JP3381180B2 - How to read a symbol string displayed on a spherical surface - Google Patents

Description

Description: 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 particularly to a method for reading a symbol string displayed on a spherical surface or a surface similar to a spherical surface. The present invention relates to a method of reading a symbol string such as a number, for example, a container number written on a shoulder of a high-pressure gas container. 2. Description of the Related Art Conventionally, as a method of automatically reading a symbol displayed on the surface of various articles, after displaying the displayed symbol optically and securing it as graphic data, image processing is performed. Each graphic data is identified as a symbol such as an alphanumeric character. For example, in reading a postal code, individual figures displayed on a paper such as a postcard are detected as graphics by an optical character reader, and graphic data is secured in a memory or the like. Image processing and recognition as numbers. [0004] At this time, image processing from figures to numbers is performed as follows.
Some basic patterns are stored in advance for each of the numbers from 0 to 9, and the optically read graphic data is appropriately scaled up and down. If so, the process is repeated by rejecting it if it does not match, and each figure data is identified as a number and recognized as a postal code. In addition, reading of a license plate and the like of an automobile is performed similarly. However, in the conventional method, a symbol string on a plane can be identified almost accurately, but a symbol string displayed on a spherical surface, for example, a high-pressure gas container It was not possible to identify the container number etc. engraved on the shoulder. The reason 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 spherical surface. For example, the container number of the high-pressure gas container is:
It is stamped so as to be at the same height as the shoulder of the container when placed upright, that is, at approximately the same latitude as the spherical surface forming the shoulder of the container. Therefore, as shown by an imaginary line in FIG.
When the container number is photographed as shown in FIG. 2, as shown in FIG. In addition, as shown by the solid line in FIG. 1, when the image is taken by the television camera 2 from the normal direction of 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 of the image taken from the horizontal direction, but the inclination of the characters at both ends is almost the same as that of the image taken from the horizontal direction. Therefore, when the above-described image data is processed by the conventional method to identify a symbol string, the symbol read at a large inclination matches the basic pattern of the symbol previously stored in the reader. Therefore, the symbols at both ends of the symbol string cannot be identified. Therefore, the container number of the high-pressure gas container cannot be automatically read, and even if an attempt is made to automate the management of the high-pressure gas container at a gas filling factory or the like, the container number is read by an operator. Had to rely on his visual inspection. For this reason, there is a disadvantage that productivity is reduced due to a reading error of the operator, and the operator is burdened. Accordingly, an object of the present invention is to provide a reading method capable of reliably 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 of reading a symbol string displayed on a spherical surface according to the present invention is a method for reading a symbol string displayed at substantially the same latitude on a spherical surface. After photographing from the approximate normal position of the spherical surface and taking in the symbols constituting the symbol string as individual graphic data in XY orthogonal coordinates, the individual graphic data are parallel to the X axis and the Y axis, respectively. Circumscribed squares to form a circumscribed rectangle, determine the center point of an arc approximating the curve connecting the centroids of each circumscribed square, and make a straight line connecting the centroids of the individual circumscribed rectangles from the center point parallel to the Y axis. It is characterized in that each figure data is rotated around each centroid so that each figure data obtained is compared with a basic pattern and recognized as a symbol. The spherical surface in the present invention is not limited to a perfect spherical surface, but may be a spherical surface such as the shoulder of the high-pressure gas container, or an elliptical or parabolic rotating body. And various surfaces that approximate a spherical surface, such as a curved surface composed of [Operation] When a symbol string is photographed from a substantially normal position on a spherical surface, the symbol string is secured as graphic data arranged in a sector shape.
The individual figures of the figure data arranged in a sector are surrounded by straight lines parallel to the X and Y axes to form a circumscribed rectangle, and when the centroids of the obtained circumscribed rectangles are connected, an arc centered on a point is approximated Will be located on the curved line. Next, drawing straight lines connecting the center point of the arc approximating the above curve and the centroid of each circumscribed quadrangle results in an erect line of each figure, and these straight lines are parallel to the Y axis. If the individual graphic data is rotated around the center of gravity, the respective graphic data will be in an erect state, thereby enabling reading by image processing. The present invention will be described below in more detail with reference to the drawings. First, as shown by a solid line in FIG. 1, a container number (“NL 135” in this embodiment) 3 stamped at substantially the same latitude on a spherical portion forming a shoulder of the high-pressure gas container 1.
Is photographed by the television camera 2 from the normal direction of the spherical surface, and the image is projected on the monitor television 4 as shown in FIG. It is preferable that the television camera 2 is set so that the center of the container number 3 is located on the vertical center line of the screen. The high-pressure gas container 1 may be settled at a predetermined position, or may be moving while being transported by a cart or a belt conveyor. The container number 3 of the high-pressure gas container 1 includes not only the alphanumeric characters constituting the container number 3 but also symbols indicating the type of gas to be filled in the high-pressure gas container 1 (this embodiment). In the case of the example, N ₂ is stamped to indicate that the container is a nitrogen filling container). In addition, the part engraved with the container number 3 is painted in a color different from the color painted on the outer wall of the high-pressure gas container 1, so that not only the visual but also the television camera 2 is painted.
Can also be easily identified. 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, since it is not necessary to read the symbol of the gas type, only the container number 3 arranged in a fan shape is extracted by the image processing. As described above, the symbol string of the container number 3 extracted by the image processing is inscribed at the same latitude of the spherical surface of the shoulder of the high-pressure gas container 1. When the image is taken by the television camera 2, the symbols are read in a state where the symbols at both ends of the symbol string are inclined more greatly in a fan-shaped state. The symbol string read in this way is taken into the XY orthogonal coordinates shown in FIG. 4, and first, the graphic data of each symbol is converted into four straight lines X1 parallel to the X and Y axes. ,
X2, Y1 and Y2, form a circumscribed rectangle 11 for each figure data, and a centroid 12 of each circumscribed rectangle 11
Ask for. Next, when the centroids 12 of the respective graphic data are connected, a curve 13 is obtained. This curve 13 is approximated to a part (arc) of a circle centered on a certain point by the least square method. Can be. 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 determined 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.
Are rotated by an angle α about the centroid 12 so that the data is parallel to the Y axis. By this operation, each graphic data is in an upright state as shown in FIG. 5, so that it is possible to collate the symbols stored in the reader 5 with some basic patterns. Can be respectively recognized. As a result, the symbol string engraved on the shoulder of the high-pressure gas container 1 can be read as a container number unique to the container, and from the read container number, the manufacturing year of each container previously stored in the database is obtained. By importing management data such as month, serial number, filling gas name, weight, and location,
The high-pressure gas container 1 can be managed. As shown in FIG. 2, in the graphic data read from the parallel direction, not only the symbols at both ends are inclined but also distorted. However, as shown in FIG. 6, since the graphic data 3a at both ends of the graphic data 3 are still distorted, it is difficult to collate with the basic pattern and cannot be recognized as a symbol. In this embodiment, the reading of the symbol string representing the container number stamped on the high-pressure gas container has been described. However, the method of the present invention is not limited to this. The present invention can also be applied to reading of various types of information composed of symbol strings described at substantially the same latitude on similar surfaces. As described above, according to the method of the present invention, a symbol string displayed on a spherical surface, for example, a container number or the like stamped on the shoulder of a high-pressure gas container is automatically read. In addition, since the high-pressure gas container and the like can be managed reliably and easily, the burden on the operator can be greatly reduced, and the productivity can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing a state in which a container number stamped on a shoulder of a high-pressure gas container is photographed by a television camera. FIG. 2 is a diagram showing a state of a container number when photographing from a horizontal direction of a high-pressure gas container. FIG. 3 is a diagram showing a state of a container number when photographing from a normal direction of a spherical surface of a shoulder 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 processing by the method of the present invention. FIG. 6 is a diagram showing a state after graphic data taken from a horizontal direction is processed in the same procedure as the method of the present invention. [Description of Signs] 1 ... High-pressure gas container, 2 ... TV camera, 3 ... Container number,
11: circumscribed rectangle, 12: centroid of circumscribed rectangle, 13: curve, 14: center point, 15: straight line

Continued on the front page (72) Inventor Junichiro Sashikata 4-320 Tsukagoshi, Saiwai-ku, Kawasaki-shi, Kanagawa Japan Oxygen Corporation (72) Inventor Yoshimi Oda 4-6-22 Kanonshinmachi, Nishi-ku, Hiroshima-shi, Hiroshima Mitsubishi Heavy Industries, Ltd. In-company (56) References JP-A-60-27078 (JP, A) JP-A-1-220075 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G06K 9/00- 9/76 G06K 7/10

Claims (1)

(57) [Claim 1] In reading a symbol string displayed on a spherical surface at substantially the same latitude, the symbol string is photographed from a position of a substantially normal line of the spherical surface, and the symbol string is read. After taking the constituent symbols as individual graphic data in the XY orthogonal coordinates, the individual graphic data is surrounded by straight lines parallel to the X axis and the Y axis, respectively, to form circumscribed rectangles. The center point of the arc approximating the curve connecting the centroids is obtained, and each figure data is rotated about each centroid so that the straight line connecting the centroids of the individual circumscribed rectangles from the center point is parallel to the Y axis. A method of reading a symbol string displayed on a spherical surface, wherein each of the obtained graphic data is compared with a basic pattern and recognized as a symbol.