JPH05189589A - Bar code read method and bar code reader - Google Patents

Abstract

PURPOSE:To provide the bar code read method and the bar code reader which can read bar codes without adjusting in a long readable range even in the case when positions of bar codes to be read are not uniform. CONSTITUTION:First and second optical axes 26, 27 of two first and second light throwing devices 21, 22 different in positions of readable ranges are made parallel by a reflection mirror 23, and both of these optical axes 26, 27 are scanned by a polygon mirror 24; and in this case, light throwing devices 21, 22 are alternately flickered with each reflection face of the polygon mirror 24 as the unit by a switch 25 synchronized with the polygon mirror 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bar code reader, and more particularly to a method for increasing the readable range and a bar code reader therefor.

[0002]

2. Description of the Related Art In order to read a bar code, a laser beam having a diameter smaller than the minimum width b of the bar code is scanned over the bar code to detect a change in reflected light from the bar code. For this purpose, the diameter d of the laser light needs to be smaller than the minimum width b of the barcode.

As shown in FIG. 5, in order to make the diameter d of the laser light smaller than the minimum width b of the bar code shown in FIG. 6, the light source 12 for the laser light is generally provided inside the projector 1.
And, a lens system 13 for converging this laser light to a required diameter is built in.

As a result of the convergence by the lens system 13 described above, the point P (called the beam waist) at which the diameter d of the laser light becomes the smallest is uniquely determined by the focal length of the lens system 13. The diameter d of the laser beam thus converged increases as the distance from the point P increases (both in the front-back direction), and when it exceeds a certain distance, it becomes larger than the minimum width b of the bar code. Code resolution is lost. The distance to this limit is the readable range l ₀ .

In order to provide this readable range l ₀ at a required distance from the exit window 8a of the bar code reader 8,
When the projector 1 is used at a distance exceeding the readable range l ₀ , the lens system 13 having a different focal length or the projector 1 incorporating such a lens system 13 is selected and replaced.

However, when replacing the projector 1 or the lens system 13 as described above, it is difficult to adjust the mounting position and the like even in the same model, and in particular, much labor is required to adjust the optical axis.

There is also a method of using an autofocus type lens system as a method of changing the position of the readable range l ₀ , but this device is expensive and a spare lens system 13 or the projector 1 is prepared. It is not preferable to keep the cost.

Therefore, the applicant has proposed an improved bar code reader in Japanese Patent Application No. 3-16267. This is to change the length of the optical axis 2 between the mirror 5 and the projector 5 before the polygon mirror 6 which deflects the optical axis 2 of the laser light emitted from the projector 1 as shown in FIG. The cartridge 3 provided with a plurality of mirrors 4 so as to repeat repetitive reflection between the light projector 1 and the polygon mirror 6 is inserted so as to be regulated by the positioning pin 10 and the positioning guide 11 of the barcode reader 8 side. It is configured as possible.

In this way, the optical axis 2 of the laser light emitted from the light projector 1 is incident on the cartridge 3 having a plurality of mirrors 4. The cartridge 3 internally repeatedly reflects the laser light incident by the plurality of mirrors 4 a plurality of times and emits the laser light in the direction opposite to the incident optical axis 2a (emission optical axis 2b).

As a result, by replacing the cartridge 3, the distance L of the beam waist P from the exit window 8a can be changed even if the lens system 13 is constant, so that the bar code 7 is positioned within the readable range l ₀ . Since the projector 1 itself is fixed, there is no need for troublesome adjustment of the optical axis.

[0011]

However, even in this case, since it takes time to replace the cartridge 3, it is difficult to read an object to be read that has a nonuniform distance to each bar code and has a fast moving speed. There is a problem.

The present invention solves the above-mentioned problems and provides a bar code reading method capable of reading a long range without requiring replacement or adjustment, and a bar code reader capable of this reading method. It is an issue.

[0013]

In order to solve the above-mentioned problems, a laser beam emitted from a light projector is reflected by a polygon mirror to irradiate a bar code, and the bar code is read. A plurality of light projectors having different positions are operated alternately to prolong the total readable range.

In addition, a continuous long total readable range is obtained by using a light projector in which the position of the beam waist is adjusted so that the readable ranges before and after the beam waist of each of the light projectors may overlap to some extent.

A device for this purpose is to emit light from a light projector.
Reflected laser light with a polygon mirror
A barcode reader that illuminates the barcode and reads the barcode
First and second beam waist P₁, P₂Position of
Of different first projector 21, second projector 22, and
First and second optical axes 26 of the first and second projectors 21, 22;
A reflecting mirror 23 for reflecting 27 in the same direction;
The first and second projectors 21 in synchronization with the mirror 24,
And a switching device 25 for alternately operating
First and second readable of the first and second projectors 21, 22
Noh range l₀₁, L ₀₂So that there is some overlap
First and second beam waist P₁, P₂Adjust to about 2
Double readable range l₀Configured to get
It was done.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of the structure of a bar code reader of the present invention, FIG. 2 is an explanatory view of the optical axis of the same, and (a) is a plan view.
(B) is a side view seen from the direction of emitted light of the barcode reader, and (C) is a side view seen from a direction perpendicular to (B). This bar code reader 28 has the same internal polygon mirror 24, exit window 28a, and reading sensor 29 as the polygon mirror 6, exit window 8a, and reading sensor 9 shown in FIG.

The projector is arranged such that the first projector 21 and the second projector 22 face each other at a vertical position on a vertical line, and the first optical axis 26 and the second optical axis 27 of the respective emitted lights are on the same straight line. There is.

Between the first and second projectors 21 and 22, there is arranged a right-angle prism-shaped reflecting mirror 23 for reflecting the first and second optical axes 26 and 27 at right angles and in the same direction. The first and second optical axes 26 and 27 are configured to enter the reflecting surface of the polygon mirror 24 in parallel.

The first and second optical axes 26 and 27 that have entered the polygon mirror 24 are simultaneously deflected to the left and right as the polygon mirror 24 rotates, and the bar code 30 of the object placed on the belt conveyor 31 or the like is displayed. Scan horizontally.

The first and second projectors 21 and 22 are switched by a switching device 25 in synchronization with the rotation of the polygon mirror 24.
Each of the mirrors is configured to emit light by switching so that the light along the first or second optical axis 26, 27 is alternately incident.

Next, the operation of the bar code reader 28 of the present invention will be described.
Describe the work. As shown in FIG. 3, the first projector 2
1 is the first beam waist due to the internal lens system 21a
P₁, First readable range l₀₁Configured to be
The second light projector 22 is provided by an internal lens system 22a.
Second beam waist P₂, Second readable range l
₀₂Is configured to be. Moreover, these first and second
And second readable range l₀₁, L₀₂Is slightly overlaid
First and second beam waist P₁, P₂
Focal lengths of the lens systems 21a and 22a so that the positions of
Total readable range l because the distance is changed₀Is first
And the second readable range l₀₁, L₀₂About twice as long as
Is becoming

Moreover, since the first and second projectors 21 and 22 are switched and blinked by the switch 25 so as to alternately blink for each reflecting surface of the polygon mirror 24, the first or second projectors 21 and 22 are switched for each scanning. Bar code 30 with the second projectors 21 and 22
Is read.

[0023]

As described above, even if the bar code 30 of an object placed at random on the belt conveyor 31 as shown in FIG. 1 has an irregular distance from the bar code reader 28, the total readable range is obtained. Within l ₀ , the first and second optical axes 2 are provided for each reflecting surface of the polygon mirror 24.
Since 6 and 27 are switched, it is possible to read with light of any optical axis.

Therefore, it is not necessary to replace the projectors and the like, and a plurality of projectors are automatically switched.
The readable range of double the length can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration explanatory view of a main part of a barcode reader of the present invention.

FIG. 2 is an explanatory diagram of an optical axis from a light source to a barcode direction,
(A) is a plan view, (B) is a side view seen from the outgoing light direction of the barcode reader, and (C) is a side view seen from a direction perpendicular to (B).

FIG. 3 is an explanatory diagram of a laser beam of the barcode reader of the present invention.

FIG. 4 is a configuration diagram of a conventional improved barcode reader.

FIG. 5 is an explanatory diagram of a laser beam of a conventional barcode reader.

FIG. 6 is an explanatory diagram of an example of a barcode.

[Explanation of symbols]

21 First Projector 21a First Lens System 22 Second Projector 22a Second Lens System 23 Reflector 24 Polygon Mirror 25 Switcher 26 First Optical Axis 27 Second Optical Axis 28 Bar Code Reader 28a Exit Window 29 Reading Sensor 30 Bar Code P ₁ 1st beam waist P ₂ 2nd beam waist l ₀ Total readable range l ₀₁ 1st readable range l ₀₂ 2nd readable range

Claims (3)

[Claims] 1. A method of irradiating a bar code by reflecting laser light emitted from a light projector with a polygon mirror and reading the bar code, wherein the light projector is a plurality of light projectors having different beam waist positions, and the respective light projectors are alternately arranged. A bar code reading method characterized by extending the total readable range by operating the bar code. 2. The bar code reading method according to claim 1, wherein a projector is used in which the position of each beam waist is adjusted so that the readable ranges before and after the beam waist of each projector slightly overlap. .. 3. A bar code reader for reading a bar code by irradiating a bar code with a laser beam emitted from a light projector reflected by a polygon mirror, wherein the first and second light projectors have different first and second beam waist positions. When,
A reflecting mirror for reflecting the first and second optical axes of the first and second projectors in the same direction, and a switching device for alternately operating the first and second projectors in synchronization with the polygon mirror are provided. A bar code reader, wherein the first and second beam waists are adjusted so that the first and second readable ranges of the first and second projectors are slightly overlapped.