JP2897147B2 - Optical information reader - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical information reading device such as a bar code reader using a line image sensor.

In particular, an optical information reading apparatus capable of reliably reading optical information (barcode information, etc.) on an optical recording medium (label, etc.) even under strong disturbance light such as direct sunlight. About.

[Conventional technology]

An optical information reading device generally reads optical information such as a barcode, characters, and symbols recorded on an optical recording medium such as a label.

However, optical information reading devices are installed or used, and the optical working environment used varies widely. In some cases, very high illuminance, such as outdoors or near a window, which is susceptible to sunlight.

Therefore, in the case of an optical information reading device designed to be readable in a low-illumination optical working environment, the output of the line image sensor is saturated in a high-illumination optical working environment due to direct sunlight or the like. As a result, an unreadable situation occurs.

Therefore, it has been proposed to control the clock frequency of the line image sensor in order to enable reading of a bar code even in the presence of such disturbance light.

According to this, when the illuminance of the barcode label is high, the clock frequency or the like supplied to the line image sensor is increased to control the entire storage time of the barcode sensor, and to reduce the effective non-saturation area related to the illuminance. When the illuminance of the bar code label is low, the clock frequency supplied to the sensor is reduced, thereby controlling the entire accumulation time of the sensor.
The effective saturation region is enlarged (the non-saturation region is reduced).

[Problems of the prior art]

However, if the clock frequency used in the line image sensor is changed according to the intensity of the disturbance light as in the above-described related art, there is a problem that peripheral circuits of the line image sensor become complicated. At times, the frequency of the output signal of the line image sensor changes extremely. It is very difficult to make the illuminance range from several tens of lux to about 100,000 lux in sunlight readable, considering the possible range of the microprocessor for processing the signal.

When optical information other than barcode information is read, there is a problem similar to the above problem.

[Object of the invention]

Therefore, a first object of the present invention is to provide an optical information reading device capable of reliably reading optical information even when disturbance light on a member to be read (for example, a bar code label) changes. Is to do.

A second object of the present invention is to make it possible to reliably read optical information (for example, barcode information) even when disturbance light on a member to be read (for example, a barcode label) changes. An object of the present invention is to provide an optical information reading device in which peripheral circuits of a line image sensor are simplified as much as possible.

A third object of the present invention is to provide an optical information reader capable of coping with a change in illuminance due to disturbance light over a wide range.

[Means for achieving the purpose]

In order to solve the above problems and achieve the above object, an optical information reading apparatus according to the present invention comprises: an irradiating unit 10 for irradiating a member L to be read; A light receiving optical system 22 that forms an image at a position, a line image sensor 30 that photoelectrically converts an optical image arriving at the light receiving surface into an electric signal by electronic scanning, and an illuminance detection that detects the illuminance of the member to be read L Means 41 ・ 40
The higher the illuminance of the member to be read L, the more the line image sensor
30 includes a control means 51 for controlling the actual optical signal accumulation time during each scanning period to be shortened, and conversion circuits 60 and 62 for converting the electric signal into a binary signal.

[Action]

The present invention relates to a member to be read (eg, a bar code label).
The higher the illuminance is, the shorter the actual optical signal accumulation time during each scanning period in the line image sensor 30 is, so that even when the intensity of disturbance light on the member to be read changes, reading of optical information is ensured. You can do it.

Thereby, the peripheral circuits of the line image sensor 30 can be simplified as much as possible.

Further, it is possible to cope with a change in illuminance due to disturbance light over a wide range.

〔Example〕

FIG. 1 is an explanatory diagram of one embodiment of the optical information reading apparatus of the present invention.

In the figure, 1 is a bar code reader, 10 is a light emitting diode (LED), 21 is a reflection mirror, 22 is a light receiving optical system (for example, a convex lens), 30 is a line image sensor, 40 is an illuminance detecting light receiving element, and 41 is illuminance detection Optical system (for example, a convex lens), 50 is a sensor drive circuit, 51 is an accumulation time control circuit (control means), 60 is a comparator, 61 is an amplifier, 62 is a slice level setting circuit, and L is a bar code label.

The barcode label L is illuminated with the irradiation light from the LED 10 and disturbance light.

The barcode reader 1 is an LED 10 that emits a certain amount of light.
A reflecting mirror 21 for reflecting light (image) reflected from the barcode label L, a light receiving optical system (for example, a convex lens) 22,
And an image sensor 30. Also, the bar code label L
It has an illuminance detecting light receiving element 40 for detecting the illuminance, an illuminance detecting optical system (for example, a convex lens) 41, an amplifier 42, and a sensor driving circuit 50 for driving the line image sensor 30.

The line image sensor 30 reads a barcode based on an image reflected on the barcode label L, that is, reads optical information based on an image reflected on the member to be read.

The illuminance detection optical system 41 is adjusted so that the barcode label L is viewed as a whole and an image is formed on the light receiving surface of the illuminance detection light receiving element 40.

Sensor drive circuit 50 is a circuit for driving the line image sensor 30, the clock .phi.1, phi _2, shift pulses φT
This is a circuit for outputting control pulses such as G and a reset pulse RS, and is provided with an accumulation time control circuit (control means) 51. This accumulation time control circuit 51 is a means for controlling the line signal sensor 30 to shorten the actual optical signal accumulation time during each scanning period as the illuminance of the barcode label L increases.

Further, an amplifier 61 for amplifying an output signal of the line image sensor 30, a comparator 60, and a slice level setting circuit 62 for setting a slice level of the comparator 60 are provided. Thus, when the level of the input signal is higher than the slice level, the comparator 60 converts the input signal into an off signal (or an on signal) and outputs it. And output.

 FIG. 2 is an explanatory diagram of the line image sensor 30.

The line image sensor 30 includes a photodiode array 31 that converts an optical signal into an electric signal, storage electrodes 32a and 32b, transfer gates 33a and 33b, and CCD shift registers 34a and 34b.
And an output gate 35 that processes output signals from the shift registers 34a and 34b, and a reset gate 36 that inputs a reset pulse RS and fixes a signal from the output gate 35.

The storage electrodes 32a and 32b perform storage when the storage time control signal received from the storage time control circuit 51 is on, and the transfer gates 33a and 33b store the charge stored in the storage electrodes 32a and 32b. Are shifted by the shift pulse φTG, and the CCD shift registers 34a and 34b
Are supplied with clock pulses φ ₁ and φ ₂ , respectively.

(Operation of Embodiment) Next, the operation of the above embodiment will be described.

FIG. 3 is a time chart showing an operation for one scanning period in the above embodiment. In the figure, T represents (optical signal accumulation time when the accumulation time control circuit 51 does not exist) the maximum optical signal accumulation time, .phi.TG shift pulse, phi ₁ and phi ₂ are clock pulses, RS is the reset pulse, OS output Signal.

The output signal OS comprises a first dummy signal portion, an intermediate effective pixel signal portion, and a last dummy signal portion, as is well known to those skilled in the art.

In FIG. 3, an accumulation time control signal that is turned on at time t ₂ is output by an accumulation time control circuit 51.

If the storage time control signal is off, the storage electrode 32
The storage electrodes a and 32b do not perform charge storage, but when the storage time control signal is turned on, the storage electrodes 32a and 32b start storing charge.

To begin with the charge accumulation, to put it analogously, a so-called shutter is opened, and the image formation on the light receiving surface of the bar code label L is caused by the photodiode array 31 in the line image sensor 30 to generate the charge signal. That is, it is photoelectrically converted into a column.

At that time, if the predetermined value illuminance of the bar code label L illuminance detection light receiving element 40 has detected, illuminance accumulation time control signal starts on state time t _2, the illuminance detecting light-receiving element 40 has detected if There lower than a predetermined value, accumulation time control signal starts on state at time t _1, conversely, if the illuminance of the illuminance detecting light-receiving element 40 has detected is higher than a predetermined value, accumulation time control signal the time to start an on-state at t _3.

That is, if illuminance illuminance detecting light-receiving element 40 is detected by a predetermined value, during the time T2 from the time t ₂ until the maximum optical signal accumulation time (period) T is completed (elapsed), the shutter is opened,
If the illuminance detected by the illuminance detecting light receiving element 40 is lower than the predetermined value, the shutter is opened for a longer time T1, and conversely, if the illuminance detected by the illuminance detecting light receiving element 40 is higher than the predetermined value. , The shutter is open only during the shorter time T3.

Therefore, in the conventional apparatus, since the shutter is opened at all times (points) of the maximum optical signal accumulation time (period) T during each scanning period, if the disturbance light at that time is strong,
The output of the line image sensor 30 is, of course,
It saturates and ends.

However, in the above embodiment, if the disturbance light is strong, the shutter open time is shortened, so that the line image sensor 30 does not saturate, and a constant level output can be obtained.

As apparent from FIG. 3, a period obtained by adding the duration (period) of the shift pulse φTG to the maximum optical signal accumulation time (period) T is one scanning period.

Although the above embodiment is configured to read optical information of a barcode label, the above embodiment can be applied to the case of reading optical information including characters and symbols other than a barcode. .

〔The invention's effect〕

Since the present invention is configured as described above, as follows:
A remarkable effect can be achieved.

(A) Even when the intensity of disturbance light on a member to be read (for example, a bar code label) changes significantly, it is possible to reliably read optical information (for example, bar code information) on the member to be read. .

(B) The peripheral circuits of the line image sensor can be simplified as much as possible.

(C) It is possible to cope with a change in illuminance due to disturbance light over a wide range.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of one embodiment of the optical information reading apparatus of the present invention. FIG. 2 is an explanatory diagram of the line image sensor in the above embodiment. FIG. 3 is a time chart showing an operation for one scanning period in the above embodiment. (Explanation of symbols) L: bar code label, 1: bar code reader, 10: light emitting diode (LED), 21: reflection mirror, 22: light receiving optical system (for example, convex lens), 30: line image sensor, 40 ...
Illuminance detecting light receiving element, 41 ... illuminance detecting optical system (for example, convex lens), 50 ... sensor drive circuit, 51 ... accumulation time control circuit (control means), 60 ... comparator, 61 ... amplifier, 62 ... slice level setting circuit.

Claims (1)

(57) [Claims] An irradiation means (1) for irradiating a member to be read (L).
0), a light receiving optical system (22) for forming an image of the reflected light from the member to be read (L) at a predetermined position, and a light image arriving at the light receiving surface is photoelectrically converted into an electric signal by electronic scanning. A line image sensor (30), illuminance detecting means (41, 40) for detecting the illuminance of the member to be read (L), and the line image sensor ( Control means (51) for controlling so as to shorten the actual optical signal accumulation time during each scanning period in (30).
And a conversion circuit (60/62) for converting the electric signal into a binary signal.
An optical information reading device, comprising: