JPH0230643B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an optical rangefinder suitable for example, but not exclusively, for automatically tracing weld lines, and in particular to almost completely eliminate noise. related to what was done.

For example, welding robots are well known in order to automatically follow welding lines and perform welding. Various proposals have been made in the past as optical distance sensors for this tracing (for example, Japanese Patent Laid-Open No. 1983-1999).
46065 and Japanese Unexamined Patent Publication No. 57-511). However, with conventional optical systems, it is always a challenge to eliminate disturbances caused by noise caused by strong arc light, especially during welding.

By the way, in optical measurements, if a sufficient amount of light for measurement cannot be obtained, it is difficult to distinguish between signals and noise. Therefore, when measuring in a place where there is no difference between the surrounding brightness and the light intensity of the measurement light source, which varies depending on the location, the light source is intermittent, and the image signal when the light source is disconnected is different from the image signal when the light source is connected. A method for identifying a signal to be detected by taking the difference is known from Japanese Patent Laid-Open No. 56-64605. However, such a method is not suitable for emitting light onto a local area with strong noise that fluctuates over time, such as welding light, and measuring the amount of received light.

The present invention aims to provide an optical distance meter for tracing that can almost eliminate the influence of such noise.

The outline of this invention is that the distance measurement direction includes a light projecting means including a light source intermittent means whose optical axis is inclined and whose period is 2Ts, and a light spot on the object to be measured by this light projecting means is included in the field of view. A first light receiving means provided with a means for detecting information (St+Nt)n on point n at time t and information (Nt ₊ Ts)n on point n at time t+Ts in the field of view, the light point not being included in the field of view; A second light receiving means has a field of view in the vicinity and is provided with a means for detecting information NMt at time t and information NMt+Ts at time t ₊ Ts of the entire field of view, and these optical systems are arranged approximately along the measurement target. The apparatus further comprises a control means, which includes at least a means for calculating _NMt+Ts /NMt(St+Nt)n−(Nt _+Ts )n. , an optical distance meter for tracing.

The information of the first light receiving means that includes the light point in its field of view is information around the light point when the light source is intermittent, and the noise contained therein does not vary due to the intermittent light source, but it depends on the surrounding situation. It changes over time with changes in , and it is not possible to detect a signal by taking the difference. On the other hand, the information of the second light receiving means, which does not include the light spot in its field of view, detects only the fluctuation of surrounding noise, and this noise fluctuation also applies to the light spot portion. Therefore, it is safe to consider that N _t+Ts /Nt≒NM _t+Ts /NMt=b. The present invention does not simply subtract noise from signal plus noise to obtain a signal, but instead obtains a signal by subtracting noise from the signal plus noise multiplied by b.

An embodiment of this invention will be described in detail below with reference to the drawings. Although FIG. 1 provides the background of the present invention and shows an embodiment of the present invention in an effective welding robot, the present invention is not limited to this embodiment.

R is a welding robot having a mechanical configuration of a rectangular coordinate (XYZ) system, and is provided with a welding torch T as an end effector. The robot R is controlled by the torch T by a well-known computer (mainly composed of a CPU and memory) CO as a control means.
It is configured to control the position, etc. of the device by known means. Then, the torch T moves along the developed welding line WL of the work W to perform welding.

D is an optical system of an optical rangefinder according to an embodiment of the present invention, and has the following configuration.

1 is a light source. The light source 1 uses a light source containing a specific wavelength, for example a He--Ne laser oscillator.

Reference numeral 2 denotes an optical fiber that guides the light from the light source 1, and its tip 2a is configured as a microlens (for example, SELFOC manufactured by Nippon Sheet Glass Co., Ltd.). Thus, the optical fiber 2 and the microlens 2a
The focused light projecting means _L1 is constituted by the above. Note that the light projecting means _L1 is provided so that its light projecting direction is inclined with respect to the distance detection direction (in this case, the Z direction).

The light projection means _L1 further includes a light source intermittent means 2b. The means 2b in this embodiment is a light projecting means
The disk is rotated by power 2c during light emission at _L1 , and the light emission is interrupted at a period of 2Ts by means of a hole on the disk. In this embodiment, the time lengths of the disconnection and continuation of the disconnection means 2b are approximately equal.

The configuration of the first light receiving means _L2 will be described below.

3 is a condensing lens as a front lens system.
The lens 3 has a diameter A on the welding line WL of the focused light projected by the light source 1 via the optical fiber 2.
The light point P is included in the field of view and is arranged to form an image thereof.

4 is a one-dimensional image guide. This one-dimensional image guide 4 has a minute diameter (for example, a diameter of 0.05
It is a rectangular bundle of 100 x 6 optical fibers (mm). And the front end 4a of the guide 4
In this case, the lens 3 is positioned on the image forming plane. Further, the longitudinal direction (that is, one-dimensional direction) of the rectangle of the front end 4a is arranged on a plane including light emission and light reception (parallel to the YZ plane in this embodiment) and in a direction perpendicular to the light reception.

Reference numeral 5 designates two sets of condensing lenses as a rear lens system provided facing the rear end 4b of the guide 4.

6 is a filter inserted between these two sets of lenses that allows only a specific wavelength of light from the light source 1 to pass through. The lens 5 is configured to project parallel light rays onto the filter 6.

Reference numeral 7 denotes a one-dimensional image sensor, which is provided on the imaging plane of the lens 5. The one-dimensional direction of the image sensor 7 is configured to be the same as the longitudinal direction of the rectangle of the rear end 4b. It is also assumed that the image sensor 7 has, for example, 512 light receiving elements arranged in one dimension.

Reference numeral 8 denotes a known A/D converter, which is configured to input the output of the image sensor 7 and convert the information into numerical values.

The configuration of the second light receiving means _L3 will be further described below.

Reference numeral 9 denotes an optical fiber of a light receiving optical system whose tip 9a is a microlens, and is constructed so that the light point P within the distance measurement range is not included in its field of view. Further, it is desirable that the diameter B of this field of view is set to be approximately several times the diameter A.

A known photodiode 10 is connected to the rear end of the optical fiber 9 and is configured to measure the brightness of the visual field of the optical fiber 9.

Reference numeral 11 denotes an A/D converter, which is configured to input the output of the photodiode 10 and convert the information into numerical values.

In each of the above configurations, the intermittent timing signal of the means 2b and the output signals of the A/D converters 8 and 11 are both input to the computer CO.

The optical system D consisting of these means L ₁ , L ₂ and L ₃ is attached to a frame (not shown), and is placed in front of the torch T in the traveling direction (X direction in the drawing) using a known structure, although details are not shown. It is assumed that the structure is configured to be able to swing symmetrically in the left-right direction (Y direction in the drawing) with respect to the main body.

The effects of the above-mentioned embodiments will be described below.
See also Figure 2.

The light flux from the light source 1 passes through the fiber 2 and is focused by the lens 2a, forming a light point P on the surface of the welding line WL.
Connect.

This light point P is imaged by the lens 3 on the front end (4a) of the guide 4 as P'.Then, this image passes through the guide 4 and reaches the rear end 4b.The image at the rear end 4b is parallelized by the lens 5. It becomes a light beam and passes through the filter 6. At this time, since the filter 6 passes only the wavelength of the light source 1, only a small part of this arc light passes through this filter while the torch T is in welding operation, so the S/N ratio is Furthermore, since the light in the filter 6 is parallel, its characteristics will not be impaired.

Thus, the image at the rear end 4b is formed on the light receiving surface of the sensor 7, and its output is sent to the A/D converter 8.
digitized by , and input into the computer CO. This input information is expressed as (St+Nt)n. Here, St is the brightness of the image of the light point P by the light source 1 at time t, Nt is the brightness of the image due to noise (for example, the arc light of the torch T) at the same time t, and n is the nth element of the image sensor 7. It is a number that represents

Each process performed by the computer CO will be explained below.

The computer CO uses the light source intermittent means 2b to determine whether the focused light of the light projecting means _L1 is in the "continuation" state (processing _PR1 ).

At time t in the "continue" state, the computer CO converts the output from the image sensor 7 into an A/D converter.
Input via converter 8 and store (processing)
_PR2 ). This input information is as described above (St +
Nt)n, where n is 1 to 512. It should be noted that the information in this case is the sum of the brightness St due to the light spot and the brightness Nt of noise due to the torch T, etc.

At the same time, the computer CO inputs the output from the photodiode 10 via the A/D converter 11 and stores it (processing PR ₃ ). This input information is
It is NMt. This is because the field of view of the optical system connected to the photodiode 10 does not include the light point P.

Next, it is determined whether or not time Ts has elapsed (processing PR ₄ ).

When the time Ts has elapsed, the light projection is blocked by the means 2b, and the output of the A/D converter 11 at this time is input and stored (processing PR ₅ ). The input information at this time is NM _t+Ts .

At the same time, the computer CO inputs and stores the output from the image sensor 7 (processing PR ₆ ). This input information is (Nt _+Ts )n.

The computer CO then calculates NM _t+Ts /NMt(St+Nt)n−(N _t+Ts )n using the values stored above. If this value is obtained as a value for n=1 to 512 (processing PR ₇ ), information related to the intensity of light at each n, from which noise has been substantially removed, can be obtained using this value.

The reason for this will be explained in detail below.

Since the position of the light spot P moves between times t and t+Ts, the reflectance naturally differs slightly, but since this moving distance is generally small (for example, 1 mm), objects whose reflectance changes rapidly depending on the surface position are excluded. Then, b=NM _t+Ts /NMt≒N _t+Ts /Nt, and since Nt+Ts≒ bNt, b(St+Nt)n−(N _t+Ts )n≈bSt.

Using the information from which noise has been substantially removed in this way, the distance between the torch T and the surface of the workpiece W can be determined based on where the maximum brightness is at each position in n=1 to 512. That is, if the distance in the Z direction between this embodiment device and the surface on the workpiece W is short, the light point will be P ₁ , and the image on the front end 4a will be P' ₁ on the right side in the figure; _P2
Therefore, the image becomes P′ ₂ on the left. Therefore, the distance to the surface on the workpiece W can be measured based on the position of the image on the sensor 7 in the left and right direction.

By the above-mentioned left and right rocking of this embodiment device, the center of the rocking and the center of the welding line WL depend on at which position in the rocking the farthest point on the surface of the workpiece W is detected. (deepest part) can be detected in the left and right direction. The computer CO controls the Y direction in a direction that eliminates this deviation, and
Further, while controlling the Z direction to optimize the distance between the torch T and the workpiece W, the torch T is advanced in the X direction following the welding line WL to perform groove welding.

In this way, it is determined whether or not the tracing of the welding line WL by the torch T has been completed (process PR ₈ ), and processes PR ₁ to PR ₇ are executed cyclically until the process is completed.

In addition to the embodiments described above, this invention can also be modified as described below.

(a) In addition to a laser oscillator, the light source 1 may be, for example, a colored light source in which a color filter is attached to white light.

(b) Only the components 2a, 2b, 3, 4a and 9a are integrally mounted on a frame (not shown) and swung left and right, and the components 1, 2, 4 to 7 and 9,
Each of the components 10 may not be allowed to swing from side to side.

(c) The detecting device of the present invention may be swung integrally with the torch T instead of with respect to the torch T.

(d) The lenses of the front and rear lens systems may be semicylindrical lenses instead of spherical lenses.

(e) The filter may be provided on the lens 3 side.

(f) The means for moving the optical system may be any other type of industrial robot, or may have a configuration other than a so-called robot.

(G) The intermittent time of the means 2b may be set to be different instead of being the same.In short, since accurate information cannot be extracted in a very short time due to the function of the sensor 7, it should be determined appropriately.

(H) Other replacements of each component with equivalents within the scope of the technical idea of this invention are also included within the technical scope of this invention.

As described above, this invention provides a second light receiving means for measuring noise in the vicinity of the light spot P, measures this noise when the light spot occurs and disappears, calculates the ratio, and calculates the distance to the light spot. Since the noise in the output of the first light receiving means is processed as the noise measured by the second light receiving means, even if strong noise is mixed in, such as from a welding torch, the accuracy can be maintained. It is possible to measure long distances.

[Brief explanation of drawings]

The drawings all show one embodiment of this invention, and the first embodiment is shown in the drawings.
The figure is an overall perspective view, and FIG. 2 is a flow chart. 1...Light source, _L1 ...Focused light projecting means, 2b...
...Light source intermittent means, WL...Welding line (measurement object),
P...light spot, _L2 ...first light receiving means, _L3 ...second light receiving means, R...robot (means for moving the optical system), CO...computer (controlling means).

Claims (1)

[Claims] 1. The distance measurement direction refers to a light projecting means including a light source intermittent means whose optical axis is inclined and whose period is 2Ts, and a light point on the object to be measured by this light projecting means in the field of view. Contains information on point n at time t in this field of view (St
+Nt)n and information on point n at time t+Ts (Nt _+Ts )n; a first light-receiving means having a field of view in the vicinity that does not include the light point; comprising a second light receiving means provided with means for detecting information NMt at time t and information NMt+Ts at time t+ _Ts , and means for moving these optical systems at a certain speed substantially along the measurement target, An optical distance meter for tracing, further comprising a control means, the control means including at least a means for calculating NM _t+Ts /NMt(St+Nt)n−(N _t+Ts )n.