JPS61217875A - Optical reader - Google Patents

Abstract

PURPOSE:To reduce the amount of noise component mixed into the reflection beam light by having the difference between a scan optical path reaching up to a surface to be scanned and a reflection optical path reaching up to a photoelectric transduser. CONSTITUTION:A beam condenser lens 8 is set between a scanning rotary polyhedral mirror 3 and a scan subject 5. The lens 8 has a function to focus the laser beam light onto a surface 5a to be scanned as well as a function to lead the laser beam light reflected on the surface 5a to a condenser rotary polyhedral mirror 4 approximately in the form of parallel luminous fluxes. Then both mirrors 3 and 4 are revolved by a motor 1 synchronously with each other. Thus the laser beam light reflected from the surface 5a illuminated by the laser beam can be condensed. Then the noise components due to a fact that no difference exists between the scan and reflection optical paths can be reduced since both optical paths are different from each other.

Description

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

<Prior Art> Conventionally, an information beam emitted from a laser light source is guided to a scanning rotating polygon mirror, and the information beam is swung in the direction of rotation of the scanning rotating polygon mirror.

A scanned surface on which a bar code, etc. is recorded is scanned, and the reflected information beam reflected from the scanned surface is focused and guided to a photoelectric conversion element, where it is photoelectrically converted and recorded on the scanned surface. An optical reading device that optically reads recorded information is known (see Japanese Patent Laid-Open No. 152246/1983).

This conventional optical reading device includes, as its light focusing means,
A condenser lens is provided to condense and image the reflected information beam light reflected on the surface to be scanned onto the light receiving surface of the photoelectric conversion element, and it is possible to determine which part of the surface to be scanned in the scanning direction is illuminated by the information beam light. Irrespective of whether or not, there is a scanning area-wide condensing system in which the light within the entire scanning range is condensed as reflected information beam light by a condensing lens, and the reflected information beam light is reflected again by a scanning rotating polygon mirror. There is an illuminated point light condensing system that is configured to guide the information beam light to a photoelectric conversion element, and to receive only the reflected information beam light from the spot on the scanning surface that is illuminated by the information beam light.

A device that adopts this illumination point light condensing method has a perforated mirror for optical path splitting placed between the laser light source and the scanning rotating polygon mirror, and information beam light is passed through the hole in the perforated mirror. At the same time as the image is projected, the reflected information beam reflected from the surface to be scanned is reflected by a scanning rotating polygon mirror and a perforated mirror and guided to a 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 reflected information beam light as reflected information beam light. If outside light is taken in as noise and the ambient illuminance of the scanned surface due to indoor lighting is high, the reflected information beam light cannot be read as a signal due to the influence of the ambient illuminance. be. In addition, in conventional devices that adopt the illumination point light condensing method, the scanning optical path and the reflected optical path of the information beam light are the same between the perforated mirror and the scanned surface, and the projected information beam There is a problem in that the light diffracted by the perforated mirror and the scattered light by the scanning rotating polygon mirror and other optical components are directly guided as noise to the photoelectric conversion element. Furthermore, since the reflected information beam light is received through the reflective surface of the perforated mirror, there is a problem in that the amount of the reflected information beam light guided to the photoelectric conversion element is limited.

Furthermore, if an optical member such as a reflecting prism is placed in the scanning optical path in order to divide the projected information beam into a plurality of scanning beams and draw a plurality of scanning trajectories on the scanned surface,
These optical members limit the amount of reflected information beam light that can be received, so it is a national policy to increase the level of the amount of reflected information beam light that is received. Therefore, a scanning rotating polygon mirror that reflects the information beam light and guides it to the scanning surface is used, and the reflected information beam light that is rotated in synchronization with the scanning rotating polygon mirror and reflected on the scanning surface is photoelectrically converted. A scanning optical path from the information beam light emitting light source to the scanned surface via the scanning rotary polygon mirror and a condensing rotating polygon mirror from the scanned surface to the scanning surface are provided. The reflected information beam is configured to condense the reflected information beam light reflected at the illumination location of the scanned surface that is currently illuminated by changing the reflected optical path to the photoelectric conversion element via the polygon mirror. It is conceivable to adopt a configuration that reduces the increase in noise based on the light separation optical means, but in that case,
In addition to the beam focusing lens that focuses the information beam reflected by the scanning rotating polygon mirror and guides it to the scanned surface, a lens for focusing the reflected light must be provided, so the optical system becomes complicated. Become.

<Object of the Invention> The present invention has been made in view of the above-mentioned problems of the prior art.The purpose of the present invention is to reduce the amount of noise mixed into the reflected information beam light, and to reduce the amount of noise mixed in the reflected information beam light. It is an object of the present invention to provide an optical reading device that can increase the light intensity level and have a larger signal-to-noise ratio (S/N) than before, and that has a compact configuration.

<Means for Solving the Problems> The optical reading device of the present invention includes a scanning rotating polygon mirror that reflects an information beam light and guiding it to a surface to be scanned, and a scanning rotating polygon mirror that rotates in synchronization with the scanning rotating polygon mirror. a condensing rotary polygon mirror that guides the reflected information beam light reflected on the scanned surface to a photoelectric conversion element; and a beam condenser that focuses the information beam light reflected on the scanned rotary polygon mirror on the scanned surface. a scanning optical path from the information beam light emitting light source to the scanned surface via the scanning rotating polygon mirror, and a photoelectronic optical path from the scanned surface via the condensing rotating polygon mirror. The reflected optical path up to the conversion element is different, and the beam condensing lens is shared by the scanning optical system and the reflecting optical system to convert the reflected information beam reflected on the scanned surface into a substantially parallel light beam. It is characterized by guiding the light to the condensing rotating polygon mirror.

<Operation> According to this, the information beam light 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 reflected information beam reflected at the currently illuminated spot on the scanned surface is different from the scanning optical path from the information beam emission light source to the scanning rotating polygon mirror to the scanned surface. The light is guided through a reflective optical path to a condensing rotating polygon mirror, and is deflected by the condensing polygon mirror in the direction where the photoelectric conversion element is present, and then guided to the photoelectric conversion element.

<Embodiment> FIG. 1 shows the optical system of an optical reading device, where l is a drive motor and 2 is its rotation axis.

A scanning rotating polygonal mirror 3 forming part of a scanning optical system and a condensing rotating polygonal mirror 4 forming part of a reflecting optical system are integrally attached to the rotating shaft 2. The scanning rotating polygon mirror 3 is as shown in FIG.

It has an octagonal prism shape, and has parallel reflecting surfaces 38 to 3d on the 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 rotational direction of the scanning rotating polygon mirror 3, and the parallel reflecting surface 3a, the parallel reflecting surface 3b,
Parallel reflective surface 3c, parallel reflective surface 3d, and upwardly inclined reflective surface 3e
The upwardly inclined reflecting surface 3f, the downwardly inclined reflecting surface 3h, and the downwardly inclined reflecting surface 3g are located at opposite positions with the output shaft 2 as a boundary. This scanning rotating polygon mirror 3.

It has a function of scanning the scanned surface 5a of the scanned object 5 by swinging the information beam light in its rotation direction.

As shown in FIG. 3, a bar code 5b, for example, is recorded on the scanned surface 5a.

The information beam light is herein referred to as a laser beam light, and in FIG. 4, 6 is a laser light source as a light source for emitting the information beam light. It is reflected by the reflecting mirror 7 and guided to the reflecting surface of the rotating polygon scanning mirror 3. In this figure, arrow A indicates the rotation direction of the rotating polygon scanning mirror 3, and arrow B indicates the direction of rotation of the rotating polygon scanning mirror 3. is the scanning direction.

Between the scanning rotating polygon mirror 3 and the object to be scanned 5.

A beam condensing lens 8 is provided, and reference numeral a indicates its front axis. This beam focusing lens 8 is.

It has a function of converging the laser beam light onto the surface to be scanned 5a, and also has a function of guiding the reflected laser beam light reflected on the surface to be scanned 5a to the condensing rotating polygon mirror 4 as a substantially parallel beam. The condensing rotating polygon mirror 4 has an octagonal prism shape and has parallel reflecting surfaces 48 to 4h on the side surfaces.
This condensing rotating polygon @4 directs the reflected laser beam 10 to the photoelectric conversion element I via the condensing lens 9 and the slit plate 10.
The reflecting mirror is provided above the reflected optical path of the reflected laser beam so as not to obstruct the reflected laser beam. This condensing rotating polygon @ 4 is rotated in synchronization with the scanning rotating polygon mirror 3, and each of its reflective surfaces is always directed toward the illumination spot to be scanned that is illuminated by the laser beam light. There is. The aforementioned slit plate 10 is provided with slits that are perpendicular to the scanning direction and have a sufficiently small width relative to the scanning area, and block out ambient external light that causes noise and block 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 making the external light blocking diaphragm into a slit shape in this way, even when oblique scanning is performed by the scanning rotating polygon mirror 3, as will be described later, the light from the scanning illumination area can always be guided to the photoelectric conversion element 11. Can be done.

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 reflecting surfaces 3a,
As shown in FIG. 7, 3f has a function of reflecting the laser beam upward and guiding it to the reflecting prism 12, and is a downwardly inclined surface 3g.

3h has a function of reflecting the laser beam downward and guiding it to the 1-reflection prism 13, as shown in FIG. As shown in FIG. 3, the upwardly inclined reflecting surfaces 3a and 3f have a constant incident direction of the laser beam light, and the apparent angle of inclination changes from time to time during the rotation of the scanning rotating polygon mirror 3. It has a function of drawing a scanning trajectory Y oblique to the scanning trajectory X obtained by the parallel reflecting surfaces 38 to 3,
The downwardly inclined reflecting surfaces 3g and 3h create a scanning locus Z oblique to the scanning locus X obtained by the parallel reflecting surfaces 38 to 3d during the rotation of the scanning rotary polygon 11t3 with the incident direction of the laser beam light constant. It has a drawing function,
The reflective prisms 12.13 are optically arranged so that the scanning trajectories x, y, z intersect with each other.

As a result, accurate reading is possible even when the barcode 5b is arranged at an angle with respect to the scanning locus. In addition, when the condensing 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 1o described above, which causes noise. External light can be blocked more effectively.

According to this, since the rotating polygon mirror 3 for scanning and the rotating polygon mirror 4 for condensing are rotated synchronously, the reflected laser beam light from the illuminated spot on the scanned surface that is illuminated by the laser beam light is condensed. In addition, the scanning optical path from the laser light source 6 to the scanned surface 5a via the scanning rotating polygon mirror 3 and the reflection from the scanned surface 5a to the photoelectric conversion element 11 via the condensing rotating polygon tIt4. Since the optical paths are configured to be different from each other, the reflected laser beam light can be guided to the photoelectric conversion element 11 through different optical paths.
When the scanning optical path and the reflected optical path are the same, there is no need for an optical means to separate the reflected laser beam from the scanning optical path, and the scanning optical path and the reflected optical path are at least partially the same. It is possible to reduce the noise based on the Furthermore, since the beam focusing lens 8 has both the function of focusing the laser beam light on the scanned surface 5a and the function of focusing the reflected laser beam light, it is possible to downsize the optical reading device. can.

In the embodiments described above, the rotating polygon mirror 3 for scanning and the rotating polygon mirror 4 for condensing were separately attached to the rotating shaft 2 of the same motor l 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 condensing are configured as separate bodies, but they can also be configured as one body.

<Effects of the Invention> As explained above, the present invention provides an optical reading device configured to condense reflected information beam light from a scanned surface illumination location illuminated by the information beam light. A scanning optical path from an emission light source to a surface to be scanned via a scanning rotating polygon mirror.

This is because the reflection optical path from the scanning surface to the photoelectric conversion element via the condensing rotating polygon mirror has a different configuration.

This has the effect that noise due to the fact that the scanning optical path and the reflection optical path are the same can be reduced and the signal-to-noise ratio can be increased. And even in that case,
A beam condensing lens is shared by the scanning optical system and the reflective optical system, and converts the reflected information beam reflected from the surface to be scanned into a substantially parallel beam of light and guides it to the condensing rotating polygon mirror. Therefore, its configuration is also compact.

[Brief explanation of the drawing]

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. FIG. 4 is a plan view of the optical system of the optical reading device shown in FIG. 1, and FIG. 5 is a sectional view taken along the line v--v 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. ■...Drive motor, 2...Rotating shaft. 3... Rotating polygon mirror for scanning, 4... Rotating polygon mirror for focusing, 5a... Surface to be scanned, 6... Laser light source, 8... Lens for beam focusing. 11...Photoelectric conversion element.

Claims (2)

[Claims] (1) A scanning rotating polygon mirror that reflects the information beam light and guides it to the scanned surface, and a scanning rotating polygon mirror that rotates in synchronization with the scanning rotating polygon mirror and converts the reflected information beam light reflected on the scanned surface into a photoelectronic mirror. It has a condensing rotating polygon mirror that guides the light beam to the conversion element, and a beam condensing lens that focuses the information beam light reflected by the scanning rotary polygon mirror onto the scanned surface, and the information beam light is guided from the information beam light emitting light source to the The scanning optical path to the scanned surface via the scanning rotating polygon mirror is different from the reflected optical path from the scanning surface to the photoelectric conversion element via the condensing rotating polygon mirror, and the beam condensing optical path is made different. A lens is used in common by the scanning optical system and the reflecting optical system to convert the reflected information beam reflected from the scanned surface into a substantially parallel beam of light and guide it to the condensing rotating polygon mirror. Optical reader. (2) Claim 1, characterized in that the condensing rotating polygon mirror and the scanning rotating polygon mirror are integrally constructed.
Optical reading device as described in section.