JPH0516939B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a monitoring device for a welding arc, and particularly to a monitoring device that can clearly image the peripheral area of a welding arc without causing halation. .

[Conventional technology]

Generally, in automatic welding, devices used to monitor the welding arc include an optical television camera that images the welding arc, and a monitor image receiver that displays an image of the arc based on the video signal from the television camera. Monitoring devices consisting of vessels are already known.

By the way, in order to perform welding operations accurately, it is necessary to obtain a clear image in which the welding arc and the surrounding area are clearly distinguished. However, the brightness of the welding arc is significantly higher than that of the surrounding area. When imaging the arc part, due to the nature of the TV camera, the second
As shown in the figure, significant halation 2 occurs in the image centered around the arc portion 1, making it impossible to clearly recognize peripheral areas such as the electrode 3 and the molten pool 4.

Therefore, in order to suppress this halation phenomenon, a dimming filter is provided in front of the television camera to reduce the overall amount of incident light.

[Problem that the invention seeks to solve]

However, when the brightness of the entire image is reduced using a darkening filter as described above, there is a problem in that the peripheral area is excessively attenuated, resulting in only the arc being reflected, making it impossible to see the peripheral area.

Therefore, it is also possible to use a partial attenuation filter in which the attenuation filter is formed in advance only in the part corresponding to the arc, but this allows the positional relationship between the arc and the partial attenuation filter to be adjusted even slightly. If it deviates, it will not be possible to exhibit a sufficient light reduction effect, so there is a problem in that it cannot be applied to moving images, although this does not pose a problem when capturing fixed images.

[Purpose of the invention]

The present invention has focused on the above-mentioned problems and has been devised to effectively solve the problems.

An object of the present invention is to provide a monitoring device that can clearly image the surrounding area of a welding arc part without causing halation by reducing the brightness of only this arc part, even though the welding arc part moves. It is in.

[Summary of the invention]

The configuration of the present invention that achieves the above object uses a transmissive liquid crystal dot matrix as a dark filter, and also includes a matrix control circuit that reduces the amount of light transmitted through the matrix in response to the imaging brightness exceeding a predetermined value. By controlling the voltages of the XY coordinates of the liquid crystal dot matrix, a filter is created on the liquid crystal dot matrix that matches the shape of the arc part with high brightness, and the brightness of only the arc part is reduced to balance the brightness with the surrounding area. The summary is what we did.

〔Example〕

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic perspective view showing a monitoring device according to the present invention, FIG. 3 is a plan view showing a liquid crystal dot matrix, and FIG. 4 is a block diagram showing a matrix control circuit.

As shown in the figure, reference numeral 5 denotes an ordinary optical television camera that images the welding arc portion 6. A monitor image receiver 8 is connected to this television camera 5 via a cable 7, and based on the image signal from the television camera 5, The image of the arc portion 6 is projected. A liquid crystal dot matrix 9 is provided between the arc portion 6 and the television camera 5, as will be described later, and partially acts as a neutral density filter, and this dot matrix 9 partially reduces the transmittance of light. A known matrix control circuit 10 is electrically connected via wiring 11. The liquid crystal dot matrix 9 is integrally attached and fixed to the television camera side by a support member (not shown).

The liquid crystal dot matrix 9 is made up of a large number of transparent unit liquid crystal plates 12 that change the light transmittance by controlling the supply of pulse voltage and are arranged in a flat plate shape. For example, as shown in FIG. By arranging a total of 10,000 unit liquid crystal plates 12, 100 each on the horizontal (axis) and horizontal (X-axis), and controlling the pulse voltage applied to each of the X-axis and Y-axis, an arbitrary blackening pattern 13 can be obtained. It's getting old. A control signal for controlling this blackening pattern is output from the matrix control circuit 10. This control circuit 10 is a circuit that reduces the amount of light transmitted through the corresponding unit liquid crystal plate of the liquid crystal dot matrix 9 in response to the imaging luminance of the pixel obtained from the television camera exceeding a predetermined value. To explain in detail based on the figure, this control circuit 10 includes a separation circuit 14 that separates a composite synchronization signal a obtained from a television camera 5 into a video signal b and a synchronization signal c.
, a binarization circuit 15 that thresholds the imaging brightness of each pixel of the video signal b obtained from this using a predetermined value, and binarizes the processed image into 0 or 1; An X-axis pulse generation circuit 16 outputs an X-axis pulse signal e to the liquid crystal dot matrix 9 based on the output value from the binarization circuit 15 while synchronizing with the obtained horizontal synchronization signal d, and from the separation circuit 14. The Y-axis pulse generation circuit 17 outputs a Y-axis pulse signal g to the liquid crystal dot matrix 9 while synchronizing with a vertical synchronization signal f. The brightness threshold set in the binarization circuit 15 is preferably set to a limit brightness that makes it impossible for the image pickup tube built into the television camera 5 to recognize differences in brightness. .

Next, the operation of the present invention configured as described above will be explained.

First, the arc light generated at the welding arc section 6 passes through the liquid crystal dot matrix 9 and then enters the optical television camera 5 where it is imaged, and the video signal is transmitted to the monitor image receiver 8 via the cable 7. The image of the welding arc is shown here. Here, if the liquid crystal dot matrix 9 is not controlled in any way, the brightness of the arc part 6 is too strong, resulting in an image with halation centered on the arc part, making it impossible to clearly see the peripheral parts. According to the present invention, the composite synchronization signal a obtained by the television camera 5 is guided to the matrix control circuit 10, and the imaging brightness of the video signal b obtained by the separation circuit 14 built therein is subjected to threshold processing using a predetermined value. Based on this output, the X-axis pulse generation circuit 16 outputs an X-axis pulse signal e to the liquid crystal dot matrix 9 to operate the unit liquid crystal plates 12 . Therefore, the liquid crystal dot matrix 9
, a blackened pattern 13 similar in shape to the welding arc portion 6 whose brightness is higher than a predetermined value is obtained, and as a result, the amount of transmitted light in this blackened pattern 13 is reduced, so that the arc entering the television camera 5 is reduced. The amount of light incident on the area is suppressed and the amount of light is balanced with the peripheral area, making it possible to obtain a good image without halation as described above. Here, since the amount of transmitted light of the blackened pattern 13 corresponding to the arc portion decreases, the blackened pattern 13 instantly disappears when the brightness of the transmitted light passing through it becomes less than the threshold value in the matrix control circuit 10. However, at the same time, the brightness of the arc portion entering the television camera 5 increases again and exceeds the threshold value, and a blackening pattern is formed again as described above, thereby controlling the amount of light incident on the camera. In this way, the generation and disappearance of the blackening pattern is repeated at high speed in response to the scanning time of the X-axis or Y-axis, so that the amount of light from the arc portion captured by the television camera 5 decreases as a whole, as described above. You can get good images like this.

Furthermore, even if the welding arc portion 6 or the television camera 5 side moves and the arc portion visible through the liquid crystal dot matrix 9 moves, the blackening pattern 13 also corresponds to the movement of the arc portion due to the operation of the matrix control circuit 10 described above. Then, the blackening pattern 13a is formed by moving as shown by the broken line in FIG.
Even when converting moving images into images, good images can always be obtained.

〔Effect of the invention〕

In summary, according to the present invention, a transparent liquid crystal dot matrix is provided in front of a television camera, and in order to control this, a matrix control circuit is provided that generates a pulse voltage based on the imaging brightness obtained from the television camera. By forming a blackened pattern with low transmittance on the liquid crystal dot matrix to correspond to the shape of the arc part with high brightness, it is possible to reduce the light only in the arc part, thereby eliminating halation in the arc part and obtaining a clear image. be able to. Therefore, since the arc portion and its surroundings can be clearly recognized, remote control of the welding operation can be performed accurately, and the occurrence of welding defects can be prevented. Furthermore, even if the arc portion moves on the liquid crystal dot matrix, the blackening pattern will also move accordingly, making it possible to obtain clear images not only for still images but also for moving images.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing a monitoring device according to the present invention, FIG. 2 is a view showing an image of an arc portion where halation has occurred, and FIG. 3 is a plan view showing a liquid crystal dot matrix with a blackened pattern. FIG. 4 is a block diagram showing the matrix control circuit. In the figure, 5 is an optical television camera, 6 is a welding arc section, 8 is a monitor image receiver, 9 is a liquid crystal dot matrix, and 10 is a matrix control circuit.

Claims (1)

[Claims] 1. A welding arc monitoring device comprising an optical television camera that images the welding arc, and a monitor image receiver that displays an image of the arc based on a signal from the television camera, wherein the welding arc and the A liquid crystal dot matrix is provided between the television camera and has a plurality of unit liquid crystal plates arranged in a planar manner to control the amount of light incident on the television camera, and the imaging brightness obtained from the television camera is equal to or higher than a predetermined value. and a matrix control circuit that reduces the amount of light transmitted through the corresponding unit liquid crystal plate of the liquid crystal dot matrix in response to the change in the liquid crystal dot matrix.