JP2534638B2 - Printing monitoring method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print monitoring method and apparatus for detecting a print quality defect such as gravure printing and displaying the content of the quality defect as a still image for confirmation.

[0002]

2. Description of the Related Art A moving object is irradiated with strobe light,
The image is obtained by an image pickup device such as a CCD, and this is A
2. Description of the Related Art Monitoring devices that perform D conversion and write in a memory, read out a written signal, perform DA conversion, and display on a monitor have been used in various fields.

In gravure printing, the material to be printed (original material) is in the form of a roll, and printing is completed and wound up through a printing station of a plurality of colors. The material to be printed is continuous and usually prints while moving at a speed of about 200 m / min. For this reason, the human eye cannot monitor misregistration and quality defects specific to printing.

FIG. 4 is a block diagram of an apparatus for monitoring moving objects, in particular printed matter, for this purpose. A one-dimensional image (black and white) is periodically obtained by the line sensor 41 from the inspection object 40, and the quality defect detector 42 generates a defect detection signal by comparing this image with a reference image. The strobe light emitter 43 is operated by this defect detection signal to cause the strobe lamp 44 to emit light. An image at the time of light emission is obtained by the video camera 45, AD-converted by an AD converter (not shown), and recorded in the image memory 47 via the image selection circuit 46.
The signal of the image memory 47 is read out and displayed on the monitor television 48 via a DA converter (not shown). This monitor tv
The content of the defect can be confirmed by 48 color images.

[0005]

FIG. 5 shows the timing of the strobe emission of the above-mentioned monitoring device and the reading of the image memory. When light is emitted after the vertical (retrace line) period as in the light emitting position (1), the Nth time at that time
The (N + 1) th field becomes the first field and the (N + 2) th field becomes the second field with respect to the fields, which are read and displayed on the monitor. this is,
The same applies when light is emitted at a timing outside the vertical (retrace line) period as in the light emitting position (3).

However, when light is emitted within the vertical synchronizing period (vertical retrace line period) at the timing of the light emitting position (2) in FIG. 5, the first field is the (N + 1) th, as in the video reading (2). ) Field and the (N + 3) th field, the second field is recorded and read in the (N + 2) th field. That is, the video signal is read over three fields. In this case, the image output is lowered and the image quality is lowered to cause flicker, so that a good image cannot be obtained.

The above phenomenon is caused by an unstable band of about two horizontal synchronizing periods within the vertical blanking period. This unstable band differs depending on the TV camera. In principle, it is sufficient to shift the timing of light emission from the unstable band, but it was difficult to support all TV cameras.

Therefore, conventionally, the image obtained by the light emission in the unstable band or the vertical blanking period is ignored and not displayed on the monitor, and the stable display operation of the monitor image is guaranteed. In many cases, it cannot be ignored, and there is a demand for a method and apparatus capable of confirming all defect states. The present invention provides a method and apparatus capable of displaying an image at the time of signal generation without ignoring a defect detection signal within a vertical blanking period.

[0009]

The present invention solves the above problems by delaying the defect detection signal within the vertical blanking period until the end of the vertical blanking period.

That is, an image of a printed object to be inspected is obtained by a line sensor and compared with a reference screen. If there is a quality defect, a defect detection signal is generated, and the strobe is caused to emit light by the defect detection signal. In the print monitoring method, the image obtained by picking up the object to be inspected at that time is AD-converted and written in the image memory, the image memory is read, DA-converted, and displayed on the monitor to check the content of the defect.
When the defect detection signal is generated during the vertical blanking period, delay the defect detection signal until the end of the vertical blanking period, and after the vertical blanking period ends, the strobe light is emitted to record the image of the inspection object in the image memory. It is characterized by

Further, a line sensor for periodically obtaining an image of a printed inspection object, a detector for comparing the image of the line sensor with a reference image to detect a quality defect, and a defect detection which is an output of the detector. A strobe that emits light according to a signal, a video camera that obtains an image when the strobe emits light, an image memory in which the image is AD-converted and recorded, and a monitor that DA-converts and displays the signal read from the image memory In the printing monitoring apparatus, when a defect detection signal is generated in the vertical blanking period, a delay circuit for delaying the defect detection signal until the end of the vertical blanking period is provided, and a strobe is emitted by the defect detection signal after the vertical blanking period ends. The feature is that the image at that time is recorded in the image memory.

[0012]

The function of the defect can be stably displayed in response to the defect detection signal in the unstable zone (vertical blanking period). Further, although the position of the output image also shifts depending on the delay time of the defect detection signal, the maximum distance is about several tens of μm, so there is no practical problem.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an image memory unit used in the present invention. The image memory is composed of a first field memory 11 and a second memory field 12, and is a data classifier.
The signal of each field is written by 13 and the write control circuit 15. The video input is obtained by flash light emission, and the position of this light emission is controlled by the light emission position detector 14. The read control circuit 16 controls the data selection circuit 17 to read the recorded content from the first field memory 11 or the second field memory 12 and obtain a video output.

Here, a defect detection signal is input to the light emission position detector 14, and the timing of light emission of the strobe is controlled by this defect detection signal. This defect detection signal is input as it is outside the vertical blanking period to cause the strobe to emit light, but when it occurs within the vertical blanking period, it is delayed and input until the end of the vertical blanking period and then delayed. The light emission timing will be delayed by a certain amount of time.

FIG. 2 is a time chart of the delay processing of the defect detection signal according to the present invention. Vertical sync signal 22 and vertical sync signal having a length of 3 cycles of the horizontal sync signal 21.
A vertical blanking period (blanking) signal 23 for about 22 cycles of the rising horizontal synchronizing signal 21 at the same time as 22 is the same as a normal television synchronizing signal. When the defect detection signal 24 is generated in the vertical blanking period, the defect detection signal 24 is delayed by the delay circuit until the vertical blanking period (blanking) ends, and the delayed defect detection signal 25 is obtained. To be The delay defect detection signal 25 causes the strobe to emit light to record and display an image.

The maximum delay time of the delay defect detection signal 25 is 22H (horizontal synchronization period). Therefore, 63.5 μs × 22 = 1397 μs, which is about 1.4 ms. When moving at a speed of 200 m per minute, it corresponds to 46 μm, which is a positional deviation that is practically no problem.

FIG. 3 shows an example of the defect signal delay circuit used in the present invention. The flip-flop 31 and the flip-flop 32 are set and reset by the blanking period signal and the defect detection signal, and the outputs thereof are differentiated. A delay defect signal is obtained through a circuit. The delay circuit is not limited to this example, and is any circuit that delays the defect detection signal until the end of the vertical blanking period, that is, any circuit that can generate a signal for operating the strobe light emitter after the vertical blanking period ends. However, it can be used.

The present invention delays the defect detection signal until the end of the vertical blanking period in order to emit the strobe light outside the vertical blanking period. However, the unstable band of the vertical blanking period is removed. It is also possible to delay in the range. In that case, the delay time can be minimized.

Further, not only printing but also monitoring of other moving objects can be applied.

[0021]

According to the present invention, stable image output can be obtained and a good image can be displayed on a monitor when a defect detection signal is generated.

Further, there is almost no effect due to signal delay, and quality defects can be confirmed by visual inspection with a stable image. Note that automatic inspection is also possible by processing the image obtained by the present invention.

[Brief description of drawings]

FIG. 1 is a block diagram of an image memory unit of a print monitoring apparatus according to the present invention.

FIG. 2 is an explanatory diagram of delay processing of a defect detection signal according to the present invention.

FIG. 3 is a block diagram of an example of a delay circuit used in the present invention.

FIG. 4 is a block diagram of a print monitoring device.

FIG. 5 is an explanatory diagram of a relationship between a light emitting period and a read field.

Claims (2)

(57) [Claims] 1. An image of a printed object to be inspected is obtained by a line sensor, and this is compared with a reference screen to generate a defect detection signal when there is a quality defect, and the strobe is caused to emit light by the defect detection signal. In the printing monitoring method, an image obtained by picking up an object to be inspected at that time is AD-converted and written in an image memory, the image memory is read, DA-converted, and displayed on a monitor to check the content of the defect. When the detection signal is generated during the vertical blanking period, the defect detection signal is delayed until the vertical blanking period ends, and after the vertical blanking period ends, the strobe light is emitted to record the image of the inspection object in the image memory. Characteristic printing monitoring method. 2. A detector for detecting a quality defect by comparing a line sensor which periodically obtains an image of a printed inspection object with a reference image of the line sensor, and a defect detection which is an output of the detector. A strobe that emits light according to a signal, a video camera that obtains an image when the strobe emits light, an image memory in which the image is AD-converted and recorded, and a monitor that DA-converts and displays the signal read from the image memory In the printing monitoring apparatus, when a defect detection signal is generated in the vertical blanking period, a delay circuit for delaying the defect detection signal until the end of the vertical blanking period is provided, and a strobe is emitted by the defect detection signal after the vertical blanking period ends. A printing monitoring apparatus characterized by recording the image at that time in an image memory.