JP2809297B2 - Moving object imaging apparatus and imaging method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving object imaging apparatus and an imaging method for outputting an image signal obtained by imaging an object moving at high speed.

[0002]

2. Description of the Related Art A moving object imaging apparatus is used, for example, in a factory for inspecting the date of manufacture or the like printed on the bottom of a beer can. In a conventional moving object imaging apparatus, a sensor detects that a moving object has reached an imaging position, emits a flash at a timing (imaging timing) at which a detection signal from the sensor is taken, and images the object with a CCD camera. I do. Then, the image signal output from the CCD camera is processed by an image processing device, and is compared with an appropriate image set in advance to determine whether the date of manufacture or the like is correctly printed. The CCD camera forms an optical image of an object on an imaging device by an imaging lens, accumulates a charge corresponding to the optical image for a predetermined period (charge accumulation period), and then charges the electric charge in the next charge accumulation period. The charge is transferred during the transfer period, and an image signal is output.

FIG. 4 is a timing chart for explaining control during imaging in a conventional moving object imaging apparatus. In the case of FIG. 4, the charge transfer period is included in the first half of the charge accumulation period. When the target passes through the camera field of view at random timing, the imaging timing may overlap the charge transfer period of the CCD camera as shown in FIG. Thus, when the imaging timing and the charge transfer period overlap, even if the strobe light is emitted, the charge corresponding to the optical image of the object is not effectively accumulated on the imaging device, and an appropriate image signal can be obtained. Absent. Therefore, even if a character or the like printed by performing image processing using such an image signal is determined, a correct determination cannot be made, and even if the target is a normal product, the result is determined to be defective. Sometimes.
Therefore, in the conventional moving object imaging apparatus, a delay circuit or the like is provided, and when the imaging timing overlaps with the charge transfer period,
As shown in FIG. 4, the imaging timing is shifted by a delay circuit or the like.

[0004]

Since the charge transfer timing and the length of the charge transfer period are different for each type of CCD camera, usually, when the image pickup timing overlaps with the charge transfer period, the image pickup timing is relatively short. I'm staggering for a long time. For this reason, especially when the object is being conveyed at a high speed, the object is conveyed to a place far away from the predetermined imaging position between the time when the object is detected by the sensor and the time when the strobe is fired. Therefore, an appropriate image signal cannot be obtained. Also, when the object is being conveyed at a low speed, the object is very slightly deviated from the predetermined imaging position when the strobe light is emitted.
The strobe light is emitted from almost right above the object. However, when the object is being conveyed at a high speed, the deviation from the predetermined imaging position becomes large, and therefore, the strobe light is irradiated from obliquely above the object. To reflect. For this reason, when imaging characters or the like printed on a concave portion such as the bottom of a beer can, reflected light from the characters or the like cannot be effectively incident on the imaging lens, and an appropriate image signal is obtained. Can not.

As described above, in the conventional moving object imaging apparatus, when the imaging timing is overlapped with the charge transfer period, the imaging is performed with the imaging timing shifted, but when the object is conveyed at a high speed, an appropriate image is taken. An image signal cannot be obtained, and therefore the quality of characters and the like printed on the object is good.
There is a problem that it is not possible to accurately determine a defect.

The present invention has been made based on the above circumstances, and provides a moving object imaging apparatus capable of obtaining an appropriate image signal without shifting the imaging timing even when the imaging timing overlaps the charge transfer period. It is intended for.

[0007]

A moving object imaging apparatus according to the present invention for achieving the above object detects a moving object reaching a predetermined position, and outputs a detection signal; An illumination unit that receives a detection signal from the detection unit and irradiates the moving object with flash light; and an imaging device that receives a detection signal from the detection unit and receives an optical image of the moving object under illumination by the illumination unit. After accumulating the charge corresponding to the optical image, the accumulated charge is transferred within the charge transfer period for each odd-line pixel and even-line pixel whose charge storage period is shifted by half, A frame accumulation type imaging means for sequentially outputting an image signal of an odd field and an image signal of an even field; and the odd field transmitted from the imaging means when receiving a detection signal from the detection means. Of the image signal of the even field and the image signal of the even field, when the charge accumulation period is divided into two periods, the image of the field imaged during the divided period that does not include the charge transfer period Output field determining means for outputting a signal.

The output field determining means includes a timing generating means for generating a timing signal for operating the imaging means, and a timing signal from the timing generating means when receiving a detection signal from the detecting means. Based on the image signal of the odd field and the image signal of the even field, when the charge accumulation period is divided into two periods, the charge transfer period is not included in the divided period. Field determination means for determining the imaged field and outputting a determination signal, and, based on a determination signal from the field determination means, imaged within the divided period that does not include the charge transfer period. And a field selecting means for selecting the selected field and outputting an image signal of the selected field. Desirable.

[0009]

According to the present invention, the charge storage period of the image signal of the odd field and the image signal of the even field is reduced when the detection signal is received from the detection means using the frame storage type imaging means. When divided into two periods, the image signal of the field imaged during the divided period that does not include the charge transfer period is output, so that an appropriate image signal can be obtained without shifting the imaging timing. it can. Therefore, an appropriate image signal can be obtained even when the object is being conveyed at a high speed.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a moving object imaging device according to an embodiment of the present invention, FIG. 2 is a schematic block diagram of a main part of an image processing device in the moving object imaging device, and FIG. FIG. 6 is a timing chart for explaining control at the time.

The moving object imaging apparatus shown in FIG.
, A strobe light source 4, a strobe drive unit 6, a CCD camera 8, and a conveying means 1 such as a conveyor for conveying the object X.
2 and an image processing device 20. In this embodiment, the object X is a beer can, the beer can is transported at a high speed (1000 pieces / min), and characters such as manufacturing date printed on the concave portion at the bottom of the beer can by an inkjet printer. Let us consider a case of checking whether or not is printed correctly.

The sensor 2 is such that the object X to be conveyed is a CCD.
It detects that it has approached the camera 8 and has reached the imaging position, and outputs a detection signal. Strobe light source 4
Is a flash light source that irradiates the object X, and the object X is imaged under this illumination. Also, the strobe drive unit 6
The strobe light source 4 emits light at a timing (imaging timing) at which a detection signal from the sensor 2 is taken. Here, the light emission period of the strobe light source 4 is about 1/10000 second.

The CCD camera 8 forms an optical image of the object X as a two-dimensional image on an image sensor by an image pickup lens, performs photoelectric conversion on the image sensor, and charges electric charges corresponding to the optical image for a predetermined period. (Charge accumulation period) After accumulation, the accumulated electric charge is output as a one-dimensional electric signal. Although the optical image is constantly formed on the image sensor, the charge corresponding to the optical image of the object X is not effectively accumulated during the transfer of the charge. Then, after the transfer of the charge, the charge is accumulated again in the portion where the charge has disappeared. The one-dimensional electric signal obtained from the imaging device is output to the image processing device 20 as an image signal.

Further, the CCD camera 8 used in this embodiment
Is of the frame accumulation type. That is, in the image sensor, for example, among the pixels of the photosensitive section, first, the charges accumulated in the pixels of the odd-numbered lines are sequentially transferred to the transfer section to obtain the electric signals of the odd-numbered fields. During this time, photoelectric conversion is continued as it is in the pixels on the even-numbered lines. Next, the charges accumulated in the pixels of the even-numbered lines are sequentially transferred to the transfer unit, and electric signals of the even-numbered fields are obtained. Thereafter, the operation of transferring the charges accumulated in the pixels of the odd-numbered lines again and subsequently transferring the charges accumulated in the pixels of the even-numbered lines is repeated. In particular, in the CCD camera 8 of the NTSC standard, the charge accumulation period of one pixel is 1/30 second, and the charge accumulation period of a pixel on an odd line and a pixel on an even line is 1/30 as shown in FIG. 60 seconds off. Further, the first half of the charge accumulation period of the pixels of the odd (even) line includes a charge transfer period for transferring the charges accumulated in the charge accumulation period of the pixel of the previous odd (even) line. This charge transfer period is about 1/1600 second. Therefore, the charge transfer period between the odd line pixels and the even line pixels is also 1/6.
The time is shifted by 0 seconds, and if the pixels of the odd (even) line are transferring the electric charge, the pixels of the even (odd) line always accumulate the electric charge. For example, as shown in FIG. 3, the charges accumulated in the charge accumulation period of the pixels of the odd line are taken out in the first half of the charge accumulation period of the pixels of the odd line, and the charge accumulation period of the pixels of the even line is changed to the pixels of the even line. In the first half of the charge accumulation period.

The image processing device 20 processes an image signal from the CCD camera 8, and as shown in FIG.
An A / D converter 29 for converting an image signal output from the CCD camera 8 into a digital signal and outputting the digital signal; an image memory 30 for temporarily storing the image signal; and an image of an odd field based on the signal stored in the image memory 30 Output field determining unit 2 for outputting a signal or an image signal of an even field
2, an image processing unit 32, and an image determination unit 34. The output field determination unit 22 includes a timing signal generation unit 24, a field determination unit 26, and a field selection unit 28.

The timing signal generator 24 generates a timing signal for controlling the operation of each part of the image processing device 20 and the CCD camera 8. As shown in FIG. 3, in the CCD camera 8, the timing at which a high (low) level signal from the timing signal generation unit 24 is fetched is such that the charges accumulated so far in the pixels of the odd (even) lines are transferred and newly added. This is the timing to start accumulating charges. Also, the period of 1/60 seconds during which a high (low) level signal is received from the timing signal generator 24 is represented by C
This is the camera output period in which the odd (even) field image signal is output from the CD camera 8.

Upon receiving the detection signal from the sensor 2, the field determination unit 26 determines whether the timing signal from the timing signal generation unit 24 is at a high level or a low level, and outputs the determination signal. Is what you do.
Since the CCD camera 8 is synchronized with the image processing device 20 by the timing signal from the timing signal generator 24,
The image signal of the odd field and the image signal of the even field corresponding to the detection signal are those that were captured in the first half of the charge accumulation period of the pixels in the odd line and the pixels in the even line, respectively, or those that were captured in the second half. You know if there is. That is, if the timing signal from the timing signal generator 24 is at a high level when the detection signal is sent from the sensor 2, the image signal of the odd field corresponding to this detection signal is generated during the charge accumulation period of the pixel of the odd line. It is determined that the image was captured in the first half, and that the image signal of the even field was captured in the second half of the charge accumulation period of the pixels in the even line. If the timing signal is at a low level, it is determined that the image signal of the odd-numbered field was captured in the latter half of the charge accumulation period of the pixel of the odd-numbered line, and the image signal of the even-numbered field is determined during the charge accumulation period of the pixel of the even-numbered line. Is determined to have been taken in the first half of the process.

The field selecting section 28 picks up an image of an odd field image signal and an even field image signal corresponding to a certain detection signal in the latter half of the charge accumulation period based on the judgment signal from the field judgment section 24. The other field is selected. In the present embodiment, since the charge transfer period is included in the first half of the charge accumulation period, the image signal of the field captured in the second half of the charge accumulation period is
Since the imaging timing does not overlap with the charge transfer period, an appropriate image signal can be selected by the field selection unit 28.

The image processing section 32 performs image processing such as binarization, and outputs only the appropriate image signal selected by the field selection section 28 to the image determination section 34. Also,
The image determination unit 34 converts the image signal from the image processing unit 32 into
For example, the image is compared with a preset reference image to determine whether the printed character is good or bad, and outputs a result of the determination.

Next, the operation of the moving object imaging apparatus according to the present embodiment will be described. When the beer can approaches the CCD camera 8 and the sensor 2 detects the beer can, the sensor 2 outputs a detection signal to the strobe drive unit 6 and the field determination unit 26. Now, it is assumed that the strobe drive unit 6 captures a detection signal at, for example, a timing A shown in FIG. At this time, the image of the beer can is captured in the second half of the charge accumulation period in the pixels of the odd-numbered lines, and is captured in the first half of the charge accumulation period in the pixels of the even-numbered lines. Then, after the charges are transferred from the pixels of each line, the image signal of the odd field and the image signal of the even field are output from the CCD camera 8 during the camera output period and the camera output period, respectively. On the other hand, when receiving the detection signal from the sensor 2, the field determination unit 26 sets the image signal of the odd field in the second half of the charge accumulation period of the pixel of the odd line based on the timing signal from the timing signal generation unit 24. It is determined that an image has been taken. The field selection unit 28 discards the image signal of the even field based on the determination signal from the field determination unit 26 and extracts only the image signal of the odd field. Then, after image processing is performed on the image signal of the odd-numbered field by the image processing unit 32, the image is compared with a reference image by the image determination unit 34, and characters such as the date of manufacture are accurately printed on the bottom of the beer can. It is determined whether or not it has been performed.

Further, it is assumed that the strobe drive unit 6 captures a detection signal at, for example, a timing B shown in FIG. At this time, the image of the beer can is captured in the second half of the charge accumulation period in the pixels of the even-numbered lines, and is captured in the first half of the charge accumulation period in the pixels of the odd-numbered lines. Then, after the charges are transferred from the pixels of each line, the image signal of the even field and the image signal of the odd field are respectively output to the camera output period,
Output from the CCD camera 8 during the camera output period.
On the other hand, when receiving the detection signal from the sensor 2, the field determination unit 26 determines, based on the timing signal from the timing signal generation unit 24, the image signal of the even field in the second half of the charge accumulation period of the pixel of the even line. It is determined that an image has been taken. The field selection unit 28 discards the image signal of the odd field based on the determination signal from the field determination unit 26 and extracts only the image signal of the even field. Then, after the image processing section 32 performs image processing on the image signal of the even field, the image determination section 34 determines whether or not characters such as the production date are accurately printed on the bottom of the beer can. .

In the moving object imaging apparatus of this embodiment, a frame accumulation type CCD camera is used, and when the field determination section receives a detection signal from the sensor, the timing signal from the timing signal generation section is at a high level. By determining whether the signal is at the low level or not, the image signal captured in the latter half of the charge accumulation period that does not include the charge transfer period is selected from the odd-field image signal and the even-field image signal corresponding to the detection signal. Therefore, even when the imaging timing overlaps the charge transfer period, an appropriate image signal can be obtained without shifting the imaging timing. Therefore, according to the moving object imaging apparatus of the present embodiment, when the object is being conveyed at a high speed, the strobe light is always emitted from almost directly above the object even when imaging a portion having a complicated shape. Therefore, it is possible to accurately determine whether the character or the like printed on the object is good or bad.

The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the invention.

[0024]

As described above, according to the present invention, when an image signal of an odd field and an image signal of an even field are received when a detection signal is received from the detection means using the frame accumulation type imaging means. From the above, when the charge accumulation period is divided into two periods, the image signal of the field imaged during the divided period that does not include the charge transfer period is selected. Image signals can be obtained, and therefore, even when the object is being conveyed at a high speed, it is possible to accurately determine whether the characters or the like printed on the object are good or bad, thereby improving the reliability of the inspection. A moving object imaging device that can be improved can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a moving object imaging apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic block diagram of a main part of an image processing device in the moving object imaging device of the present embodiment.

FIG. 3 is a timing chart for explaining control at the time of imaging in the moving object imaging apparatus of the present embodiment.

FIG. 4 is a timing chart for explaining control at the time of imaging in a conventional moving object imaging apparatus.

[Explanation of symbols]

 Reference Signs List 2 sensor 4 strobe light source 6 strobe drive unit 8 CCD camera 12 transport unit 20 image processing unit 22 output field determination unit 24 timing signal generation unit 26 field determination unit 28 field selection unit 29 A / D converter 30 image memory 32 image processing unit 34 Image judgment unit

Claims (4)

(57) [Claims] 1. A detecting means for detecting that a moving object has reached a predetermined position and outputting a detection signal; and an illuminating means for receiving a detection signal from the detecting means and irradiating the moving object with flash light. Receiving a detection signal from the detection unit, forming an optical image of the moving object on an image sensor under illumination by the illumination unit, accumulating electric charges corresponding to the optical image, and then storing the electric charge. Frame accumulation type imaging means for transferring charges within the charge transfer period for each of the odd-line pixels and even-line pixels whose charge accumulation period is shifted by half, and sequentially outputs an odd-field image signal and an even-field image signal; When receiving the detection signal from the detection unit, the charge accumulation period is set to two of the odd field image signal and the even field image signal transmitted from the imaging unit. And output field determination means for outputting an image signal of a field imaged during the divided period in which the charge transfer period is not included when divided into periods. Object imaging device. 2. The image processing apparatus according to claim 1, wherein said output field determination means includes a timing generation means for generating a timing signal for operating said imaging means, and a timing signal from said timing generation means when receiving a detection signal from said detection means. Based on the image signal of the odd field and the image signal of the even field, when the charge accumulation period is divided into two periods, the charge transfer period is not included in the divided period. Field determination means for determining the imaged field and outputting a determination signal, and, based on a determination signal from the field determination means, imaged within the divided period that does not include the charge transfer period. A field selecting means for selecting the selected field and outputting an image signal of the selected field. Mounted moving object imaging device. 3. The time when a moving object reaches a predetermined position.
Illuminate the moving object with a flash Charge storage and transfer of pixels on odd and even lines
Type shooting that alternates Transfer to the image means at the above timing
To form an optical image of the moving object, The image signals of the odd-numbered lines and the even-numbered lines of the accumulation type
The above timing is included in the charge transfer period
Moving object characterized by outputting the image signal of the moving object
How to image the body. 4. A method for detecting when a moving object has reached a predetermined position.
Outputs an intelligent signal, Irradiating a flash on the moving object according to the detection signal, In response to the above detection signal, charge accumulation and transfer
On the storage type imaging means that alternates between the pixels of
To form an optical image of the moving object, When the above detection signal is received, the odd line and even line
Of the field image signal within the charge accumulation period
Outputting an image signal of the selected field.
Imaging method for moving objects.