JPH0721295A - Optical reader - Google Patents

Abstract

PURPOSE:To provide an optical reader to obtain a binary signal free from a width error component by eliminating the influence of a swell component contained in a bar code readout signal. CONSTITUTION:In the optical reader provided with a photoelectric sensor part 1 to read a bar code and generate an analog signal having two signal levels corresponding to a white and a black levels, a signal amplifying part 2 to amplify the analog signal obtained by the photoelectric sensor part 1, and a binarizing part 3 to binarize the analog signal amplified by the signal amplifying part 2, a level error detection circuit 4 which detects the level error from a specified value of the amplified analog signal, and generates error detection information, a storage part 5 which stores the error detection information obtained by the level error detection circuit 4, and a gain correcting part 6 which changes the signal gain of the signal amplifying part 2 in accordance with the error detection information stored in the storage part 5, and controls the signal level of one analog signal so as to be constant are provided with.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical reading device for reading a bar code, and more particularly to correcting the undulation component of the signal level contained in the bar code read signal read by the optical sensor section to obtain the bar code. The present invention relates to an optical reading device that prevents a width error from occurring when a code reading signal is binarized.

[0002]

2. Description of the Related Art Conventionally, in an optical reading device for reading a bar code using a line sensor, that is, a so-called bar code scanner, a bar code is irradiated by a light emitting diode (LED) arranged in large numbers, and based on the irradiation. The light reflected from the bar code is read. In this case, the technical significance of irradiating a bar code with a large number of LEDs is not only to uniformly illuminate the paper surface on which the bar code is printed, but also to compensate for the sensitivity decrease in the peripheral area due to vignetting of the lens. In order to achieve these technical meanings, among the LEDs arranged in a large number,
It is necessary to make the light emission illuminance of the LEDs arranged in the peripheral portion larger than the light emission illuminance of the LED arranged in the central portion.

By the way, among the LEDs arranged in a large number, compared with the illuminance of the LED arranged in the central portion,
As a configuration for increasing the light emission illuminance of the LED arranged in the peripheral portion, for example, a means for increasing the drive current of the LED arranged in the peripheral portion as compared with the drive current of the LED arranged in the central portion, or L placed in the center
LEDs arranged in the peripheral area compared to the arrangement density of EDs
It is known to increase the arrangement density of the.

[0004]

However, in the above-mentioned known bar code scanner, when the bar code is irradiated using a large number of arranged LEDs and the above-mentioned light emission illuminance distribution is obtained, Not only is it considerably difficult to adjust the drive current and the layout density, but it is also necessary to suppress variations in the emission brightness of a large number of LEDs in addition to the adjustments described above. And
Once the above-mentioned adjustments and the above-mentioned variations are adjusted for a large number of LEDs, and the LEDs are arranged so as to obtain a desired light emission illuminance distribution, even if another external light is used there, the array There is a problem that it cannot be used like the set large number of LEDs.

Further, in the known bar code scanner, even if the variation in the light emission illuminance at the time of irradiating the bar code can be corrected by appropriately selecting the light emission brightness characteristics of a large number of LEDs, the known bar code is known. In addition to the above variations in bar code irradiation, there are variations in the light receiving sensitivity of a large number of light receiving elements used in a line sensor, variations in the optical system, and the like.
Therefore, in the known barcode scanner, unless all these variations are completely corrected, the barcode reading signal obtained at the time of reading the barcode has a signal level including the undulation component. If the bar code read signal including the component is binarized as it is, there is a problem that a binarized signal having a width error is obtained.

The present invention eliminates the above-mentioned problems, and its purpose is to substantially eliminate the influence of the waviness component contained in the bar code read signal, and to perform binarization without a width error component. An object is to provide an optical reader capable of obtaining a signal.

[0007]

In order to achieve the above object, the present invention provides a photoelectric sensor unit for reading a bar code and generating an analog signal having two signal levels corresponding to a white level and a black level, In the optical reading device including a signal amplification unit that amplifies the analog signal obtained by the photoelectric sensor unit and a binarization unit that binarizes the analog signal amplified by the signal amplification unit, A level error detection circuit that detects a level error from a specified value of an analog signal to generate error detection information, a storage unit that stores the error detection information obtained by the level error detection circuit, and a storage unit that is stored in the storage unit. And a gain correction unit that controls the signal gain of the signal amplification unit according to the error detection information so that one of the analog signals has a constant signal level. Comprising a.

In order to achieve the above object, the present invention provides a photoelectric sensor unit for reading a bar code and generating an analog signal having two signal levels corresponding to a white level and a black level, and the photoelectric sensor. A signal conversion unit for analog-digital converting the analog signal obtained in the section,
In the optical reading device including a digital correction unit that corrects the digital signal converted by the signal conversion unit and a binarization unit that binarizes the output digital signal of the digital correction unit, the converted digital signal Level error detection circuit for detecting a level error from a specified value of the error detection information, a storage unit for storing the error detection information obtained by the level error detection circuit, and an error stored in the storage unit. There is provided a second means for changing the correction value of the digital correction unit according to the detection information and controlling so that one signal level of the digital signal supplied to the binarization unit becomes constant.

[0009]

According to the first means, in the correction mode state, the analog signal obtained by reading the bar code is amplified by the signal amplification section and then input to the level error detection circuit. The level error detection circuit sequentially compares the signal level of each signal portion of the analog signal with a preset standard signal level, and obtains a level error from a specified value in the signal level of each signal portion of the analog signal. Of the analog signal, that is, the undulation component in the analog signal is detected, the detected undulation component is digitized and converted into error detection information, and then stored in the storage unit. In the read mode, when the analog signal is amplified by the signal amplifying unit, the error detection information is sequentially read from the storage unit in synchronization with the supply of the signal level of each signal portion of the amplified analog signal. The gain correction unit converts the sequentially read error detection information into an analog control signal and supplies the analog control signal to the signal amplification unit. The signal amplifying section has a variable signal gain characteristic in accordance with the supplied analog control signal, whereby the swell component in the analog signal is substantially removed,
The black level or white level of the analog signal is made constant.

As described above, in the first means,
When in the reading mode, the amplification of the bar code reading signal substantially removes the swell component contained in the bar code reading signal, thereby stabilizing the black level or the white level of the bar code reading signal. Therefore, a width error does not occur when the barcode read signal is binarized.

According to the second means, in the correction mode state, the analog signal obtained by reading the bar code is converted into a digital signal by the analog / digital signal conversion unit, and then the level error is detected. Supplied to the circuit. The level error detection circuit digitally sequentially compares the signal level of each signal portion of the digital signal with a preset standard digital signal level, and determines a prescribed value at the signal level of each signal portion of the digital signal. Of the level error, that is, the swell component in the digital signal is detected, the detected swell component is converted into error detection information, and then stored in the storage unit. In the read mode, when the signal level of each signal portion of the digital signal is digitally corrected by the digital correction unit, error detection is performed in synchronization with the supply of the signal level of each signal portion of the digital signal to be corrected. Information is sequentially read from the storage unit and supplied to the digital correction unit. The digital correction unit
The digital value is made variable according to the error detection information sequentially supplied, whereby the swell component in the digital signal is substantially removed, and the black level or white level of the digital signal is made constant.

As described above, in the second means,
In the reading mode state, the digital signal after the barcode reading signal is digitized is digitally corrected to substantially remove the swell component contained in the digital signal, thereby the black level of the digital signal or Since the white level is made constant, no width error occurs when binarizing the digital signal.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the construction of the first embodiment of the optical reading apparatus according to the present invention.

In FIG. 1, 1 is a CCD sensor (photoelectric sensor section), 2 is a variable gain amplifier (signal amplification section), and 3 is 2.
A binarization circuit (binarization unit), 4 is a level error detection circuit, 5 is a PROM (storage unit), 6 is a gain correction circuit (gain correction unit), 7 is a reference signal generator, 8 is a divider, and 9 is It is an OR gate.

The CCD sensor 1 is composed of a large number of photodiodes and CCDs arranged to read a bar code (not shown) and outputs a bar code reading signal (an analog corresponding to the black level and the white level of the bar code). A variable gain amplifier 2 has a signal gain characteristic controlled by a gain control signal supplied from a gain correction circuit 6 to generate a signal (hereinafter, this signal is referred to as an analog signal). The binarization circuit 3 converts the amplified analog signal (hereinafter, this signal is referred to as an analog amplified signal) into a binarized signal The level error detection circuit 4 includes at least a reference signal generator 7 and a division unit. The reference signal generator 7 generates a standard signal level (specified value) of the analog amplified signal. Then, the divider 8 performs division between the analog amplified signal level and the standard signal level (specified value) output by the reference signal generator 7 to detect the digitized error detected in the output of the level error detection circuit 4. The PROM 5 stores the error detection information, and the stored error detection information is read out and supplied to the gain correction circuit 6. The gain correction circuit 6 receives the supplied error detection information. Is converted into an analog gain control signal and supplied to the variable gain amplifier 2. The OR circuit 9 supplies the logical sum output of the scanning start signal and the correction start signal to the CCD sensor 1.
The scanning start signal is supplied to the PROM 5 and the gain correction circuit 6, and the correction start signal is supplied to the PROM 5 and the divider 8.

In this case, the level error detection circuit 4 outputs the analog amplified signal obtained when the bar code is read before the optical reading device is used, for example, before the optical reading device is shipped from the factory. Standard signal level, that is, each signal part (each black level part or each white level part) in an analog amplified signal that does not include any swell component
The signal levels of are defined as prescribed values, and the prescribed values determined here are stored in the reference signal generator 7 in advance.

The present embodiment having the above-described configuration operates as described below.

First, when a correction start signal is supplied to the CCD sensor 1 via the OR circuit 9 when the optical reading device is started to be used, that is, in the so-called correction mode state, the CCD sensor 1 is sequentially operated. A signal portion in which a bar code is scanned and read in response to a read clock signal (not shown) supplied, and the signal level sequentially changes in time corresponding to the scanning and reading of the black level and the white level of the bar code. To generate an analog signal (barcode reading signal). In this case, the analog signal has a white level (or black level) of the signal due to variations in the light emission brightness of a large number of LEDs for irradiating a barcode, variations in the light receiving sensitivity of a large number of photodiodes in the CCD sensor 1, and the like. It includes a component that changes with time, that is, a swell component. The analog signal containing the swell component is amplified by the variable gain amplifier 2, and similarly, the variable gain amplifier 2 outputs an analog amplified signal having a signal portion whose signal level sequentially changes with time. This analog amplified signal is supplied to the level error detection circuit 4. In the correction mode, the divider 8 is set to the correctable state by the supply of the correction start signal, and the PROM 5 is set to the storable state by the supply of the correction start signal.

Next, in the level error detection circuit 4, the signal portion in the analog amplified signal is divided by the divider 8
, The standard signal level (specified value) stored in advance in the reference signal generator 7 is sequentially taken out in synchronization with the sequential input of the signal portion in the analog amplified signal, and the divider is 8 is input. The divider 8 compares the signal levels of the respective signal levels of the analog amplified signals, which are sequentially input in synchronization with each other, with the corresponding standard signal level (specified value), and As a result of the comparison, an error signal indicating each signal level difference between each signal level of the signal portion of the analog amplified signal and a standard signal level (specified value) is sequentially generated. Subsequently, this error signal is converted into digitized error detection information and then supplied to the PROM 5 and sequentially stored therein, and the correction mode state is ended.

In the reading mode state described later, the error detection information stored in the PROM 5 is subsequently read out sequentially and supplied to the gain correction circuit 6. The gain correction circuit 6 converts the sequentially supplied error detection information into an analog control signal that sequentially changes according to the content of the error detection information, and the analog control signal has a signal gain characteristic of the variable gain amplifier 2 ( It is supplied to the variable gain amplifier 2 for setting the amplification gain). In this case, the analog control signal always indicates the signal level difference between each signal level of the signal portion of the analog amplified signal amplified by the variable gain amplifier 2 and the corresponding standard signal level (specified value). It can be changed at any time so that it has a polarity and size that can be lost.

Next, when a scanning start signal is supplied to the CCD sensor 1 via the OR circuit 9 in a state where the optical reading device is reading a bar code in earnest, that is, in a reading mode state, The CCD sensor 1 scans and reads the bar code in response to the supply of the read clock signal, and similarly, the signal level sequentially changes in time corresponding to the scanning and reading of the black level and the white level of the bar code. An analog signal (bar code reading signal) having a signal portion for generating is generated. Also in this case,
The analog signal includes the swell component, and the analog signal including the swell component is supplied to the variable gain amplifier 2. On the other hand, when the scanning start signal is supplied to the PROM 5, the stored error detection information is sequentially read, and the read error detection information is immediately supplied to the gain correction circuit 6. When the scanning start signal is supplied, the gain correction circuit 6 converts the error detection information sequentially supplied into an analog control signal corresponding to the information content, and the analog control signal obtained here is obtained. The control signal is supplied to the variable gain amplifier 2.

When each signal portion of the analog signal is sequentially input to the variable gain amplifier 2, PRO is synchronized with the sequential input of each signal portion to the variable gain amplifier 2.
The error detection information is sequentially read from M5, the read error detection information is converted into an analog control signal in the gain correction circuit 6, and then the analog control signal is sequentially input to the variable gain amplifier 2. At this time, in the variable gain amplifier 2, the signal portion of the sequentially input analog signal is amplified by the gain determined by the signal gain set by the similarly sequentially input analog control signal, and the waviness component is present on the output side. That is, the removed analog amplified signal is obtained.

The reason why the swell component included in the analog signal is removed by the variable gain amplifier 2 in the process of amplifying the analog signal, and the analog amplified signal containing no swell component is obtained is as follows.

First, the analog signal read by the CCD sensor 1 of the same optical reading device has almost the same tendency of changing the signal level in each signal portion every time it is read, That is, paying attention to the fact that an analog signal having almost the same swell component can be obtained each time it is read, and the signal level of each signal portion of the first read analog signal is preset. Each signal level difference from the standard signal level (specified value) (hereinafter, referred to as each initial signal level difference) is 2
Each signal level difference between the signal level of each signal portion of the analog signal read after the first time and the specified value (hereinafter,
This is almost equal to the signal level difference at each normal time), so in order to eliminate the signal level difference at each normal time, in other words, to remove the swell component from the analog amplified signal, The inventors have found that the correction may be performed by using the signal level difference at each initial time that shows the same change tendency as the signal level difference at each normal time.

Then, as a concrete correction means, CC
When the analog signal read by the D sensor 1 is amplified by the variable gain amplifier 2, it is created corresponding to the signal level input of each signal portion of the analog signal based on the already obtained signal level difference at each initial stage. The respective analog control signals thus generated are sequentially supplied to the variable gain amplifier 2. By the analog control signal having the polarity and the magnitude corresponding to the deviation amount of the signal level of each signal portion of the analog signal, The deviation amount of the signal level of each signal portion is corrected.

That is, in the comparison of the signal level difference between the signal portion of the signal portion and the specified value at a certain time point, the signal level of the signal portion is larger in the positive direction than the specified value. Sometimes, at a time corresponding to the certain time, the analog control signal generated based on the signal level difference at the initial time which is already large in the positive direction greatly reduces the gain of the variable gain amplifier 2. Therefore, when the signal level of the signal portion at the certain time point is amplified by the variable gain amplifier 2, the amplification rate is suppressed. On the other hand, in the comparison between the signal level of the signal portion at the other time and the specified value, when the signal level of the signal portion is smaller than the specified value, at the time corresponding to the other time, Since the analog control signal created based on the already obtained large signal level difference in the negative direction at the initial time greatly increases the gain of the variable gain amplifier 2, the analog control signal of the signal portion at the other time point is increased. When the signal level is amplified by the variable gain amplifier 2, the amplification rate is increased.

Similarly, in the comparison of the signal level difference between the signal portion of the signal portion and the prescribed value at a certain time point, the signal level of the signal portion becomes smaller in the positive direction than the prescribed value. In this case, the analog control signal generated based on the small signal level difference in the positive direction which has already been obtained at the time corresponding to the certain time reduces the gain of the variable gain amplifier 2 to some extent. Therefore, when the signal level of the signal portion at the certain point of time is amplified by the variable gain amplifier 2, the amplification degree is slightly suppressed. On the other hand, in comparison with the signal level difference between the signal level of the signal portion and the specified value at another time point, when the signal level of the signal portion is smaller in the negative direction than the specified value, At the time corresponding to the other time, the analog control signal created based on the already-obtained small initial signal level difference in the negative direction slightly increases the gain of the variable gain amplifier 2. When the signal level of the signal portion at the other time point is amplified by the variable gain amplifier 2, its amplification degree is slightly increased.

As described above, when the signal level of each signal portion in the analog signal is amplified by the variable gain amplifier 2, the polarity of the signal level of each signal portion depends on the deviation from the specified value. And the gain of the variable gain amplifier 2 fluctuates so as to cancel the fluctuation, the analog amplified signal obtained at the output side of the variable gain amplifier 2 has a constant white level (or black level). And it does not contain swell components.

When the analog amplified signal not containing the swell component is supplied to the binarization circuit 3, accurate binarization corresponding to the white level component and the black level component in the signal is executed, At the output of the binarization circuit 3, a binarized signal with no width error can be obtained.

In the present embodiment, the divider 8 is used to derive the signal level difference between the signal level of each signal portion in the analog amplified signal and the specified value. A similar function can be achieved by using a subtracter instead of the device 8.

Next, FIG. 2 is a block diagram showing the configuration of the second embodiment of the optical reading apparatus according to the present invention.

In FIG. 2, 10 is an EPROM (erasable programmable read only memory), and 11 is a first memory.
2 is a second switch, and the same components as those shown in FIG. 1 are denoted by the same reference numerals.

A correction mode switching signal is supplied to each of the first switching device 11 and the second switching device 12. The correction mode switching signal has a negative polarity or zero polarity in the correction mode state, and has a positive polarity in the reading mode state. The first switch 11 is turned off when the correction mode switching signal has a negative polarity or zero polarity, and the second switch 12 is turned on when the correction mode switching signal has a negative polarity or zero polarity.

Here, comparing this embodiment with the configuration of the above-mentioned first embodiment, the first embodiment uses the EPROM 10 for storing error detection information, whereas the first embodiment does not. In the example, the PROM 5 is used, and in the present embodiment, the first switch 11 is connected between the variable gain amplifier 2 and the gain correction circuit 6, and the level error detection circuit 4 and the EPR are connected.
The second switch 12 is connected to the OM 10, whereas the first embodiment does not have such a first switch 11 and a second switch 12. There are differences,
Other than that, there is no difference in structure between this embodiment and the first embodiment.

Next, the operation of this embodiment will be compared with the operation of the above-mentioned first embodiment.

First, in the correction mode state, in the present embodiment, the correction mode switching signal of negative polarity or zero polarity is supplied to the first switching device 11 and the second switching device 12, respectively, whereby the first switching device 11 and the second switching device 12 are supplied. The switch 11 is turned off to open the gap between the gain correction circuit 6 and the variable gain amplifier 2, and the second switch 12 is turned on to connect the level error detection circuit 4 and the EPROM 10. In contrast to the connection between the gain correction circuit 6 and the variable gain amplifier 2 and the level error detection circuit 4, the first embodiment does not supply the correction mode switching signal as described above. PROM5
There is an operational difference in that both are connected to each other. However, when the remaining operation, that is, the operation in which each signal portion of the analog signal is amplified by the variable gain amplifier 2 and the analog amplified signal is obtained, and the analog amplified signal is sequentially input to the divider 8, the analog amplified signal is obtained. In synchronism with the sequential input of the signal portion in, the standard signal level (specified value) stored in advance in the reference signal generator 7 is sequentially taken out and inputted to the divider 8; , The signal levels of the signal portions of the analog amplified signal that are sequentially input in synchronization with each other and the standard signal level (specified value) corresponding thereto are compared with each other. An operation of sequentially generating an error signal indicating each signal level difference between each signal level of the signal portion and a standard signal level (specified value), which error signal After being converted into digitizing has been error detection information, PROM5 (or EPROM1
0) is supplied to and sequentially stored therein, there is no difference between this embodiment and the first embodiment. Therefore, regarding the operation of this embodiment in the correction mode state, Further detailed description will be omitted.

Next, in the reading mode state, similarly, the present embodiment is similar to the first switching device 11 and the second switching device 1.
2 is supplied with a positive polarity correction mode switching signal,
As a result, the first switch 11 is turned on, and the gain correction circuit 6 and the variable gain amplifier 2 are connected,
At the same time, the second switch 12 is turned off and the level error detection circuit 4 and the EPROM 10 are opened, while the first embodiment changes the correction mode switching signal as described above. There is no supply, and there is an operational difference in that the connection between the gain correction circuit 6 and the variable gain amplifier 2 and between the level error detection circuit 4 and the PROM 5 are maintained. However, the remaining operation, that is, when the signal level of each signal portion in the analog signal is amplified by the variable gain amplifier 2, the deviation is caused according to the deviation amount from the specified value of the signal level of each signal portion. Each time the polarity and the degree of the signal fluctuate, an analog control signal having a polarity and a magnitude that cancels the fluctuation is supplied to the variable gain amplifier 2, thereby increasing the amplification gain of the signal level of each signal portion in the analog signal. Regarding the operation of sequentially changing the white level (or black level) of the analog amplified signal obtained at the output side of the variable gain amplifier 2, there is no difference between the present embodiment and the first embodiment. Because there is no
The detailed description of the operation of this embodiment in the read mode is also omitted.

As described above, also in this embodiment, the analog amplified signal obtained at the output side of the variable gain amplifier 2 does not include the swell component, and the analog amplified signal not including the swell component is a binary signal. When it is supplied to the binarization circuit 3, accurate binarization corresponding to the white level component and the black level component in the signal is executed, and the binarized signal in which the width error does not occur at the output of the binarization circuit 3. Can be obtained.

Also in the present embodiment, a similar function can be achieved by using a subtracter instead of the divider 8.

Next, FIG. 3 is a block diagram showing the configuration of the third embodiment of the optical reading apparatus according to the present invention, showing an example in which the swell component of an analog signal is removed by a digital correction circuit. It is a thing.

In FIG. 3, 13 is a fixed gain amplifier, 1
Reference numeral 4 is an analog-digital (A / D) converter, 15 is a digital correction circuit, and the same components as those shown in FIG. 1 are denoted by the same reference numerals.

The output of the CCD sensor 1 is connected to the input of the fixed gain amplifier 13, and the output of the fixed gain amplifier 13 is connected to the input of the A / D converter 14. The output of the A / D converter 14 is connected to the input of the digital correction circuit 15, and the output of the digital correction circuit 15 is connected to the input of the binarization circuit 3. The output of the A / D converter 14 is connected to one input of the divider 8 of the level error detection circuit 4, and P
The output of the ROM 5 is connected to the control input of the digital correction circuit 15.

The operation of this embodiment having the above-mentioned structure is as follows.

When the correction start signal is supplied to the CCD sensor 1 through the OR circuit 9 in the correction mode state, C
The CD sensor 1 scans and reads a barcode according to the supply of a read clock signal (not shown), and the signal level sequentially changes in time corresponding to the scanning and reading of the black level and the white level of the barcode. An analog signal having a signal portion and an analog signal containing a swell component are generated. The analog signal containing the undulation component is amplified to a proper level by the fixed gain amplifier 13, and the fixed gain amplifier 13 outputs an analog amplified signal also containing the undulation component. The analog amplified signal containing the undulation component is converted into a digital amplified signal by the A / D converter 14 and then supplied to the level error detection circuit 4. In the correction mode, the divider 8 is set to the correctable state by the supply of the correction start signal, and the PROM 5 is also set to the storable state by the supply of the correction start signal.

Next, in the level error detection circuit 4,
When each signal portion of the digital amplified signal is sequentially input to the divider 8, a standard signal stored in the reference signal generator 7 in synchronization with the sequential input of each signal portion of the digital amplified signal. Levels (specified values) are sequentially taken out and input to the divider 8. The divider 8 digitally compares the signal levels of the respective signal portions of the digitally amplified signal, which are sequentially input in synchronism, with the corresponding standard signal level (specified value). As a result of the comparison, a digital error signal (error detection information) indicating each signal level difference between the signal level of each signal portion of the digital amplified signal and a standard signal level (specified value) is sequentially generated. . Subsequently, this error detection information is supplied to the PROM 5 and sequentially stored therein, and the correction mode state ends.

When a scanning start signal is supplied to the CCD sensor 1 via the OR circuit 9 in the reading mode, the CCD sensor 1 scans and reads the bar code according to the supply of the read clock signal. Similarly, an analog signal including a waviness component is generated corresponding to scanning and reading of the black level and the white level of the barcode. The analog signal containing the swell component is
The fixed gain amplifier 13 amplifies the signal to an appropriate level to form an analog amplified signal, which is supplied to the A / D converter 14. A
The / D converter 14 converts the analog amplified signal into an analog-
It is converted to digital and converted to a digital amplified signal. The converted digital amplified signal is sequentially supplied to the digital correction circuit 15. On the other hand, when the scanning start signal is supplied, the PROM 5 sequentially reads the stored error detection information, and the read error detection information is immediately supplied to the digital correction circuit 15 as a digital correction signal.

In the present embodiment as well, in the read mode state described later, the error detection information stored in the PROM 5 is subsequently read out sequentially and supplied to the digital correction circuit 15 as a digital correction signal. This digital correction signal is used to set the digital signal transfer characteristic in the digital correction circuit 15, and is always the signal level of each signal portion in the digital amplified signal digitally corrected by the digital correction circuit 15 and the standard corresponding to it. It is variable at any time so as to have a polarity and magnitude so as to eliminate each signal level difference from a specific signal level (specified value).

Here, when each signal portion of the digital amplified signal is sequentially input to the digital correction circuit 15,
The error detection information is sequentially read from the PROM 5 in synchronization with the sequential input of the signal portions to the digital correction circuit 15, and the read error detection information is sequentially input to the digital correction circuit 15 as a digital correction signal. Is entered. At this time, the digital correction circuit 15 digitally corrects each signal portion of the sequentially input digital amplified signals by the digital correction amount set by the sequentially input digital correction signal, and swells on its output side. A digital amplified signal from which components have been removed is obtained.

As described above, when the signal level of each signal portion of the digital amplified signal is digitally corrected by the digital correction circuit 15, the deviation of the signal level of each signal portion from the specified value is caused. The digital correction amount of the digital correction circuit 15 fluctuates every time the polarity and the degree of the fluctuate, so that the digital amplified signal obtained at the output side of the digital correction circuit 15 has a white level (or a black level). Level) becomes constant, and the swell component is not included.

When the digital amplified signal not containing the waviness component is supplied to the binarization circuit 3, accurate binarization corresponding to the white level component and the black level component in the digital amplified signal is performed. It is possible to obtain a binarized signal which is executed and has no width error at the output of the binarization circuit 3.

Also in the present embodiment, a similar function can be achieved by using a subtracter instead of the divider 8.

Next, FIG. 4 is a block diagram showing the configuration of the fourth embodiment of the optical reading apparatus according to the present invention, which is an example using a correction mode switching signal.

In FIG. 4, the same components as those shown in FIGS. 2 and 3 are designated by the same reference numerals.

Then, the second switch 12 is supplied with a correction mode switching signal which has a negative polarity or zero polarity in the correction mode state and a positive polarity in the reading mode state, and The switch 12 is turned on when the correction mode switching signal has a negative polarity or a zero polarity.

Comparing the present embodiment with the configuration of the above-mentioned third embodiment, the present embodiment shows E because the error detection information is stored.
While the PROM 10 is used, the PROM 5 is used in the third embodiment, and in the present embodiment, the second switch 1 is provided between the level error detection circuit 4 and the EPROM 10.
The second embodiment is different from the second embodiment in that the third embodiment does not include such a second switching device 12, whereas the second embodiment is connected to the third embodiment. There is no structural difference between and.

The following is a comparison between the operation of this embodiment and the operation of the third embodiment described above.

In the correction mode state, this embodiment
A negative polarity or zero polarity correction mode switching signal is supplied to the second switch 12, which turns on the second switch 12 to cause the level error detection circuit 4 and the EPROM 10 to operate.
In contrast to the above, the third embodiment does not supply the correction mode switching signal as described above, and the level error detection circuit 4 and the PROM 5 are always connected. There is a difference in operation in points. However, the remaining operation, that is, after the analog gain signal is obtained by the fixed gain amplifier 13, the analog gain signal is digitally converted by the A / D converter 14, and the digital gain signal is obtained. Are sequentially input to the divider 8, the standard signal level (specified value) stored in advance in the reference signal generator 7 is sequentially extracted in synchronization with the sequential input of the signal portion in the digital amplified signal. And the operation input to the divider 8 respectively, the divider 8
As a result of digitally comparing the signal level of each signal portion of the digitally amplified signal that is sequentially input in synchronization with the corresponding standard signal level (specified value), digital amplification An operation of sequentially generating an error signal (error detection information) indicating each signal level difference between a signal level of each signal portion of a signal and a standard signal level (specified value). This error detection information is stored in the PROM 5 (or EPROM 10). There is no difference between the present embodiment and the third embodiment in the operation supplied to the () and sequentially stored therein, so that the operation of the present embodiment in the correction mode state will be described below. The above detailed description will not be given.

Also, in the reading mode state, similarly, in the present embodiment, the correction mode switching signal having the positive polarity is supplied to the second switching device 12, whereby the second switching device 12 is activated.
Is turned off, and the level error detection circuit 4 and the EPROM 1 are turned off.
In contrast to the case where 0 is opened, the first embodiment does not supply the correction mode switching signal as described above, and the level error detection circuit 4 and the PROM 5 are always connected. There is a difference in operation in that it is done. However, the remaining operation, that is, when the signal level of each signal portion in the digital amplified signal is digitally corrected by the digital correction circuit 15, according to the deviation amount from the specified value of the signal level of each signal portion, Each time the polarity and degree of the deviation change, a digital correction signal having a polarity and magnitude that cancels the change is supplied to the digital correction circuit 15, whereby the signal level of each signal portion in the digital amplified signal is changed. Regarding the operation in which the digital correction amount is sequentially changed and the white level (or black level) of the digitally amplified signal obtained at the output side of the digital correction circuit 15 is made constant, the operation between the present embodiment and the third embodiment is performed. There is no difference between them and the operation of this embodiment in the read mode state will not be described in further detail.

As described above, also in this embodiment, the digital amplified signal obtained at the output side of the digital correction circuit 15 does not include the swell component, and the digital amplified signal not including the swell component is binary. When it is supplied to the binarization circuit 3, accurate binarization corresponding to the white level component and the black level component in the signal is executed, and the binarized signal that does not cause a width error is output to the binarization circuit 3. Can be obtained.

Also in the present embodiment, a similar function can be achieved by using a subtracter instead of the divider 8.

In addition to the above, in the first to fourth embodiments, the level error detection circuit 4 is detachably attached to the main body of the optical reading device.
Is the PROM when in the correction mode before factory shipment.
5 or EPROM 10 for writing error detection information, and the level error detection circuit 4 may be removed at the time of factory shipment.

[0063]

As described above, according to the present invention, when the signal level of each signal portion in the analog signal obtained by reading the bar code is amplified by the variable gain amplifier 2, each signal portion is amplified. Each time the polarity and degree of the deviation fluctuates from the specified value of the signal level of, the analog control signal for varying the gain of the variable gain amplifier 2 is supplied so as to cancel the variation. Therefore, the analog amplified signal obtained at the output of the variable gain amplifier 2 does not include the swell component. In this case, the analog amplified signal that does not include the waviness component is 2
When it is supplied to the binarization circuit 3, accurate binarization corresponding to the white level component and the black level component in the signal is executed, and the binarization circuit 3 does not produce a width error in the output. There is an effect that a signal can be obtained.

Further, according to the present invention, when the digital correction circuit 15 digitally corrects the signal level of each signal portion in the digitally amplified signal obtained by digitally converting the analog signal obtained by reading the bar code after amplification. , A digital correction for varying the digital correction amount of the digital correction circuit 15 so as to cancel the variation each time the polarity and the degree of the variation fluctuate according to the deviation from the specified value of the signal level of each signal portion. Since the signal is supplied, the digital amplified signal obtained at the output of the digital correction circuit 15 does not include the swell component. Also in this case, when the digital amplified signal that does not include the swell component is supplied to the binarization circuit 3, accurate binarization corresponding to the white level component and the black level component in the signal is performed, and 2 The output of the binarization circuit 3 has the effect of being able to obtain a binarized signal with no width error.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing a configuration of a first embodiment of an optical reading device according to the present invention.

FIG. 2 is a block configuration diagram showing a configuration of a second embodiment of the optical reading device according to the present invention.

FIG. 3 is a block diagram showing the configuration of a third embodiment of the optical reading device according to the present invention.

FIG. 4 is a block diagram showing a configuration of a fourth embodiment of the optical reading device according to the present invention.

[Explanation of symbols]

 1 CCD sensor (photoelectric sensor part) 2 variable gain amplifier (signal amplification part) 3 binarization circuit (binarization part) 4 level error detection circuit 5 PROM (storage part) 6 gain correction circuit (gain correction part) 7 reference Signal generator 8 Divider 9 OR gate 10 EPROM (storage unit) 11 First switcher 12 Second switcher 13 Fixed gain amplifier 14 Analog / digital (A / D) converter 15 Digital correction circuit (digital correction unit )

Claims (6)

[Claims] 1. A photoelectric sensor unit for reading a bar code and generating an analog signal having two signal levels corresponding to a white level and a black level, and a signal amplification unit for amplifying the analog signal obtained by the photoelectric sensor unit. And a binarizing unit for binarizing the analog signal amplified by the signal amplifying unit, an error detection information by detecting a level error from a specified value of the amplified analog signal. Generating a level error detection circuit, a storage unit for storing the error detection information obtained by the level error detection circuit, and a signal gain of the signal amplification unit corresponding to the error detection information stored in the storage unit. An optical reading device, comprising: a gain correction unit that changes and controls one of the analog signals to be constant. 2. Opening and closing states are switched by a correction mode switching signal between the level error detection circuit and the storage section and between the signal amplification section and the gain correction section, respectively. 2. The optical reading device according to claim 1, wherein the switching device is arranged. 3. A photoelectric sensor section for reading a bar code and generating an analog signal having two signal levels corresponding to a white level and a black level, and an analog-digital conversion of the analog signal obtained by the photoelectric sensor section. An optical reading device comprising: a signal conversion unit that performs the conversion, a digital correction unit that corrects the digital signal converted by the signal conversion unit, and a binarization unit that binarizes the output digital signal of the digital correction unit, A level error detection circuit that detects a level error from the specified value of the converted digital signal to generate error detection information, a storage unit that stores the error detection information obtained by the level error detection circuit, and the storage The correction value of the digital correction unit is changed according to the error detection information stored in the unit, and one of the signal levels of the digital signal supplied to the binarization unit is changed. The optical reading device is characterized in that it is controlled so as to be constant. 4. A third switch, which is opened / closed by a correction mode switching signal, is arranged between the level error detection circuit and the storage section.
An optical reader as described. 5. The optical reading device according to claim 1, wherein the level error detection circuit is configured to be detachable from the optical reading device. 6. The optical reading device according to claim 2, wherein the storage unit is an EPROM.