JPH03172981A - Optical information reader - Google Patents

Abstract

PURPOSE:To obtain a fixed photodetector output in a state that the peripheral temperature of a discharge tube is changed in accordance with the quantity of light applied to the discharge tube by adjusting the exposure time of the photodetector in accordance with the ambient temperature. CONSTITUTION:An amplifier circuit 18 is connected to an image sensor 9 to amplify a discrete electric signal outputted from the image sensor 9 for receiving a bar code image from a label 2. A waveform shaping circuit 19 shapes the signal amplified by the circuit 18 to a continuous signal. A binarizing circuit 20 converts the continuous signal outputted from the circuit 19 into a binary level digital signal with time width corresponding to the bar width of a bar code 4 and sends the digital signal to a microcomputer 21 to be an exposure time adjusting means. A detecting circuit 22 inputs a signal from a temperature sensor 14, converts the input signal into a digital signal and sends the digital signal to the microcomputer 21. A clock generator 23 generates a reference clock and outputs the reference clock to an operation synchronizing circuit 24.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an optical information reading device.

[Conventional technology]

Conventionally, as an optical information reading device, a device that reads optical information such as a barcode printed on a recording medium such as a label using ink containing a fluorescent pigment or fluorescent dye is known.

[Problem to be solved by the invention]

However, it is known that the light intensity of discharge tubes normally used as light sources changes drastically depending on the temperature, and in order to maintain a constant temperature around the discharge tube in order to maintain a constant discharge tube output, a temperature control device is required. turn into.

An object of the present invention is to provide an optical information reading device that can obtain a constant light receiver output regardless of fluctuations in the output of the discharge tube.

[Means to solve the problem]

The present invention includes a discharge tube that irradiates an information carrier made of fluorescent material with excitation light, and a light receiver that converts the fluorescence from the information carrier into an electrical signal, and reads the information carrier using the electrical signal from the light receiver. In the optical information reading device, the temperature detector detects the ambient temperature of the discharge tube, and the exposure time adjustment adjusts the exposure time of the light receiver according to the ambient temperature of the discharge tube by the temperature detector. The gist thereof is an optical information reading device equipped with means.

[Effect]

The ambient temperature of the discharge tube is detected by the temperature detector, and the exposure time adjusting means adjusts the exposure time of the light receiver in accordance with the ambient temperature of the discharge tube determined by the temperature detector. As a result, although the amount of light in the discharge tube varies depending on the temperature, it is possible to obtain a constant output from the light receiver.

〔Example〕

An embodiment embodying the present invention will be described below with reference to the drawings.

FIG. 2 shows the external appearance of the optical information reading device, and FIG. 3 is a diagram for explaining the internal structure of the reading device.

A case l of the reading device is formed into a box shape, and an insertion opening 3 into which a card-shaped label 2 is inserted is provided on the front side of the case l. Label 2 is a barcode (information carrier) that is optical information using ink containing fluorescent pigments or fluorescent dyes.
4 is printed.

Although this barcode 4 cannot be visually observed under visible light, only the barcode 4 emits light when it is irradiated with ultraviolet light as excitation light during reading. As for the type of barcode 4, code 39, NW-7, etc. are used, and the barcode printing ink is made of zinc oxide (chemical composition formula: ZnO1), which is excited by ultraviolet light with a wavelength of 365 nm; A substance with a peak wavelength of 495 nm) is used.

Further, a cold cathode discharge tube (black light) 5 as an ultraviolet light source is disposed inside the case 1, and this cold cathode discharge tube 5 illuminates the barcode 4 of the label 2 with light having a center wavelength of 365 nm. Furthermore, a reflecting mirror 6 is disposed within the case 1, and this reflecting mirror 6 reflects the fluorescence from the barcode 4 of the label 2 in a specific direction. In the direction in which the light is reflected by the reflecting mirror 6, an imaging lens 7, an aperture member 8 having a flat slit orthogonal to the reading line, and an image sensor 9 as a light receiver are arranged in this order. Then, the reflected light from the reflection mirror 6 reaches the scanning line of the image sensor 9 through the imaging lens 7 and the aperture member 8, and an image of the barcode 4 is formed.

The image sensor 9 is a one-dimensional sensor that has the function of converting the barcode image on the scanning line into an electric signal by electronic scanning operation, and the electronic shutter function that reads out the charge accumulated in the photocell only within a certain time. It is an image sensor.

Also, inside the case 1 are light source drive circuit IO1 power supply circuit ll,
An electronic control circuit 12 is built in, and a cold cathode discharge tube 5 is driven by a light source drive circuit IO. A switching power supply is used in the power supply circuit 11, and a commercial power supply of AC 100 V is inputted through a power supply connector 13 to supply voltage used in the electronic control circuit 12 and the light source drive circuit IO. Electronic control circuit 1
2 is the barcode reading circuit and the LED
7.LCD16. It is composed of a drive circuit that drives the buzzer 15.

Further, a temperature sensor 14 as a temperature detector made of a thermistor is disposed near the cold cathode discharge tube 5 in the case 1, and the ambient temperature of the cold cathode discharge tube 5 is detected by the sensor I4. This is to indirectly detect a change in the amount of light since the amount of light of the cold cathode discharge tube 5 changes drastically depending on the temperature.

Further, a buzzer 15 is provided on the back side of the case l, and the buzzer 15 notifies the user that the barcode 4 has been decoded. As shown in FIG.
The decoding result is displayed, and the LED 17
is designed to light up when the power switch is turned on.

FIG. 1 shows a circuit for reading barcodes in the electronic control circuit 12.

An amplifier circuit 18 is connected to the image sensor 9, and the amplifier circuit 18 amplifies discrete electrical signals from the image sensor 9 that receives the barcode image from the label 2. The waveform shaping circuit 19 shapes the signal amplified by the amplifier circuit 18 into a continuous signal. Furthermore, the binarization circuit 20 converts the continuous signal from the waveform shaping circuit 19 into a digital signal of a binarization level with a time width corresponding to the bar width of the bar code 4, and sends it to the microcomputer 21 as an exposure time adjustment means. Detection circuit 22
inputs the signal from the temperature sensor 14, converts the signal into a digital signal, and sends it to the microcomputer 21.

Clock generator 23 generates a reference clock and outputs it to scan synchronization circuit 24 . The scan synchronization circuit 24 outputs an image sensor drive signal to the sensor drive circuit 25 at a predetermined timing based on the reference clock. The sensor drive circuit 25 drives the image sensor 9 using the signal generated by the scan synchronization circuit 24.

The microcomputer 21 performs predetermined processing on the digital signal input from the binarization circuit 20, decodes barcoded characters, and converts them into general-purpose codes (e.g., ASCII).
I code) and output to the external device 26 according to R8-232C. Further, the microcomputer 21 controls the signal generation timing of the scan synchronization circuit 24 based on the signal from the detection circuit 22 so as to make the exposure light amount of the video signal appropriate.

Next, the operation of the optical information reading device configured as described above will be explained based on the flowcharts of FIGS. 4 and 5.

The label 2 is irradiated with ultraviolet light from the cold cathode discharge tube 5, causing the barcode 4 to emit light. Then, an image of the barcode is formed on an image sensor 9 through an optical system including a reflection mirror 6, an imaging lens 7, and an aperture member 8.

The microcomputer 21 inputs the signal from the temperature sensor 14 in step 100, and determines an appropriate exposure time TO based on the ambient temperature K of the cold cathode discharge tube 5 measured by the sensor I4 in step 101.
is calculated as a predetermined function (TO=f(K)). At this time, as shown in FIG. 6, the ambient temperature K of the cold cathode discharge tube 5 is
When the ambient temperature K of the cold cathode discharge tube 5 is low, the exposure time TO is set long, and when the ambient temperature K of the cold cathode discharge tube 5 is high, the exposure time TO is set short. This is because, as shown in FIG. 7, when the ambient temperature K of the cold cathode discharge tube 5 is low, the light source output is weak and the cold cathode discharge tube 5
This is because the light source output is strong when the ambient temperature K is high.

In step 102, the microcomputer 21 calculates the time τ obtained by subtracting the exposure time TO from the period TL of the transfer pulse φTO, as shown in FIG. Here, the transfer pulse φTO is generated at a predetermined period TL, and the maximum exposure time is this period TL. In step 103, the microcomputer 21 issues a command to output the transfer pulse φTO, causing the scan synchronization circuit 24 to output the transfer pulse φTO to the sensor drive circuit 25 (timing tl in FIG. 8).

Then, when the time τ set in step 102 has elapsed after outputting the transfer pulse φ7°, the microcomputer 21 outputs a command signal to generate a reset pulse φTQI to the scan synchronization circuit 24 in the interrupt routine shown in FIG. the result,
A reset pulse φTGE is output from the scan synchronization circuit 24 to the sensor drive circuit 25, and the charges accumulated in the image sensor 9 are reset (timing t2 in FIG. 8).
.

Therefore, after outputting the reset pulse φTo8, the exposure time T
When O has elapsed, a transfer pulse φT6 is sent to the scan synchronization circuit 24.
is issued, and after the transfer pulse φTO is output, the drive clock φ1. The signals from the image sensor 9 are sequentially output to the amplifier circuit 18 through φ2. As a result, the time TO from the output of the reset pulse φTOE to the output of the transfer pulse φTO becomes the exposure time.

The microcomputer 21 inputs the binarized signal from the binarization circuit 20 in step 104, and performs decoding processing in step 105. After that, the microcomputer 21 determines whether the decoding was successful in step 106, and if the decoding is unsuccessful, the microcomputer 21 determines in step 106
7, a new appropriate exposure time TO is determined by a predetermined function (To = g (S, To) based on the detected value S from the temperature sensor 14 of the cold cathode discharge tube 5 and the exposure time TO at that time.
). Then, the microcomputer 21 performs step 1
In step 08, a time τ is calculated by subtracting the exposure time To from the period TL of the transfer pulse φT0. This step 107.1
Through the processing in step 08, variations in the cold cathode discharge tube 5 (light source), etc. are corrected.

After the next transfer pulse φT6 is generated in step 103, the microcomputer 21 outputs a command to generate the reset pulse φTOH to the scan synchronization circuit 24 at timing t3 in FIG. 8 using the interrupt routine shown in FIG.

Thereafter, the processes in steps 104 to 106 are executed.

If the decoding is successful in step 106, the microcomputer 21 outputs the decoding result to the external device 26 in step 109.

In this way, in this embodiment, the barcode 4 is made of fluorescent material.
A cold cathode discharge tube 5 that irradiates light onto the (information carrier), and an image sensor 9 (light receiver) that generates a charge within the exposure time according to the amount of fluorescent light from the barcode 4 by the cold cathode discharge tube 5. The optical information reading device is equipped with a temperature sensor 14 (temperature detector) for detecting the ambient temperature of the cold cathode discharge tube 5, and a microcomputer 21 ( Cold cathode discharge tube 5 by temperature sensor 14 (exposure time adjustment means)
The exposure time of the image sensor 9 is adjusted according to the ambient temperature.

As a result, when the temperature around the cold cathode discharge tube 5 is low, the light source output is weak, so the exposure time is set longer, and when the temperature around the cold cathode discharge tube 5 is high, the amount of light from the light source is large, so the exposure time is set short. Therefore, a constant output of the light receiver can be obtained with a simple configuration regardless of fluctuations in the output of the cold cathode discharge tube 5. In addition, a relatively inexpensive temperature sensor (thermistor) 14
can be used to suppress fluctuations in light amount.

Note that this invention is not limited to the above embodiments,
For example, the generation timing of the transfer pulse φ7o may be made variable, and the transfer pulse φTO may be generated after the exposure time has elapsed after the output of the reset pulse φ1°8. This allows a wide range of exposure times to be obtained and eliminates wasted exposure time.

Further, the timing of generation of the transfer pulse φTQ may be made variable, and the exposure time may be controlled by the generation cycle of the transfer pulse φra. This allows application to image sensors that do not have a normal electronic shutter function.

〔Effect of the invention〕

As described in detail above, the present invention exhibits an excellent effect of being able to obtain a constant light receiver output regardless of fluctuations in the output of the discharge tube.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the electrical configuration of the optical information reading device of the embodiment, Fig. 2 is a perspective view showing the external appearance of the optical information reading device, and Fig. 3 explains the internal structure of the optical information reading device. FIG. 4 is a flowchart for explaining the action, FIG. 5 is a flowchart for explaining the action,
Figure 6 is a diagram showing the relationship between the ambient temperature of the discharge tube and exposure time, Figure 7 is a diagram showing the relationship between the ambient temperature of the discharge tube and light source output, and Figure 8 is a time diagram showing the output timing of each signal. There is a chart. 4 is a barcode as an information carrier, 5 is a cold cathode discharge tube, 9
14 is an image sensor as a light receiver, 14 is a temperature sensor as a temperature detector, and 21 is a microcomputer as an exposure time adjustment means.

Claims (1)

[Claims] 1. A discharge tube that irradiates an information carrier made of a fluorescent substance with excitation light, and a light receiver that converts the fluorescence from the information carrier into an electrical signal, the electrical signal from the light receiver In an optical information reading device configured to read an information carrier, a temperature detector detects the ambient temperature of the discharge tube, and an exposure time of the light receiver is adjusted according to the ambient temperature of the discharge tube detected by the temperature detector. What is claimed is: 1. An optical information reading device comprising: exposure time adjusting means.