JPH056231B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention scans a surface to be scanned using a light beam such as a laser beam, and records information such as a bar code recorded on the surface to be scanned. The present invention relates to an optical reading device that optically reads.

<Prior art> Conventionally, a light beam emitted from a laser light source is guided to a scanning rotating polygon mirror, and the light beam is swung in the rotational direction of the scanning rotating polygon mirror to form a scanning beam, which records bar codes, etc. The scanning surface is scanned, and the return beam reflected from the scanning surface is focused and guided to a photoelectric conversion element, where it is photoelectrically converted and the recorded information recorded on the scanning surface is optically read. Optical reading devices are known (Japanese Patent Application Laid-open No. 1983-
(See Publication No. 152246). This conventional optical reading device is equipped with a condensing lens as its condensing means, which condenses and images the return beam reflected on the scanned surface onto the light receiving surface of the photoelectric conversion element. Regardless of which part in the scanning direction is illuminated by the scanning beam, it is a scanning area-wide condensing system in which light within a range spanning the entire scanning area is condensed by a condensing lens as a return beam. , the illumination point light concentrator is configured so that the return beam is reflected again by a rotating polygon mirror for scanning and guided to the photoelectric conversion element, and receives only the return beam from the point on the scanned surface that is illuminated by the scanning beam. There is a light method.

A device that also adopts this illumination point light condensing method has a perforated mirror placed between the laser light source and the scanning polygon mirror for optical path splitting, and a scanning beam is projected through the hole in the perforated mirror. At the same time, the returning beam reflected by the surface to be scanned is reflected by the scanning rotating polygon mirror and the perforated mirror and guided to the photoelectric conversion element.

<Problems to be Solved by the Invention> By the way, the conventional optical reading device of the entire scanning area condensing method is configured to take in external light other than the returning beam as a returning beam. If the ambient illuminance of the scanned surface due to indoor illumination light or the like is large and is taken in as noise, there is a problem that the returned beam cannot be read as a signal due to the influence of the ambient illuminance. In addition, in conventional devices that adopt the illumination spot light condensing method, the scanning optical path and the reflected optical path of the light beam are the same between the perforated mirror and the scanned surface, and the perforation of the projected light beam There is a problem in that the diffracted light by the mirror hole, the scattering part by the rotating polygon mirror for scanning, and other optical components are directly guided as noise to the photoelectric conversion element. Furthermore, since the return beam is received through the reflective surface of the perforated mirror, there is a problem in that the amount of light of the return beam guided to the photoelectric conversion element is limited.

In particular, in order to ensure reliable reading of information on the scanned surface of an object to be scanned, a reflective optical member such as a reflective prism is provided in the scanning optical path, and the light beam is divided into at least three or more scanning beams. If multiple scanning trajectories are drawn on the surface to be scanned, the received return beam is also limited by these optical members, making it difficult to increase the light intensity level of the received return beam. .

<Object of the Invention> The present invention has been made in view of the problems of the above-mentioned prior art, and its object is to provide a structure in which at least three or more scanning trajectories that intersect with each other are drawn on a scanned surface. However, it is an object of the present invention to provide an optical reading device that can reduce noise (S/N ratio) with a compact configuration.

<Means for Solving the Problems> The optical reading device of the present invention has a light source that emits a light beam and a plurality of reflecting surfaces around a rotation axis, and the light beam is reflected by the reflecting surfaces. In an optical reading device that reads information on the scanned surface, the optical reading device includes a rotating polygon mirror for scanning to form a scanning beam, and a photoelectric conversion element that photoelectrically converts a return beam reflected by the scanned surface, In order to divide the scanning direction into at least three directions and form at least three scanning beams, the inclination angles of the reflective surfaces adjacent to each other of the scanning rotating polygon mirror with respect to the rotation axis are made different, and the scanning rotation Between the polygon mirror and the surface to be scanned, scanning beams other than one of the at least three scanning beams are arranged such that the at least three scanning trajectories intersect with each other on the surface to be scanned. A reflective optical member is provided that reflects the beam and guides the beam together with the one scanning beam to the scanned surface, and reflects at least three return beams based on the reflection of the at least three scanning beams on the scanned surface. between the scanned surface and the photoelectric conversion element, in order to guide the photoelectric conversion element to the photoelectric conversion element;
A return beam rotating polygon mirror that rotates synchronously with the scanning rotating polygon mirror is provided, and each of the at least three return beams passes through an optical path avoiding the reflective optical member to the return beam rotating polygon mirror. It is characterized by being directly guided by.

<Operation> According to this, the light beam is guided to the surface to be scanned while being swung in the direction of rotation by the reflecting surface of the rotating polygon mirror for scanning, and the surface to be scanned is scanned. The scanned surface is actually illuminated. Here, in the scanning rotating polygon mirror, since the inclination angles of the reflective surfaces adjacent to each other with respect to the rotation axis are different from each other, at least three scanning beams whose at least three scanning trajectories intersect with each other on the scanned surface are formed. can get. The return beam reflected at the illuminated spot on the scanned surface is
The return beam is guided to the rotating polygon mirror for the return beam through a reflection optical path different from the scanning optical path from the light source to the surface to be scanned via the rotating polygon mirror for scanning, and the direction in which the photoelectric conversion element is present by the rotating polygon mirror for the return beam. and is guided to the photoelectric conversion element.

<Example> Fig. 1 shows the optical system of an optical reading device, in which 1 is a drive motor, 2 is its rotation axis,
A scanning rotating polygonal mirror 3 and a condensing rotating polygonal mirror 4 are integrally attached to the rotating shaft 2. As shown in FIG. 2, the scanning rotating polygon mirror 3 has an octagonal prism shape, and has parallel reflecting surfaces 3a to 3d on its side surfaces, upwardly inclined reflecting surfaces 3e and 3f, and downwardly inclined reflecting surfaces 3g and 3.
h. The parallel reflecting surface, the upwardly inclined reflecting surface, and the downwardly inclined reflecting surface are formed alternately in the rotation direction of the scanning rotating polygon mirror 3, and the parallel reflecting surface 3a
parallel reflective surface 3b, parallel reflective surface 3c and parallel reflective surface 3d, upwardly inclined reflective surface 3e and upwardly inclined reflective surface 3.
f, downwardly inclined reflective surface 3h and downwardly inclined reflective surface 3g
are located at opposite positions with the rotating shaft 2 as a boundary.
In this way, in the scanning rotating polygonal mirror 3, the reflective surfaces adjacent to each other have different inclination angles with respect to the rotation axis. The scanning rotating polygon mirror 3 has a function of scanning a surface 5a of the object 5 to be scanned by swinging a light beam in its rotational direction. This scanned surface 5a
As shown in FIG. 3, for example, a bar code 5b is recorded.

The light beam here is a laser beam, and in FIG. 4, 6 is a laser light source, and the laser beam emitted from this laser light source 6 is reflected by a reflecting mirror 7 and rotated for scanning. In FIG. 4, arrow A is the rotation direction of the scanning rotating polygon mirror 3, and arrow B is the scanning direction of the laser beam light. A beam condensing lens 8 is provided between the scanning rotating polygon mirror 3 and the object to be scanned 5, and reference numeral 1 indicates its optical axis. This beam focusing lens 8 directs the laser beam light onto the scanned surface 5.
It has the function of focusing on the scanned surface 5
It has a function of guiding the reflected laser beam reflected on the surface a to the return beam rotating polygon mirror 4 as a substantially parallel light beam. The beam focusing lens 8 has an aperture large enough to cover the area through which the light beam reflected from the scanning rotating polygon mirror 3 passes and the area through which the return beam from the scanned surface passes. It has an optical axis. The return beam rotating polygon mirror 4 has an octagonal prism shape and has parallel reflecting surfaces 4a to 4h on its side surfaces. The reflecting mirror has the function of guiding the returning beam 10 to the photoelectric conversion element 11, and the reflecting mirror is provided above the reflected optical path of the returning beam so as not to obstruct the returning beam. This return beam rotating polygon mirror 4 is
An illumination point to be scanned, which is located on the optical path between the scanned surface 5a and the photoelectric conversion element, is rotated in synchronization with the scanning rotating polygon mirror 3, and each of its reflecting surfaces is illuminated by laser beam light. It is made to always face the direction of. The aforementioned slit plate 10 is provided with slits in a direction perpendicular to the scanning direction and sufficiently small in width relative to the scanning area, and blocks ambient external light that causes noise and blocks light from the scanning illumination area. It has the function of guiding only the photoelectric conversion element 11 to the photoelectric conversion element 11. By forming the external light blocking diaphragm into a slit shape in this manner, light from the scanning illumination area can always be guided to the photoelectric conversion element 11 even when oblique scanning is performed by the scanning rotating polygon mirror 3 as described later. I can do it.

As shown in FIG. 6, the parallel reflecting surfaces 3a and 3b have the function of reflecting the laser beam in the horizontal direction and directing it directly to the beam condensing lens 8, and the upwardly inclined reflection theory 3e and 3f , as shown in FIG. 7, has the function of reflecting the laser beam upward and guiding it to the reflecting prism 12 as a reflecting optical member, and the downwardly inclined surfaces 3g and 3h are
As shown in FIG. 8, it has the function of reflecting the laser beam downward and guiding it to the reflecting prism 13. The reflecting prisms 12 and 13 are located between the scanning rotating polygon mirror 3 and the condensing lens 8. As shown in FIG. 3, the upwardly inclined reflecting surfaces 3e and 3f are parallel to each other because the incident direction of the laser beam light is fixed and the apparent angle of inclination changes from time to time during the rotation of the scanning rotating polygon mirror 3. Reflective surfaces 3a to 3d
It has a function of drawing a scanning trajectory Y oblique to the scanning trajectory X obtained by the downwardly inclined reflecting surface 3.
g, 3h draw a scanning locus Z oblique to the scanning locus X obtained by the parallel reflecting surfaces 3a to 3d while the scanning rotating polygon mirror 3 is rotating with the incident direction of the laser beam light constant. The reflecting prisms 12 and 13 have the function of
They are optically arranged so that Y and Z intersect with each other. As a result, accurate reading is possible even when the barcode 5b is arranged obliquely with respect to the scanning locus. Note that if the return beam rotating polygon mirror 4 is configured with a reflecting surface having the same shape as the scanning rotating polygon mirror 3, a pinhole plate can be used instead of the slit plate 10 described above, which causes noise. External light can be blocked more effectively.

According to this, since the scanning rotating polygon mirror 3 and the return beam rotating polygon mirror 4 are rotated synchronously,
It is possible to condense the return beam from the illuminated spot on the scanned surface that is illuminated by the laser beam light, and also to direct the scanning rotating polygon mirror 3 from the laser light source 6.
Since the scanning optical path from the scanning surface 5a to the scanning surface 5a and the reflection optical path from the scanning surface 5a to the photoelectric conversion element 11 via the return beam rotating polygon mirror 4 have different configurations, The returning beam can be guided to the photoelectric conversion element 11, and when the scanning optical path and the reflected optical path are the same, there is no need for an optical means to separate the returning beam from the scanning optical path, and the scanning optical path It is possible to reduce noise based on the fact that the reflected optical path and the reflected optical path are at least partially the same. Furthermore, since the beam focusing lens 8 has both the function of focusing the laser beam on the scanned surface 5a and the function of focusing the return beam,
It is also possible to downsize the optical reading device.

In the embodiments described above, the rotating polygon mirror 3 for scanning and the rotating polygon mirror 4 for return beam are separately attached to the rotating shaft 2 of the same motor 1 and rotated synchronously. , it is also possible to have a configuration in which they are separately attached to each rotating shaft and rotated synchronously. Further, in the embodiment, the rotating polygon mirror 3 for scanning and the rotating polygon mirror 4 for return beam are configured as separate bodies, but they may also be configured as one body.

<Effects of the Invention> As explained above, the present invention provides an inclination of adjacent reflecting surfaces of a scanning polygon mirror with respect to the rotation axis in order to divide the scanning direction into at least three directions and form at least three scanning beams. At least one of the three scanning beams is arranged at different angles and between the scanning rotary polygon mirror and the surface to be scanned, so that the at least three scanning trajectories intersect with each other on the surface to be scanned. A reflective optical member is provided that reflects the remaining scanning beam and guides it to the scanned surface together with that one scanning beam, so a simple configuration consisting of a rotating polygon mirror and a reflective optical member can be used to reflect the remaining scanning beam onto the scanned surface. At least three scanning trajectories can be drawn that intersect at Since it is not limited by the effective diameter of the reflective optical member, a sufficient amount of received light can be obtained without increasing the size of the reflective optical member, and the noise ratio (S/N ratio) can be reduced.

[Brief explanation of drawings]

FIG. 1 is a side view of the optical system of the optical reading device according to the present invention, FIG. 2 is a perspective view of the rotating polygon mirror for scanning shown in FIG. 1, and FIG. 4 is a plan view of the optical system of the optical reading device shown in FIG. 1; FIG. 5 is a sectional view taken along the line - in FIG. 1;
6 to 8 are conceptual diagrams for explaining the reflection direction of the scanning rotating polygon mirror shown in FIG. 1. FIG. DESCRIPTION OF SYMBOLS 1... Drive motor, 2... Rotating shaft, 3... Rotating polygon mirror for scanning, 4... Rotating polygon mirror for return beam, 5a... Surface to be scanned, 6... Laser light source, 8... Lens for beam focusing, 11... Photoelectric conversion element.

Claims (1)

[Scope of Claims] 1. A light source that emits a light beam, and a scanning rotating polygon mirror that has a plurality of reflective surfaces around a rotating shaft and that reflects the light beam on the reflective surfaces to form a scanning beam. and a photoelectric conversion element that photoelectrically converts a return beam reflected from the surface to be scanned, and reads information on the surface to be scanned, the scanning direction being divided into at least three directions, and at least three beams are used. In order to form a scanning beam of , excluding one of the at least three scanning beams and reflecting the remaining scanning beams together with the one scanning beam so that the at least three scanning trajectories intersect with each other on the scanned surface; a reflective optical member guiding the scanned surface;
In order to reflect at least three return beams based on the reflection of the scanning beam of the book on the scanned surface and guide them to the photoelectric conversion element, the scanning beam is provided between the scanned surface and the photoelectric conversion element. A rotating polygon mirror for return beams that rotates in synchronization with the rotating polygon mirror is provided, and each of the at least three return beams is guided directly to the rotating polygon mirror for return beams through an optical path that avoids the reflective optical member. An optical reading device characterized in that: 2. It has an aperture large enough to cover the region through which the light beam reflected from the scanning rotating polygon mirror passes and the region through which the return beam from the surface to be scanned passes, and a single optical axis, and which transmits the light beam. A condensing lens system that condenses light onto a scanned surface and converts a return beam from the scanned surface into a parallel light beam is arranged at a position where the scanning rotary polygon mirror and the return beam rotary polygon mirror are arranged and the surface The optical reading device according to claim 1, wherein the optical reading device is located between the scanning surface and the scanning surface. 3. The optical reading device according to claim 1, wherein the rotation axis of the scanning rotating polygon mirror and the rotation axis of the return rotating polygon mirror are coaxial. 4. The optical reading device according to claim 1, wherein the scanning rotating polygon mirror and the return beam rotating polygon mirror are integrally formed.