JP3036239B2 - Information reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Such an information reading apparatus is a recent PO.
With the development of the S system, it is positioned as a main input device.

The basic configuration of an apparatus for reading information such as a bar code using a laser scanning light (hereinafter referred to as a bar code reader) is a laser light source, an optical scanning means, and a laser light reflected and scattered from a bar code on an object. It has signal light detecting means for detecting and condensing as signal light corresponding to bar code information.

In the basic configuration of such an apparatus, a re-imaging system and a re-imaging system are particularly required depending on the position where the signal light detecting means is placed.
It is classified into a non-re-imaging system.

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

Accordingly, a scanning point on an object (on a bar code)
Some of the light reflected and scattered from the laser beam returns from the laser light source to the barcode on the object in the same path as the signal light placed in the path from the laser light source to the optical scanning means. The light is collected by the detecting means.

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

[0008] On the other hand, in the non-re-imaging system, the signal light detecting means is placed between the light scanning means and the object. Therefore, light from other than the scanning point on the object is also condensed on the signal light detecting means, and it becomes difficult to distinguish between the signal light corresponding to the bar code information and the noise light.

[0009] From such a viewpoint, the optical system of the bar code reader generally employs a re-imaging system.

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

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

By reducing the size of the rotary polygon mirror, the device can be made thinner and smaller. At the same time, the driving power of the rotating polygon mirror can be reduced.

[0013]

However, from the viewpoints of detection sensitivity and accuracy, it is necessary to ensure that the signal light condensed by the signal light detecting means is equal to or more than a predetermined amount. It is difficult to reduce the size of the mirror.

Therefore, in the conventional apparatus, it is difficult to distinguish between signal light and noise, so that the non-re-imaging method is not preferable. On the other hand, in the re-imaging method, the above-described method is required by reducing the size of the rotating polygon mirror. It is difficult to obtain the advantages of such a device.

An object of the present invention is to solve the problems in the 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 a reflected light signal corresponding to the above information.

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

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

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

Further, as one aspect of the present invention, the wavefront conversion element 3 is constituted by a convex lens or a hologram.

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

As another mode, 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]

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

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

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

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

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS For a better understanding of the present invention, prior art will be described in some detail before describing the embodiments.

FIG. 4 shows an example of the configuration of a conventional apparatus.
(1) is a perspective view of an example of a configuration inside thereof.

Reference numeral 1 denotes a laser light source, for example, a He-Ne laser. Laser light emitted from the laser light source 1 is reflected by the reflecting mirror 10 and travels to the small circular mirror 12 at the center of the concave mirror 11.

The laser light reflected by the small circular mirror 12 is guided to a rotating polygon mirror (polygon mirror) 2 and the rotating polygon mirror 2
Is turned into laser scanning light with the rotation of.

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

Each of the divided scanning lights leads the scanning light in three directions to each hologram 18, 19, 20 of a hollow window 17 fixed on a reading window of the apparatus via a bottom mirror 16.

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

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

When the object 4 to be scanned is scanned by the laser scanning lines 21 to 25, the laser light is reflected and scattered. The optical path of the reflected 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 rotating 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. Therefore, if the amount of reflected and scattered light input to the signal light condensing means is deviated along the optical path, a necessary recombined image can be obtained. It will not be possible.

For this reason, in the conventional apparatus, the size (area) of the rotary polygon mirror 2 is important, and if it is small, the space for the apparatus can be reduced and the rotational driving power can be reduced. However, reducing the size of the rotating polygon mirror 2 from the relation of the amount of reflected and scattered light that can be collected by the concave mirror 11 is as follows.
Have difficulty.

Next, in order to better understand the present invention in relation to the problem of the conventional apparatus, a re-imaging signal detection method and a non-re-imaging signal detection method will be considered with reference to FIG.

FIG. 5A is an explanatory diagram of the re-imaging signal detection method. A concave mirror, particularly a perforated concave mirror 11 having a central hole through which a laser beam passes is provided between the laser light source 1 and the scanning means 2. Here, the scanning means 2 shows an example of a galvano mirror that rotates repeatedly instead of a rotating polygon mirror for simplification.

In this method, the laser light source 1 and the laser scanning point on the object 4 have a point-to-point relationship via an optical system.
Therefore, disturbance light (noise light) entering the optical system from a position other than the scanning point forms an image around the photodetector 6 and is not detected.

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

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

For example, consider a case where the concave mirror 11 with holes is arranged after the optical scanning means 2 as shown in FIG. The combination of the perforated concave mirror 11 and the light detector 6 collects and detects the light reflected and scattered at the position of the object 4 shown in the figure.

In this case, the object 4 moves to the position X on the same scanning line, and the light reflected and scattered there is
Is formed at the position of Y which is outside the range. Therefore, the object information cannot be read.

As the optical signal condensing means, a perforated concave mirror 1 is used.
As shown in FIG. 5 (3), a perforated flat mirror 11
When the object 4 moves to the position of X on the same scanning line, the reflected and scattered light can be condensed and detected. But at the same time, object 4
Since disturbance light (noise light) from other sources is also collected and detected, it is difficult to detect signal light.

For this reason, the problem of the conventional device as described above arises.

The present invention has been made in order to solve such a problem of the conventional device, and one embodiment thereof is shown in FIG.

FIG. 1A is a simplified view of the optical system, particularly from the cross section of the apparatus, and FIG. 1B is a corresponding plan view.

The basic configuration is the same as that of the conventional apparatus described with reference to FIG. The first difference from the conventional apparatus is that, in the apparatus of the present invention, the concave concave mirror 5 as the optical signal condensing means is not provided between the laser light source 1 and the optical scanning means 2 but is provided in 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 50 which is the center position of the concave mirror 5 with holes. It is.

In this embodiment, a hologram is used as the wavefront conversion element 3. By the diffraction function of the hologram, an image of a light beam can be formed in the same manner as a convex lens.

With the above configuration, it is possible to make the configuration thinner (the reason will be more apparent in the following description).
, And 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 scan line formed in the space through the hollow window 17. The operation of detecting and converging the signal light reflected and scattered therefrom by the scanning will be described with reference to FIGS.

Here, for the sake of simplicity, the configuration of the embodiment shown in FIG. 1 is partially changed, as shown in FIG. Let us consider India 17 for simplicity.

A wavefront conversion element 3 for forming an image of the scanning light from the light scanning means 2, in this embodiment using a hologram, is provided after the light scanning means 2.
0 is arranged so as to correspond.

The perforated concave mirror 5 is arranged such that the optical scanning means 2 is arranged around the image forming point as shown in FIGS. 2 (2), 3 (3) and (4).
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, it is possible to obtain a re-imaging signal detection system according to the present invention. Further, the light scanning means 2
Used for optical scanning only. Therefore, the reflection area may be small.

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

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

[0061]

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

Further, if the size of the apparatus itself is maintained, a larger number of recombined images can be secured than before. Therefore, since the reflection efficiency of the mirror and the required diffraction efficiency of the hologram can be estimated at a low level, the cost of the apparatus can be reduced.

[Brief description of the drawings]

FIG. 1 shows one embodiment of the present invention.

FIG. 2 is an explanatory diagram of an 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]

 DESCRIPTION OF SYMBOLS 1 Laser light source 2 Rotating polygon mirror Working system 3 Wavefront conversion element (hologram) 4 Object 40 Barcode 5 Perforated concave mirror 6 Photodetector 10 Reflecting mirror 13, 14, 15 Scanning mirror 16 Bottom mirror 17 Hollow window

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-112120 (JP, A) JP-A-60-117213 (JP, A) JP-A-60-115913 (JP, A) JP-A-60-115 238812 (JP, A) Japanese Utility Model Showa 55-78243 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B 26/10

Claims (4)

(57) [Claims] A laser light source (1) and said laser light source (1)
Optical scanning means (2) for obtaining a laser scanning line (21) by scanning a laser beam from the scanner, and a reflected light signal corresponding to information on an object to be scanned (4) read by the laser scanning line (21). An information reading apparatus having a detector (6) for detecting, further comprising a wavefront conversion element (3) and a condensing means (5) for the reflected light signal, wherein the wavefront conversion element (3) is provided with a light scanning means ( The optical signal condensing means (5) has a function of forming an image of the laser light scanned by the optical scanning means (2), and is located at an image forming position (50) of the laser light, and the optical scanning means (2). An information reading device configured to condense the reflected light signal by changing an angle in synchronization with the light beam and to guide the reflected light signal to the detector (6). 2. An information reading apparatus according to claim 1, wherein said wavefront conversion element is constituted by a convex lens or a hologram. 3. The optical signal condensing means (5) according to claim 1, wherein the optical signal condensing means (5) comprises a concave mirror or a hologram having, at the center, a hole through which the laser light imaged by the wavefront conversion element (3) passes. An information reading device characterized by being performed. 4. The apparatus according to claim 1, wherein said wavefront converting element (3) and said condensing means (5) for said reflected light signal are provided between said light scanning means (2) and said object to be scanned (4). An information reading device provided in an optical path.