Light intensity control method for obtaining optimal images before, after, and during welding, and a compact and lightweight digital welding vision camera that embodies this method

Abstract

A small and lightweight digital welding vision camera is provided that captures optimal images during, before, and after welding. The present invention is characterized by comprising a window unit, a front case unit to which the window unit is attached, and a rear case unit connected to the rear of the front case unit and incorporating a short focal length lens. A first opening is formed in the front surface of the front case unit. A filter switching module is mounted inside the front case unit, and a second opening is provided coaxially with the first opening and positioned as far forward as possible of the short focal length lens.

Description

[Technical Field]

[0001] The present invention relates to a digital welding vision camera, and more particularly to a light intensity control method for obtaining optimal images before, after, and during welding, and a compact and lightweight digital welding vision camera that embodies the same. [Background technology]

[0002] Generally, welding methods that use an arc as a heat source, such as GTAW (Gas Tungsten Arc Welding; TIG welding), GMAW (Gas Metal Arc Welding; MIG welding), and PAW (Plasma Arc Welding), are widely used in industrial fields. In recent years, LBW (Laser Beam Welding), which utilizes a high-power laser, has also been widely used.

[0003] On the other hand, arc welding and laser welding inevitably generate high heat and strong light. Depending on the type of welding, welding fumes (metal oxides evaporated by heat) and spatter (fine particles of molten metal scattered around during welding) are generated. The welding light contains strong ultraviolet, visible light, and infrared light.

[0004] First, regarding the terms related to light used in the present invention, light intensity refers to the brightness of light emitted from a light source, and light quantity is defined as the value obtained by multiplying luminous flux (the amount of light passing through a unit area perpendicular to the direction in which the light travels per unit time) by time.

[0005] To effectively monitor the welding progress through video during welding work, it is more effective to display the color of the welding area in color, like when identifying an object with the naked eye, rather than using a monochrome image such as a black and white image.To this end, a low pass filter can be placed in front of the image sensor to block the ultraviolet and infrared rays contained in the welding light and use only visible light.

[0006] However, even if only visible light is used, welding light is much stronger than the light intensity that an image sensor can capture. Therefore, unless the amount of incoming light is properly attenuated, an image with appropriate brightness cannot be obtained. Usually, the amount of incoming light can be attenuated by narrowing the iris of the lens located in front of the image sensor. However, a lens with a built-in iris is not suitable for miniaturization and weight reduction.

[0007] On the other hand, when manually welding pipes to extend their length, it is difficult to achieve uniform quality welding around the entire 360° of the pipe due to factors such as the worker's welding posture and spatial constraints.

[0008] To solve this problem, conventionally, orbital welding has been used, in which a guide ring (orbit) is installed along the circumference of a fixed pipe, and the welding torch travels over the guide ring to perform automatic welding. This type of orbital welding not only increases work efficiency by about 1.5 to 3 times compared to regular manual welding, but also ensures consistent weld quality.

[0009] In order to monitor the welding work on video, welding cameras are attached to the front and rear of the carriage that carries the welding torch on the guide ring. Here, the camera installed in front of the carriage in the traveling direction is called the leading camera, and the camera installed behind the carriage is called the trailing camera. The leading camera and the trailing camera are installed facing each other with the welding torch as the reference.

[0010] The leading camera takes pictures facing the torch and can observe the state of filler metal supply, molten metal transfer (when the tip of the filler metal melts and becomes liquid metal), and the phenomenon of the filler metal and base metal melting in the molten metal. It can also immediately detect wear, damage, and contamination of welding electrodes during welding. The trailing camera takes pictures facing the torch and observes the molten metal behind the welding torch, which the leading camera cannot capture, and the weld bead created by welding. This allows for quick response if an abnormality occurs during welding, and maintains consistent welding quality.

[0011] However, as mentioned above, since the size and weight of additional devices that can be attached to the carriage are very limited, it is essential to make the welding camera compact and lightweight. For this reason, it is important to use a small lens in order to make the welding camera compact and lightweight. Typically, a small lens is used, which has a single focal length, but such a single focal length lens does not have an iris to adjust the amount of incoming light.

[0012] As a result, in welding cameras that use a fixed focal length lens, the strong welding light is focused by the lens, and a very large amount of light enters the image sensor. This large amount of light causes the captured image to become saturated (overexposed), making it impossible to obtain an image with appropriate brightness, even if the shutter speed (photoelectric conversion time) of the image sensor is set to the fastest (shortest photoelectric conversion time). Therefore, a means must be provided to appropriately reduce the amount of light before the strong welding light reaches the image sensor.

[0013] Generally, a means for reducing the amount of light is to use an ND (Neutral Density) filter, which attenuates the light energy across all wavelength bands when passing through a specific medium and attenuates the light intensity by a specific amount.

[0014] For a welding camera to be able to capture images with appropriate brightness while dealing with the strong light of a welding arc, the objective can be achieved simply by using an ND filter with a sufficiently high value.

[0015] However, a single-focus lens has a shallow depth of field, meaning that only a small area of ​​the subject is in focus, making it impossible to obtain a clear image (a deep image) that is evenly focused across the screen.

[0016] Therefore, in order to capture a welding image that is sharp and in focus across the entire screen, and that has adequate brightness, a deep depth of field must be ensured and light that is attenuated to an appropriate amount must be incident on the imaging element.

[0017] That is, a light attenuation means that attenuates light energy in all wavelength bands using an ND filter to reduce the light intensity, and a means that attenuates light intensity by interposing one or more circular openings of a predetermined size centered on the optical axis in front of the lens and reducing the area through which light enters (reducing the luminous flux) can be considered.

[0018] In optics, the F-number is basically calculated by dividing the focal length of a lens by the diameter of the entrance pupil. The entrance pupil is the area through which light enters. For the same focal length, if the diameter of the area increases, the F-number decreases and the amount of light entering increases (i.e., the image becomes brighter). On the other hand, if the diameter of the area decreases, the F-number increases and the amount of light entering decreases (i.e., the image becomes darker).

[0019] Generally, for a lens with the same focal length, as the F-number decreases, the depth of field becomes shallower, and an image is captured in which only a very narrow area in front of and behind the subject is clearly in focus.As the F-number increases, the depth of field becomes deeper, and an image in which the subject is clearly in focus across the entire screen can be captured.

[0020] The focal length and F-number of a single focal length lens adopted to make cameras smaller are fixed values ​​determined by the characteristics of the lens. However, as described above, the present invention reduces the area through which light enters outside the lens by providing one or more circular openings of a predetermined size centered on the optical axis in front of the lens, thereby increasing the F-number and enabling the capture of a clearly focused image of the subject across the entire screen.

[0021] Meanwhile, in conventional welding, the thicker the base material, the more V-groove (improved) is formed to perform the root pass welding, and then multiple passes are welded on top of the bead of the root pass welding.

[0022] In this case, if a certain high-value ND filter is placed in front of the lens, the intensity of the strong welding light can be appropriately reduced while welding is being performed, allowing the image sensor to capture images with appropriate brightness.

[0023] However, because the ND filter introduced to capture welding images with appropriate brightness significantly attenuates the light intensity, once welding is completed and the welding arc is turned off, the captured image is almost pitch black with only ordinary work lighting, making it impossible to see the shape of the welding torch or base material. This creates a problem in that it is not possible to perform pre-welding settings, such as adjusting the position and height of the torch and aligning the tip of the filler metal, in order to set the subsequent welding conditions. Summary of the Invention [Problem to be solved by the invention]

[0024] The present invention has been devised to solve the above problems, and aims to provide a digital welding vision camera that ensures both depth of field and an appropriate amount of light, can capture optimal images before, after, and during welding, and can be made compact and lightweight. [Means for solving the problem]

[0025] According to one embodiment of the present invention to achieve the above object, there is provided a digital welding vision camera including a window unit, a front case unit to which the window unit is attached at the front, and a rear case unit connected to the rear of the front case and having a fixed focal length lens therein, wherein a first opening is formed on the front surface of the front case unit, a filter switching module is attached inside the front case unit, and a second opening formed coaxially with the first opening is positioned as close as possible to the front of the fixed focal length lens.

[0026] The filter switching module includes a filter frame having a filter window of a certain area formed therein, and an ND filter and a low-pass filter that are laterally movable within the filter frame and selectively exposed to the filter window by being driven by a driving member.

[0027] The filter switching module holder includes a first holder member having an opening window of a certain area formed therein and a second holder member having the second opening formed therein, and an inclined groove is formed on the inner surfaces of the first holder member and the second holder member facing each other, allowing the filter switching module to be fixed at a predetermined angle inclined with respect to a plane (right-angle plane) perpendicular to the optical axis.

[0028] It is preferable that the filter switching module operates such that before and after welding, the low-pass filter is moved to expose the filter window, and light that has passed through the low-pass filter enters the image sensor, and during welding, the ND filter is moved to expose the filter window, and light that has passed through the ND filter enters the image sensor.

[0029] The present invention also provides a control method for a digital welding vision camera, in which an arc detection reference value for determining the presence of a welding arc and an arc extinction reference value for determining the extinction of an arc are set in the image processing unit (not shown) of the camera in accordance with the welding work situation, the amount of light entering the image sensor is monitored, and compared with the reference value, and the filter switching module automatically selectively exposes an ND filter or a low-pass filter to the filter window.

[0030] The present invention also provides a light amount control method for obtaining optimal images in a digital welding vision camera, which combines a means for attenuating the amount of welding light while passing through at least one opening on the path the welding light passes through, and a means for attenuating the intensity of the welding light by adjusting the ND value of an ND filter, thereby ensuring an appropriate amount of light entering the imaging element and obtaining optimal images before, after, and during welding. [Effects of the Invention]

[0031] According to the present invention, it is possible to ensure both depth of field and an appropriate amount of light, thereby obtaining optimal images before, after, and during welding, and it is also possible to make the camera smaller and lighter. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is a perspective view of a digital welding vision camera according to one embodiment of the present invention; FIG. [Figure 2] FIG. 1 is a side view of a digital welding vision camera according to one embodiment of the present invention. [Figure 3] 1 is an exploded perspective view of a digital welding vision camera according to an embodiment of the present invention; FIG. [Figure 4] 1 is an exploded perspective view of a filter switching module and first and second holder members of a digital welding vision camera according to an embodiment of the present invention; FIG. [Figure 5]3 is an operational state diagram of a filter switching module of a digital welding vision camera according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention will now be described in more detail with reference to the accompanying drawings. Prior to this, the terms and phrases used in the specification and claims should not be construed as being limited to their ordinary or dictionary meanings, but should be construed as meanings and concepts consistent with the technical concept of the present invention, based on the principle that the inventor can appropriately define the concepts of terms in order to best describe his or her invention. Furthermore, unless otherwise defined, technical and scientific terms used in the present invention have the meanings commonly understood by those of ordinary skill in the art to which the present invention pertains. In the following description and the accompanying drawings, descriptions of well-known functions and configurations that may unnecessarily obscure the gist of the present invention will be omitted. The accompanying drawings are provided as examples to fully convey the concept of the present invention to those skilled in the art. Therefore, the present invention is not limited to the drawings presented below, and may be embodied in other forms. Furthermore, throughout the specification, the same reference numerals refer to the same elements. Wherever possible, the same elements in the drawings will be designated by the same symbols.

[0034] <Explanation of composition and consolidated relationships> Referring to FIG. 1, a digital welding vision camera according to an embodiment of the present invention includes a window section 10, a front case section 20, a rear case section 30, and a mount section 40.

[0035] 2 and 3, the protective window 11 is attached to the front of the front protective case 21 via a window covering 12. Here, a first opening 21h is formed in the center of the front protective case 21.

[0036] The filter switching module 50 is installed inside the rear of the front protective case 21 and inserted laterally into the filter switching module holder 51. The front protective case 21 is attached to the rear protective case 31 with bolts B2. The filter switching module holder 51 is formed with a second opening 22h that is coaxial with the first opening 21h. The second opening 22h is preferably positioned as close as possible to the front of the prime lens 60. This is because the farther the second opening 22h is from the prime lens 60, the more likely it is that vignetting or shading will occur in the peripheral areas of the captured image.

[0037] The fixed focal length lens 60 is attached to a lens holder 61 and mounted inside the rear protective case 31. Behind the fixed focal length lens 60, a main low-pass filter 70, an imaging surface 80, an imaging element 81, and a printed circuit board (PCB) are arranged in this order.

[0038] A camera mount pad 41 is attached to the upper side of the rear protective case 31. A cable guide 43 for pulling out a cable and a cable seal member 42 for sealing are provided at the end of the rear protective case 31. Here, a lens stopper screw B3 for fixing the fixed focal length lens 60 is attached to the lens holder 61.

[0039] 4, the filter switching module holder 51 is formed by connecting a first holder member 51a having an opening 51h and a second holder member 51b having a second opening 22h with a plurality of connecting screws B5. The second opening 22h has a smaller diameter than the first opening 21h. The first and second holder members 51a and 51b each have an inclined groove 53 inclined at a predetermined angle from the vertical on their opposing sides. Therefore, the filter switching module 50, interposed between the first and second holder members 51a and 51b, is fixed in a state inclined obliquely with respect to a plane perpendicular to the optical axis.

[0040] 5, the filter switching module 50 has a filter window 50h formed on its exterior and a filter frame 56a mounted therein so as to be movable in the longitudinal direction. The filter frame 56a is movable in the longitudinal direction within the main body 50a of the filter switching module 50 by a driving lever 57 connected to a driving member 58. The filter frame 56a also has an ND filter 55 and a low-pass filter 56 arranged side by side. When the filter frame 56a is moved in the longitudinal direction by the driving force of the driving member 58, the ND filter 55 and the low-pass filter 56 are selectively positioned within the filter window 50h. This allows the filter position to be changed depending on whether the welding is being performed before, during, or after welding, as will be described in more detail in the operation description below.

[0041] <Explanation of action and effect> The function of each component is briefly explained below. The window unit 10 is fastened by a screw thread to the outer diameter of the tip protrusion of the front protective case 21. The protective window 11 is tightly attached to the tip surface of the front protective case 21 to form a sealed structure, which allows the protective window 11 to be easily replaced if it becomes contaminated with dust or spatter. The protective window 11 is made of a highly transparent and heat-resistant material to prevent external dust and spatter from entering the interior of the camera.

[0042] The front protective case 21 functions as an external case that protects the internal components of the camera. The first opening 21h not only reduces the area through which the strong welding light enters (reducing the luminous flux) to primarily attenuate the amount of light, but also restricts the inflow of light scattered by contaminants adhering to the outside of the diameter of the first opening 21h in the protective window 11.

[0043] The filter switching module 50 is equipped with two types of filter members, a low-pass filter 56 and an ND filter 55, and when a welding arc is not present (before and after welding is completed), the filter switching module 50 moves the low-pass filter 56 to match the filter window 50h. On the other hand, when a welding arc is present (during welding), the filter switching module 50 moves the ND filter 55 to match the filter window 50h.

[0044] The filter switching module holder 51 functions as a holder member for mounting the filter switching module 50 at an angle to a plane perpendicular to the optical axis of the protective window 11 and the fixed focal length lens 60 .

[0045] The second opening 22h further reduces the area into which the strong welding light enters from the outside of the lens, and appropriately adjusts the amount of light entering the image pickup element 81, thereby deepening the depth of field.

[0046] The fixed focal length lens 60 is a small lens with a single focal length and no light-adjusting aperture.

[0047] The lens holder 61 is a component for mounting the lens (single focus lens; 60) so that its optical axis is aligned with the center of the image of the image sensor 81. Its inner surface is screwed to the lens barrel, and its outer surface is screwed to the rear protective case 31. By changing the distance setting between the lens and the image sensor, the observation distance to the subject can be set separately.

[0048] The main low-pass filter 70 is a component that blocks strong ultraviolet and infrared rays generated during welding and allows only visible light to pass through to the imaging element.

[0049] The functions and effects of the present invention will be specifically described below.

[0050] The present invention forms first and second openings 21h, 22h that are formed as close as possible to the front lens surface of the fixed focal length lens 60 and are coaxial with the optical axis of the lens, thereby not only attenuating the amount of light by acting like a lens aperture, but also improving the depth of field.

[0051] In addition, the camera is equipped with a filter switching module 50 that electrically switches between an ND filter 55 and a low-pass filter 56. By using filters that correspond to the presence or absence of welding arc light, it is possible to capture images with optimal brightness before, after, and during welding.

[0052] As described above, the amount of light attenuation for the welding light required to capture an image with optimal brightness can be optimally set by combining the size of the opening 22h and the value of the ND filter 55. That is, for example, increasing the size of the second opening 22h not only reduces the depth of field and narrows the in-focus range, but also increases the amount of light entering the image sensor 81. Therefore, an ND filter 55 with a higher ND value can be combined to optimally set the amount of incoming light. On the other hand, decreasing the opening 22h deepens the depth of field and widens the in-focus range, and reduces the amount of light entering the image sensor. Therefore, an ND filter 55 with a lower ND value can be combined to optimally set the amount of incoming light resulting from this combination.

[0053] On the other hand, the filter switching module 50 is provided with two types of filter members: a low-pass filter 56 and an ND filter 55 .

[0054] As a result, before and after welding, light that has passed through low-pass filter 56 enters image sensor 81, and during welding, light that has passed through ND filter 55 enters image sensor 81. In other words, the camera filter selection can be determined by manually or automatically switching filters according to the welding work situation.

[0055] Furthermore, in accordance with the welding work situation, an 'arc detection reference value' for determining the presence of a welding arc and an 'arc extinction reference value' for determining the extinction of the arc are set in the image processing unit, and the amount of light entering the image sensor is monitored and compared with the reference values, so that the camera can automatically switch filters and determine the filter selection depending on whether a welding arc is present or not.

[0056] That is, the image processing unit of the camera monitors in real time the digital image data values ​​photoelectrically converted from the amount of light entering the image sensor, and when it detects that the image data values ​​exceed the arc detection reference value, it determines that a welding arc has occurred. Then, the filter switching module 50 positions the ND filter 55 so that it matches the filter window 50h.

[0057] On the other hand, if the image data value is detected as being less than the arc extinction reference value, it is determined that the welding arc has been extinguished, and the low-pass filter 56 in the filter switching module 50 is positioned to match the filter window 50h.

[0058] The present invention is devised so that the window 10 protects the optical and circuitry of the camera from dust and spatter, and if the window becomes contaminated after prolonged use, it can be easily replaced without using tools.

[0059] On the other hand, when looking at the arrangement of the components from the front end of the camera to the image sensor 81, in the present invention, the components are arranged in the following order: protective window 11, first opening 21h, filter switching module 50, second opening 22h, single focus lens 60, main low-pass filter 70, and image sensor 81.

[0060] With this configuration, when we look at the process by which the amount of light attenuates along the path that the strong welding light travels to the imaging element 81, the strong light generated from the welding arc during welding passes through the protective window 11 and is primarily attenuated at the first opening 21h.

[0061] Next, the ND filter 55 disposed within the filter switching module 50 is moved and positioned so as to align with the filter window 50h, and the ND filter 55 secondarily attenuates the light intensity. Then, thirdly, the second opening 22h finally attenuates the light amount. At this time, the second opening 22h also serves to deepen and improve the depth of field.

[0062] On the other hand, strong welding light can be reflected by the surface of each component as it passes through multiple components, causing ghosts (virtual images caused by multiple reflected light).

[0063] For reference, in the following description, the 'outside' of the surface of each component refers to the surface facing the welding light source, and the 'inside' refers to the surface facing the image pickup element 81.

[0064] Returning to the explanation of virtual images caused by reflected light, after the strong welding light entering at a slight angle of incidence with respect to the optical axis of the lens passes through the protective window 11, multiple reflections may occur between the outside of the ND filter 55 in the filter switching module 50 and the inside of the protective window 11, and between the outside of the lens (single focus lens; 60) and the inside of the ND filter 55.

[0065] These examples are examples of the possibility of reflections occurring between components, and when one or more reflections occur, the reflected light is directed away from the original incoming light and appears as a ghost (virtual) image in the captured image, which can cause double images in the image or the ghost to overlap the image of the important imaging area, resulting in a decrease in image quality.

[0066] To solve this problem, in the present invention, as shown in Figure 2, the filter switching module 50 is positioned at a predetermined angle so that it is not parallel to the protective window 11, so that the reflected light moves away from the central axis of the optical axis and is far away from the target subject to be imaged.

[0067] On the other hand, the observation distance (separation distance) of the camera from the welding torch needs to be changed depending on the conditions for observing the welding situation. When the distance between the lens and the image sensor 81 increases, the fixed focal length lens 60 focuses on a subject at a close distance. On the other hand, when the distance between the lens and the image sensor 81 decreases, the focus becomes on a subject at a long distance.

[0068] The fixed focal length lens 60 is attached to the inner peripheral surface of the lens holder 61 by screw connection. The outer peripheral surface of the lens holder 61 is provided with a screw thread, which is connected to a screw connection portion provided on the inside of the tip of the rear protective case 31. The observation distance can be set separately by adjusting the connection positions of the screw connection portions on the inner and outer peripheral surfaces of the lens holder 61.

[0069] Although the present invention has been illustrated and described above with reference to specific embodiments, the present invention is not limited to the above-described embodiments, and those skilled in the art will be able to implement the present invention in a variety of different ways without departing from the spirit of the technical idea of ​​the present invention as set forth in the following claims.

Claims

1. a protective window, a front protective case, and a rear protective case; the protective window is disposed at the front end of the front protective case; a first circular opening is provided in the center of the front surface of the front protective case; a filter switching module including a filter frame in which two filters with different characteristics are arranged side by side is installed behind the first opening, a second circular opening is provided behind the filter switching module; a single-focus lens is located behind the second opening; an image sensor is provided behind the single focal length lens; A digital welding vision camera characterized in that the central axes of the first opening and the second opening are arranged so as to be coaxial with the optical axis of the single focus lens.

2. The filter switching module includes:

2. The digital welding vision camera according to claim 1, wherein the camera is installed at a predetermined angle from a plane perpendicular to the optical axis of the single focus lens.

3. 2. The digital welding vision camera of claim 1, wherein the second opening is smaller than the first opening so as to attenuate the amount of light entering the single-focus lens, thereby improving the attenuation of the amount of light and the depth of field.

4. The filter switching module includes: The two filters having different characteristics are composed of a low-pass filter and an ND filter, and are mounted side by side on the filter frame, and are selectively exposed to a filter window by driving a driving unit, the low-pass filter is exposed to the imaging element before and after welding; During welding, the ND filter is exposed, and the first opening, the ND filter, and the second opening are exposed to welding light, respectively. The digital welding vision camera of claim 1 .

5. The digital welding vision camera according to claim 1 , wherein the filter switching module is disposed in front of the second opening.

6. The method for controlling a digital welding vision camera according to claim 4, According to the welding work situation, an arc detection reference value for determining the presence of a welding arc and an arc extinction reference value for determining the extinction of an arc are set, the light incident through the protective window is exposed by a combination of the first opening, the ND filter, and the second opening; monitor in real time the digital image data values ​​photoelectrically converted by an image processing unit with respect to the amount of light entering the image sensor; If the amount of light entering the imaging device is greater than the arc detection reference value, the ND filter is selected, and if the amount of light entering the imaging device is less than the arc extinction reference value, the low-pass filter is selected and exposed to the filter window. How to control a digital welding vision camera.

7. 5. The light amount control method for a digital welding vision camera according to claim 4, Attenuating the amount of the welding light while passing through at least one opening on a path through which the welding light passes; A light amount control method comprising adjusting the ND value of the ND filter to attenuate the intensity of the welding light, thereby adjusting the amount of light entering the imaging element.

Images