JPH0627397A - Information reader - Google Patents

Abstract

PURPOSE:To make the depth of a device thinner and to reduce the driving power of an optical scanning means, as well in the device which reads information such as bar codes printed on materials by a laser scanning beam. CONSTITUTION:The device consists of a laser optical source 1, an optical scanning means 2 from which laser scanning lines 21 are obtained by scanning the laser beam from the source 1 and a detector 6 which detects reflected light signals corresponding to the information on the scanned item 4 read by the lines 21. Moreover, a wave surface converting element 3 and the converging means 5 of the reflected optical signals are provided. The element 3 has a function for forming image from the laser beam scanned by the means 2 and the means 5 is placed at the image formation position 50 of the laser beam, converges the reflected optical signals by changing the angles in synchronization with the means 2 and guides them to the detector 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information reading device, and more particularly to a device for reading information such as a bar code attached on an object by laser scanning light.

[0002]

2. Description of the Related Art Such information reading devices are used in recent POs.
It is positioned as a major input device with the development of the S system.

A device for reading information such as a bar code by a laser scanning light (hereinafter referred to as a bar code reader) has a basic configuration of a laser light source, an optical scanning means, and a laser light reflected and scattered from a bar code on an object. It has a signal light detection means for performing focused detection as signal light corresponding to the bar code information.

In the basic structure of such an apparatus, depending on the position where the signal light detecting means is placed, a re-imaging method is used.
It is classified into a non-re-imaging method.

In the re-imaging method, a signal light detecting means (for example, a concave mirror for collecting the signal light) is placed between the laser light source and the light scanning means.

Therefore, the scanning point on the object (on the bar code)
Part of the light reflected and scattered from the laser beam returns through the same path as the laser light from the laser light source is emitted to the bar code on the object, and is placed in the path from the laser light source to the optical scanning means. It is collected by the detection means.

As described above, in the re-imaging method, the scanning point on the object and the position of the signal light detecting means have a point-to-point correspondence, and the noise light from other than the scanning point on the object is the signal light. An image is formed at a point other than the detecting means.

On the other hand, in the non-re-imaging method, the signal light detecting means is placed between the light scanning means and the object. Therefore, the light from other than the scanning point on the object is also focused on the signal light detecting means, and it becomes difficult to distinguish the signal light corresponding to the barcode information from the noise light.

From this point of view, conventionally, the optical system of the bar code reader has generally adopted the re-imaging method.

Here, a rotary polygon mirror is generally used as the optical scanning means of the bar code reader. In the re-imaging method, the signal light reflected and scattered from the scanning point on the object returns to the rotating polygon mirror, where it is reflected and directed to the signal light detecting means.

Therefore, the amount of signal light collected by the signal light detecting means is related to the size of the rotating polygon mirror (area of the mirror).

By reducing the size of the rotary polygon mirror, the device can be made thin and compact. At the same time, it is possible to reduce the driving power of the rotary polygon mirror.

[0013]

However, from the viewpoint of detection sensitivity and accuracy, it is necessary to secure the signal light collected by the signal light detection means in a predetermined amount or more. For this purpose, the rotating polyhedral It is difficult to reduce the size of the mirror.

Therefore, in the conventional apparatus, the non-re-imaging method is not preferable because it is difficult to distinguish the signal light and the noise. On the other hand, in the re-imaging method, the size of the rotating polygon mirror is reduced. It is difficult to obtain the advantages of such a device.

An object of the present invention is to solve the problem in such a conventional device.

[0016]

An information reading apparatus according to the present invention comprises a laser light source 1 and an optical scanning means 2 for scanning a laser beam from the laser light source 1 to obtain a laser scanning line 21.
And the scanned object 4 read by the laser scanning line 21.
It has a detector 6 for detecting the reflected light signal corresponding to the above information.

Further, a wavefront conversion element 3 and a means 5 for collecting reflected light signals are provided. The wavefront conversion element 3 has a function of forming an image of laser light scanned by the optical scanning means.

The optical signal condensing means 5 is arranged at the image forming position 50 of the laser light, condenses the reflected light signal and guides it to the detector 6.

Further, the optical signal condensing means 5 comprises the optical scanning means 2
The reflected light signal is condensed and guided to the detector 6 by changing the angle in synchronism with.

As another aspect of the present invention, the wavefront conversion element 3 is composed of a convex lens or a hologram.

Further, as an aspect of the present invention, the optical signal condensing means 5 is composed of a concave mirror or a hologram having a hole at the center through which the laser light imaged by the wavefront conversion element 3 passes.

As another aspect, the wavefront conversion element 3 and the optical signal condensing means 5 are provided in the optical path between the optical scanning means 2 and the object to be scanned.

[0023]

In the present invention, the laser light emitted from the optical scanning means is
An image is once formed by the wavefront conversion element 3. Further, it becomes a laser scanning line 21 which is emitted again from the image forming point and scans information such as a barcode on the object.

The laser scanning line 21 scans the information on the object, and the reflected light is focused by the optical signal focusing means 5 and directed to the detector 6.

Therefore, according to the present invention, since the reflected light does not pass through the optical scanning means 2, the amount of the reflected light detected by the detector 6 does not depend on the size of the optical scanning means 2.

Further, the wavefront conversion element 3 forms an image of the laser beam scanned by the optical scanning means 2, the optical signal condensing means 5 is placed at the image forming position 50, and the optical signal condensing means 5 is ,
The angle is changed in synchronization with the optical scanning means 2. As a result, the information position on the object scanned by the laser beam and the detector 6 are
The point-to-point correspondence is maintained.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS For a more accurate understanding of the present invention, the conventional apparatus will be described in some detail before describing the embodiments.

FIG. 4 shows an example of the configuration of the conventional device.
FIG. 1A is a perspective view of a configuration example of the inside thereof.

Reference numeral 1 is a laser light source, for example, a He-Ne laser. The laser light emitted from the laser light source 1 is reflected by the reflecting mirror 10 and heads for the small circular mirror 12 in the center of the concave mirror 11.

The laser light reflected by the small circular mirror 12 is guided to a rotary polygon mirror (polygon mirror) 2 and is rotated by the rotary polygon mirror 2.
Becomes the laser scanning light with the rotation of.

The laser scanning light from the rotary polygon mirror 2 is divided into scanning light in three directions by three scanning line division mirrors 13, 14, 15.

The respective divided scanning lights guide the scanning lights in the three directions to the respective holograms 18, 19, 20 of the hollow window 17 fixed on the reading window of the apparatus via the bottom mirror 16.

In the figure, as the hollow window 17, a supporting glass plate and a plate with a hologram placed thereon are shown in common.

The holograms 18, 19 and 20 diffract the laser light incident thereon and form laser scanning lines 21 to 25 in five directions in space. This laser scanning line 21-
The barcode 40 on the scanned object 4 is scanned by 25.

When the scanned object 4 is scanned by the laser scanning lines 21 to 25, the laser light is reflected and scattered. The optical path of the reflected and scattered light is shown in FIG.

FIG. 4 (2) is a simplified cross-sectional view of the device of FIG. 4 (1). The reflected and scattered light reflected and scattered from the scanned object 4 passes through the hollow window 17, the bottom mirror 16, the split mirror 14, the rotary polygon mirror 2 and the concave mirror 11 and is guided to the photodetector 6.

Here, the concave mirror 11 has a function of a signal light condensing means, and therefore, when the amount of reflected scattered light input to the signal light converging means is eclipsed in the optical path, a necessary recombined image can be obtained. I can't do it.

Therefore, in the conventional device, the size (area) of the rotary polygon mirror 2 is important, and when it is small, the device space can be downsized and the rotary drive power can be reduced. However, in order to reduce the size of the rotary polygon mirror 2 from the relationship of the amount of reflected and scattered light that can be condensed by the concave mirror 11,
Have difficulty.

Next, in order to better understand the present invention in relation to the problem of the conventional apparatus, the re-imaging signal detection system and the non-re-imaging signal detection system will be considered based on FIG.

FIG. 5A is an explanatory diagram of the re-imaging signal detection method. A concave mirror, especially a perforated concave mirror 11 having a hole through which laser light passes is provided between the laser light source 1 and the scanning means 2. Here, for the sake of simplification, the scanning means 2 is not a rotary polygon mirror, but an example of a galvano mirror that repeatedly rotates.

In this system, the laser light source 1 and the scanning point of the laser on the object 4 have a point-to-point relationship via an optical system.
Therefore, ambient light (noise light) that enters the optical system from other than the scanning point is imaged around the photodetector 6 and is not detected.

As a result, it is possible to read even a very weak light amount which is a part of the reflected and scattered light from the object 4.

However, in order to realize the re-imaging signal detection method, it is necessary to place the concave mirror 11 which is the optical signal condensing means in the optical path from the laser light source 1 to the optical scanning means 2.

For example, consider the case where the perforated concave mirror 11 is arranged after the optical scanning means 2 as shown in FIG. 5 (2). By combining the perforated concave mirror 11 and the photodetector 6, the light reflected and scattered at the position of the object 4 shown in the figure is condensed and detected.

In this case, the object 4 moves to the X position on the same scanning line, and the light reflected and scattered there is detected by the photodetector 6.
The image is formed at a position of Y which is outside of. Therefore, the object information cannot be read.

Further, as the optical signal focusing means, the concave mirror 1 with a hole is used.
Instead of 1, as shown in FIG.
With the combination of the convex lens 60 and the convex lens 60, even if the object 4 moves to the X position on the same scanning line, the reflected and scattered light can be condensed and detected. But at the same time, the object 4
Since ambient light (noise light) from other than the above is also collected and detected, it is difficult to detect the signal light.

For this reason, the above-mentioned problems of the conventional device arise.

The present invention was made to solve the problem of the conventional device, and one embodiment thereof is shown in FIG.

FIG. 1 (1) shows a simplified optical system in particular from the cross section of the device, and FIG. 1 (2) is a corresponding plan view.

The basic structure is the same as that of the conventional device described in FIG. The first difference from the conventional device is that in the device of the present invention, the concave mirror 5 having a hole as an optical signal condensing means is provided between the laser light source 1 and the optical scanning means 2 instead of the optical scanning means 2. It is a point placed on the back side.

A second difference is that the wavefront conversion element 3 is provided so that the light beam from the optical scanning means 2 is once focused on the hole portion 50 which is the center position of the perforated concave mirror 5. Is.

In this embodiment, a hologram is used as the wavefront conversion element 3. Due to the diffraction function of the hologram, the light beam can be imaged like a convex lens.

With the above structure, it is possible to make the structure thinner (the reason will be more apparent from the description below). The laser beam from the rotary polygon mirror 2 has a perforated concave mirror 5.
After passing through the hole 50, the light is reflected by the splitting mirrors 14, 15, 16 and the bottom mirror 16 and enters the hollow window 17.

The bar code 40 on the object 4 is scanned by the laser scanning line formed in the space through the hollow window 17. The operation of condensing and detecting the signal light reflected and scattered from the scanning by scanning will be described with reference to FIGS. 2 and 3.

Here, in order to simplify the explanation, as shown in FIG. 2A, the configuration of the embodiment of FIG. 1 is part of the optical system, that is, the splitting mirrors 13, 14, 15, the bottom mirror 16 and the hollow. Consider India 17 omitted.

A wavefront conversion element 3 for forming an image of the scanning light from the optical scanning means 2, a hologram is used in the embodiment, is provided after the optical scanning means 2, and the hole 5 of the concave mirror 5 with a hole is provided at the imaging point of the scanning light.
0s are arranged so as to correspond to each other.

This perforated concave mirror 5 is centered on the image forming point, and as shown in FIGS. 2 (2), 3 (3) and (4), the optical scanning means 2 is used.
The angle changes according to the rotation angle of. Therefore, the position of the laser scanning line 21 and the position of the photodetector 6 maintain a point-to-point correspondence.

Therefore, according to the present invention, it is possible to obtain the re-imaging signal detection system. Further, the optical scanning means 2 is
Used only for optical scanning. Therefore, the reflection area may be small.

Further, since the concave mirror 5 can be placed at the position shown in the figure, the re-imaging signal light amount can be secured as in the conventional case even if the apparatus is made thin.

In the above description, the case where the perforated concave mirror 5 is used as the optical signal condensing means has been described, but the present invention is not limited to this case. For example, the same effect can be obtained by using a perforated reflection type hologram.

[0061]

As described above, according to the present invention, the device can be thinned and the driving power of the optical scanning means can be reduced.

Further, if the size of the apparatus itself is maintained, a large number of recombined images can be secured as compared with the conventional case. Therefore, since the reflection efficiency of the mirror and the required diffraction efficiency of the hologram can be estimated to be low, the cost of the device can be reduced.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention.

FIG. 2 is an explanatory diagram of the operation of the embodiment of the present invention.

FIG. 3 is an explanatory diagram of an operation of the embodiment of the present invention.

FIG. 4 shows a configuration example of a conventional device.

FIG. 5 is an explanatory diagram of a problem of the conventional device.

[Explanation of symbols]

 1 Laser Light Source 2 Rotating Polygon Mirror Current System 3 Wavefront Conversion Element (Hologram) 4 Object 40 Bar Code 5 Perforated Concave Mirror 6 Photodetector 10 Reflector 13, 14, 15 Scan Dividing Mirror 16 Bottom Mirror 17 Hollowed

Claims (4)

[Claims] 1. A laser light source (1) and the laser light source (1)
An optical scanning means (2) for obtaining a laser scanning line (21) by scanning a laser beam from the laser beam, and a reflected light signal corresponding to information on the scanned object (4) read by the laser scanning line (21). In an information reading device having a detector (6) for detecting, a wavefront conversion element (3) and a condensing means (5) for the reflected light signal are further provided, and the wavefront conversion element (3) is provided for the optical scanning means ( 2) has a function of forming an image of the laser beam scanned, the optical signal condensing means (5) is placed at the image forming position (50) of the laser light, and the optical scanning means (2) An information reading device configured to collect the reflected light signal and guide the reflected light signal to the detector (6) by changing an angle in synchronism with the above. 2. The information reading device according to claim 1, wherein the wavefront conversion element (3) is composed of a convex lens or a hologram. 3. The optical signal condensing means (5) according to claim 1 or 2, wherein the optical signal condensing means (5) is composed of a concave mirror or a hologram having a hole through which a laser beam imaged by the wavefront conversion element (3) passes. An information reading device characterized in that 4. The wavefront conversion element (3) and the condensing means (5) for the reflected light signal according to claim 1, between the optical scanning means (2) and the scanned object (4). An information reading device provided in an optical path.