JPH1049618A - Laser scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form the reflecting surface of a polygon mirror into a specific shape without altering the mirror driving mechanism, etc., and to obtain scanning angles and scanning directions by forming the reflecting surfaces of the polygon mirror different in shape and curving some reflecting surfaces. SOLUTION: The laser light emitted by a laser collimator 1 is made incident on the polygon mirror 2 at a constant angle. The polygon mirror 2 is driven as shown by an arrow in the figure to rotate, and reflects the laser light from the laser collimator 1 to scan a bar code. Here, the polygon mirror 2 is, for example, in a polygonal shape on the whole and has its one reflecting surface curved convexly into a convex mirror and other reflecting mirrors made into plane mirrors as usual. Thus, the polygon mirror 2 is provided with the convex mirror in the specific shape as a reflecting surface in addition to the plane mirrors, and then a scanning angle Θ0 for the plane mirrors and the scanning angle Θ1 for the convex mirror are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser scanner that scans an object to be read by irradiating a laser beam, and receives reflected light of the object to perform photoelectric conversion.

[0002]

2. Description of the Related Art This type of laser scanner reflects a laser beam with a polygon mirror or a vibration mirror,
By changing the emission angle, the object to be read (bar code) is scanned to read bar code information. FIG. 8 shows a laser scanner using a polygon mirror as a reflector. The polygon mirror forms a regular polygon (regular hexagon) in which a plurality of flat mirrors are bonded, and a drive shaft is provided at the center of the polygon to rotate. As a result, the angle between the laser light and the reflection surface changes, thereby changing the emission angle of the reflected light. In this case, the variation of the injection angle (scanning angle) theta ₀ is equal to the angle between the rotation axis and the end point of the reflection surface (the center angle of one side). In this way, the laser light is diffused according to a predetermined scanning angle,
The diffusion width (scanning range) changes according to the distance between the object to be read and the laser scanner. Further, since the reflection surface of the polygon mirror is a flat surface, the scanning direction is fixed to the rotation direction (one direction) of the polygon mirror.

[0003]

When a barcode is read by a handy type laser scanner, the distance from the barcode is left to the discretion of the user. However, the laser scanner has to be repeatedly moved away from the bar code or moved closer to the bar code so as to exceed the length of the bar code. Also, when a plurality of small barcodes are arranged in a straight line, if only a desired barcode is read from the barcodes without adjusting the distance to the barcode, only a specific barcode is used. Could not be read accurately. In addition, before and after the bar code, there is usually a start margin and an end code, but if there is printing dust or dirt on one side of the margin or the periphery, the received light intensity changes accordingly, In scanning from one direction, a margin portion cannot be accurately detected, and reading of a barcode may be impossible. An object of the present invention is to make it possible to realize a plurality of scanning angles / scanning directions by changing the reflection surface of a polygon mirror into a predetermined shape without changing a mirror driving mechanism or the like, and to realize a bar even in various environments. The purpose is to enable a code or the like to be read accurately.

[0004]

The means of the present invention are as follows. In a laser scanner that irradiates a laser beam and scans an object to be read, a plurality of reflecting surfaces having different shapes are formed, and a polygon mirror having a polyhedral shape formed by curving at least a part of the reflecting surface is provided.
By rotating the polygon mirror, a plurality of scan angles / scan directions are obtained. The plurality of reflecting surfaces having different shapes may be a combination of reflecting surfaces having the following shapes. , A combination of a plane mirror and either a concave mirror or a convex mirror. Combination of convex and concave mirrors. In the laser scanner configured as described above, it is possible to realize a plurality of scan angles / scan directions by changing the reflection surface of the polygon mirror to a predetermined shape without changing the mirror driving mechanism and the like. It is possible to accurately read a barcode or the like even under the above environment.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. First, the principle of obtaining a plurality of scanning angles by curving at least a part of the reflection surface in a laser scanner using a polygon mirror will be described with reference to FIGS. Laser light emitted from the laser collimator 1 is incident on the polygon mirror 2 at a fixed angle. The polygon mirror 2 is driven to rotate in the arrow direction (counterclockwise direction) shown in FIG. 1, and reflects a laser beam from the laser collimator 1 to scan a bar code. Here, for example, as shown in FIG. 2, the polygon mirror 2 has a regular polygon (regular hexagon) as a whole, and one of the reflection surfaces is a convex mirror curved in a convex shape. Forms a plane mirror as usual. 1 to 3 exemplify a convex mirror whose curvature is smaller than a circumscribed circle of the polygon mirror 2. As described above, when a convex mirror having a shape as shown in the figure is formed as a reflection surface of the polygon mirror 2 in addition to the plane mirror, a scanning angle Θ corresponding to the plane mirror is obtained.
_0, the scanning angle theta ₁ which corresponds to the convex mirror is obtained. That is, when the reflecting surface is a plane, a scanning angle Θ ₀ having an angle equal to the central angle の 一 of one side of the polygon mirror 2 is obtained as described above. On the other hand, when the reflecting surface is curved in a convex shape, the scanning angle changes at an angle ratio corresponding to the curvature. That is, as a law of reflection, the reflected light folds at an angle (incident angle) between the incident light and the perpendicular to the reflecting surface. However, when the reflecting surface is curved, the curvature is the same as the circumcircle of the polygon mirror 2. When the laser beam is incident on the end point position (the corner of the polyhedron), the emission angle (reflection angle) of the reflected light becomes “0 °”. On the other hand, when the polygon mirror 2 is driven to rotate from this end point position and the curvature of the reflection surface gradually changes, a reflection angle corresponding to the curvature is obtained.

FIG. 3 shows a state in this case. When incident light from a certain direction is reflected at a position shown in FIG. 3 deviating from an end point, the incident light is reflected by a plane mirror A Is reflected at a large angle, but the reflected light B from the convex mirror having the curvature shown in the figure is reflected at an angle of about 1/2 as compared with the case of the plane mirror. . Therefore, the scanning angle of a convex mirror having such a shape is small theta ₁ than theta ₀ as shown in FIG. Consequently, by rotating the polygon mirror 2, so that the two types of large scan angles theta ₀ small scan angle theta ₁ is obtained. That is, the scanning angle differs between the case where the laser light from a certain direction enters the reflecting surface of the flat mirror and the case where the laser beam enters the curved reflecting surface, so that two types of scanning ranges can be obtained.

In this case, the scanning angle obtained by the convex mirror becomes smaller than that of the plane mirror, but if the rotation speed of the polygon mirror 2 is constant, the scanning line speed decreases by reducing the scanning angle. Will do. That is, even in the case of a convex mirror, the central angle Θ is constant and the angular velocity does not change, as in the case of the flat mirror.
A smaller scan angle means that the speed of the scan line will be lower than with a plane mirror. For this reason,
The intensity of light reflected from one point reflected by the convex mirror increases. Also, since the scanning line speed is reduced, the length of scanning by the laser beam per unit time (scanning range) is shortened, so that the resolution can be increased under the same sampling rate (processing speed). Will be able to In FIGS. 1 to 3, a convex mirror having a curvature smaller than the circumscribed circle of the polygon mirror 2 is exemplified as the curved reflecting surface. However, the shape of the curved reflecting surface is arbitrary. The convex mirror having a curvature larger than the circumscribed circle may be used, and not limited to the convex mirror, a concave mirror may be used, and the scanning angle can be obtained at an angle ratio corresponding to the curvature. Is the same as

Next, the principle of obtaining a plurality of scanning directions by bending at least a part of the reflection surface in a laser scanner using a polygon mirror will be described with reference to FIGS. When the reflection surface of the polygon mirror 2 is curved, the curvature is
As described above, when the laser beam is incident on the end point position having the same curvature as the circumscribed circle, the change amount of the reflected light becomes “0 °” as described above. It changes according to the curvature. That is, as shown in FIG. 5, when the reflection surface of the polygon mirror 2 is curved with a curvature (curvature in the positive direction) more convex than its circumscribed circle (in the example of FIG. 5, a convex mirror). The scanning is performed in a direction opposite to the rotation direction of the polygon mirror 2. For example, in the figure, the reflected lights a1, a2, and a3 are reflected on the reflecting surface A having the positive curvature, and the reflected lights change in the order of a1, a2, and a3 as the polygon mirror 2 rotates counterclockwise. Then, scanning is performed in the direction opposite to the rotation of the polygon mirror 2 (see FIG. 4B). This can be understood from the fact that, as compared with the case of the circumscribed circle, the angle formed between the incident light and the reflecting surface is smaller as the position is closer to the end point of the reflecting surface, and the angle is similar at the center of the reflecting surface.

On the other hand, when the reflecting surface of the polygon mirror 2 has a concave curvature (curvature in the minus direction) from its circumscribed circle (the plane mirror in the example of FIG. 5), the rotation direction of the polygon mirror 2 is changed. Scan in the same direction. For example, the reflected lights b1, b2, and b3 are reflected on the reflecting surface B having a negative curvature, and the reflected lights change in the order of b1, b2, and b3 in accordance with the rotational driving of the polygon mirror 2, so that the polygon mirror 2 Scanning is performed in the same direction as the rotation direction (see FIG. 4A). This can be understood from the fact that, as compared with the case of the circumscribed circle, the angle formed between the incident light and the reflecting surface becomes larger as the position is closer to the end point of the reflecting surface, and becomes the same at the center of the reflecting surface. By changing the curvature on the reflection surface of the polygon mirror 2 as described above, it is possible to perform scanning in both the left and right directions even with the polygon mirror 2 rotating in a fixed direction. Note that the curved surface having a curvature in the minus direction is the same even for a concave mirror, and the scanning direction is the same as the rotation direction of the polygon mirror 2.

FIG. 6 is a diagram for explaining how the scanning angle and the scanning direction change depending on what kind of curvature the reflecting surface of the polygon mirror 2 has. In the figure, the reflecting surface is a plane mirror as usual, and the scanning angle at this time is “medium” and the scanning direction is “positive”. The scanning angle and the scanning direction change. The reflecting surface is a concave mirror, and the scanning angle increases at an angle ratio corresponding to the curvature, so that the scanning angle becomes “large”. In addition, the scanning direction is “positive” because the curvature is in the minus direction. The reflection surface is a convex mirror, but the scanning angle changes according to the magnitude of the curvature. Therefore, the reflection surface is “large”, the reflection surface is “medium”, and the reflection surface is “small”. Further, since the scanning direction changes depending on whether the curvature is in the plus direction or the minus direction, the scanning direction is “reverse” for the reflective surface and “correct” for the reflective surface.

FIG. 7 shows a specific shape of the polygon mirror. Each polygon mirror has a regular hexahedron as a whole. FIG. 7A shows a polygon mirror 2A in which a plane mirror and a convex mirror having the same curvature are alternately formed. (B) shows a polygon mirror 2B in which a plane mirror and a concave mirror having the same curvature are alternately formed.
(C) shows a polygon mirror 2C in which convex mirrors having the same curvature and concave mirrors having the same curvature are alternately formed. (D) shows a polygon mirror 2D in which six convex mirrors having different curvatures are formed. (E) shows a polygon mirror 2E in which six concave mirrors having different curvatures are formed. (F) is a polygon mirror 2 in which a plane mirror, a concave mirror, and a convex mirror are alternately formed.
F is shown.

In the laser scanner configured as described above, since a plurality of reflecting surfaces having different shapes are formed on the polygon mirror 2 having a polyhedral shape and at least a part of the reflecting surfaces is curved, a plurality of scanning surfaces are formed. You can get the angle. Therefore, for example, when a plurality of small-size barcodes are linearly arranged, it is possible to read only one desired barcode at a small scanning angle. In addition, when a part of the barcode deviates from a small scanning angle, the barcode can be read at a large scanning angle. When the reflecting surface is a flat mirror, the scanning line speed is constant, but the scanning line speed can be controlled by bending the reflecting surface, so the reading performance is optimized under various conditions. Can be For example,
By reading from a small size barcode to a large size barcode on the reflecting surfaces having the corresponding resolution, stable performance can be maintained over a wide range. In this case, a large bar code is read at a wide scanning angle (low resolution), and a small bar code or a bar code at a long distance is read at a narrow scanning angle (high resolution). It is not necessary to make adjustments artificially, and the burden on the operator can be reduced accordingly.

[0013] Further, by making the reflecting surface of the polygon mirror have a large curvature and a small curvature with respect to its circumscribed circle,
Scanning from both left and right directions can be realized. Therefore, for example, of the start margin and the end margin before and after the bar code, even if the margin on one side is damaged, or if there is printing dust or dirt on the margin on one side, it can be correctly scanned by scanning from both directions. Bar code information can be read. Similarly, it becomes possible to read images and characters from the opposite direction.

Further, the reflecting surface of the polygon mirror is, for example,
By adopting various shapes as shown in FIGS. 7A to 7F, it is possible to increase or decrease the type of the scanning angle and freely change the scanning direction. As a result, when reading barcodes and characters, various environmental conditions,
In other words, it is possible to deal with a wide range of factors such as the distance and size of the object to be read, resolution, scanning speed, scanning angle, scanning direction, etc. Characters and the like can be read accurately. The specific shape of the polygon mirror is shown in FIG.
(A) to (F) are illustrated, but the shape is arbitrary.

[0015]

According to the present invention, since a plurality of reflecting surfaces having different shapes are formed on the polygon mirror and at least a part of the reflecting surfaces is curved, the polygon mirror can be formed without changing the mirror driving mechanism or the like. By forming the reflecting surface in a predetermined shape, a plurality of scanning angles / scanning directions can be realized, and a barcode or the like can be accurately read even under various environments.

[Brief description of the drawings]

FIG. 1 is a diagram showing that a plurality of scanning speeds can be obtained by applying a curve to a part of each of the reflecting surfaces constituting a polygon mirror.

FIG. 2 is an enlarged view of the polygon mirror shown in FIG.

FIG. 3 shows the polygon mirror shown in FIG. 2 in which the reflected light when the reflecting surface is flat and the reflected light when the reflecting surface is curved in a convex manner with respect to the incident light from a certain direction. FIG. 7 is a diagram for explaining whether or not light is reflected by the light source.

FIG. 4 is a diagram showing that a plurality of scanning directions can be obtained by applying a curvature to a part of the reflecting surfaces constituting the polygon mirror;

FIG. 5 shows a polygon mirror shown in FIG. 4 in which a reflection surface is reflected by a reflection surface A having a convex curvature with respect to its circumscribed circle, and a reflection surface is reflected by a reflection surface having a concave curvature.
FIG. 4 is a diagram showing how reflected light changes by rotation driving of a polygon mirror.

FIG. 6 is a diagram showing how a scanning angle and a scanning direction change depending on what kind of curvature having curvature is applied to a reflection surface of a polygon mirror.

FIG. 7 is a diagram showing a specific shape of a polygon mirror.

FIG. 8 is a diagram showing a conventional laser scanner.

[Explanation of symbols]

1 Laser collimator 2, 2A, 2B, 2C, 2D, 2E, 2F Polygon mirror

Claims (3)

[Claims] 1. A laser scanner for scanning an object to be read by irradiating a laser beam, wherein a plurality of reflection surfaces having different shapes are formed, and at least a part of the reflection surfaces is curved. 1. A laser scanner comprising: a polygon mirror having a polyhedral shape for reflecting light; and a plurality of scanning angles / scanning directions being obtained by rotating the polygon mirror. 2. A laser scanner according to claim 1, wherein said polygon mirror is formed by combining any one of a plane mirror, a concave mirror and a convex mirror as a plurality of reflection surfaces having different shapes. 3. The laser scanner according to claim 1, wherein a convex mirror and a concave mirror are formed on the polygon mirror as a plurality of reflecting surfaces having different shapes.