JP2003295089A - Code reader and method of driving the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect and adjust the quantity of light of a light source without being affected by the variance in the light quantity of reflected light. <P>SOLUTION: When a bar code 11 is read, a light source 20 is turned on by an LD controller 26, and a reflection plate 23 is driven to be rotated by a reflection plate controller with the light source 20 on, and a luminous flux from the light source 20 is made to scan the bar code 11, and reflected light is detected by a reflected light detector and is transduced to an electric signal corresponding to the detection level and is decoded to the original code. Since it is necessary for the LD controller 26 to keep the optical output of the light source 20 at a fixed level on the basis of the detection signal from a PD 21, the quantity of light of the PD 21 is detected in a period other than the scanning period of the luminous flux by the reflection plate controller 25 and the reflection plate 23, and the quantity of light of the PD 21 is not detected during scanning of the luminous flux, and thus the quantity of light is stably detected without being affected by reflected light. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a code reading device for optically reading various pattern codes such as a one-dimensional bar code and a two-dimensional pattern code, and a driving method thereof.

[0002]

2. Description of the Related Art Conventionally, in this type of code reading apparatus, for example, a bar code having a regularity in the one-dimensional direction or a pattern code having a regularity in the two-dimensional direction, which is printed on the surface of a label or a product package, is used. Optically reading and outputting code information according to its regularity, the reflected light of the light emitted from the code reading device is imaged by various image pickup devices, and the picked-up image is analyzed to obtain a one-dimensional image. The regularity of the bar code or the two-dimensional pattern code is judged and converted into the corresponding code information.
In the present description, one-dimensional bar codes, two-dimensional pattern codes, etc. will be generically referred to as pattern codes.

By the way, a semiconductor laser is often used as a light source of such a code reading apparatus because of its convenience. However, in general, the semiconductor laser has a large negative coefficient of the amount of emitted light with respect to temperature. Therefore, when the semiconductor laser is driven with a constant current, the heat generation thereof causes the amount of emitted light to decline with time.
Therefore, in the conventional code reading device, as a countermeasure against this, a detector such as a photodiode for detecting the amount of emitted light is used, and a light amount control circuit by feedback that increases the drive current of the semiconductor laser by the amount of the decreased amount of emitted light is used. Is used to control so that the light amount is always constant.

[0004]

However, although the change of the light emission amount of the semiconductor laser is greatly improved by the light amount control circuit as described above, the reflected light is coded from the emission port of the light source or the reception window of the reflected light. It is necessary to strictly shield the reflected light so that it does not enter the inside of the reading device and affect the semiconductor laser emission amount detection device, but the reflected light to the exit of the light beam cannot completely prevent the entry. . When such reflected light reaches the light emission amount detection device, the accurate light emission amount cannot be detected. Here, if the reflected light always has a constant intensity, it is possible to make a correction in advance,
Like a handy bar code reader,
In the case of a code reading device in which the distance to the object to be read and the environment change, the intensity of the reflected light also changes significantly, so that there is a problem in that the amount of light emission cannot be controlled accurately. Incidentally, for example, JP-A-2-14478.
As disclosed in Japanese Unexamined Patent Publication No. 6-1871 and Japanese Unexamined Patent Publication No. 8-171604, a scanning device and method having a function of adjusting the range of a light beam bundle have been proposed. It is difficult to solve various problems.

Therefore, an object of the present invention is to provide a code reading apparatus and its driving method capable of detecting the light amount of a light source and adjusting the light amount without being affected by the fluctuation of the light amount of reflected light.

[0006]

In order to achieve the above object, the present invention provides a light source for irradiating an object provided with a pattern code with a light flux, and a scanning means for scanning the light flux emitted from the light source. A light amount detecting means for detecting the light amount of the light flux emitted from the light source, a light amount control means for controlling the emitted light amount of the light source based on the light amount detected by the light amount detecting means, and a reflected light from the object. In the code reading device having the reflected light detecting means for detecting and converting into an electric signal, and the decoding means for decoding the pattern code into the original code based on the electric signal outputted by the reflected light detecting means, The light amount is detected by the light amount detecting unit during a period other than the scanning period of the light beam bundle, and the light amount is not detected by the light amount detecting unit during the scanning of the light beam bundle. .

Further, according to the present invention, a light source for irradiating an object provided with a pattern code with a light flux, a scanning means for scanning the light flux emitted from the light source, and a light quantity of the light flux emitted from the light source are detected. Light amount detection means, a light amount control means for controlling the emitted light amount of the light source based on the light amount detected by the light amount detection means, and a reflected light detection for detecting reflected light from the object and converting it into an electric signal. And a decoding means for decoding a pattern code into an original code based on an electric signal output from the reflected light detecting means, in a period other than a scanning period of a light flux by the scanning means. In addition, the light amount detection unit detects the light amount, and the light amount detection unit does not detect the light amount during the scanning of the light flux.

In the code reading apparatus and the driving method thereof according to the present invention, the light amount is detected by the light amount detecting means during the period other than the scanning period of the light beam by the scanning means, and the light amount is detected by the light amount detecting means during the scanning of the light beam. Since it is not performed, the light amount of the light source can be detected and the light amount can be adjusted without being affected by the change in the light amount of the reflected light due to the scanning of the light beam, and the appropriate light amount control can be performed. The reading performance can be improved.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a code reading apparatus and a driving method thereof according to the present invention will be described below. The embodiments described below are preferred specific examples of the present invention, and various technically preferable limitations are given. However, the scope of the present invention is not limited to the present invention in the following description. Unless otherwise stated, the present invention is not limited to these embodiments.

FIG. 1 is a schematic explanatory view showing a configuration example of a code reading device according to an embodiment of the present invention. As shown in FIG. 1, the code reading apparatus of this example is configured as a bar code reader that reads a bar code 11 or the like printed on an object 10 such as a label, and a semiconductor element such as a laser diode (LD). Light source 20 and a photodetector (PD) 2 for detecting the light output of this light source 20
1, a lens 22 for converting a light ray bundle emitted from the light source 20 into a parallel light ray bundle, a reflection plate 23 for scanning the light ray bundle converted by the lens 22 in parallel toward the object 10, And a shield plate 24 for limiting the scanning range of the light beam scanned by the reflection plate 23.

Further, as a control system, a reflector control device 25 for driving the reflector 23, an LD control device 26 for controlling the light output of the light source 20 by a signal from the PD 21, a reflector control device 25 and an LD control device. And a timing control device 27 that determines the control timing of the control signal 26. The LD control device 26 compares the detected value from the PD 21 with a preset reference value, and outputs an operating current corresponding to the difference between the detected value and the light source 2.
0, and operates so as to maintain the output of the light source 20 at a constant value. Although not shown in the drawing, a lens for condensing the reflected light from the object 10 and a signal reproduction (photodiode (PD)) for capturing the speed of the light passing through the lens and converting it into an electric signal ( A reflected light detection device for decoding) is provided.

In such a structure, the bar code 11
When reading the
In a state in which 0 is emitted, the reflector 23 is rotationally driven by the reflector controller 25 to scan the light beam from the light source 20 along the barcode 11, and the reflected light is detected by the reflected light detector. Then, the reflected light detecting device converts the electric signal corresponding to the detection level, and decodes the bar code 11 to the original code from the converted signal. Then, in such a reading operation, the LD control device 26 needs to maintain the light output of the light source 20 at a constant level based on the detection signal from the PD 21, but the reflection plate control device 25 drives the reflection plate 23. When the light quantity is detected by PD21 inside,
The reflected light of the object 10 enters the code reading device, and P
The detected value of D21 is affected. Therefore, in the present embodiment, the reflector control device 25 and the reflector 23 (scanning means)
The light amount is detected by the PD (light amount detection means) 21 during a period other than the scanning period of the light beam by the PD, and the light amount is not detected by the PD 21 during the scanning of the light beam, so that it is stable without being affected by the reflected light. Performs proper light intensity detection. In particular,
The driving method according to the two operation examples described below is used.

FIG. 2 is a timing chart showing a first operation example according to this embodiment. Hereinafter, FIG. 1 and FIG.
The first operation example according to the present embodiment will be described in detail with reference to FIG. For example, bar code readers are roughly classified into handy type bar code readers and stationary bar code readers. The operation timing according to the first operation example is mainly effective for the handy type bar code reader. That is, in the case of a handy type bar code reader, a switch (not shown) for instructing reading is provided, and the operator points the bar code reader at the bar code to be read and then presses the switch for instructing reading. Then, in the case of performing such work, the LD does not emit a light beam before pressing the read instruction switch.

Further, as shown in FIG. 1, since the optical output of the LD 20 greatly changes depending on the temperature and the use time,
Normally, the light output from the LD 20 is placed in the vicinity of P
Monitor with D21 to ensure a constant light output. However, since the PD 21 is installed in the vicinity of the LD 20, the light output of the LD 20 can be accurately detected when the light flux from the LD 20 is reflected by a barcode or the like and enters the PD 21. You will not be able to do it. Since the amount of reflected light in this case is not constant depending on the target barcode and environment, P
The detection value of D21 is also not constant, and the output of the LD20 becomes unstable due to the reflected light. Therefore, as shown in FIG. 1, a shield plate 24, which is slightly narrower than the scanning range of the light beam, is installed in the vicinity of the reflection plate 23 for scanning the light beam,
With this shield plate 24, the shield plate 2 can be used within a certain range of the light flux.
As described in 4, the reflected light of the light bundle is always generated under a constant condition for a part of the time of scanning the light bundle.

Since the reflecting plate 23 operates so as to always scan the light flux during the reading of the bar code,
The ray bundle is scanned in the order of points B, D and E in FIG.
Then, after scanning to the point E, the reflecting plate 23 operates in the opposite direction and scans the ray bundle in the order of the points E, D, and B. Here, the position of the reflection plate 23 is configured such that the ray bundle hits the point B in advance, and the ray bundle is scanned as shown in FIG. Then, in the first operation example,
After the scanning switch of the barcode is pressed and before the beam bundle reaches the point D after scanning is started, the light amount of the LD 20 is adjusted to a target value by the signal from the PD 21.
This timing is controlled by the timing control device 27. In this way, while the condition of the reflected light from the LD 20 is guaranteed to be constant, the LD
By adjusting the light amount of 20, it is guaranteed that the light amount is always constant.

FIG. 3 is a timing chart showing a first operation example according to this embodiment. Hereinafter, FIG. 1 and FIG.
The second operation example according to the present embodiment will be described in detail with reference to FIG. This second operation timing is mainly effective for a stationary bar code reader. That is, in the stationary bar code reader, the LD 20 is always made to emit light, and the bar code 1
This is a case where the object 10 marked with 1 is held up. In this case, unlike FIG. 2, the barcode reading timing is irregular, so that it is necessary to constantly adjust the light amount of the LD 20. Therefore, during the repeated scanning of the light bundle, the light amount of the LD 20 is adjusted during the time when the light bundle is scanned from the point B to the point D to avoid the influence of the reflected light.

By using the first operation example or the second operation example as described above, the light emission amount of the LD 20 can be accurately controlled without the influence of the reflected light from the object, and the bar code is read. It is possible to improve the performance of the device. In the above example, the code reading device intended for a one-dimensional bar code reader is described as an example, but the present invention is also applicable to a code reading device for a two-dimensional pattern code. The specific configuration and arrangement of the elements are not limited to the above example. For example, the shield plate 24 may be replaced with a casing forming the device. Further, the reflector 23 is not limited to reciprocating motion, but may be configured to rotate.

[0018]

As described above, according to the code reading apparatus of the present invention, the light amount is detected by the light amount detecting means during the period other than the scanning period of the light beam by the scanning means, and the light amount is detected during the scanning of the light beam. Since the light amount is not detected by the detecting means, the light amount of the light source can be detected and the light amount can be adjusted without being affected by the change in the light amount of the reflected light due to the scanning of the light flux, and the appropriate light amount control can be performed. Therefore, the reading performance of the code pattern can be improved.

Further, according to the driving method of the code reading apparatus of the present invention, the light amount detecting means detects the light amount during the period other than the scanning period of the light beam bundle by the scanning means, and the light amount detecting means is in operation during the scanning of the light beam bundle. Since the light amount is not detected by, the light amount of the light source can be detected and the light amount can be adjusted without being affected by the change in the light amount of the reflected light due to the scanning of the light beam, so that the appropriate light amount control can be performed. The reading performance of the code pattern can be improved.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram showing a configuration example of a code reading device according to an embodiment of the present invention.

FIG. 2 is a timing chart showing a first operation example of the code reading device shown in FIG.

FIG. 3 is a timing chart showing a second operation example by the code reading device shown in FIG.

[Explanation of symbols]

10 ... Object, 11 ... Bar code, 20 ... Light source (LD), 21 ... Photodetector (PD), 22 ...
… Lens, 23 …… Reflector, 24 …… Barrier plate, 25 ……
Reflector control device, 26 ... LD control device, 27 ... Timing control device.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hisataka Izawa             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation (72) Inventor Masayuki Ota             3-53-2, Shiratori, Shiroishi, Miyagi Prefecture Sony             Shiraishi Semiconductor Co., Ltd. F-term (reference) 2H045 BA18 CB22 CB42 DA41                 5B072 CC24 DD01 LL12 LL15 LL18

Claims (8)

[Claims] 1. A light source for irradiating an object provided with a pattern code with a light flux, a scanning means for scanning the light flux emitted from the light source, and a light amount detection for detecting the light intensity of the light flux emitted from the light source. Means, a light quantity control means for controlling the emitted light quantity of the light source based on the light quantity detected by the light quantity detection means, and a reflected light detection means for detecting reflected light from the object and converting it into an electric signal, A code reading device having a decoding unit that decodes a pattern code into an original code based on an electric signal output by the reflected light detection unit, wherein the light amount detection unit is included in a period other than a scanning period of the light flux by the scanning unit. The code reading device is characterized in that the light amount is detected by the light amount detecting means and the light amount is not detected by the light amount detecting means during scanning of the light beam bundle. 2. The code reading apparatus according to claim 1, wherein the light amount detection by the light amount detection unit is completed before the light beam is scanned by the scanning unit. 3. The code reading apparatus according to claim 1, wherein when the scanning unit repeatedly scans the light flux, the light amount detection unit detects the light amount in a constant period in the middle of each scanning period. . 4. The code reading device according to claim 1, wherein the light source is a light source made of a semiconductor element. 5. The light quantity control means compares the light quantity detection value obtained by the light quantity detection means with a reference value and supplies an operating current corresponding to the difference to the light source to keep the light quantity constant. The code reading device according to claim 1, wherein 6. A light source for irradiating an object provided with a pattern code with a light flux, a scanning means for scanning the light flux emitted from the light source, and a light amount detection for detecting the light intensity of the light flux emitted from the light source. Means, a light quantity control means for controlling the emitted light quantity of the light source based on the light quantity detected by the light quantity detection means, and a reflected light detection means for detecting reflected light from the object and converting it into an electric signal, In a driving method of a code reading device having a decoding unit that decodes a pattern code into an original code based on an electric signal output by the reflected light detection unit, in a period other than a scanning period of a light flux by the scanning unit, A method for driving a code reading device, wherein the light amount is detected by the light amount detecting means, and the light amount is not detected by the light amount detecting means during scanning of the light beam bundle. 7. The method of driving a code reading apparatus according to claim 6, wherein the light amount detection by the light amount detection unit is completed before the light beam is scanned by the scanning unit. 8. The code reading device according to claim 6, wherein when the scanning unit repeatedly scans the light flux, the light amount detection unit detects the light amount in a constant period in the middle of each scanning period. Driving method.