JP3612119B2 - Imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging apparatus that inputs video such as characters and symbols written on an object and uses them for pass / fail determination.
[0002]
[Prior art]
As an inspection method to check whether the character code such as the serial number and date of manufacture written on the bottom of metal cans for beverages etc. is correctly written, generally the character symbol on the bottom of the can is imaged with a TV camera. An analysis process is performed by the processing device to determine whether it is good or bad.
[0003]
As a precondition for the above image processing, it is important to input a clear video into a television camera, and various lighting devices have been proposed for this purpose.
[0004]
For example, the illumination device shown in FIG. 5 irradiates the can bottom 11 by transmitting and diffusing the light from the annular light source 22 with the diffusion plate 26. The diffusing plate 26 includes a cylindrical portion 26a and a flat plate portion 26b as shown in the figure. The character symbol on the can bottom 11 is picked up by the TV camera 4 and the lens 4b from above through the central hole of the cylindrical portion.
[0005]
As an improvement plan for the method shown in FIG. 5, an illumination device shown in FIG. 7 has been proposed. The light from the annular source 22 is transmitted and diffused by the diffusion plate 27 to irradiate the can bottom 11. The diffusion plate 27 is composed of a conical portion 27a and a flat plate portion 27b as shown in the figure, and the character symbol of the can bottom 11 is imaged from above through the central hole of the conical portion by the TV camera 4 and the lens 4b. In the improved plan of FIG. 7, the shape of the diffuser plate is improved like the cone 27 of FIG. 7 with respect to the cylindrical portion 26a shown in FIG. It is intended to reflect and irradiate evenly.
[0006]
Japanese Patent Publication No. 5-17744 discloses an example of the above prior art, and Japanese Patent Publication No. 5-49971 also discloses a method in which conical diffusion plates are stacked in two stages.
[0007]
[Problems to be solved by the invention]
In an inspection device that uses a TV camera to capture the characters and symbols on the bottom of metal cans for cans and drinks, and to input good images to the TV camera, the can bottom must be uniform. However, depending on the shape, it is difficult to obtain uniform illumination depending on the shape of the bottom of the can.
[0008]
Among the above-mentioned conventional techniques, the image by the illumination device shown in FIG. 5 is as shown in FIG. 6, and the dark field 14 appears depending on the shape of the bottom of the can, and the difference in contrast with the character image 13 is reduced, resulting in erroneous determination. There is a problem that the character image 13 is buried in the dark field 14 and cannot be discriminated.
[0009]
The cause of the occurrence of the dark field 14 is that the end face dark part of the lens 4b is reflected on the can bottom 11, and as an improvement plan, the illumination device of FIG. 7 has been proposed. The upper part of the diffusion plate 27a is inserted into the lens barrel of the lens 4b.
[0010]
The image according to FIG. 7 is as shown in FIG. 8, and the dark field 14 at the center is improved. However, depending on the shape of the bottom of the can, a dark ring 15 appears and may be misidentified at the part overlapping the character image 13. There was a problem that it became indistinguishable.
[0011]
The cause of the dark ring 15 in FIG. 8 is that the illumination light is poorly transmitted at the joint portion 27c of the diffusion plate 27 in FIG. 7, and a ring-shaped shadow is reflected on the bottom of the can.
[0012]
In addition, metal cans for beverages, PET bottles, various vials for chemicals, etc. may be colored in various ways on the product image. There was a problem of difficulty.
[0013]
The object of the present invention has been made to solve the above-mentioned problems, and the generation of a partial dark field, which could not be achieved by the above-described prior art, is reduced as much as possible to form a versatile can bottom shape such as a metal can. It is another object of the present invention to provide an imaging device that provides a uniform illuminance and obtains a clear image that is easy to perform image processing even if it is a character symbol written on a colored ground color.
[0014]
[Means for Solving the Problems]
The present invention is an imaging apparatus that irradiates a subject such as a metal can with light from an annular light source and images the reflected light thereof.
Imaging means;
A pinhole lens provided on the optical axis incident optical path side of the imaging means and having a pinhole at the tip;
It has a flat plate shape with an opening large enough not to obstruct the visual field of the pinhole. The pinhole abuts on this opening, and the surface opposite to the pinhole abutment side is the reflecting surface. A reflective light diffuser;
Provided between the reflective surface side of the reflective light diffusing plate and a subject such as a metal can, and has a smooth arcuate shape with a top having an opening that does not obstruct the field of view of the imaging means at the center. It has a flat plate-like skirt extending in the outer direction perpendicular to the optical axis, and has a cylindrical body that is smoothly connected to the skirt provided between the top and the skirt in a skirt shape. A bell-shaped translucent light diffusing portion in which the top portion, the cylindrical portion, and the skirt portion are integrally molded and are translucent,
An annular light source having substantially the same outer diameter as the reflective light diffusing plate, and disposed around the cylindrical body of the bell-shaped translucent diffuser;
An imaging device is disclosed.
[0015]
Furthermore, the present invention provides an imaging apparatus that irradiates a subject such as a metal can as a subject with light from an annular light source and images the reflected light thereof.
Imaging means;
A pinhole lens provided on the optical axis incident optical path side of the imaging means and having a pinhole at the tip;
It has a flat plate shape with an opening large enough not to obstruct the visual field of the pinhole. The pinhole abuts on this opening, and the surface opposite to the pinhole abutment side is the reflecting surface. A reflective light diffuser;
An annular illumination device provided between the reflecting surface side of the reflective light diffusing plate and a subject such as a metal can as a subject, and in close contact with the reflecting surface;
Consisting of
The annular illumination device is
A box having an upper opening corresponding to the reflecting surface and a lower opening corresponding to the subject, and an inner surface forming a reflecting surface;
Provided inside the box body, facing the upper opening side, having a smooth arc shape and having a top portion having an opening that does not obstruct the field of view of the imaging means at the center, and the bottom of the box on the lower opening side A cylindrical body that has a flat skirt extending in the outer direction perpendicular to the optical axis and is smoothly connected to the skirt provided between the top and the skirt. A bell-shaped translucent light diffusing portion that has a top portion, a cylindrical portion and a bottom portion that are integrally molded, and is translucent.
An annular light source having substantially the same outer diameter as the reflective light diffusing plate, and disposed around the cylindrical body of the bell-shaped translucent diffuser;
An imaging device is disclosed.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
An example of the present invention will be described with reference to FIGS.
FIG. 1 shows an example of the overall configuration when the present invention is applied to, for example, a character / symbol inspection device written on the bottom of a metal can, and the can of a metal can 1 conveyed on a conveyor 3. In order to inspect the characters and symbols written on the bottom 11, the illuminating device 2 is arranged on the upper side, and further, through the center hole 24 a of the illuminating device 2, a television camera is able to image the can bottom 11 of the metal can from above. 4 is mounted with a pinhole lens 4a.
[0020]
The sensor 5 generates a detection signal at the moment when the metal can 1 passes almost directly below the illumination device 2 and the television camera 4, and this detection signal activates the illumination power source 2 a via the image processing device 6. Light is emitted and the bottom 11 of the metal can is irradiated. At the same time, the video signal of the TV camera 4 is input to the image processing device 6 in synchronization with the detection signal. The image processing device 6 performs a predetermined analysis process from the video signal to determine whether it is good or bad, and rejects defective products by the sorting mechanism 7.
[0021]
FIG. 2 shows a central cross section of the lighting device in the overall configuration shown in FIG. 1, and the metal can 1, the lighting device 2, the TV camera 4, and the pinhole lens 4a are in a positional relationship as shown in the figure. . A dotted arrow indicates an example of an optical path.
[0022]
The structure of the illuminating device is that the annular light source 22 is housed in the main body frame 21, and a bell-shaped transmissive diffuser plate 23 is disposed below the main body frame 21, with the bell opening facing the bottom 11 of the metal can. A reflective diffusion plate 24 is disposed above the main body frame 21. The inner side surface 21A of the main body frame 21 may be white so as to be easily reflected. However, since it does not have a great influence on the entire light diffusion, the inner side surface 21A may have a metal color of a simple metal plate.
[0023]
The opening of the bell-shaped transmissive diffusing plate 23 is formed with a smooth arc from the vicinity of the center of the annular light source 22, and the bell-shaped upper end is formed with a smooth arc.
[0024]
As for the shape of the bell-shaped transmission type diffuser plate 23, it is desirable that the joint portion between the bell-shaped upper part and the flat plate and the cylinder is integrally formed so as not to be shaded. The material may be any material that can be uniformly transmitted and diffused, such as translucent plastic, rubbed glass, translucent paper, or cloth. Normally, milky white material is used, but when a character symbol is written on a colored ground color such as a metal can or a bottle, the color of the diffusion plate is a colored translucent material, and the ground color and the character symbol are The contrast can be increased and clear images can be taken.
[0025]
The reflection type diffuser plate 24 is arranged on the upper side of the annular light source, and the position thereof can be adjusted by changing the thickness of the distance piece 25, for example.
[0026]
The central hole 24a of the reflective diffuser 24 is set as small as possible within a range that does not obstruct the visual field of the pinhole lens 4a.
[0027]
The reflection surface of the reflection type diffuser plate 24 may be a satin-like reflection surface coated with a material having good reflection efficiency such as aluminum powder, glass powder, and ceramic powder from which scattered light can be obtained.
[0028]
A representative example of the character image of the bottom of the can imaged by the illumination device of FIG. 2 is shown in FIG. Compared to FIGS. 6 and 8 shown in the prior art, a uniform can bottom image is obtained, and the character image 13 is imaged with clear contrast. The image of the step 12 on the bottom of the can in FIG. 2 corresponds to 12a in FIG. 3, but in the conventional lighting device, the shadow of the step appears as a clear dark ring. However, according to this example, the ring portion 12a due to the shadow of the step on the bottom of the can hardly appears, and even a subject whose character end is on the step portion can be easily determined. can do.
[0029]
FIG. 4 shows an embodiment applied to the bottle character inspection. For example, the character symbol 16 indicated on the surface of the bottle 10 or the character symbol 17 indicated on the bottle cap portion is discriminated. A dotted arrow indicates an example of an optical path.
[0030]
The illuminating device 2 is disposed so as to face the irradiated surface of the bottle, and the pinhole lens 4a and the television camera 4 are disposed coaxially. The illuminating device 2 is provided with an annular light source 22, and a flat translucent diffuser plate 28 is provided on the irradiated side, and the visual field of the pinhole lens 4 a is obstructed at the center of the flat translucent diffuser plate. Make as little holes as possible. The inner side surfaces 2A and 2B of the device 2 may be white or black, but the side surface 2B is also white and preferably serves as a diffusion plate.
[0031]
Further, a guide portion 29 is provided outside the diffusion plate so that various colored filters 29 can be attached. Depending on the background color of the bottle and the color of the printed character symbol, the pass filters for various colors and brightness can be easily exchanged so that the contrast can be obtained most clearly.
[0032]
In the above embodiments, the illumination device and the imaging device for character and symbol inspection of metal cans and bottles have been described. However, the present invention is not limited to metal cans and bottles, and there is a carton or gloss, the printing surface is colored, or irradiation. The present invention can be applied to an object in which the shape of the surface is complicated, such as unevenness, and a normal illumination means cannot obtain uniform illumination, or an object in which a clear image with low contrast cannot be obtained. The example of the filter can also be applied to FIG.
[0033]
According to the present embodiment, the cross-sectional shape of the bell-shaped transmissive diffuser plate is set to an appropriate radius from the vicinity of the center of the annular light source, and the upper end of the diffuser plate is rounded with a smooth arc. Brightness is applied, and the irradiated object side is irradiated uniformly. In addition, the reflective diffuser installed behind the annular light source compensates for the illuminance near the center and suppresses the occurrence of dark field.
[0034]
Furthermore, the combination with a pinhole lens having a small objective lens diameter eliminates the reflection of the lens and suppresses the occurrence of dark field.
[0035]
Furthermore, since the filter is detachable, it is possible to obtain an image with clear contrast and easy image processing.
[0036]
【The invention's effect】
According to the present invention, the light of the annular light source of the illumination device is obtained by the uniform transmission light by the bell-shaped transmission type diffusion plate, the reflection type diffusion plate, and the pinhole lens to the irradiated object such as a metal can bottom. By irradiating, a clear image with no illumination unevenness can be input to the television camera.
[0037]
For example, by applying the illumination device and the imaging device to a character symbol inspection device for a metal can or a bottle, even if the shape of the bottom of the can is a variety of shapes such as a middle concave shape and a middle convex shape, a character symbol image can be displayed. It is possible to extract clearly and to judge the quality.
[0038]
In addition, a clear image can be obtained even if the printed surface and character symbols are colored.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a metal can character symbol inspection apparatus.
FIG. 2 is a central sectional view of the annular illumination device.
FIG. 3 is an image view of a metal can bottom irradiated with an annular illumination device.
FIG. 4 is a view showing another embodiment of the annular illumination device.
FIG. 5 is a view showing an example of a lighting device according to the prior art.
FIG. 6 is a picture of a metal can bottom according to the prior art.
FIG. 7 is a view showing an example of a lighting device according to the prior art.
FIG. 8 is a picture of a metal can bottom according to the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Metal can 2 Annular illumination device 2a Illumination power supply 3 Conveyor 4 Television camera 4a Pinhole lens 5 Sensor 6 Image processing device 7 Sorting mechanism 10 Bottle 11 Can bottom 12 Can bottom step 13 Character image 14 Can bottom dark field 15 Can Bottom dark field 16 Bottle character symbol 17 Bottle cap character symbol 21 Illumination body frame 22 Annular light source 23 Ring-shaped transmissive diffuser plate 24 Reflective diffuser plate 25 Distant piece 26 Transmitter diffuser plate 27 Transmitter diffuser plate 28 Transmitted Diffusion plate 29 Filter

Claims (2)

In an imaging device that irradiates a subject such as a metal can with light from an annular light source and images the reflected light,
Imaging means;
A pinhole lens provided on the optical axis incident optical path side of the imaging means and having a pinhole at the tip;
It has a flat plate shape with an opening large enough not to obstruct the visual field of the pinhole. The pinhole abuts on this opening, and the surface opposite to the pinhole abutment side is the reflecting surface. A reflective light diffuser;
Provided between the reflective surface side of the reflective light diffusing plate and a subject such as a metal can, and has a smooth arcuate shape with a top having an opening that does not obstruct the field of view of the imaging means at the center. It has a flat plate-like skirt extending in the outer direction perpendicular to the optical axis, and has a cylindrical body that is smoothly connected to the skirt provided between the top and the skirt in a skirt shape. A bell-shaped translucent light diffusing portion in which the top portion, the cylindrical portion, and the skirt portion are integrally molded and are translucent,
An annular light source having substantially the same outer diameter as the reflective light diffusing plate, and disposed around the cylindrical body of the bell-shaped translucent diffuser;
An imaging apparatus comprising: In an imaging device that irradiates a subject such as a metal can as a subject with light from an annular light source and images the reflected light thereof,
Imaging means;
A pinhole lens provided on the optical axis incident optical path side of the imaging means and having a pinhole at the tip;
It has a flat plate shape with an opening large enough not to obstruct the visual field of the pinhole. The pinhole abuts on this opening, and the surface opposite to the pinhole abutment side is the reflecting surface. A reflective light diffuser;
An annular illumination device provided between the reflecting surface side of the reflective light diffusing plate and a subject such as a metal can as a subject, and in close contact with the reflecting surface;
Consisting of
The annular illumination device is
A box having an upper opening corresponding to the reflecting surface and a lower opening corresponding to the subject, and an inner surface forming a reflecting surface;
Provided inside the box body, facing the upper opening side, having a smooth arc shape and having a top portion having an opening that does not obstruct the field of view of the imaging means at the center, and the bottom of the box on the lower opening side A cylindrical body that has a flat skirt extending in the outer direction perpendicular to the optical axis and is smoothly connected to the skirt provided between the top and the skirt. A bell-shaped translucent light diffusing portion that has a top portion, a cylindrical portion and a bottom portion that are integrally molded, and is translucent.
An annular light source having substantially the same outer diameter as the reflective light diffusing plate, and disposed around the cylindrical body of the bell-shaped translucent diffuser;
An imaging apparatus comprising:

Images