JPH1153462A - Laser system bar code scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To read even a bar code of high density distant from a scanner by varying the oscillation speed of an oscillatory mirror and then setting a proper scanning speed corresponding to the distance between the read bar code and scanner. SOLUTION: A rotator 11 is composed partially of a permanent magnet and rotates with the magnetic field of a driving coil 10. A reflector is provided in front of the rotator 11. A frame 12 supports the rotator 11 rotatably. A spiral spring 13 has its one end fixed to the rotator 11 and the other end fixed to the frame 12. This spiral spring 13 allows the rotator 11 have a natural oscillation frequency in its rotating direction. Then a link driving shaft is moved along its axis and then a link arm can have its arm expanded and contracted around an axis of rotation. In this case, the moment of inertia of the rotator 1 is changed by an inertial moment varying part 14 and the arm of the link arm is put away from the axis of rotation to increase the moment of inertia. Consequently, the laser light scanning speed decreases.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser barcode scanner capable of reading a high-density barcode even at a distant distance within an allowable reading distance of the laser barcode scanner.

[0002]

2. Description of the Related Art A laser bar code scanner reflects light emitted from a laser light source by a reflecting mirror that rotates at a specified angle, and scans a bar code with a laser beam according to the rotation. Read.

The rotating reflecting mirror of the above-mentioned laser bar code scanner has a mechanism so that its rotation has a specified natural frequency, and is called a vibrating mirror (scan mirror). I have.

[0004] Such a bar code scanner is disclosed in
As described in Japanese Patent Application Laid-Open No. 8-16698, improvements in reading barcodes of various physical lengths have been considered, but the density of barcodes, especially of high-density barcodes located away from the scanner, has been considered. Reading was not considered.

Therefore, in the conventional laser bar code scanner, the scanning laser beam becomes faster almost in proportion to the distance at the scanning speed of the bar code at a distance close to the bar code scanner and at the scanning speed at the far distance. . Furthermore, the energy density per unit length of the reflected light decreases as the scanning speed increases.

As a result, readable bar codes are limited to those having a lower density as the distance increases, because of the resolution of the light receiving side.

[0007]

As described above, a high-density bar code at a distant distance may exceed the resolution of the light receiving side, and cannot be read.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems. That is, claim 1
The variable scanning speed of the vibrating mirror makes the scanning speed appropriate for the distance between the bar code to be read and the scanner so that high-density bar codes far from the scanner can be read. It is.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to an embodiment shown in the drawings.

FIG. 1 is a configuration diagram of a laser bar code scanner. In FIG. 1, reference numeral 1 denotes a laser light generator.
Reference numeral 2 denotes a laser beam emitted from the laser light generator 1. Reference numeral 3 denotes a vibrating mirror for operating the laser beam 2 in the left-right direction, and is configured to be rotatable. Reference numeral 4 denotes a scanning light of a bar code which is oscillated in the left-right direction by the vibration mirror 3. Reference numeral 5 denotes a light receiver for receiving a reflected signal of the bar code scanned by the scanning light 4. In this figure, an area between L1 and L2 is an optical light receiving area of the light receiver 3.

In this light receiving area, the ratio of the scanning speed of the scanning light between the point L1 near the laser barcode scanner side and the point L2 at a remote position is L2 / L1 of the point L1 at the point L2. It is twice as fast.

FIG. 2 is a conceptual diagram of an electric signal for reading a bar code. In FIG. 2, reference numeral 6 denotes a bar code in which black bars and spaces are arranged so as to form an arbitrary character according to the bar code standard. 7 is a bar code 6
Is an analog signal generated by the photodetector 5 when the scanning light 4 scans and receives light, and is generated so as to coincide with the bar code 6 along the time axis t. Reference numeral 8 denotes a digital signal generated by shaping the analog signal 7 into a digital waveform. The digital signal is analyzed by a microcomputer or the like and converted into a character.

Assuming that the left side of FIG. 2 is a signal read out at the point L1 described above, the right side is a signal read out similarly at the point L2.

At the point L2, the signal width of the analog signal 7 generated by the photodetector 5 is reduced by the rate at which the scanning speed is increased.

Further, the energy density per unit length of the reflected light is reduced by increasing the scanning speed, so that the height of the analog signal 7 generated in the photodetector 5 is also reduced.

If the reduction in the signal width and height exceeds the resolution of the photodetector 3 or the digital waveform shaping side, reading becomes impossible. In particular, a bar code with a higher density is disadvantageous for reading at a greater distance.

FIGS. 3 and 4 are an external view and an internal structural view of the vibrating mirror 3 according to one embodiment of the present invention.

In FIG. 3, reference numeral 9 denotes a reflecting mirror, 10 denotes a driving coil, and 11 denotes a rotator, which is partially constituted by a permanent magnet and is rotated by a magnetic field of the driving coil 10.

A reflecting mirror 9 is provided on the front surface of the rotator 11. Reference numeral 12 denotes a frame, which supports the rotating element 11 with a rotating shaft. Reference numeral 13 denotes a spiral spring, one end of which is a rotating element 11.
And the other end is fixed to the frame 12.

The spiral spring 13 allows the rotating element 11 to have a natural frequency in the rotating direction.

In FIG. 4, reference numeral 14 denotes a variable moment of inertia which is provided inside the rotor 11.

An adjustment lever 15 operates the inertia moment variable section 14.

FIG. 5 is a detailed configuration diagram of the inertia moment variable section 14.

In FIG. 5, 14a is a link arm, 1
4b is a movable fulcrum that supports one end of the link arm 14a.

Reference numeral 14c denotes a fixed fulcrum, which is the aforementioned movable fulcrum 14b.
And the other end of the link arm 14a.

Reference numeral 14d denotes a link drive shaft. Here, by moving the link drive shaft 14d in the axial direction, the link arm 14a can expand and contract its arm around the rotation axis.

Here, the spring constant of the spiral spring 13 is k
(N · m / rad) and the moment of inertia of the rotator 11 is M, the rotator 11 has a natural frequency f expressed by the following equation.
(Hz).

[0028]

F = √ (k / M) / (2 · π) (Equation 1) Further, the vibration velocity V0 (rad / s) (peak value) of the rotator 11 and the The scanning speed V1 (m / s) (peak value) of the laser beam at the distance position is
If the rotation amplitude of 1 is 2 · φ (rad), it is expressed by the following equation.

[0029]

V0 = φ · √ (k / M) (Expression 2)

[0030]

V1 = L · V0 (Equation 3) The moment of inertia M is changed by the moment of inertia variable unit 14, and the moment of inertia M is increased by moving the arm of the link arm 14a away from the rotation axis. Thus, it can be seen from the equations (2) and (3) that the laser beam scanning speed V1 decreases. Further, as the scanning speed of the laser beam is reduced, the density range of the readable barcode is widened. In addition to the embodiments described above, an electromagnetic vibrating mirror having a configuration as shown in FIG. 6 can be used.

In FIG. 6, reference numeral 16 denotes a rotator which has a permanent magnet having the polarity shown in the figure on the outside. 17 is a reflecting mirror. Reference numeral 18 denotes an electromagnet for a repulsive spring, which faces the permanent magnet portion of the rotor 16 and has a polarity of the rotor 1.
An arbitrary constant current is supplied so as to have the same polarity as the repulsive force 6. Reference numeral 19 denotes a drive coil for driving the rotator 16. Here, a repulsive spring having a spring constant k is formed approximately between the rotor 16 and the electromagnet 18 for repulsive springs.

The spring constant k is determined by the electromagnet 18 for the repulsive spring.
, The laser beam scanning speed V1 can be changed as can be seen from the above-described equations (Equation 2) and (Equation 3). Further, in addition to the two embodiments, FIG.
The laser beam scanning speed V1 can be changed by changing the amplitude as shown in FIG.

In FIG. 7, reference numeral 20 denotes a laser scanner main body, 21 denotes a normal laser beam scanning amplitude, and 22 denotes a scanning amplitude in the present invention. Here, the energy supplied for maintaining the resonance is considered to be substantially the same as the mechanism loss energy of the rotating mechanism and the like, and the mechanism loss energy is considered to be substantially proportional to the scanning amplitude. Therefore, the following equation is established.

[0034]

Φ = C · E (Equation 4) (E is the energy supplied for maintaining resonance, C is a constant) Therefore, the scanning amplitude depends on the supplied energy for maintaining resonance, and the equation (Equation 2) As can be seen from (Equation 3), the laser beam scanning speed V1 can be changed.

This makes it possible to read a high-density bar code at a distant place by reducing the supply energy for maintaining resonance, reducing the laser beam scanning amplitude, and decreasing the laser beam scanning speed. Becomes

[0036]

According to the laser bar code scanner of the present invention, the vibration speed of the vibrating mirror can be made variable using the means as described in the second, third and fourth aspects. This makes it possible to read even a high-density barcode far from the scanner, which was difficult to read at a constant laser beam scanning speed, by lowering the laser beam scanning speed.

[Brief description of the drawings]

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

FIG. 2 is a conceptual diagram of an electric signal for reading a bar code.

FIG. 3 is an external view of the vibrating mirror of FIG.

FIG. 4 is an internal structural diagram of the vibrating mirror of FIG. 3;

FIG. 5 is a detailed configuration diagram of an inertia moment variable unit in FIG. 3;

FIG. 6 is a configuration diagram of an electromagnetic vibrating mirror of a rotator.

FIG. 7 is a configuration diagram of a laser barcode scanner in which a scanning amplitude is changed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Laser light generator, 2 ... Laser beam, 3 ... Vibration mirror, 4
... scanning light, 5 ... light receiver.

Claims (1)

[Claims] A laser beam generator and a laser beam emitted from the laser beam generator are traversed to perform one-dimensional linear scanning or two-dimensional planar scanning such as in the left-right direction. A laser bar code comprising: a vibrating mirror for causing the laser beam to be received, a light receiver for receiving a bar code reflection signal by scanning with the laser beam, and a waveform shaping circuit for shaping the bar code signal received by the light receiver into a digital waveform. A laser barcode scanner, wherein the vibration speed of the vibrating mirror is variable.