JPS6139651B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus that optically scans an object to be recognized and recognizes information such as a code pattern, scratches, etc. on the surface of the object.

In general, this type of optical recognition device has many uses, such as code reading in POS (point of sales), etc., which will be described below.

Conventionally, in this type of device, as shown in FIG.
The beam is guided through a condensing system 2 to a scanner 3, and by the action of the scanner 3, a scanning bright line 4 is generated on a code mark 5 pasted on the surface of an object 6,
The code is read by photoelectrically converting the reflected and scattered light by a light receiver 7 such as a photo multiplier. In addition, FIG. 1a is a perspective view,
FIG. 1b is a plan view.

Incidentally, in such a device, the deflection angle 2θ of the beam deflected by the scanner 3 must be made as small as possible. That is, if the deflection angle 2θ is large, the light incident on the code mark 5 will have a greatly different incident angle depending on the location, even if the code mark 5 is flat. As a result, the directional distribution of the reflected and scattered light becomes different, as indicated by symbols a and b in FIG. As a result, the signal obtained by the photoreceiver 7 has large undulations, as shown in FIG. 3a. Since it is difficult to detect signals with such undulations with high accuracy, the deflection angle 2θ is usually kept as small as possible.

Now, as shown in FIG. 1, the above-mentioned problem similarly occurs even when the surface of the object 6, and thus the code mark 5, has a predetermined curvature. In this case, as shown by symbol c in Fig. 2, the directional distribution of the reflected and scattered light changes greatly, so the output of the photoreceiver 7 becomes an extreme peak, as shown in Fig. 3b, and the signal is significantly reduced. Only a small portion of the code deteriorates and can be identified.

The present invention provides a device that can minimize the signal deterioration that occurs in the conventional example and can accurately and accurately recognize the surface of an object by making extremely simple modifications to the configuration. , this will be explained in detail below.

FIG. 4 is a plan view of essential parts of an embodiment of the present invention, and FIG. 5 is a perspective view thereof, in which the same parts as those explained in connection with FIG. 1 are indicated by the same symbols.

The differences between this embodiment and the conventional example in terms of configuration will be explained next. That is, in this embodiment, the receivers are 7 and 8.
As shown in , two are used, and they are positioned above the plane containing the scanning line of the beam 10, and the optical receiver 7 is positioned so that the left end of the code mark 5 is the center of its field of view. , and the receiver 8 is connected to the cord/
They are arranged so that the right end of the mark 5 is the center of the field of view, and between the scanner 3 and the object 6 is a lens 9 whose focal length is short compared to the lens diameter, that is, a short focal length lens 9. is located.

In this embodiment, a light beam 1 generated by a light source 1
0 is deflected at a deflection angle of 2θ by the scanner 3, and follows the path shown by symbols 10a and 10b, and is focused at a point O inside the object 6 by the action of the short focal length lens 9. being done. Here, the object 6 is a cylinder, and a cord is attached on the side circumference of the object 6.
Assuming that mark 5 exists and point O is the center of the circle, the surface of code mark 5 will always be scanned from the vertical direction regardless of its location. That is,
When viewed from the scanning beam side, it is actually an angular scan centered on point O, but it is as if the code/code on a plane is being scanned.
The result is the same as scanning the marks in parallel.
Therefore, the main reflection direction of the reflected and scattered light coincides with the direction of the incident beam at any location on the code mark 5, and its range is also limited within the scanning angle 2ψ.

The output signals of receivers 7 and 8 in this embodiment have the waveforms shown in Figures 6a and 6b, and when these output signals are added together, an extremely high quality signal waveform is obtained as shown in Figure 6c. .

In the above embodiment, the effectiveness was explained in the case where code marks etc. are present on a curved surface, but the present invention is applicable not only to this case, but also to objects where information such as code marks etc. is present on a curved surface, and to a flat surface. It is also effective when applied to cases where there are objects present above.

FIG. 7 is a diagram explaining this, and 11 to 1
4 is the beam path, f is the focal length of the lens, a-
a' is the center of the lens, b-b' is the code on the plane object.
the surface on which the mark is present, O is the center of the object of minimum detectable curvature, P is the curvature of said object with center O;
O' is the center of the virtual detection surface, p' is the curvature of the virtual detection surface with center O', and C-C' is the plane containing the focal point of the lens with focal length f placed at a-a'. .

Now, if there are marks and codes located on the plane b-b' and on the circumference of the circle with the center O, then if the scanning beam is perpendicular to one mark code, it will not be possible to・Since the directional distribution of reflected and scattered light from the code changes significantly,
It becomes impossible to detect the signal from the other mark code with high accuracy. For example, in FIG. 7, if the focal length of the lens is set so that the scanning beam is perpendicular to the circumference of the circle with the center O, then the mark on the plane b-b' is located at the same position as the beam path 11. The beam path for scanning the code is 15
The incident angle Θ ₁ becomes smaller at both ends of the mark code, and the main reflection direction of the reflected and scattered light from the mark code is in a direction different from that of the receivers provided on both sides. Detection accuracy decreases. Therefore, in the embodiment of the present invention, surface b--
Assume a virtual detection surface of curvature ρ' with center O' such that the circumferential surface is located midway between b' and the circumference of a circle with center O, and use this center O' as the center point of the angular scan. A lens with a focal length f is used. Note that the other configurations are the same as those in FIGS. 4 and 5. By doing this, the beams on paths 11 to 14 will be incident perpendicularly to the curved surface with curvature ρ, and with respect to the front and rear surfaces b-b' and the circumference of the circle with the center O. are incident at Θ and Θ′, respectively. If we compare these Θ and Θ′ with _Θ1 , it becomes clear that Θ
As is clear from comparison with Θ ₁ , there is less change than Θ ₁ , so detection can be performed without significantly reducing detection accuracy. In this way, the scanning beam does not necessarily have to be perpendicular to the surface as long as it is close to perpendicular to the surface, so in many cases it is not necessary to completely focus the scanning beam at the center O′, and It is sufficient if it is close enough to result in angular scanning.

In the present invention, many modifications can be made to the structure other than the embodiments described above. For example, two or more light receivers may be used, and their arrangement positions may be selected as appropriate depending on the application. Further, the optical lens for angle scanning (for example, 9 in FIGS. 4 and 5) can be replaced with a reflecting mirror or optical fiber system having a similar function. Furthermore, although not shown in the drawings, the present invention can be implemented by constructing a condensing optical system disposed above the light receiver using a plane mirror, a curved mirror, a lens, a fascia, etc., and guiding the reflected light to one or more light receivers. The effect can also be further improved.

In addition to POS, the device of the present invention is suitable for reading surface patterns on cans, bottles, ampoules, pap-like objects, spherical objects, etc., and inspecting for scratches on the surfaces of such objects. can.

As can be seen from the above explanation, according to the present invention, it is possible to accurately recognize the presence of information with high accuracy regardless of whether it is on a curved surface or a flat surface, and the necessary The configuration is easy to implement because it is sufficient to add an optical system for performing angular scanning.

[Brief explanation of the drawing]

1A and 1B are a perspective view and a plan view of the main part of the conventional example, FIG. 2 is a line diagram explaining the directional distribution of reflected and scattered light, and FIG. 3 is a line diagram showing the output waveform of the light receiver. 4 and 5 are a plan view and a perspective view of essential parts of one embodiment of the present invention, FIG. 6 is a diagram showing the output waveform in the first embodiment of the present invention, and FIG. 7 is a diagram showing another embodiment. It is an explanatory diagram of an example. In the figure, 1 is the light source, 2 is the focusing system, 3 is the scanner, 4 is the scanning bright line, 5 is the code mark, 6 is the object, 7 and 8 are the receivers, 9 is the lens, and 10 is the beam. Each is shown below.

Claims (1)

[Claims] 1. A light source that generates a light beam, a scanner that deflects the light beam to scan the object to be recognized with the light beam, and a scanner that deflects the light beam by the scanner to scan the object to be recognized. Optical systems such as lenses and reflectors are arranged to connect the intersection points and perform angular scanning, and the light reflected by the light beam from the object to be recognized is detected at multiple locations spaced apart in the scanning direction, and each detection output is detected. 1. An optical recognition device comprising: reading means for reading objects to be recognized by overlapping them.