JPS5820410B2 - optical scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical scanning device that performs optical scanning by deflecting a light beam using a polygonal rotating mirror.

When scanning a conventional code (for example, a bar code) with a light beam, only one scanning line 1 scans all the bars that make up the code if the code 2 is tilted on the scanning plane. Since it is not possible to cross in one scan (first
For example, there is an optical scanning device as shown in FIG. 2 that attempts to solve the above-mentioned problem by providing a plurality of scanning lines that are not parallel to each other.

To explain the outline of this device, the multifaceted rotating mirror 3 is a thin regular octagonal prism having eight reflecting surfaces, and is rotated by a drive system (not shown) ζ.

A light beam 5 emitted from a light beam generator 4 (for example, a laser device) is incident on the reflective surface of the polygonal rotating mirror 3, is reflected, and is deflected as the polygonal rotating mirror 3 rotates.

At this time, if the spot diameter of the light beam 3 can be ignored, the deflection angle will be 90°.

The light beam deflected in this way is reflected again by three reflecting mirrors, and the conveyor 1 moving in the direction of arrow 9
0 to form scanning lines 12, 13, and 14, and scan the code written on the article 11 conveyed by the conveyor.

An example of the arrangement of the reflecting mirrors 6, 7, 8 at this time is simply shown in a plan view as shown in FIG. 3.

The deflection angle of the light beam deflected around point O4 is divided into three equal parts by three reflecting mirrors 6 and 7.8, and the angle is 0. A.

0, B, , 01C, are the perpendicular bisectors of the reflecting mirror 6° 7.8 in Figure 3, /A101B, = /B,
0. A reflecting mirror is arranged so that the angle is 30° to C, and the extension lines of reflecting mirrors 6 and 8 intersect at point B1, and the light beam is reflected perpendicularly to the paper surface by the reflecting mirrors 6 and 7.8. When parallel to is projected onto the scanning surface, the scanning lines will intersect at one point on the scanning surface that extends beyond a certain distance from the reflecting mirror, and in this case the scanning lines will become as shown in FIG.

A'1, B') and C1' are respectively A1°B,
, C, is the arrival point of the light beam reflected by C, and the intersection angle of each scanning line is 30°.

In the case of the above method, the length on the scanning line is determined by the deflection angle determined by the number of reflective surfaces of the polygonal rotating mirror and the optical distance from the reflection point on the reflective surface of the polygonal rotating mirror to the scanning surface. , if the optical distance is limited, the scan line length may not reach the required length.

Therefore, in order to increase the length of the scanning line, there is a method of decreasing the number of reflecting surfaces and increasing the deflection angle.

For example, if a polygonal rotating mirror with a regular rectangular prism with four reflecting surfaces is used, the deflection angle is twice that of a case with eight reflecting surfaces, 18
If this deflection angle is divided into three equal parts using three reflecting mirrors in the same manner as described above to create a scanning line, the length of the scanning line will nearly double.

However, the intersection angle of the scanning lines becomes wider to 45°, which makes it more resistant to the inclination of the code. However, if the width w1 and height h of the code are set, and tan-' h / w is 22.5° or less, the code is not in the scanning plane. If it is tilted at an angle of about 22.5 degrees, it will be impossible to scan the code with any scanning line.

(See FIG. 5) Furthermore, if the number of reflective surfaces decreases, the intersection angle becomes wider than necessary, causing the disadvantage that the above-mentioned tendency becomes more noticeable.

The present invention provides an angle (hereinafter referred to as a tilt angle) between a reflecting surface of a polygonal rotating mirror and a reference plane perpendicular to the rotation axis of the polygonal rotating mirror.
Therefore, it is necessary to use a different polygonal rotating mirror for each reflecting surface, thereby providing an optical scanning device which eliminates the above-mentioned disadvantages.

The present invention will be explained in detail below with reference to the drawing ζ.

FIG. 6 shows an embodiment of the present invention, FIGS. 7 and 8 show its principle, a front view and a plan view, respectively, and FIG. 9 shows a scanning line created by an embodiment of the present invention. .

The polygonal rotating mirror 15 has a tilt angle of (90+θ) degrees and (90
-θ) degrees is a polygonal rotating mirror having eight identical reflecting surfaces alternately, and is rotated by a drive system (not shown).

Now, when the light beam 16 travels perpendicularly to the rotation axis of the polygonal rotating mirror 15, it is reflected by the reflecting surface, and as the polygonal rotating mirror 15 rotates, it is deflected by 90 degrees around the 0□ point.

Actually, since the spot diameter of the light beam 16 is finite, the deflection angle is less than 900, and since the size of the polygonal rotating mirror is finite, the point 02 is on the incident optical axis as the polygonal rotating mirror 15 rotates. However, in order to simplify the explanation, the following description will be made assuming that the deflection angle is 90° and the 02 point is one point.

Now, the light beam 16 incident on the reflecting surface having a tilt angle of (90-.theta.) degrees is reflected in the direction of the dashed arrow and is deflected by 90.degree. as the polygonal rotating mirror 15 rotates.

The reflector 17.19 is symmetrical with respect to the light beam 16 and forms a line segment 02A2,0□ having an angle of 22.5° with the light beam 16.
B2 is arranged so as to overlap the perpendicular bisector Q of each reflecting mirror (see FIG. 8), and the light beam 16 is reflected in the plane direction ζ perpendicular to the plane of the paper in FIG.

The light beam 16 incident on the reflecting surface with the next ζ tilt angle (90+θ) is reflected in the direction of the solid arrow, and the polygonal rotating mirror 15
It is deflected by 90 degrees as it rotates, is reflected again by the reflecting mirror 19 arranged perpendicular to 0202 in FIG. This is a scanning line that passes near the intersection of the scanning lines of the book.

(See FIGS. 7 and 8) The scanning lines created in this way are as shown in FIG. 9.

A4, B4, and Cl3 are the reflecting mirrors 17.
18. Point A2 on 19. B2. This is the arrival point of the light beam 16 reflected by C2, and when the scanning plane is parallel to the reference plane,
The crossing angle of each scanning line is 22.5°, so the crossing angle does not become wide and a long scanning line can be obtained.

As explained above, according to the present invention, by using a polygonal rotating mirror having reflecting surfaces with different folding angles, the light beam reflected by the reflecting surfaces with different folding angles is directed in the direction determined by the folding angle of each reflecting surface. Since it is deflected, the deflection angle that can be used by the scanning reflector can be widened, and a long scanning line can be obtained.

When the reflecting mirrors are arranged in the manner described above, the intersecting angle of the scanning lines does not become wider than necessary by Q, so the height h of the code that is the object of scanning symmetry can be reduced.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between a barcode and a scanning line when scanning a barcode with a single scanning line, Figure 2 is a conventional optical scanning device, and Figure 3 is a plan view of its principle. , Figure 4 shows the scanning line created by the conventional method, and Figure 5 shows the relationship between the scanning line and barcode when the reflective surface of the polygonal rotating mirror is reduced and the deflection angle is increased to lengthen the scanning line. 6 are schematic diagrams showing one embodiment of the present invention, FIGS. 7 and 8 are front and plan views showing the principle, and FIG. 9 is a scanning line created by this method. be.

Claims (1)

[Claims] 1. A light source that generates a light beam, a polygonal rotating mirror that has a plurality of reflecting surfaces having two different angles of inclination with respect to a rotation axis and receives the light beam, and a polygonal rotating mirror that receives the light beam as the polygonal rotating mirror rotates. A mirror that reflects one of the two deflected light beams extracted from the mirror and is set at angles that are not parallel to each other to create a cross-shaped scanning pattern.
and a second plane reflecting mirror, which reflects the other light beam from the polygonal rotating mirror and passes through the intersection of the cross-shaped scanning pattern formed by the first and second plane reflecting mirrors and is not parallel to each scanning pattern. and a third plane reflector for creating another scanning pattern.