element that converts the light reflected by the bar code and incident through the optical system into an electric signal, and the electric signal to the bar. A binarization circuit that binarizes and converts the code into a digital signal according to the bar and space of the code, a distance measuring sensor that detects the distance to the bar code to be read, and a bar from the digital signal output from the binarization circuit. A decoding processing unit for decoding display data by a code, and the decoding processing unit calculates the reading time width of each of the margin, the thin bar and the thick bar in the bar code by the distance detection signal of the distance measuring sensor. And converting the output digital signal of the binarizing circuit into data by comparing the signal widths of 1 and 0 thereof with the reading time width by the arithmetic means. Is configured as characterized in that the provided decoding means that.

Further, a rotation angle detection circuit for detecting the rotation angle of the rotary mirror is provided, and each reading time width by the arithmetic means is corrected in the decoding processing section by an angle detection signal output from the angle detection circuit. It is preferable to provide angle correction means for changing the corrected reading time width and sending it to the decoding means.

[0009]

Before reading the bar code, the reading time width of the margin adapted to the reading distance based on the distance detection signal from the distance measuring sensor by the calculating means of the decoding processing section,
The reading time width of the thin bar and the reading time width of the thick bar are calculated. Then, the optical information that the reflected light from the barcode is collected by the optical system and is incident on the light receiving element is
It is converted into an analog electric signal according to the intensity of light with respect to the black thick bar and thin bar of the bar code and the white space, and this electric signal sets black as "1" and white as "0" in the binarization circuit. Is converted to a binary digital signal and then sent to the decoding processing unit. In this decoding processing unit, when a signal having a signal width matching the margin reading time width data calculated by the calculating unit is input from the binarizing circuit, it is determined that the margin has been detected, and the decoding unit detects the barcode. The bar code symbol reading process is started, and the time width of "1" of the bar code symbol reading digital signal input from the binarization circuit is calculated by the calculating means to be the thin bar reading time width and the thick bar reading time width. The barcode symbol is decoded and converted into character data by comparing with each data of.

Therefore, since the margin reading time width, the thin bar reading time width and the thick bar reading time width data are automatically set according to the distance to the bar code, a single reader is installed. Even if the reading distance from the reader to the bar code changes, the margin, the thin bar, and the thick bar can be read with high accuracy without any adjustment work or the like.

Further, each data of the margin reading time width, the thin bar reading time width and the thick bar reading time width calculated by the calculating means may be corrected by the angle correcting means based on the rotation angle detection signal of the rotating mirror. For example, even if the rotation angle of the rotating mirror changes
The thick and thin bars can be read more accurately.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a perspective view of a schematic configuration of one embodiment of the present invention, in which a laser beam of a light projecting element (1) composed of a laser diode as a light source is condensed by a projecting lens (2) composed of a collimator lens. After being converted into a laser beam, it is projected on a rotating mirror (3) for optical scanning. The rotating mirror (3) is provided with reflecting mirrors on each of eight side surfaces of an octagonal prism, and the central axis (4) is continuously rotated at a constant speed in the same direction indicated by an arrow by a motor (not shown), The above laser beam is a product (5)
The surface of the bar code (7) marked on the label (6) attached to is scanned. The reflected light from the bar code (7) is condensed by the light receiving lens (8) and is incident on the light receiving element (9) such as a photo detection element. The light projecting element (1) and the light projecting lens (2) are attached to a focus adjusting mechanism section (10) described later.

Then, in the vicinity of the rotating mirror (3),
A distance measuring sensor (11) for contactlessly measuring the distance to the bar code (7) of the label (6) attached to the product (5) sequentially transferred to the predetermined position of the bar code reader of the present invention. It is arranged. The distance measuring sensor (11) includes a light projecting unit (not shown) that projects a beam for projecting light composed of pulse-modulated light onto an object to be detected for detecting a distance, and a light projecting unit from the light projecting unit. A known one is used which is composed of a light projecting portion and a light receiving portion (not shown) arranged in a triangulation manner with respect to an object to be detected, which are laterally spaced apart from each other by a predetermined distance. That is, in the light receiving portion, the semiconductor position detecting element (not shown) which is incident after the reflected light of the projected light from the detected object is condensed by the light receiving lens is a position detecting sensor using a photodiode. Since it is formed to have a uniform resistance value over the entire light receiving surface, the photocurrent obtained by photoelectrically converting the light incident on this is divided and output in inverse proportion to the distance to the electrodes on both sides, that is, the resistance value. , The light receiving spot position of the semiconductor position detecting element can be detected by calculating the currents of the both electrodes, and the light receiving spot position of the position detecting element corresponds to the distance from the light projecting lens to the detected object. The distance to the object reflected by the projection beam can be detected by calculation. A distance detection signal output from the distance measuring sensor (11) is input to a decoding processing unit and a focus adjusting mechanism unit (10), which will be described later, of the control circuit unit (12).

FIG. 2 shows a block configuration of an electric control system.
The same parts as those in FIG. 1 are designated by the same reference numerals. The distance detection signal from the distance measuring sensor (11) is read by the decoding processing unit (1) prior to reading the barcode (7).
9) Margin calculating means (20), Fine bar calculating means (2)
1) and the thick bar calculation means (22), respectively. In each of the calculating means (20) to (22), the margin for the change in the distance to the bar code (7) which is experimentally obtained in advance and is stored in each, the reading time width of each of the thin bar and the thick bar. Is calculated based on the data regarding the change in the distance and the distance detection signal input from the distance measuring sensor (11), and the reference reading time width of the margin, the reference reading time width of the thin bar, and the reference reading time width of the thick bar are calculated. To be done.

The margin reference reading time width, the thin bar reference reading time width and the thick bar reference reading time width calculated by the margin calculating means (20), the thin bar calculating means (21) and the thick bar calculating means (22), respectively. Of the respective data of the respective angle correction means (23), (24),
It is corrected in (25). That is, the angle correction means (23) to (24) detect the rotation angle of the rotating mirror (3) based on the output signal of, for example, an encoder for driving the rotating mirror (3) to rotate accurately at a constant speed by a motor. Based on the rotation angle detection signal from the rotation angle detection circuit (32), each data of the margin reference reading time width, the thin bar reference reading time width and the thick bar reference reading time width is associated with the change as described in FIG. Then, each data of margin correction reading time width, thin bar correction reading time width and thick bar correction reading time width is calculated. Then, the margin correction reading time width data is sent to the coincidence determining means (26), and the thin bar correction reading time width data and the thick bar correction reading time width data are sent to the decoding means (27).

On the other hand, the optical information that the reflected light from the bar code (7) is condensed by the light receiving lens (8) and is incident on the light receiving element (9), is the black thick bar and the thin bar of the bar code (7). The black and white striped pattern of the barcode (7) obtained by scanning the barcode (7) surface with the rotating mirror (3) with light is converted into an analog electric signal according to the intensity of light with respect to the white space. It becomes an analog ripple electric signal proportional to the bar width of the thin bar and the thick bar, and after this electric signal is amplified by the amplifier circuit (17), for example, black is set to "1" in the binarization circuit (18). Moreover, after being converted into a binary digital signal with white being "0", it is input to the coincidence determination means (26) and the decoding means (27) of the decoding processing section (19).

Then, in the coincidence discriminating means (26),
It is determined whether or not a signal having a signal width matching the margin correction time width data from the angle correction means (23) is input from the binarization circuit (18), and the margin is detected when the matching signal is input. Decoding means (27)
To the bar code (7) to start the reading process of the bar code symbol. Here, the margin-corrected reading time width data is obtained by correcting the reference reading time width of the margin corresponding to the distance to the bar code (7) with the ever-changing rotation angle of the rotating mirror (3). Even if only a single reader is installed and the reading distance to the barcode (7) changes, the margin can be detected with high accuracy without any adjustment work or the like.

Then, in the decoding means (27), 2
The time width of “1” of the read digital signal of the bar code symbol input from the binarization circuit (18) is set to the thin bar correction read time width and the thick width which are input from both angle correction means (24) and (25), respectively. The bar code symbol is decoded in comparison with each data of the bar correction reading time width, converted into character data such as ASCII code and output to the host computer or the like through the output circuit (28). Here, each data of the thin bar correction reading time width and the thick bar correction reading time width is a rotation that changes the reference reading time width of each of the thin bar and the thick bar corresponding to the distance to the barcode (7) momentarily. Since it is corrected according to the rotation angle of the mirror (3), even if the reading distance to the bar code (7) changes with a single reader, there is no need for adjustment work, etc. Can be detected with high accuracy.

By the way, in a bar code reader using this type of laser beam, especially when a semiconductor laser is used as a light source, the divergence angle of the beam is large, and the divergence angle in the longitudinal direction and the divergence angle in the lateral direction are different from each other. It is extremely difficult to perform collimation. Therefore, since the readable distance range in the same bar code reader is naturally limited, many models have conventionally been produced according to the distance to the read bar code in each process. Therefore, in the above-described embodiment, the optical system is automatically displaced in accordance with the distance to the barcode (7) to be read, and the single model can accurately read regardless of the difference in the distance to the barcode (7). A focus adjustment mechanism section (10) is provided, a vertical cross-sectional view of this focus adjustment mechanism section (10) is shown in FIG. 3, and its block configuration is shown in FIG.
This will be described. In FIG. 3, the light projecting element (1)
Is fixed to the base plate (13) by inserting the laser emitting portion through the through hole of the base plate (13). The cylindrical laminated piezoelectric actuator (14) is mounted on the base plate (13). The light projecting element (1) is fixed in a state of being positioned in the center. This laminated piezoelectric actuator (1
In 4), the maximum displacement amount of 50 μm is piled up in three layers, and the maximum displacement amount of the whole is as large as 150 μm. In the piezoelectric actuator (14), a lens mount (15) having a bottomed cylindrical shape is loosely inserted, and a flange portion integrally protruding outward from an upper edge of the mount (15) is provided. The piezoelectric actuator (14) is fixed to the peripheral surface of the upper edge of the opening, and the projection lens (2) has its own lens portion at the center of the bottom plate on the bottom surface of the bottom plate of the lens fixture (15). The lens portion is opposed to the light projecting element (1) by being inserted through the formed through hole and fixed. The piezoelectric actuator (14) is connected to a voltage generating circuit described later through a pair of electrode plates (16) provided on the upper end surface and the lower end surface, respectively.

Then, in FIG. 2, the distance measuring sensor (1
The distance detection signal from 1) is corrected in the correction circuit (29) so as to obtain linearity with respect to the detected distance, and the corrected distance detection signal is input to the voltage generation circuit (30) and the voltage generation circuit (30). ) Generates a voltage having a preset value with respect to the input distance detection signal, and supplies this voltage to the piezoelectric actuator (14). As a result, the piezoelectric actuator (14) is deformed and displaced, and the light projecting lens (2) is displaced in the direction of approaching and separating from the light projecting element (1). The displacement correction circuit (31) controls the correction circuit (29) to correct the correction based on the temperature signal of the piezoelectric actuator (14) output from the temperature sensitive element and the hysteresis characteristic of each piezoelectric actuator (14) itself. .. As a result, the piezoelectric actuator (14), that is, the light projecting lens (2) is displaced by the displacement amount corresponding to the distance detection signal, and the distance of the light projecting lens (2) to the light projecting element (1) becomes the bar code (7). The spot diameter of the laser beam is automatically corrected according to the change in the distance to.

[0021]

As described above, according to the bar code reader of the present invention, the distance to the bar code to be read is detected by the distance measuring sensor, and the margin reading time width corresponding to the distance to the bar code is detected by the distance detection signal. Each data of the thin bar reading time width and the thick bar reading time width is automatically set, and the digital signal by binarizing the electric signal photoelectrically converted from the reflected light of the bar code is calculated as the calculated reading time width data. Since it is configured to decode in contrast, even if a single reader is installed and the reading distance from this reader to the barcode changes, the margin, thin bar and thick bar can be adjusted without any adjustment work. It can be read with high accuracy.

Further, the margin reading time width, the thin bar reading time width and the thick bar reading time width calculated by the calculating means may be corrected by the angle correcting means based on the rotation angle detection signal of the rotating mirror. For example, even if the rotation angle of the rotating mirror changes
The thick and thin bars can be read more accurately.

Therefore, for a user, it is possible to cope with various reading distances up to the bar code by installing only one unit, and even if the reading distance up to the bar code is changed, there is no troublesome work such as replacement or adjustment of the model. There is a great advantage that it is not necessary, while the manufacturer can reduce costs by reducing the number of production models.

[Brief description of drawings]

FIG. 1 is a perspective view of a schematic configuration of an embodiment of the present invention.

FIG. 2 is a block diagram of a signal processing system of the above.

FIG. 3 is a vertical sectional view of a focus adjusting mechanism section of the above.

FIGS. 4A and 4B are explanatory diagrams showing a difference in margin read signal with respect to a difference in distance to a barcode.

5A and 5B are explanatory diagrams showing a difference in bar read signal with respect to a rotation angle of a rotating mirror.

[Explanation of symbols]

 3 rotating mirror 7 bar code 8 light receiving lens (optical system) 9 light receiving element 11 distance measuring sensor 18 binarization circuit 19 decoding processing unit 20 margin calculating means 21 thin bar calculating means 22 thick bar calculating means 23 to 25 angle correcting means 27 Decoding means

Claims (2)

[Claims] 1. A rotating mirror for reflecting a projected laser beam to scan a bar code to be read, a light receiving element for converting light reflected by the bar code and incident through an optical system into an electric signal, and this electric element. A binarization circuit that binarizes a signal by converting it into a digital signal by binarizing the bar and space of a bar code, a distance measuring sensor that detects a distance to a bar code to be read, and an output digital of the binarization circuit. A decoding processing unit for decoding display data by a bar code from the signal is provided, and the decoding processing unit calculates the reading time width of each of the margin, the thin bar and the thick bar in the bar code by the distance detection signal of the distance measuring sensor. And the output digital signal of the binarizing circuit by comparing the signal widths of 1 and 0 with the reading time width by the arithmetic means. A bar code reader, characterized in that it is provided with a decoding means for converting the data. 2. A rotation angle detection circuit for detecting the rotation angle of the rotary mirror is provided, and each decoding time width by the arithmetic means is corrected in the decoding processing unit by an angle detection signal output from the angle detection circuit. The bar code reader according to claim 1, further comprising angle correction means for changing to a corrected reading time width and sending it to the decoding means.