JPH07182450A - Reading method of symbol string shown on spherical surface - Google Patents

Abstract

PURPOSE:To provide a reading method which can surely identify a symbol string shown on a spherical surface such as the number of a high-pressure gas container, etc. CONSTITUTION:A symbol string shown on a spherical surface approximately in the same latitude is photographed approximately at a normal line position, and each symbol of the string is fetched into the X-Y orthogonal coordinates as the graphic date. Each of these graphic date is enclosed by a straight line that is parallel to the X end Y axes in the form of a circumscribed square 11. Then a center point 14 is calculated for 8 circular arc approximating to a curve is that connects together the centroids 12 of each square 11. Each graphic data is turned around each centroid 12 so that the straight lines 15 connecting the centroids 12 to the point 14 are set in parallel to the Y axis. Then each turned graphic data is compared with 8 basic pattern end recognized as a symbol.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reading a symbol string displayed on a spherical surface, and more specifically, a symbol string such as alphanumeric characters displayed on a spherical surface or a surface similar to the spherical surface, for example, high pressure gas. The present invention relates to a method for reading a container number or the like written on the shoulder of a container.

[0002]

2. Description of the Related Art Conventionally, as a method of automatically reading symbols displayed on the surface of various articles, after the displayed symbols are optically captured and secured as graphic data, individual processing is performed by image processing. Graphic data are identified as symbols such as alphanumeric characters.

For example, when reading a postal code, individual numbers displayed on the paper surface of a postcard or the like are detected as a figure by an optical character reading device, and after figure data is secured in a memory or the like, these figures are displayed. The image is processed and recognized as a number.

Image processing from figures to numbers at this time is as follows.
Some basic patterns are stored in advance for each number from 0 to 9, and the optically read graphic data is appropriately scaled up and down, and compared and compared with the basic pattern by, for example, an overlay method or the like to find a match. If so, the answer is used as the answer, and if they do not match, the process of eliminating them is repeated to identify each figure data as a numeral and recognize it as a postal code. Further, the reading of license plates of automobiles is also carried out in the same manner.

[0005]

However, in the conventional method, although the symbol string on the plane can be identified almost accurately, the symbol string displayed on the spherical surface, for example, the shoulder portion of the high pressure gas container. It was not possible to identify the container number etc. stamped on the. The reason for this is that when the symbol string displayed on the spherical surface is read by an optical character reader such as a television camera, the symbol string is distorted and photographed due to the influence of the spherical surface.

For example, the container number of the high pressure gas container is
It is engraved so as to be at the same height of the shoulder portion of the container when placed upright, that is, at approximately the same latitude of the spherical surface forming the shoulder portion of the container. Therefore, as shown by the phantom line in FIG. 1, the television camera 2 is viewed from the horizontal direction of the high-pressure gas container 1 placed upright.
When the container number is photographed with, the characters at the both ends of the symbol string appear to be greatly tilted and distorted due to the influence of the spherical surface, as shown in FIG. Further, as shown by the solid line in FIG. 1, when the television camera 2 shoots from the direction normal to the spherical surface of the shoulder, the symbol strings 3 are arranged in a fan shape as shown in FIG. In this case, the distortion of each symbol is smaller than that when the image is taken from the horizontal direction, but the degree of inclination of the characters at both ends is the same as that when the image is taken from the horizontal direction.

Therefore, when the image data as described above is processed by the conventional method to identify the symbol string, the symbol read with a large inclination matches the basic pattern of the symbol stored in the reading device in advance. Therefore, the symbols at both ends of the symbol string cannot be identified.

For this reason, the container number of the high-pressure gas container cannot be automatically read, and even if the management of the high-pressure gas container is to be automated at a gas filling factory or the like, the operator can read the container number. I had to rely on his eyesight. For this reason, there is an inconvenience that productivity is reduced due to an operator's reading error, which is a burden on the operator.

Therefore, an object of the present invention is to provide a reading method capable of surely identifying a symbol string displayed on a spherical portion such as a container number of a high pressure gas container.

[0010]

In order to achieve the above object, a method for reading a symbol string displayed on a spherical surface of the present invention is a method for reading a symbol string displayed at approximately the same latitude on the spherical surface. After photographing from the normal position, the symbols constituting the symbol string are taken in as XY Cartesian coordinates as individual figure data, and then each of the figure data is formed by straight lines parallel to the X axis and the Y axis. Form a circumscribed quadrangle by enclosing it, find the center point of an arc that approximates the curve connecting the centroids of each circumscribed quadrangle, and make the straight line connecting the centroids of each circumscribed quadrangle from the center point parallel to the Y axis. It is characterized in that each figure data is rotated around each centroid, and each obtained figure data is recognized as a symbol by comparing and comparing with the basic pattern.

The term "spherical surface" as used in the present invention does not mean only a perfect spherical surface, but a spherical surface such as a shoulder portion of the high-pressure gas container, or an elliptic or parabolic curved rotary member. It includes various surfaces that are close to a spherical surface, such as a curved surface consisting of.

[0012]

[Operation] When the symbol string is photographed from the position of the normal line on the spherical surface, the symbol string is secured as fan-shaped figure data,
Enclosing each figure of fan-shaped figure data with a straight line parallel to the X-axis and Y-axis to form a circumscribed quadrangle, and connecting the centroids of each circumscribed quadrangle to approximate a circular arc centered at a certain point It will be located on the curve.

Next, when a straight line connecting the center point of the arc approximated to the above curve and the centroid of each circumscribing quadrangle is drawn, it becomes an upright line of each figure. Therefore, these straight lines are parallel to the Y axis. If the individual graphic data are rotated around the centroid so that each graphic data becomes upright, the image data can be read by image processing.

[0014]

The present invention will be described in more detail below with reference to the drawings. First, as shown by the solid line in FIG. 1, the container number (“NL 135” in this embodiment) is stamped at approximately the same latitude on the spherical portion forming the shoulder of the high-pressure gas container 1 3
Is photographed by the television camera 2 from the normal direction of the spherical surface, and its image is displayed on the monitor television 4 as shown in FIG. 3 and taken in by the reading device 5 for image processing.

The television camera 2 is preferably set so that the central portion of the container number 3 is on the vertical center line of the screen. Further, the high-pressure gas container 1 may be left stationary at a predetermined position, or may be moving while being conveyed by a carriage or a belt conveyor.

The container number 3 portion of the high pressure gas container 1 includes not only the alphanumeric characters constituting the container number 3 but also a symbol indicating the kind of gas filled in the high pressure gas container 1 (this embodiment). In the case of the example, N ₂ is engraved to indicate that the container is a nitrogen filling container). In addition, a color different from the color applied to the outer wall of the high-pressure gas container 1 is applied to the part where the container number 3 is engraved.
Can be easily identified by.

The graphic data of the symbol string read in this way is processed in the following procedure and recognized as a symbol. First, when reading the container number 3, it is not necessary to read the symbol for the gas type, and therefore only the container numbers 3 arranged in a fan shape are extracted by image processing.

The symbol string of the container number 3 extracted by image processing is imprinted at the same latitude on the spherical surface of the shoulder of the high-pressure gas container 1 as described above. When photographed by the TV camera 2, the symbols are read in a state in which they are arranged in a fan shape, and the symbols at both ends of the symbol string are inclined more greatly.

The symbol string read in this way is taken in the XY Cartesian coordinates shown in FIG. 4, and first, the graphic data of each symbol is four straight lines X1 parallel to the X axis and the Y axis. ，
Enclosed by X2, Y1 and Y2, a circumscribed quadrangle 11 is formed for each figure data, and a centroid 12 of each circumscribed quadrangle 11 is formed.
Ask for.

Next, the centroids 12 of the respective graphic data are connected to form a curve 13. This curve 13 is approximated to a part (circle) of a circle centered on a certain point by the method of least squares. You can Therefore, the centroid 1 of each figure data
Since 2 can be assumed to exist on the arc of the approximated circle, the center point 14 of the arc is obtained on the XY orthogonal coordinates.

Then, the centroid 12 of each figure data and the center point 14 are connected by a straight line 15, an intersection angle α between the straight line 15 and the Y axis is obtained, and a straight line 15 connecting the centroid 12 and the center point 14 is obtained.
The respective graphic data are rotated about the centroid 12 by an angle α so that is parallel to the Y axis.

By this operation, each figure data is brought to the upright state as shown in FIG. 5, so that it is possible to collate with some basic patterns of the symbols stored in the reading device 5 in advance, and the individual patterns can be collated. The figure data can be recognized respectively.

As a result, the symbol string engraved on the shoulder portion of the high-pressure gas container 1 can be read as the container number unique to the container, and the read manufacturing container number stored in advance in the database can be used from the read container number. By importing management data such as month, serial number, filling gas name, weight, location,
The high pressure gas container 1 can be managed.

As shown in FIG. 2, the graphic data read from the parallel direction is not only inclining the symbols at both ends but also in a distorted state. However, as shown in FIG. 6, since the graphic data 3a at both ends of the graphic data 3 remains distorted, it is difficult to collate with the basic pattern and cannot be recognized as a symbol.

In the present embodiment, the reading of the symbol string representing the container number stamped on the high-pressure gas container has been described, but the method of the present invention is not limited to this, and other articles may be spherical or spherical. It can also be applied to the reading of various kinds of information consisting of symbol strings written at substantially the same latitude on similar surfaces.

[0026]

As described above, according to the method of the present invention, the reading of the symbol string displayed on the spherical surface, for example, the container number stamped on the shoulder portion of the high-pressure gas container, can be performed automatically and Since it can be performed accurately, the high-pressure gas container and the like can be managed reliably and easily, the burden on the operator can be significantly reduced, and the productivity can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a state in which a container number engraved on a shoulder portion of a high-pressure gas container is photographed by a television camera.

FIG. 2 is a diagram showing a state of container numbers when the high-pressure gas container is photographed from the horizontal direction.

FIG. 3 is a diagram showing a state of container numbers when images are taken from a direction normal to a spherical surface of a shoulder portion of a high-pressure gas container.

FIG. 4 is an explanatory diagram of a procedure for processing graphic data by the method of the present invention.

FIG. 5 is a diagram showing a state of graphic data after being processed by the method of the present invention.

FIG. 6 is a diagram showing a state after the graphic data photographed from the horizontal direction is processed in the same procedure as the method of the present invention.

[Explanation of symbols]

1 ... High-pressure gas container, 2 ... TV camera, 3 ... Container number,
11 ... circumscribed quadrangle, 12 ... centroid of circumscribed quadrangle, 13 ... curve, 14 ... center point, 15 ... straight line

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichiro Sugakata 4-320 Tsukagoshi, Sachi-ku, Kawasaki-shi, Kanagawa Nihon Oxido Co., Ltd. (72) Yoshimi Oda, 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima-shi, Hiroshima Issue Mitsubishi Heavy Industries Ltd.

Claims (1)

[Claims] 1. When reading a symbol string displayed at approximately the same latitude on a spherical surface, the symbol string is photographed from a position approximately normal to the spherical surface, and the symbols constituting the symbol string are treated as individual graphic data. An arc that approximates to a curve connecting the centroids of each circumscribed quadrangle by enclosing each of the graphic data with straight lines parallel to the X axis and the Y axis after capturing in the XY orthogonal coordinates. Is obtained, and each figure data is rotated about each centroid so that the straight line connecting the centroids of the circumscribed quadrangles from the center point is parallel to the Y-axis. A method of reading a symbol string displayed on a spherical surface, characterized by being recognized as a symbol by comparing and contrasting with a basic pattern.