JPS6385886A - Bar code reader - Google Patents

Abstract

PURPOSE:To extremely reduce power consumption and to extend the life of a power supply by controlling ON/OFF of a light emitting element during a scanning period. CONSTITUTION:During the scanning period, the light emitting element is turned on and off an a detecting signal from a light detecting means is held in synchronism with the lighting period of the light emitting element. At the time of scanning, the internal resistance of a sensor 14 is changed in accordance with the timing of an LED driving pulse and the color of a bar code 13 and the change appears as the level difference of the potential of a signal on a point A. Namely, when the black part of a bar code 13 is scanned even when the LED driving pulse is in the 'L' period (off of the LED 11) or in the 'H' period (on of the LED 11), no light is inputted to the sensor 14, so that impedance is increased, current does not almost flow into the sensor 14 and the potential of the point A is increased. When the white part of the bar code 13 is scanned during the 'H' period (on of the LED 11) of the driving pulse, light is inputted to the sensor 14, the impedance is reduced and the potential of the point A is also reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a barcode reading device, and particularly to a barcode reading device that reduces power consumption.

(Prior Art) A barcode reading device requires a light emitting element such as an LED that illuminates the barcode to be read. Since this light-emitting element consumes relatively large power, it is recommended to use a small-capacity power source such as a battery or dry cell battery.・In portable, especially wireless barcode reading devices, power consumption can be reduced to extend the life of the power source. was an issue.

Therefore, as a barcode reading device for reducing power consumption, there is a barcode reading device shown in FIG.

That is, instead of lighting the LED 31 as a light emitting element all the time, a switch 32 is provided and the LED 31 is lit only when the switch 32 is pressed, and the light reflected from the barcode 33 is detected by a sensor 34 such as a phototransistor. It was structured.

In the barcode reading device having the above configuration, as shown in FIG. 4, the waveforms of each part of the device are as follows. When the switch 32 is turned on at time t31, the working current i of the LED 31 starts flowing, and the L
ED31 lights up. When scanning, barcode 33
The internal resistance of the sensor 34 changes depending on the degree of reflection of light from the sensor 34, which appears as a rise or fall in the potential of the signal at point A.

The signal at point A is binarized by the buffer 35 and sent to a decoding circuit (not shown) as a digital barcode signal. Note that when the switch 32 is turned on and off, signal fluctuations appear due to the influence of chattering of the switch.

In the above configuration, since the LED 31 is turned on only for a short period of time during which the barcode 33 is read, the overall power consumption can be reduced.

(Problems to be Solved by the Invention) As described above, it has been possible to reduce the 52 current and power to some extent using conventional devices. However, in a portable barcode reading device that uses a power source with low capacity such as a dry battery, it is desirable to further reduce power consumption and extend the life of the power source.

The present invention has been made in view of the above points, and an object of the present invention is to provide a barcode reading device with extremely low power consumption.

[Structure of the Invention] (Means for Solving the Problems) The present invention comprises a blinking control means for blinking a light emitting element, and a light detection means for detecting reflected light that is reflected on a barcode and enters the barcode. and holding means for holding the detection signal in synchronization with the period during which the light emitting element is lit.

(Function) In the present invention, a sample and hold operation is performed in which the light emitting element is driven to blink during the scanning period and the detection signal from the photodetecting means is held in synchronization with the period in which the light emitting element is lit. By keeping the lights on all the time, power consumption can be further reduced compared to conventional methods.

(Embodiments) Hereinafter, embodiments of the barcode reading device of the present invention will be described with reference to the drawings.

In FIG. 1 showing an embodiment of the present invention, 11 is an LED as a light emitting element, 12 is a switch for lighting the LED II, 14 is a phototransistor, etc., which detects light reflected from a barcode 13 and incident thereon. sensor, 15
is a buffer for binarizing the detection signal from the sensor 14.

16 is a counter that counts the clock from the oscillator 17 and outputs a drive pulse that defines the drive period of the LED; 18 is a latch pulse obtained by gated the clock with the drive pulse; latches the output of the buffer 15; This is a latch circuit.

Next, regarding the operation of the embodiment configured as above,
This will be explained with reference to the waveforms of each part shown in FIG.

When switch 12 is turned on at time t11, barcode 1
LED with a frequency sufficiently higher (for example, 100 KHz) than the barcode signal obtained by scanning 3.
A drive pulse is applied to the base of transistor 10.

In this embodiment, even after the switch 12 is turned on, the LED
II is not always lit, but the LED drive pulse is “
It lights up only for the period H' to irradiate the bar code 13. L
During the period when the ED drive pulse is "L", the transistor 10 is turned off, so the LEDll is turned off.

When scanning, the internal resistance of the sensor 14 changes depending on the timing of the LED drive pulse and the color of the barcode 13 (white or black (shaded area)), and the potential of the signal at point A changes. appears.

In other words, even if the LED drive pulse is in the "L2" period (LED II is off) or the "H" period (LED II is on), when the black part of the barcode 13 is being scanned, no light is input to the sensor 14. The impedance increases, almost no current flows through the sensor 14, and the potential at point A rises.On the other hand, during the period when the drive pulse is “H” (LED II
is on) and when the white part of the barcode 13 is being scanned, light enters the sensor 14, so the impedance becomes low and the potential at point A decreases.

The potential of the signal at point A is binarized by the buffer 15 and appears at point B. The signal at point B is the latch pulse from the AND gate 19, that is, the oscillator 17
The pulse obtained by gating the clock from the counter 16 with the drive pulse from the counter 16 is latched into the latch circuit 18. The latch pulse is a pulse that rises at the middle timing of the "H" period of the drive pulse, and indicates the timing when the detection level of the reflected light sufficiently appears at 8 points after the LED II is turned on. Therefore, the latch circuit 1
The output of 8 can be a barcode signal.

In the above embodiment, the power consumed by the LED II and the sensor 14 can be expressed as Vcexi in FIG. Now, L.E.
If a pulse with "H" period: "L" period - min is used as the D drive pulse, the power consumption will be approximately m+ compared to the conventional one.
. This makes it possible to reduce the amount to Therefore, the lifespan of a power source such as a dry battery and the accuracy of the barcode signal depend on the frequency of the drive pulse and latch pulse corresponding to the sampling pulse, and may be appropriately selected depending on the scanning speed and the like.

[Effects of the Invention] According to the present invention, since the light emitting element is not constantly turned on during the scanning period but is controlled to blink, it is possible to extremely reduce power consumption and extend the life of the power supply. can.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the barcode reading device of the present invention, Fig. 2 is a waveform diagram explaining the operation of the embodiment shown in Fig. 1, and Fig. 3 is a conventional barcode reading device. FIG. 4 is a waveform diagram illustrating the operation of the circuit shown in FIG. 3. 10...Transistor, 11...LED. 12...Switch, 13...Barcode, 1
4...Sensor, 16...Counter, 17.
...Oscillator, 18...Latch circuit.

Claims (1)

[Scope of Claims] A light emitting element that illuminates a barcode; a blinking control means that blinks the light emitting element at a predetermined frequency; and light from the light emitting element that is blinked by the blinking control means is reflected on the barcode. and a holding means for holding a detection signal from the light detecting means in synchronization with a period during which the light emitting element is lit. Barcode reader.