JPS5820411B2 - optical reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an optical reading device, more specifically, a light beam such as a laser beam is deflected to illuminate a target pattern such as a price tag composed of a bar code, etc., and the reflected light is used as a photoelectric reader. The present invention relates to an optical reading device for reading the information content of a converted and irradiated object pattern.

In this type of optical reading device, mechanical methods and electroacoustic methods are known for deflecting a light beam such as a laser beam, but generally the mechanical method is employed.

As a mechanical light beam deflection device, a polygon mirror with symmetrical surfaces is fixed to a rotation axis directly connected to a motor, and a light beam is directed to it by rotating a regular prism polygon mirror around that axis. What to irradiate is known.

In this known device, the irradiated laser beam is reflected and deflected by the mirror surface of the rotating polygon mirror.

However, since this polygon mirror is symmetrical with respect to its rotation axis, the light beam reflected by this polygon mirror is always deflected along only one straight line on the pattern surface to be scanned, and its scanning trajectory follows one straight line. limited to.

With such a scanning method, if the pattern to be scanned (barcode) is inserted obliquely to the scanning trajectory, all the information of the target pattern cannot be scanned in one scan, and its position cannot be scanned. A significant disadvantage is that it requires correction and rescanning.

In order to overcome this drawback, so-called radial scanning has been performed in which the scanning locus forms a plurality of radial straight lines on the target pattern.

In the main scanning, the condensed light beam is split into two directions by a half mirror, and a polygon mirror 2 whose mirror surface is symmetrical about the rotation axis is used.
The two beams are arranged so that their rotation axes are inclined to each other, and the separated light beams are projected and reflected by the rotating polygon mirror to obtain two deflected light beams, which mutually form scanning trajectories. This is to obtain two straight lines that intersect, that is, to perform line scanning in an X shape.

In this radial scanning, the scanning light spot is deflected on two straight lines, and scanning is performed on straight lines that intersect with each other on the target pattern, so the target pattern, such as a price tag, is tilted diagonally to the scanning line. Even so, since the target pattern only needs to be on one of the scanning lines, the probability of completing the scanning in one go is much higher.

However, since the scanning light is divided into two by a half mirror, the amount of scanning light is halved, which deteriorates the S/N ratio in the photoelectric conversion system and makes it difficult to read the information content. However, this would significantly increase the cost for the light source and increase the size of the device.

In addition, two polygonal reflecting mirrors are arranged with their rotation axes tilted to each other, and a set of bevel gears is required to rotate them synchronously, which increases the load on the drive motor and makes it difficult to perform high-speed scanning. Accordingly, high-speed reading is not possible, the accuracy of the scanning beam cannot be obtained due to the backlash of the gears, and the mechanical parts tend to lose accuracy with use and have a short lifespan.

The present invention is capable of radial scanning, that is, scanning on a plurality of straight lines passing through a certain center point and in different directions within the range in which an object pattern is to be read, and is capable of avoiding the drawbacks of the above-mentioned known devices. The object of the present invention is to obtain an optical reading device of this kind that is economical and economical.

This purpose, according to the invention, consists of a light source emitting a light beam, one reflective surface parallel to the rotation axis and two at a predetermined angle to the rotation axis so that the cross section is in the form of a parallelogram. a rotating deflection mirror having at least one reflecting surface, which receives the light beam, reflects the light beam in different directions by the reflecting surface, and deflects the light beam; This is achieved by comprising a photoelectric conversion device for reflected light and scanning the target pattern radially with the light beam reflected in different directions by the reflecting surface.

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic explanatory diagram of an embodiment of the present invention. In FIG. 3, a light beam emitted from a light source 1 composed of, for example, a laser oscillator is focused by a condenser 2 and exits from the condenser 2. The light beam LB is reflected by a reflecting mirror 3, its optical path is changed, and it reaches a deflecting mirror 5 made of a polygon mirror.

The shaft 11 of this deflecting mirror 5 is directly connected to the motor 4 and rotates at high speed, polarizing the light beam LB incident on the deflecting mirror 5 and reflected from it, which reaches the target pattern 7 and reaches the scanning line b
, b' or on b', the target pattern 7 is scanned.

The light reflected from the scanning of the target pattern 7 passes through an optical filter 8 and reaches a photoelectric conversion device 9 composed of an element such as an inverter or a photodiode, where it is converted into an electrical signal.

This electrical signal is guided to a determination device 10 mainly composed of a logic circuit, and the content of the information is read.

Next, an example of a polarizing mirror (5 in FIG. 1) that can be used in the present invention will be described.

FIG. 2 is a plan view of the deflecting mirror (5 in FIG. 1), FIG. 3 is a side view of the deflecting mirror (5 in FIG. 1), and FIGS.
The state is shown in positions corresponding to a, b, and c in the figure.

In Figures 2 and 3, the shaft 11 is a motor (4 in Figure 1).
), and a parallelepiped-shaped deflection mirror 5 is fixed to this shaft 11.

As shown here, planes A and B are parallel to axis 11, equidistant from axis 11, and symmetrical about axis 11.

The C plane and the D plane are set parallel to each other except for special purposes, and form an angle θ with the axis 11.

However, the C plane and the D plane are asymmetrical with respect to the axis 11.

The A and B planes and the C and D planes are at right angles to each other.

FIG. 2a is a plan view of the deflection mirror 5 in one position, and FIG. 3a is a corresponding side view.

At this time, the light beam LB is in a plane perpendicular to the axis 11, that is, a horizontal plane, as shown in FIG. The light beam LB is reflected at a certain angle ψ to deflect the light beam LB.

b in FIGS. 2 and 3 shows that the shaft 11 is further extended by nine points in the direction of the arrow.
This shows the state rotated by 0°, and the incident light beam LB is reflected on a plane parallel to the axis 11, and as the axis 11 rotates, it is deflected by the plane B at the same angle as the incident direction, that is, in the horizontal plane. .

If the shaft 11 is further rotated by 90 degrees, the state shown in FIG. 2 and FIG. It is reflected and deflected in a different direction than in the case of the C-plane.

Although not shown, if the shaft 11 is further rotated by 90 degrees, then A
The light beam LB is reflected at the surface, which is similar to b in FIGS. 2 and 3.

Furthermore, since the C plane or the D plane is an inclined plane having a positive or negative angle θ or 10 with respect to the rotation axis 11, when these inclined planes are rotated, the angle ψ (or −ψ
), a three-dimensional change in the reflection angle occurs.

Therefore, the scanning line on the target pattern γ caused by the light beam LB reflected on the C plane or the D plane has an appropriate polarity with respect to the scanning line on the target pattern caused by the light beam LB reflected on the A plane or the B plane. Or it can be made to have a negative slope.

Therefore, when the deflecting mirror 5 shown in FIGS. 2 and 3 is rotated, scanning lines as shown in FIG. 4 are obtained on the target pattern 7.

Here the scanning line s, 4. sb is obtained from planes A and B, which overlap, and scanning lines Sc and Sd are obtained from planes C and D, respectively, and scanning on these scanning lines is performed in a time-sharing manner. As a result, radial sequential scanning is performed.

FIG. 5 is a diagram showing different configuration examples of the deflection mirror 5, and a
is a plan view, b is a front view, and C is a side view.

This deflecting mirror 5 has four reflecting surfaces for the light beam LB, in other words, one of the two surfaces parallel to the axis 11, as shown in FIGS. 2 and 3. The plane B is inclined at an angle θ' with respect to the axis 11.

That is, as can be easily seen from FIG. 5, the reflecting surfaces of the deflecting mirror 5 are such that the A side is parallel to the axis 11, the B side is at -θZ with respect to the axis 11, the C side is at θ, and the D side is at -θ'. It forms an angle.

FIG. 6 shows the scanning lines on the target pattern generated by the deflection mirror shown in FIG. 5, and the scanning lines Sa, Sb, S
c and Sd are obtained by planes A, B, C and D, respectively.

FIG. 7 is a diagram showing still another example of the structure of the deflection mirror 5, in which a is a plan view, b is a front view, and C is a side view.

This deflecting mirror has the shape of a hexagonal prism cut diagonally, and the light beam LB
There are 6 reflective surfaces for
1, the adjacent surfaces of C and E are each inclined at the same angle .theta. with respect to the axis, and the adjacent surfaces of F are each inclined at the same angle -.theta. with respect to the axis.

The scanning line generated on the target pattern by this deflection mirror is one scanning line Sab by planes A and B, as shown in FIG.
However, scanning lines Sce and Sdf are generated by both sides of C2F and both sides of F, respectively.

In this case, each scanning line is generated twice per rotation of the shaft 11, allowing high-speed reading.

According to the present invention, as described above, by setting the number of reflective surfaces of the deflecting mirror and the angle of inclination thereof with respect to the axis 11 variously, correspondingly various scanning lines can be obtained.

As described above, according to the present invention, it is possible to scan a wide range with a single operation using a plurality of radial scanning trajectories, so whether the target pattern is static or moving,
This has the effect of providing an optical reading device that can read information in one scan even when the orientation of the target pattern is particularly tilted.

Moreover, since the device of the present invention does not require the use of a half mirror to divide the light beam into two, the light source device does not need to be large or expensive, and the S/N ratio does not deteriorate. Since it is directly connected to the shaft and does not require gears, especially bevel gears, there is less load on the motor, high-speed rotation is possible, high-speed reading is possible at low cost, and the drive mechanism is simple, so there is less play and adjustment is possible. It is easy to use and has the effect of increasing the lifespan considering play.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing the configuration of an embodiment of the present invention, and FIG.
The figure is a plan view of an example of a deflecting mirror, FIG. 3 is a front view, FIG. 4 is a diagram showing the scanning trajectory on the target pattern generated by the deflecting mirror shown in FIGS. 2 and 3, and FIG. 5 is a diagram showing the deflection mirror. Figure 6 is a diagram showing a scanning trajectory obtained from the deflection mirror of Figure 5, Figure 7 is a diagram showing a further example of a different deflection mirror, Figure 8 is the deflection of Figure 7. It is a figure which shows the scanning locus obtained from a mirror. 1...Light source, 2...Concentrator, 3...
・・・Fixed reflector, 4...Motor, 5...
... Deflection mirror, 7... Target pattern, 8...
...Optical filter, 9...Photoelectric conversion device, 1
0... Determination device, 11... Rotation axis of deflection mirror, LB... Light beam, b, b', b
', 5a-8d, Sab. Sce, Sdf...Scanning line.

Claims (1)

[Claims] 1 A light source that emits a light beam and 1 parallel to the rotation axis
and at least two reflecting surfaces having a parallelogram-shaped cross section at a predetermined angle with respect to the axis of rotation. and a rotating deflection mirror that deflects the light beam, and a photoelectric conversion device for the reflected light from the target pattern scanned by the light beam, the light being reflected in different directions by the reflecting surface. An optical reading device configured to radially scan the target pattern with a beam.