DE3438187A1 - OPTICAL HEIGHT MEASURING DEVICE FOR USE IN A NOISY ENVIRONMENT - Google Patents

Description

G 54 696 Ij

Elco R&D Associates
23. Jabotinky Street
Ramat Gan 52 101 - Israel

Optical height measuring device for use in a noisy environment

The present invention relates generally to an optical detector, and more particularly to an optical one Detector with high image resolution and high noise immunity.

In the field of automatic welding with the aid of robots, the height of partial surfaces along the Weld Bead Designated to Produce a Tidy Weld Bead The height of each face will normally be determined by an optical assembly containing a light source, e.g. B. a laser beam, which is directed towards the sub-area. The height is determined on the basis of the arrangement of an image of the light, which is reflected from the partial surface onto the surface of an array of light-sensitive cells. This arrangement is commonly referred to as an optical detector, or simply a detector.

It is understood that a high altitude resolution is required for good operation. Hence the altitude display signal should be quite high. With the currently used detectors either none or only one 5 of these requirements met.

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Cells of the order of 1oo Jum χ 2oo ^ m ensure high signals but low resolution. While CCDs guarantee high resolution but low signals.

In addition, the welding process is accompanied by significant noises. These include frequencies within the laser bandwidth. Despite filtering, the noise largely affects the performance of the detector. That is, the displayed altitude is subject to the noise. In addition, a large amount of smoke is generated during welding. This smoke often affects the size of the image projected onto the detector and thus its performance _; which is highly undesirable. The present invention aims to solve these problems.

The present invention consists of an arrangement comprising: ". ■

Means for directing a beam of light onto an element; and

an optical detector to receive light reflected from this element onto the detector to the height as a function of a preselected functional ratio of the performance of the cells of an array of cells forming part of the optical detector.

According to the invention, an optical detector is used which consists of a linear arrangement of a certain number of cells, e.g. B. 16 cells. Optical devices are provided so that the size of the Cells' reflected image is larger than one cell size and smaller than two cell sizes.

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The power output from neighboring cells is processed, to cause certain functions and the height of the element is based on one of these Functions are determined when they are between certain functional limits lies.

Assuming the image size is w and the size of each cell is d, we get d tv <2d. Is one called the Power output of neighboring cells with C- and C-, so the function caused for each pair of cells is as follows :;

^C i

One of these values of these functions is used to indicate the altitude.

According to a further aspect of the invention, optical ρ devices are provided to ensure that the size of the Image directed at the optical detector remains on the order of w, although the light passes through - Can step into a window that is partially obscured by smoke generated during the welding process.

The novel features of the invention are particularly set out in the appended claims. The invention is best illustrated by the following description in conjunction with the accompanying drawings:

Fig. 1 is a simple isometric diagram used to explain one possible use of the invention;

Fig. 2 is a simple diagram explaining the use of the optical detector for height measurements;

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Pig. 3 and 4 are diagrams explaining the basic aspects of the invention; and

5a and 5b are optical diagrams with which a novel optical arrangement of the present invention - will be explained.

- In Fig. 1, an optical device is shown above a welding robot 12 is arranged, which produces an arc 14. The function of the device 1O exists in arranging the weld seam 15 between the parts 16 and 17 to be welded, as shown at point 18. The arrangement of the weld 15 is ensured by determining the height of sub-areas thereof while moving moves the device along the weld and scans it to determine the lowest point of each face.

The optical device 1o is shown in Fig. 2, where a light source, e.g. B. a laser 22 light on the weld conducts the light onto an optical multi-line detector 25 is reflected by an optical system formed by lens 26. As every professional knows is the position on the detector surface on which the Light impinges in relation to the height of the surface from which the light is reflected to the detector.

According to a preferred embodiment of the invention the detector 25 consists of a linear arrangement of a plurality of photocells. For example, he exists from sixteen photocells, which are designated in Fig. 3 from left to right with C1 -C16. For the purpose of Explanation is assumed that the · directed to the cell CI Light represents a minimum height, while the light directed at cell C16 indicates the maximum height.

It is further assumed that the size (width) of each cell is d.

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According to the invention, the image of the light which is directed onto the detector 25 is formed by optical devices 26 so that its size, denoted by w, is always greater than 1d and smaller than 2d, ie d L w * - * 2a. As a result, the image of the light labeled 3o, which will be referred to below as the light spot, always illuminates more than one cell. As shown, the power output of each cell is directed to a signal processor 35. The order of magnitude of the output of each cell depends on how much of its surface is illuminated by the light spot 3o. For purposes of explanation, it will be assumed that the total cell illumination is equal to one unit or one (1), while zero illumination results in an output of zero (o), neglecting noise.

In contrast to the prior art, at least parts of two cells are illuminated by the light spot 3o.

According to the invention, the processor 35 prepares the output power of the cells to obtain an altitude reading which is a function of the output of two adjacent cells that are illuminated simultaneously, In short, the processor 35 generates a function f.

for each pair of neighboring cells, i. H. Ci and C2, C2 and C3 etc.,

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in which f. = and C and C. the tax is easy to do-

^lf J ■ C + C. ^J

genes of cells C ^ and C.

Assuming w is equal to 3/2 d and only half of C2 is illuminated while C3 is completely illuminated, then f ₂ ο = ^O> ^ ~ ¹ = - ° ' ⁵ = -o, 33 represents a specific one

ος 'o, 5 +1 "1.5 ■

^{J :?} Height.

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Should the height increase slightly (the light spot 3o moves to the right), then there would be less of C2 and a Part of C4 to be illuminated. For example, if 4/10 of C2, the entire area of C3 and 1/10 of C4 are illuminated, the processor generates 2 and C3 and for C4 ■ for C3 and C4 the following functions

o.4 - 1 0.6

- ^f 2,3 = Ö74-TT = - TT4 = - ° ' ^{428 and}

1 - o, 1 o, 9

f, _A = = = 0.818

^3t * 1 + o _f 1 1.1

If the output of each cell C2 and C4 is 0.25 and that of C3 is a unit, one obtains

o, 25 -

f _p . =

while

^J ^ 1 + 1.25
2o

It is clear from the foregoing that a slight change in the height, which results from a slight movement of the light spot 3o, causes a significant change in the functional value. In some cases, for a given position of the light spot, which represents a specific height, two adjacent functions have different values, for example f - = -0, β and f_ . = + 0.6.

It should be noted that each function is largely S-shaped with a central largely linear part in which the change in the function value proportional to the Change in altitude is. Also, as from the foregoing emerges when the light spot is arranged so that it fully illuminates a cell and at the same time adjacent., bare cells illuminated on opposite sides, the

represent the same height but with the opposite sign, e.g. B. f _o , = -0.6 and P-. = +0.6. These properties are used by the processor 35 to select the function, the value of which is then used to provide the altitude indication signal.

In short, the detector is first calibrated by moving the light spot 3o from one end of the detector arrangement to the other end, so that the light spot is reflected from different heights. The functions are generated for each position of the light spot and the value of the function is recorded in its linear part. At the end of the linear range of a function • the corresponding value of the adjacent function is used for the same position of the light spot. For example, if f _o _ = -0.6 represents a certain height, then the function f_. = +0.6 passed over to the same

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Represents height. This process continues until a specific value of a function within for each level its linear range is determined.

This process can be described in connection with FIG in which only three functions f_ _, f-. and f are shown, with the crossovers taking place, when adjacent functions have values of -0.6 and +0.6. The vertical direction of each function is represented their values, while the corresponding heights are horizontal.

be in operation in order to determine the unknown height of a part surface along a welding seam or the like, the output capacities of the cells C1 -.. C16 first processed once, f the functions _ to generate f _o ,, etc. Then it is determined which function produces an output that is within the linear range of the

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Function lies, ζ. - ⁰ . + ο, 6 to -ο, 6. Then the power output is used to locate an altitude value derived during the initial calibration for that value of this function. Successive outputs of the same function are used to: - derive height values based on the generated values of the function. When "the AbgabeIeistung function then reaches one of its linear boundaries, z. ^B. -O.6, the values of the next function to be used to determine consecutive height values.

It should be noted that, since elevation values are determined not as a function of the light on a cell, but rather as a function of the light on at least two cells, the detector according to the invention is largely immune to noise is. This is due to the fact that noise affecting one cell also affects the neighboring: · Cell: affects and the difference is turned off. So there here ■ the power output is only a function of two cells out of a large number of cells, for example 16, the noise affects. which affects the output of the other cells, not the output power of the novel detector according to the invention.

The optical detector according to the invention can therefore work successfully and precisely in a noisy environment

The foregoing were the functions performed by the signal processor 35 are clearly described. It was made clear that he was equipped with arbitrary circles can be to provide the following service:

1. Generation of the functions f., Z. B. f. _O , f _o «etc. 2. Determination of the function whose value lies between

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predetermined upper and lower limits, ζ. B. +0.6 and -o, 6.

3. Using the value of the selected function to determine the peak value based on the pre-calibration.

4. Switching to the use of values from an adjacent function when the value of a function that was previously used reaches its linear limit,

z. B. the value is equal to or greater than +0.6 or equal to or less than -0.6.

Since circles that can carry out individual or all of these operations are known to the person skilled in the art, must they are not described in detail here. It is also clear that all of these operations can be performed with one Calculator that is programmed on the basis of the functions that are performed and which have been described. Based on the description can vary depending on the used. Calculator different programs are created. The foregoing description is sufficient to make anyone knowledgeable To allow programmers to create the appropriate program without having to be inventive would have to.

It is clear that the novel optical detector is based on the fact that the size of the light image or light spot is equal to w, which value is larger than a cell dimension d and smaller than 2d. Typically, the light reflected from the workpiece to optical system 26 (see FIG. 2) passes through a transparent window indicated by line 50 in FIG. The ^T ASK 5o of the window is

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in letting only the light pass through while polluted Air, for example smoke, which is produced by welding, is retained. Because of that smoke od ". Like. There is a risk that the window is partially fogged and so the amount of light is reduced, • who got through this window. This in turn would affect the size of the Lichtfleclcs 3o and him reduce more than desired. In other words, the size of the light spot 3o can be d or less sink, which would affect the overall operation of the detector. There could also be a shift in occur at the position of the light spot, which would result in an incorrect height display.

This problem has been solved by a novel optical arrangement 26 which, for the sake of simplicity, is shown in FIG. is represented by lens 26 only. The novel optical assembly 26 is best used in conjunction with FIGS. 5a and 5b described, to the now reference ge - is taken.

5a shows a classic optical arrangement in which a light source 6o of a predetermined size reaches a lens 62 through a window 5o. By suitable selection of the lens and the distances, an image 65 of predetermined size of the light source 6o is formed. The image intensity is normally Gaussian or bell-shaped and is designated by the number 66 in FIG. 5a. The intensity runs symmetrically about the axis 7o of the optical arrangement. .

However, if the window 5o is partially fogged, as indicated in Fig. 5a by the number 75, so that a part, for example the lower half of the source 6o is covered, the image size would not be that

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same as described above. In fact, the size of the image 65 would only be half with one Intensity distribution, which is denoted by 66a. Although the intensity peaks are about the same, the one is offset from the axis by a value Ah from 66a. This replacement means an error in the altitude display due to smoke or the like on the window 5o. From this it becomes clear that classical straight optical arrangements cannot be used in which the light must pass through a window which is obscuring or partially can become opaque.

Reference is now made to Fig. 5b, in which the The solution offered by the present invention is shown. According to the invention, the lens arrangement comprises 26 a single optical element 8o and a plano-concave lens 62x, which is arranged in front of the element 8o.

The flat side 82 of the element 8o lies on the flat side of the lens 62x, while the opposite side of the element 8o a plurality of small cylindrical plano-convex lenses. 85 forms. That through these little ones Light entering lenses converges and forms image 65. The contribution of these lenses to image 65 is such that that although part of the window is covered, for example by smoke 75, the size of the image 65 is largely remains constant. The image intensity is that of a mesa with a plateau of even height with two steep narrow sides. In contrast to the arrangement shown in FIG. 5a, in the novel arrangement according to Fig. 5b the fogging of the window 5o, d. H. the reduction in the size of the source 6o is only a reduction in height the intensity of image 65 without affecting its size. In Fig. 5b, the intensities of the image are without nebulized window or with partially nebulized window designated 9o and 91.

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In one embodiment, which was reduced to practice, a lens 62x with f = 4o and an element 80 with cylindrical lenses with a width, d = ο, 55 mm and a radius R = 50 mm or f = -I00 were used, around a mesa-shaped image 9o with a plateau width of. 200 ytm with beveled sides of 52 ym each. at a distance of 45 mm from the flat side of the lens 62x and 9 mm from the flat side 82 of the element 80. Partial obscuration of the window 5o only affected the height of the picture, not its width.

Although above special embodiments of the invention It goes without saying that the person skilled in the art could make changes and changes and therefore it is intended that the claims be interpreted to accommodate such changes and variations cover.

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Claims (10)

Claims 1. Optical height measuring device for use in a noisy environment _ environment, especially for welding robots, ο characterized in that there is an array of photosensitive cells (C) with the essential - - loan size (d), each of which has an output power in relation to the impinging on the cell light field, means (26) to a light spot size to direct w onto cells (C) of the cell arrangement, where d <w <2d, so that the light spot (30) impinges on at least two adjacent cells, and Means (35) for signal conditioning connected to these cells (C) are to receive their output and a signal (40) 15 to produce the value of which is a function of the output powers of at least two neighboring cells. 2. Apparatus according to claim 1, characterized in that the function is defined as follows: C. - C.
ι J C. + C.
ι J where i and j are two neighboring cells and C. and C. are the output powers of cells i and j. 3. Apparatus according to claim 1 or 2, characterized in that the Cell arrangement has a linear arrangement of a predetermined number of cells (C). 4. Device according to one of claims 1 to 3, characterized in that that the means (35) for signal conditioning means for generating signals, the value of which is a function of the output power different rows of adjacent cells, and to select the - 14 COPY . Value of the signal from a function if this value is within which is located for the function predetermined limits. 5. Apparatus according to claim 4, characterized in that the function is defined as follows: C. ₊ C. where i and j are two neighboring cells and C. and C. are the output powers of cells i and j. 6. Apparatus according to claim 5, characterized in that the cell arrangement a linear arrangement of a preselected number of cells (C) - comprises. 7. Device according to one of claims 1 to 6, characterized ⁿ gekennzeich et that it for guiding a robot (12) along a path (15) as a function for determining the height of each partial area of the path, a light source (22) to a light beam to direct an array of photosensitive cells at the patch of the path from which light is reflected as a function of the height of the patch (C) in the path of reflected light, being the size of each cell is largely the same and is defined by d, optical means (26) between this path and this arrangement to adjust the size of the light spot (30) which impinges on the cells of the array, so that it has the size w, where d <w <2d, whereby the light spot appears on at least two neighboring cells at all times, and means (35) for signal conditioning responsive to the output powers of these cells to be an altitude indicating signal To ensure the function of the cells on which the light spot is pointing meets, has. Copy - 15 - 8. Apparatus according to claim 7, characterized in that the means (35) for signal processing facilities for generating Functions for neighboring cells i and j include ", where the function C. - C. rc: C ¹ y is where C. and C. are the outputs of neighboring cells i and j are to select a value of one of these generated functions, which is included in falls predetermined limits, and to provide an altitude indication signal that is related to the chosen value of one of these functions. 9. Device according to one of claims 1 to 8, characterized in that that a largely directed in a selected direction 20 Beam of light and optical means in the path of the beam of light to produce an image of the beam of a certain size which is independent of the size of the beam impinging on the optical means are provided. 10.Vorrichtung according to claim 9, characterized in that the optical Means including an element one side of which defines a plurality of cylindrical convex lenses (62). - 16 -