JPH0131235B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field of the Invention) This invention uses a semiconductor laser (mainly a laser diode) as a light source and a special polygon scan mirror, and detects one rotation of the mirror with an optical sensor. The present invention relates to a barcode reader that improves the reliability of reading by scanning.

(Technical background of the invention and its problems) Figure 1 shows the principle of the light source section of a conventional barcode reader, in which a light beam 5 emitted from a light source 1 such as an LED passes through a lens 2 and a beam scanning mirror. 3. As illustrated in FIG. 3, the beam scanning mirror 3 has a polygonal prism structure having a plurality of reflecting surfaces 32 that are rotatable around a rotation shaft 31. As shown in FIG. All of the reflecting surfaces 32 are parallel to the rotation axis 31 as shown in FIG. The beam reaches the surface of the code 4 and is scanned (main scanned) in the M direction shown in FIG. 2 as the beam scanning mirror 3 rotates.
That is, the reflection path after a slight rotation of the beam scan mirror 3 reaches the same position on the barcode 4 as shown by the broken line in FIG. 1, and is scanned by such rotation of the beam scan mirror 3. The point moves in the M direction and eventually reaches an arbitrary reflective surface 3.
2, one line in the shaded area 4A in FIG. 2 can be scanned and read.

In the above barcode reader,
Because the beam intensity from LEDs etc. is not very strong,
There is a disadvantage that the light receiving part becomes complicated and large, and furthermore, since the inclination angles of the reflecting surfaces 32 are all the same, when the beam scanning mirror 3 is further rotated, the other reflecting surfaces 32 will similarly have the shaded area 4A. You will have to scan it. For this reason, if the shaded area 4A is soiled, reading errors will occur, so to prevent such reading errors, move the scanner in the direction D in the figure or move the barcode 4 (sub-scanning). There is a disadvantage in that the operation of main scanning the area 4B on the barcode 4, for example, must be repeated several times.

(Objective of the Invention) The present invention has been made in view of the above-mentioned circumstances, and uses a semiconductor laser as a light source of the scanning beam, and also by giving appropriate inclinations to each reflecting surface 32 of the beam scanning mirror 3. Alternatively, by tilting the rotation axis of the polygon mirror, it is possible to scan not only in the main scanning direction (horizontal) but also in the sub-scanning direction (vertical), and further scan while detecting one rotation of the polygon scan mirror with an optical sensor. The object of the present invention is to provide a barcode reader that improves reading reliability.

(Summary of the Invention) The present invention relates to a barcode reader that can scan a barcode surface using a laser beam, and uses a semiconductor laser as a beam source and a polygon scan having a plurality of reflective surfaces. It is possible to scan in the main scanning direction (horizontal) by rotating the mirror, and it can also be scanned in the sub-scanning direction (vertical) by giving each reflecting surface an appropriate slope that changes stepwise, or by tilting the rotation axis. It is designed so that it can be scanned, and furthermore, it can be scanned while detecting one revolution of the polygon scan mirror using an optical sensor.

(Embodiment of the Invention) An embodiment of the invention is shown in FIG. A laser diode (LD) 7 is used as a light source, and since the laser diode 7 emits a light beam much stronger than the light emitted by an LED or the like, it is possible to reduce reading errors at the barcode light receiving section.

In addition, the polygon scan mirror 3' is shown in Figure 7.
As shown in FIGS. 8 and 9, the reflective surface 32' is provided with an inclination .theta. that varies stepwise by a predetermined angle. Multiple reflective surfaces 3 like this mirror 3'
By slightly varying the inclination θ of each surface 2', the laser beam 5 irradiated from the same position onto the reflective surface 32' at a constant angle is reflected by the reflective surface in a direction shifted by a predetermined angle. By rotating the polygon scan mirror 3', the above-mentioned sub-scanning can be performed simultaneously. That is, FIG. 5 and FIGS. 6A to 6C show how the barcode 4 is scanned by the polygon scan mirror 3', and the laser beam 5 irradiated from the same position
On the other hand, since the inclination θ of the reflective surface 32' differs depending on its rotational position, the reflective surface 32'A moves from the row L1 to the adjacent reflective surface 3 as shown in FIG. 6A.
2'B scans the row L2 as shown in B in the same figure, and the reflective surface 32'C next to it scans the row L3 in the M direction (main scanning) as shown in C in the same figure, and also scans the sub-scan in the vertical direction. Scanning can be performed. A polygon scan mirror having, for example, eight reflecting surfaces can perform eight lines of sub-scanning with one rotation of the mirror.

Therefore, by detecting the change in the amount of light reflected from the barcode 4 with an optical sensor 10 such as a photodiode disposed at the bottom of the reader 6, and comparing the detected signal with the reference pattern signal, ,
The contents of barcode 4 can be read. In this case, not only is the main scanning performed several times with one rotation of the mirror 3', but also the barcode 4 is read at different scanning positions during the sub-scanning.
It becomes possible to read the barcode 4 with high precision.

In order to further ensure the reading, an optical sensor 8 is attached to the end of the scanning section 1 on the bottom surface of the reader 6, as shown in FIGS. 10A and 10B, so as to synchronize the rotation of the mirror 3' with the scanning position. do. In other words, the scan start of each main scan performed several times in one rotation is
As shown by the broken line in FIG. 10B, the laser beam 5 is detected by the optical sensor 8 immediately before scanning the barcode 4, so that the light beam 5 corresponding to the rotational position of the mirror 3' and the barcode are detected by the optical sensor 8. The reading of the optical sensor 10 can be synchronized based on the amount of light reflected from the optical sensor 4. Therefore, the reading circuit is the optical sensor 8
The light beam 5 detected by the bar code 4 may be detected as a starting point, and the amount of light from the bar code 4 may be detected and read.

In addition, since the laser beam from a semiconductor laser is invisible to the naked eye, in order to confirm that the reading is being performed correctly using visible light like in a conventional barcode reader, a barcode reader is installed as shown in Figure 11. , visible light 12 emitted by a light source 11 such as an LED is sent along the path of the laser beam 5 using a half mirror 9. Thereby, it can be confirmed from the outside that the four sides of the barcode are irradiated with a light beam for reading, and it is possible to easily set the position of the barcode reader.

In addition, in the above description, the inclination θ of each reflection angle of the polygon mirror is varied, but FIGS. 12A and B
The rotating shaft 47 may have an inclination α as shown in FIG. That is, as shown in the figure, the polygon mirror 45 has a polygonal prism structure with a plurality of opposite surfaces 46, and each reflective surface has the same inclination (θ=90°), but the rotation axis 47 has a polygonal prism structure. It is set at an appropriate inclination angle α with respect to the center line 48 of the prism. Here, as shown in Figure B, a beam (laser, etc.) 43 that is incident on any one of the reflective surfaces 46 is reflected by the reflective surface 46, and the reflected light passes through a path as shown by the solid line onto the scanning surface 44. and is scanned in the X direction in the figure as the polygon mirror 45 rotates. The reflected light after the slight rotation of the polygon mirror 45 reaches the same position on the scanning surface 44 through a path as indicated by the broken line, and the location scanned by such rotation of the polygon mirror 45 moves in the X direction. After all, recording, reading, etc. can be performed by scanning in the primary scanning direction (X direction) using any one of the reflective surfaces 46. Furthermore, since the rotation axis 47 is tilted, the reflection angle y of the beam 43 that is incident on each of the plurality of reflection surfaces 46 from the same direction is different, and due to the rotation of the polygon mirror 45, the above-mentioned secondary scanning direction (Y direction ) can also be scanned.

(Effects of the Invention) As described above, according to the present invention, by using a semiconductor laser, it is possible to ensure reading at the light receiving section, and there is also an advantage that the scanner can be made smaller and lighter, and the new polygon scan mirror 3 ' allows sub-scanning of several locations to be performed simultaneously in one rotation,
It is possible to scan while detecting one rotation of the polygon scan mirror using an optical sensor, and furthermore, by visualizing the laser beam, there are advantages in that there are fewer reading errors and reliability is higher.

[Brief explanation of drawings]

Figs. 1 and 2 are diagrams showing the scanning state of a conventional barcode reader, Figs. 3 and 4 are diagrams showing the structure of a conventional polygon scan mirror, and Figs. 5 and 6 A to C. 7 and 8 are diagrams showing the scanning state of the barcode reader of the present invention.
The figure shows the structure of a polygon scan mirror used in the present invention, Figure 9 shows how the angle of inclination of the reflective surface of the polygon mirror changes, and Figures 10A and B show a barcode reader using an optical sensor. 11 is a diagram showing a scanner using a half mirror, and FIGS. 12A and 12B are diagrams showing an example in which the axis of a polygon mirror is tilted. 1...Light source (LED etc.), 2...Lens, 3, 3'...
Polygon scan mirror, 4... Barcode, 5...
Beam, 6... Reader body, 7... Light source (laser diode), 8, 10... Optical sensor, 9... Half mirror, 31, 31'... Rotation axis, 32, 32'... Reflecting surface.

Claims (1)

[Scope of Claims] 1. A light source consisting of a semiconductor laser that irradiates a light beam, a rotatable polygon scanning mirror having a plurality of reflective surfaces with slopes that change stepwise;
It is composed of a light receiving sensor that receives reflected light from the barcode reading surface, and an optical sensor provided at one location facing the barcode reading surface, and the light beam is reflected by the reflective surface of the polygon scan mirror. At the same time, the polygon scanning mirror is rotated, and the optical sensor detects each rotation while scanning the barcode, thereby scanning the barcode with a repetitive signal obtained by the light receiving sensor. A barcode reader characterized by being adapted to read. 2. The barcode reader according to claim 1, wherein the reflective surfaces of the polygon scan mirror have all the same inclination angle and the rotation axis is inclined.