JPH02211593A - Optical information reader - Google Patents

Abstract

PURPOSE:To decrease the generation of a read failure and to exactly read optical information of a low speed and a high speed by providing a filter element having a prescribed low frequency passing characteristic on a signal processing means and suppressing the influence of a void and a spot mixed in the optical information. CONSTITUTION:By an image sensor 9 of an optical information scanner, optical information stored optically is scanned along a read line, and the optical information is converted to an electric signal and inputted to a control circuit 11. It is brought to signal processing by the control circuit 11, and a binary signal corresponding to the optical information is obtained from a binarizing circuit 116. Also, in accordance with a decoder circuit 12, a filter element having a low frequency passing characteristic is formed by a frequency dividing circuit 111, a clock generating circuit 112 and a sample holding circuit 114 in the control circuit 11. Subsequently, by adjusting a relation of an input speed to the filter element and the low frequency passing characteristic of the filter element, an information signal is read with high accuracy and at a high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a reading device for optically recorded information, and particularly to a device for reducing reading failures due to defects in the optical information.

[Conventional technology]

As a conventional optical information reading device, for example, JP-A-59-
The one disclosed in Japanese Patent No. 58582 is generally known.

The device disclosed in this publication is equipped with a -dimensional image sensor, and achieves low-resolution, high-speed reading by alternately reading signals from odd-numbered row pixels and even-numbered row pixel signals of this image sensor and decoding each of them. However, high-resolution, low-speed reading is achieved by combining odd and even columns, reading them out, and decoding them.

[Problem to be solved by the invention]

In the conventional technology as described above, high resolution and low resolution are switched by changing the number of pixels used for one barcode reading. However, in order to increase or decrease the number of effective pixels, the method disclosed in the above-mentioned publication, for example, requires controlling the transfer timing between odd-numbered column pixels and even-numbered column pixels, which has the disadvantage of complicating the circuit configuration. Ta.

Furthermore, the electrical signal from the image sensor is smoothed and
Matching with the waveform shaping circuit that converts into values is the same during high-resolution processing and low-resolution processing, so if there are voids or spots in the optical information to be read (for example, a bar code), reading errors may occur. was there. This is because what is disclosed in the above-mentioned publication achieves high-resolution processing and low-resolution processing simply by increasing or decreasing the number of pixels, and the accuracy of signal processing is not achieved in processing the output signal from the image sensor. This is because it is not taken into account.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to achieve a high reading rate by suppressing the effects of voids and spots even if the optical information is mixed in when reading optical information.

[Means to solve the problem]

In order to achieve the above object, the present invention provides: photoelectric conversion means for scanning optically recorded optical information along a reading line and converting the optical information into an electrical signal; and from the photoelectric conversion means. and a signal processing means for processing an electrical signal to obtain a binary signal corresponding to the optical information, wherein the signal processing means includes a filter element having a predetermined low-pass characteristic. Prepare,
Furthermore, the relationship between the input speed of the electrical signal outputted from the photoelectric conversion means to the filter element and the low-pass characteristic of the filter element is adjusted to make the input speed higher, or The pass characteristic of the filter element may be made lower to achieve a less accurate reading of the optical information, or the input speed may be made slower, or the pass characteristic of the filter element may be made higher to achieve a more accurate A technical means is adopted in which a precision adjustment means for realizing reading of the optical information is provided.

[Operation] According to the configuration of the present invention as described above, the relationship between the input speed of the electrical signal converted into optical information to the filter element and the reduced pass characteristic of this filter element is adjusted, and high precision reading or A low precision reading is achieved.

Here, if the input speed is made higher or the pass characteristic of the filter element is made lower, minute changes in the electrical signal are attenuated by the filter element. This reduces the reading accuracy, but it reduces the influence of voids and spots mixed into the optical information, reduces the occurrence of reading failures due to these voids and spots, and makes it possible to accurately read large and low-density optical information. can be read.

Moreover, if the input speed is made slower or the pass characteristic of the filter element is made higher, small changes in the electrical signal will pass through the filter element. Therefore, optical information can be read with high precision, and even optical information recorded in fine detail and high density can be read.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to suppress the influence of voids and spots mixed in optical information, thereby reducing the occurrence of reading failures, and even when optical information is of low density or high density. can be read accurately.

〔Example〕

Embodiments to which the present invention is applied will be described below based on the drawings.

In this embodiment, an image sensor is used to scan an image of optical information to obtain an electrical signal corresponding to this optical information, and a system is used to sequentially read out the signals of multiple pixels of this image sensor as the above-mentioned electrical signals. By switching the period of the clock signal between high and low values, high-precision, high-resolution, low-speed processing and low-precision, low-resolution, high-speed processing are realized.

First, the configuration of one embodiment will be explained.

FIG. 1 is a block diagram showing the overall structure of the barcode reading device of this embodiment.

Reference numeral 1 denotes a hand-held scanning unit, which has the configuration described below.

Reference numeral 2 denotes an illumination light source consisting of ten high-intensity red light emitting diodes used as a light source. A light scattering material 3 scatters the illumination light from the red light emitting diode 2 to make it uniform over a predetermined range.

4 is a label of the recording medium on which a barcode 5 of optical information is printed.

Reference numeral 6 denotes a flat reflecting mirror, which reflects the light reflected from the barcode label 4 and changes its direction. A lens 7 collects reflected light from the barcode label 4, passes through an aperture member 8, and forms a barcode image at a predetermined position. Reference numeral 9 denotes a silicon-based image sensor as a reading sensor, which has a one-dimensional resolution of 2048 bits by arranging a large number of photo elements in a line, and has a peak region of spectral sensitivity near the emission spectrum of the illumination light source 2. It is something you have. 10 is a handheld case.

11 is a control circuit including a drive circuit for the illumination light source 2 and the image sensor 9, and a signal processing circuit for binarizing the electric signal from the image sensor 9, and is connected to a decoder circuit 12 and a power source 13 via a cable. . The decoder circuit 12 includes a microcomputer that decodes the binary signal output from the control circuit 11 into a predetermined character code, and converts this code into the POS system 14.
Output to.

FIG. 2 is a block diagram of the control circuit 11 in FIG. 1.

The frequency dividing circuit 111 divides the frequency of the basic clock signal supplied from the decoder circuit 12 according to the clock control signal. Here, frequency division by 1/1 and frequency division by 1/2 are switched according to the clock control signal.

This frequency dividing circuit 111 is composed of a frequency divider 1110, analog switches 1111, 1112, and an inverter 1113. When the clock control signal is at a high level, the analog switch 1112 is turned on and the basic tarokk is set to 1.
The frequency is divided by /2. When the clock control signal is at a low level, the analog switch 1111 is turned on and the basic clock is output as is. The clock generation circuit 112 operates on the image sensor 9 and a sample hold circuit 114 (to be described later) based on the clock signal supplied from the frequency dividing circuit 111.
Generates various signals to drive.

The signals of each pixel sequentially output from the image sensor 9 are amplified by an amplifier circuit 113, and then sent to a sample hold circuit 114.
The signal is sampled and held, and the waveform is shaped by the waveform shaping circuit 115. This analog signal is converted by the binarization circuit 116 into a binarized signal corresponding to the bars and spaces of the barcode, and sent to the decoder circuit 12.

FIG. 3 shows the sample and hold circuit 114 in FIG.
2 is a detailed circuit diagram of a waveform shaping circuit 115 and a binarization circuit 116. FIG. The details of this figure 3 can be found in Japanese Patent Application Laid-open No. 59-59.
8582 can be referred to.

FIG. 4 is an explanatory diagram illustrating the operation of the binarization circuit 116.

3 and 4, when reading a barcode as shown in FIG. 4(a) along the reading line indicated by a dashed line, the input waveform of the binarization circuit 116 is as shown in FIG.
It looks like the solid line in b). This is comparator 1160
is input to the input terminal a of the .

On the other hand, the input terminal of the comparator 1160 receives a waveform (dashed line in FIG. 4) which is delayed by diodes 1161, 1162 and a capacitor 1163 and has a voltage drop.

As a result, the comparator 1160 of the binarization circuit 116
outputs a binary output (FIG. 4(C)) according to the barcode, but if there are voids or spots as shown in FIG. 4, misreading may occur.

This can be removed by increasing the value of the capacitor, but the signal waveform changes quickly, that is, the response of the circuit to high-density video information is slow, making it unreadable? frff. In addition, if the sensor drive clock is set to a faster circuit configuration in advance, the image information will be processed at a lower resolution with less information, and the voids and spots can be removed, and the barcode can be prevented from being misread. There was a problem that code with high density was unreadable.

Such a problem is solved by the image sensor 9 in this embodiment.
The solution is to change the speed of the output signal from the .

The operation of this embodiment will be explained below according to the flowchart shown in FIG.

This flowchart is executed in a microcomputer built into the control circuit 12.

Note that in this flowchart, step 280.
Establishment of data in 330 means that the data obtained in k scans match.

When barcode reading is started, initial settings are first made, a high resolution mode is set, and the clock control signal is set to a high level (step 210).

First, data for k scans is captured and analyzed (steps 220, 230). Therefore,! If the width of the module is 0.5 mm or more, it is determined that it is low-density information, and the clock control signal is set to a low level (steps 240, 250).

As a result, the basic clock enters the clock ordering circuit,
The mode is switched to low resolution mode in which the operating time is half that of high resolution. Therefore, data for a new scan is taken in, analyzed and transferred, and then the setting is returned to high resolution mode to end the series of reading processes (step 260,
270, 280° 290.300).

On the other hand, ■If the module width is determined to be less than 0.5 trm, data acquisition will be resumed in high resolution mode (k-
1) scanning is performed, and after analysis processing and transfer, a series of reading processing ends (steps 310, 320, 330,
340).

Also, if data cannot be established after switching to low-resolution mode (i.e., the barcode cannot be read), move the reading port away from the barcode.
-Reset the degree data (Rachel Reset) or, for example, after scanning once in low resolution mode, automatically return to high resolution mode (steps 280, 350, 360) (however, this (The number of times data is taken in and the number of times this timer 2 is ≦2).

The same applies when data cannot be established in high resolution mode (steps 330, 370, 380, 390).
.

[Actions and effects in Examples]

The operation and effects of the second embodiment will be discussed in detail with reference to FIGS. 6 to 8.

For example, in the case of sensor 2, to move the captured charge of 2048 bits, in high resolution mode, the
), it requires (nx204B) of time. In low resolution mode, (n/2×20
4B) and 1/2 the time required for high resolution. In reality, since it takes time to analyze and process data in both high-resolution mode and low-resolution mode, the time required for one scanning is in high-resolution mode (nX2
048+α), and in low resolution mode (n/2X
2048+α).

However, this one scanning time is the exposure time of the sensor, which is proportional to the amount of charge, so as shown in Figure 7, the analog waveform before binarization is smaller in low-resolution mode than in high-resolution mode. It's attenuated by 10%. For this reason, a high-density barcode can be read in the high-resolution mode, but cannot be read in the low-resolution mode.

Considering the above, the effects of the examples will be described.

First, let's consider processing time. Normally, processing (capturing and decoding) is performed twice until one piece of data is transferred, and if the data is lost once, the data is transferred.

This is necessary to improve read reliability and k
The larger the value, the higher the reliability. Therefore, it is usually desirable that ≧4.

When reading in high-resolution mode, assuming that it takes an average of 14m5ec to capture and process one data, it will take (14x
k) It takes msec. The average here means, for example, 13. 14. 15.
14. This is because data acquired at different scanning times, such as -msec, are analyzed.

On the other hand, in the method according to the present invention, data is acquired once in high resolution mode, processed, and then data is acquired again in low resolution mode two times. In low-resolution mode, the clock cycle is half that of high-resolution mode, so the processing time is also halved, and the time it takes to transfer data is (14+
7Xk) msec. From the above, 14k>(7Xk
+14); is ≧4, indicating that the processing time is shortened.

Next, consider the effect of preventing misreading due to dirt or the like on the barcode. As shown in Figure 8, it takes 10 clocks to read one bar. Suppose there is dirt on this bar. If the clock period at low resolution is T/2,
When the resolution is high, it becomes T. In the high-resolution mode, the clock cycle is longer and the exposure time is longer, so the amplitude of the sensor output waveform becomes larger and the sensitivity per bit becomes better. For this reason, a void in a portion of the bar as shown in FIG. 8 may be recognized, resulting in a possibility of unreadability or misreading. On the other hand, in low-resolution mode, the period is shorter than in high-resolution mode, so the amplitude is smaller and the sensitivity per bit is lower, so even if there is a void, its effect is less apparent, resulting in erroneous readings and errors. reading can be prevented.

In addition, in low-resolution mode, the amplitude of the output waveform due to voids is small, and the fluctuation time of the output waveform due to voids and spots is also shortened, so the response (low-pass characteristics) of the waveform shaping circuit is affected more by voids. Variations in the output waveform are removed. Similarly, in the binarization circuit, the responsiveness to fluctuations in the output waveform due to voids and spots deteriorates, so these influences are removed, and misreading and misreading can be prevented.

Note that although the above explanation deals with voids in a portion of the bar, the same effect can be obtained for spots (printing mistakes, dust, dirt, etc.) in the space portion.

In this way, this embodiment focuses on the fact that the processing speed and reading accuracy (resolution) change when the clock cycle of the sensor changes, and by automatically changing the clock cycle according to the density of optical information, This has the effect of increasing processing speed and preventing misreading or misreading due to voids and spots.

In addition, in the above embodiment, it has been explained that misreading and misreading are reduced by changing the exposure time by changing the clock cycle and changing the fluctuation speed of the output waveform from the image sensor. Adjustment of pass characteristics or charge/discharge time constant of capacitor in binary circuit,
Furthermore, misreading and misreading can be reduced by implementing a method within the scope of the present invention, such as a method of changing only the signal read clock from the image sensor.

Furthermore, the present invention is applicable not only to barcodes but also to various recording methods as optical information.

Furthermore, barcode reading units are not limited to those that convert barcode images into electrical signals using image sensors.
The present invention can also be applied to a device that scans a barcode with a laser beam and detects the reflected light. In that case, by changing the scanning speed of the laser beam, etc. effect can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment to which the present invention is applied, Fig. 2 is a block diagram of an embodiment, Fig. 3 is an electric circuit diagram of an embodiment, and Fig. 4 is an explanatory diagram explaining the operation. , FIG. 5 is a flowchart explaining the operation of one embodiment, FIGS. 6 and 7,
FIG. 8 is an explanatory diagram for explaining the operation. 9... Image sensor, 11... Control circuit, 12.
. . . Decoder circuit, 111 . . . Frequency divider circuit, 1111.
1112...Analog switch, 1113...Inverter, 112...Clock generation circuit, 113...
Amplification circuit, 114... Sample and hold circuit, 115
...Waveform shaping circuit, 116...Binarization circuit. Representative patent attorney Takashi Okabe (one idiot)

Claims (1)

[Scope of Claims] Photoelectric conversion means for scanning optically recorded optical information along a reading line and converting the optical information into an electric signal; and processing the electric signal from the photoelectric conversion means. , a signal processing means for obtaining a binary signal corresponding to the optical information, the signal processing means comprising a filter element having a predetermined low-pass characteristic, and further comprising: a filter element having a predetermined low-pass characteristic; The relationship between the input speed of the electrical signal output from the conversion means to the filter element and the low-pass characteristic of the filter element is adjusted to make the input speed higher, or the pass characteristic of the filter element is adjusted. can be lowered to achieve a less accurate reading of the optical information, or the input speed can be lowered, or the pass characteristic of the filter element can be made higher to achieve a more accurate reading of the optical information. An optical information reading device characterized by comprising an accuracy adjustment means for realizing reading.