JP2003132301A - Bar code reader and reading method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely read a bar code at high speed and to drive a sensor at low power consumption in a bar code reader capable of taking a still picture. SOLUTION: This bar code reader capable of reading an image picture and the bar code is provided with the image sensor for producing a two-dimensional picture by photoelectric conversion and control means reading only signals of pixels thinned down in the both horizontal and vertical directions in the preexposure action of the image sensor when reading the bar code, performing a real exposure according to the signals read in the preexposure action, and reading all the signals of the pixels.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bar code reading technique, and more particularly to a bar code reading technique using an image sensor.

[0002]

2. Description of the Related Art Today, for example, a method and a device for converting product information into a bar code and reading the bar code with a bar code reader, such as a POS system, are in widespread use. However, in logistics, distribution and industry, there is a need for a barcode that can handle a greater variety of products and the amount of information that cannot be stored in a one-dimensional barcode. I started. Along with this, two-dimensional barcodes have emerged in recent years, and the amount of information has dramatically increased.

At the same time, a bar code reader is also available.
Line sensors that are only for reading two-dimensional barcodes and those that scan with laser light are being replaced by area sensors that can decode two-dimensional barcodes.

Further, such an area sensor can read not only a bar code but also a normal image. For this reason, such a bar code reading device capable of capturing an image image, combined with the recent miniaturization,
It is fully expected to be incorporated in mobile terminals.

As described above, in the bar code reading device integrated in the portable terminal, since the secondary battery is generally used as a battery, the power consumption of each part must be suppressed as much as possible in order to extend the continuous operation time. And that's no exception for sensors. Further, when viewed from the whole of the device, the light source for illumination has the largest power consumption (LED is generally used), and reducing the power of this light source is also one of the most effective means. .

[0006]

In view of such a background, when a bar code reader in the world is examined,
Most of those that read using CCD drive with the timing conceptual diagram as shown in FIG. First, the sensor drive is in a sleep state until the reading trigger is turned on, and the power supply, clock (CLK), and pulses necessary for sensor drive are not input. In this state, when a trigger is applied, the sensor first discards unnecessary charges accumulated in the photodiode when the device is powered off, and at the same time, performs a reset operation for eliminating unnecessary charges in the vertical transfer path.

Next, when the reset is completed, the charge of the photodiode is accumulated for an arbitrary exposure time. At the stage where the charge accumulation was completed, the charge was carried to the vertical and horizontal transfer paths and transferred to the outside of the sensor.

However, this reset operation requires resetting the electric charges for one screen, and therefore requires a scanning time for one screen. Therefore, it took a long time to rise from the time the trigger switch was pressed until the bar code was read. In order to solve this problem, Japanese Patent Application Laid-Open No. 08-044812 has proposed an idea of driving only the reset period with a high-speed pulse to shorten the rise time. However, this idea still has the problem of increased power consumption.

As shown in FIG. 2, the bar code reading apparatus operates for three frames, the first reset operation according to the above description, the second pre-exposure, the third main exposure and the second pre-exposure. The output is multiplied by the gain determined in.

In this series of operations, the exposure time is constant, and since the main exposure is performed only by adjusting the gain, it can be considered that binarization cannot be sufficiently performed under the situation where the light quantity cannot be sufficiently obtained. .

SUMMARY OF THE INVENTION It is an object of the present invention to reliably read a barcode at a high speed in a barcode reading apparatus capable of picking up a still image and to drive the sensor with low power consumption.

[0012]

According to one aspect of the present invention, there is provided a bar code reader capable of reading an image and a bar code, and an image sensor for generating a two-dimensional image by photoelectric conversion, When reading the bar code, only the signals of the pixels thinned out in both the horizontal and vertical directions in the pre-exposure operation of the image sensor are read out, and the main exposure operation is performed in accordance with the signals read out in the pre-exposure operation. There is provided a bar code reading device having a control means for reading out a signal of a pixel.

According to another aspect of the present invention, there is provided a bar code reading method for reading a bar code by an image sensor for generating a two-dimensional image by photoelectric conversion,
When reading the bar code, only the signals of the pixels thinned out in both the horizontal and vertical directions in the pre-exposure operation of the image sensor are read out, and the main exposure operation is performed in accordance with the signals read out in the pre-exposure operation. A bar code reading method is provided, which comprises a control step of reading a signal of a pixel.

The readout time can be shortened by reading out the pixel signals thinned out in the pre-exposure operation. Further, the main exposure operation is performed in accordance with the pixel signal read in the pre-exposure operation to read the pixel signal, so that a reading error can be prevented.

[0015]

1 is a block diagram of a bar code reader according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a lens unit for forming a general subject image or a subject image of a barcode described in a black and white pattern on a sensor surface. 2 to 5 are red light emitting diodes (LEDs) for illuminating barcodes
Then, in order to illuminate the object to be photographed around the image sensor 1 uniformly with a sufficient amount of light, the high-brightness type is up, down,
A total of 16 units are arranged, 4 units each on the right and left. Reference numeral 6 denotes an image sensor unit, which uses a CMOS type image sensor for generating a two-dimensional image by photoelectric conversion. Reference numeral 7 is a timing signal generator (TG) that supplies a drive clock to the image sensor 6, which receives information on the exposure time calculated by the system controller 8 and changes the exposure time of the image sensor 6 accordingly. Reference numeral 10 denotes an amplification variable amplifier (AGC) for amplifying the image output signal of the image sensor 6, which receives the information of the amplification calculated by the system control unit 8 and changes the amplification according to the information. The image signal amplified by the amplifier 10 is
It is quantized by 11 A / D converters and enters 12 signal processing units (circuits). Here, the bar code signal is binarized and decoded, the average value of the image signal is calculated, and the threshold value is sent to the system control unit 8. System control unit 8 is LED
The ON / OFF of the LED is controlled through the driving unit 9, and the threshold value from the signal processing unit 12 determines the photoelectric conversion time information sent to the timing signal generation unit and the amplification degree information sent to the amplifier. In addition, the initial setting of the exposure time and the system control unit 8
The initial settings of are stored in the ROM 18. Next, 13 is an image memory for signal processing. Further, in the state where the decoding is completed, the information is transmitted to an external personal computer (personal computer) 14, displayed on a monitor 15, or transmitted to a buzzer 16 for transmitting the decoding completion or the decoding error. It is also possible to prepare the recording medium 17 and store the decrypted information up to now.

FIG. 3 is a block diagram of a CMOS type image sensor according to this embodiment. The sensor is a pixel of m rows × n columns.
Although it is composed of S11 to Smn, it is not limited to m rows × n columns.

FIG. 4 is a detailed view of the pixel. In this figure, the photodiode PD for generating optical signal charges is grounded on the anode side. The cathode side of the photodiode PD is connected to the gate of the amplification MOS transistor M3 via the charge transfer switch TX. In addition, the amplification MOS transistor M
The gate of 3 has a reset MOS to reset it.
The source of the transistor M1 is connected, and the drain of the reset MOS transistor M1 is connected to the reset voltage VR. Further, the drain of the amplification MOS transistor M3 is connected to the row selection MOS transistor M2 for supplying the operating voltage VDD.

Next, a method of driving the solid-state image pickup device of this embodiment will be described with reference to the timing charts of FIGS. 3, 4 and 5.

The signal TXa for simultaneously selecting the gates of the transfer MOS transistors TX of FIG. 3 for all the pixels from the first row to the m-th row is compared with the transfer pulses TX1 to TXn of the signals for selecting all the pixels for each row. It is connected to each transfer MOS transistor TX through an OR circuit. Further, in order to reset the gates of the amplification MOS transistors M3 of all the pixels at the same time, the reset MO of all the pixels from the first row to the m-th row is reset.
Signal RESa that selects the gates of S-transistor M1 at the same time
However, pulse RES1 to reset all pixels for each row
Each reset MOS transistor M1 through OR circuit with RESn
It is connected to the.

In this image sensor, first, a pulse φRESa to the gate of the reset MOS transistor M1 and a transfer M are transmitted.
Gate pulse φTXa of OS transistor TX and pulse φV to the gate of vertical signal line reset MOS transistor M8
RES goes high. As a result, the gate of the amplification MOS transistor M3 and the photodiode PD are reset to the voltage VR, and the vertical signal lines V1 to Vn are reset to the voltage VVR (until t2 in FIG. 5).

Next, φTXa becomes low level, and it becomes possible to generate charges in the photodiode PD according to light (t
2). In the LED lighting mode, prior to t2, the control signal φLED goes high and lights the LED (t1). continue,
Pulse to reset MOS transistor M1 gate φRES
The gate pulse φVRES of the vertical signal line reset MOS transistor M8 becomes low level, and the reset of the gate of M1 and the vertical signal line is released (t3). After a lapse of a predetermined time from the time t3, φTXa is set to the high level again to transfer the charge of the photodiode PD to the gate of the amplification MOS transistor M3 (t4).

After a sufficient time for transfer, φTXa is set to the low level again to complete the charge transfer of the photodiode PD (t5). At this time, the photoelectric conversion time is between t2 and t5. In the mode in which the LED is turned on, the LED is turned off after the transfer is completed (t6). Next, the gate pulse φSEL1 of the selection MOS transistor M2 and the gate pulse φTS of the optical signal transfer MOS transistor M5 become high level (t7). As a result, the optical signal voltage is read out to the optical signal holding capacitor CTS (t
7-t8). After reading to the capacitor CTS, the pulse φRES1 to the gate of the reset MOS transistor M1 and the gate pulse φVRES of the vertical signal line reset MOS transistor M8 become high level, and the gate of M1 and the vertical signal line are reset (t9). Then φRES1 and φVRES go low (t1
0), after the reset of the gate of M1 and the vertical signal line is released, the gate pulse φSEL1 of the selection MOS transistor M2 and the gate pulse φTN of the noise signal transfer MOS transistor M4 become high level (t11). As a result, the noise voltage is read out to the optical signal holding capacitor CTN (t11 to t1
2). After this, the signals H1 to H1 from the horizontal scanning circuit block HSR
Due to Hn, the gates of horizontal transfer switches M6 and M7 in each column sequentially go to high level (t14 to t15), and noise holding capacitance CT
N and the voltage held in the optical signal holding capacitor CTS are sequentially read to the differential circuit block. In the differential circuit block,
The difference between the optical signal and the noise signal is taken and sequentially output to the output terminal VOUT.

With the above, reading of the pixel cells connected to the first row is completed. After this, prior to reading the second row, the noise signal holding capacitance CTN and the optical signal holding capacitance C
ΦCTR to the gates of the reset switches M9 and M10 of TS becomes high level and is reset to VRCT.

Similarly, the signals of the pixel cells C21 to Cmn connected to the second row to the m-th row are sequentially read by the signal from the vertical scanning circuit block VSR, and the reading of all the pixel cells is completed. To do.

From the above description of the operation, such a CMOS image sensor does not require scanning for one screen when returning from the sleep state of the sensor, completes the start-up by batch reset, and requires a high-speed pulse. Without this, it is possible to drive with low power consumption, and it is also possible to quickly start up the sensor until the barcode is read.

Next, the thinning mode of this embodiment will be described. FIG. 6 is a circuit configuration diagram of the horizontal scanning circuit block HSR for performing the thinning mode in the sensor circuit diagram described in FIG. 3, and FIG. 7 is a timing diagram for explaining the thinning mode.

The configuration is such that the vertical scanning circuit block
Since the VSR is the same, the horizontal scanning circuit block HSR is used here.
I will explain it only.

The normal mode described here is an operation performed during main exposure when reading a bar code. Although not illustrated here, the operation of the HSR in the normal mode will be described. At this time, φHMODE is always low level (LOW). As a result, the AND circuit attached to the inputs of the flip-flops FF2 and FF5 becomes the through state. Also, the other AND circuits are always in the non-conductive state. In this state, φPHST is first input as the HSR start pulse. After that, the start pulse is delayed in scanning in synchronization with φPH. At the same time, output from H1
Hn is output. Next, the thinning-out mode will be described together with the timing of FIG.

This thinning-out mode is an operation performed during the pre-exposure period. First, at t1, φHMODE is set to high level. In that state, input a start pulse to flip-flop FF1 by φPHST (t2), and when φPHST is High, φPHST
Is input (t3), the information is delayed and propagated to the next flip-flop. After that, when φPH is input at t4, it is output to H1 at the same time as the output from FF1.
It is input to the AND circuit at the input of F2. But here φH
When MODE is High, the input on one side of the 2-input AND circuit
Since it is LOW, LOW will be input no matter what is input to the other input. Even if FF2 is driven at the next φPH, only LOW, that is, 0 is output from H2. At the same time, the output of FF1 is also transmitted to the AND circuit arranged above FF2. At this time, this AND circuit allows the output from FF1 to pass through only when φHMODE is High. As a result, the output of FF1 exceeds FF2 and propagates to FF3. Therefore, at t5, the output from FF3 and the output of φH3 are obtained at the same time. At the same time as this output, it jumps over FF4 and FF5 and propagates to FF6. When a pulse is input to φPH at t6, the output from φH6 is output simultaneously with the output from FF6. Here, for convenience, FF6
Although only described up to this point, it propagates to FFn as it is, and finally outputs up to φHn. The flip-flop to be skipped at this time can be performed by the method described above.

Finally, φHMODE is set to LOW at t7 and φHRST is set at t8.
Input a and reset the flip-flops at once. The above is a series of operations for performing the thinning mode in the HSR.

Although a circuit in which a start pulse is propagated while being delayed by a flip-flop is described here, the invention is not limited to this. For example, a switching circuit may propagate information or a counter may be used. ,
A circuit that outputs H1 to Hn with that value may be configured.

With such a thinning circuit, for example, FIG.
As shown in FIG. 5, the reading is performed by reading only the read pixel 902 at the black dot position in the entire pixel area 901. In this case, the area where the ratio of the subject in the center is large is read out finely, and the other areas are read out by widening the reading interval in the horizontal and vertical directions. As described above, the pixels are read in the thinning mode during the pre-exposure period, and the read transfer time is shortened. This makes it possible to shorten the time until the main exposure, and it becomes possible to read the barcode in a short time after the trigger switch for reading the barcode is pressed.

FIG. 8 is a flow chart for explaining the operation of the bar code reading apparatus of this embodiment.

First, a trigger switch is turned on for reading a bar code (S801). Immediately after that, the pixels of the sensor are collectively reset as described above (S80
2). In addition, the device itself has two types of settings: bar code reading or imaging mode for still image reading, and switches to each mode depending on the condition judgment (S80
3).

First, in the imaging mode, the lighting LED is turned off (S805). This is because when a specific color LED is used as illumination light, only a specific color is emphasized as the color of the subject, and another specific color loses sensitivity. Also, in the barcode reading mode, turn on the LED for lighting (S80
Four).

Then, the thinning data for pre-exposure is read (S806). At this time, in the barcode reading mode, the illumination time when the LED is turned on may be shorter than the illumination time used in the main exposure. After that, these data are digitally converted by the A / D converter 11 in FIG. 1 and integrated and smoothed by the processing circuit 12 to calculate an average value (S807). The processing in the subsequent main exposure is changed depending on whether this average value is larger or smaller than the preset reference value. Also, each set amount is changed depending on how far from the reference value.

First, the case where this average value is smaller than the reference value will be described. This situation is when the subject is dark. In such a case, first, the exposure time is calculated in order to lengthen the exposure time by the shutter time of the electronic shutter of the sensor or the like (S809). At the same time, the LED lighting time is also lengthened in the barcode reading mode (S81
0). To calculate this time, the average value described above is changed depending on how far it is from the reference value.
Since the LED has already been turned off in the imaging mode, the LED lighting time will be omitted. Since this exposure time affects camera shake when holding the barcode reader by hand, about 1/120 seconds as the maximum value of the exposure time is written in advance in the ROM 18 described in FIG. In the next step S811, the maximum value of the exposure time is used as a reference judgment and the condition is branched.

Here, if the exposure time calculation result does not exceed the maximum value, all data are read with the calculated exposure time setting (S821). If the maximum value is about to be exceeded, the process proceeds to the next step, and it is determined whether or not the power saving mode is set (S812). This can be preset by the user. In the case of this power saving mode, how much gain should be given in the next step S814 is calculated, and the all data reading operation is started with the desired value (S821). At this time, the exposure time and the gain to be given are adjusted so that the optimum one is selected. Further, in the imaging mode, processing is performed so that YES is unconditionally selected.

Next, when not in the power saving mode, the LED for lighting
Increase the emission intensity of (S813). Here we calculate how much strength should be increased. For example, the voltage used to increase the intensity of light emission, but the LED used at this time
The maximum value is uniquely determined by the characteristics of and the system voltage of the entire device. This maximum value is written in advance in the ROM 18 of FIG. 1, and if it exceeds this value, the analog gain is adjusted in the next step (S814). In this way, the exposure time, the emission intensity, and the gain amount are adjusted so that the optimum one is selected, and all the data is read for the main exposure with that setting (S821). If the maximum value is not exceeded, the gain is not changed and only the exposure time and emission intensity are adjusted to read all data.

Next, the case where the average value of the thinned-out data is larger than the reference value after the calculation, that is, the case where the subject is bright will be described.

First, the exposure time is calculated in order to shorten the exposure time using the electronic shutter of the sensor or the like (S815). At the same time, the LED lighting time is shortened in the barcode reading mode (S816). To calculate this time, the average value described above is changed depending on how far it is from the reference value. Since the LED has already been turned off in the imaging mode, the LED lighting time will be omitted. This exposure time depends on the sensitivity of the sensor, LE
The minimum value of the exposure time changes according to the brightness of D. This minimum value is written in advance in the ROM 18 described in FIG. In the next step S817, the minimum value of the exposure time is used as a reference judgment and the condition is branched.

Here, if the exposure time calculation result does not exceed the minimum value, all the data are read with the setting of the calculated exposure time (S821). If the calculation result is about to exceed the minimum value, the process proceeds to the next step, and it is determined whether or not the power saving mode is set (S818). If not in this power saving mode, how much gain should be given in the next step S820 is calculated, and the all data reading operation is started with the calculated value (S82
1). At this time, the exposure time and the gain to be given are adjusted so that the optimum one is selected. Further, in the imaging mode, processing is performed so that NO is unconditionally selected.

Next, in the power saving mode, the emission intensity of the lighting LED is weakened (S819). Here, calculate how much you should weaken. For example, the light emission intensity is weakened by lowering the voltage, etc., but eventually the LED is turned off. If adjustment is still necessary in this state, the analog gain is adjusted in the next step S820. In this way, the exposure time, the emission intensity, and the gain amount are adjusted so that the optimum one is selected, and all the data is read for the main exposure with that setting (S821). If the LED is not OFF, the gain is not changed and only the exposure time and emission intensity are adjusted to read all the data.

By the above operation, all the data which is the main exposure is read, converted into digital by the A / D converter 11 in FIG. 1, and then binarized and decoded by the processing circuit 12 to decode the bar code. (S822). As a result, if the decoding is OK (S823), the decoding result is output (S825), and in the case of an error, for example, an error sound is output to the buzzer 16 of FIG. 1 to notify the user of the error (S824).

Although not shown in this flowchart,
In the case of the imaging mode, after reading all the data, digital conversion is performed by the A / D converter 11, and then the processing circuit 12 performs edge enhancement or applies a gamma characteristic matched to the characteristic of the monitor. In the shooting mode, step S810,
S816 and S821 to S824 are omitted.

The conceptual diagram of this embodiment described above is shown in FIG.
Will be described in. This is in contrast to the conventional example of FIG. The reading operation includes a pre-exposure operation 1011 and a main exposure operation 1012. The pre-exposure operation 1011 includes reset 1001, accumulation 1002 and transfer 1003. The main exposure operation 1012 also includes reset, accumulation and transfer.

The reset 1001 of the collective reset method accelerates the rise of the sensor and enables the reading in a short time after the trigger switch is pressed.

Further, by using the thinning-out mode for the pre-exposure operation 1011, the time for the read transfer 1003 is shortened. As a result, it is possible to shorten the time until the main exposure operation 1012, and it is possible to read the barcode in a short time after the trigger switch for reading the barcode is pressed. Moreover, since high-speed pulses are not used, the power consumption is low.

Further, by adopting the setting obtained in the pre-exposure operation 1011 in the main exposure operation 1012 immediately after that,
Read errors can be minimized. The accumulation time 1002 (LED ON time) in the pre-exposure operation 1011 may be shorter than the accumulation time (LED ON time) in the main exposure operation 1012.

By changing the exposure time with the electronic shutter, it is possible to read in a wide dynamic range from a dark state to a bright state of the subject.

It should be noted that the above-mentioned embodiments are merely examples of specific embodiments for carrying out the present invention.
The technical scope of the present invention should not be limitedly interpreted by these. That is, the present invention can be implemented in various forms without departing from its technical idea or its main features.

[0053]

As described above, the readout time can be shortened by reading out the pixel signals thinned out in the pre-exposure operation. Further, the main exposure operation is performed in accordance with the pixel signal read in the pre-exposure operation to read the pixel signal, so that a reading error can be prevented.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a barcode reading device according to an embodiment of the present invention.

FIG. 2 is a timing conceptual diagram of driving a light emitting diode and driving a sensor according to a conventional technique.

FIG. 3 is a configuration diagram of a sensor.

FIG. 4 is a configuration diagram of a sensor pixel unit.

FIG. 5 is a timing diagram of driving a sensor.

FIG. 6 is a circuit configuration diagram for dealing with thinning.

FIG. 7 is a timing diagram of a thinning mode.

FIG. 8 is a flowchart showing the processing of the barcode reading device.

FIG. 9 is a conceptual diagram of pixel arrangement in a thinning mode.

FIG. 10 is a timing conceptual diagram of driving a light emitting diode and driving a sensor according to the present embodiment.

[Explanation of symbols]

1 lens part 2-5 Light emitting diode (LED) 6 image sensor 7 Timing signal generator (TG) 8 System control unit 9 LED driver 10 Amplifier (AGC) 11 A / D converter 12 Signal processing unit (circuit) 13 Image memory 14 personal computer 15 monitor 16 buzzer 17 recording media

Claims (8)

[Claims] 1. A bar code reading device capable of reading an image image and a bar code, comprising: an image sensor for generating a two-dimensional image by photoelectric conversion; and a pre-exposure operation of the image sensor when reading the bar code. In the above, only the signals of the pixels thinned out in both the horizontal and vertical directions are read out, and the main exposure operation is performed according to the signals read out in the pre-exposure operation to read out the signals of all the pixels. And a bar code reader. 2. The control means controls the shutter time of the electronic shutter of the image sensor in the main exposure operation and the irradiation time of the light emitting diode based on the information determined by the pre-exposure operation. The bar code reading device according to claim 1, wherein 3. The bar code according to claim 1, wherein the control means controls the light emission intensity of the light emitting diode in the main exposure operation based on the information determined by the pre-exposure operation. Reader. 4. The control means controls ON / OFF of a light emitting diode in the main exposure operation based on information determined by the pre-exposure operation. The bar code reader described in. 5. The control unit adjusts an analog gain for a read signal in the main exposure operation based on the information determined by the pre-exposure operation. The bar code reading device described in Crab. 6. The bar code reading device according to claim 1, wherein the image sensor is a CMOS image sensor. 7. The bar code reading device according to claim 1, wherein the control unit does not turn on the light emitting diode when reading an image. 8. A bar code reading method for reading a bar code by an image sensor for generating a two-dimensional image by photoelectric conversion, wherein the bar code is read in horizontal and vertical directions in a pre-exposure operation of the image sensor. A bar code reading method comprising: a control step of reading out only the signals of pixels thinned out by both, performing a main exposure operation according to the signals read out in the pre-exposure operation, and reading out the signals of all the pixels.