DE1573955A1 - Device and method for recording optically recognizable surface defects, e.g. in wood - Google Patents

Description

Godfather Irish, v sit

Karl A. L-irosa _Λ - """Tr

Dipl.-Ing. , 1573955

8023 Munich - Pullach

WienerStr.2 - Tel. Munich 790570

to 774 Munich-Pullach, December 6, 1966

Gerald Lester Watson, 12 89o Southwest 63rd Avenue, Portland,

Oregon, USA and

Donald Lawrence Stradley, Route 4, Box 322A, Sherwood, Oregon, USA

Device and method for recording optically recognizable surface defects, e.g. in the case of »wood

The invention relates to a fault detector for detecting Defects in products and in particular a detector for the automatic sorting of such products.

Plywood, veneers and the like are looking for color defects and color deviations sorted. For a specific purpose, for example, board or veneer material may be required, which has a minimal number of knots or other color defects, while for others Uses a product with a larger number of branches can be worn -'or even desirable. When processing boards, strips of veneer and the like, defective sections can then be produced marked and cut out, after which the defective section is replaced.

Some products, such as chipboard, can be completely unusable if the detected color errors indicate an incorrect composition of the plate. With other products it can happen that they are delivered with an excessively rough surface, which means that further surface processing, e.g. sandblasting is required. Anyway, it is

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visual examination of the material to determine such color deviations or errors not only time-consuming and exhausting, and thus economically disadvantageous; furthermore, checking with the eye is by no means a guarantee always a uniform sorting of the material.

The invention is therefore directed to the Sehaffun. one automatic device for detecting color deviations in products. The invention continues to a facility that sorts material quickly and automatically according to standard criteria, with the defectiveness eliminated from human observation.

According to the invention, a material strip which has color errors, color deviations, knots (in boards) or the like, optically with means generating an electrical output signal sampled »where the amplitude of this signal is from the light reflection depends on the material examined. At the same time there is a relative movement between the optical scanning device and the material to be examined so that the entire surface of the material is scanned. So then has for example the electrical output signal is a given level when scanning a standard or norm wood surface but at a different level if the scanning beam detects a darker point on the wood surface, e.g. originates from a branch or the like.

A suitable scanning device is zlB. from a television camera formed, which optically scans the image of the material strip across the width and a signal with greater amplitude generated when a darker or incorrectly colored area is being scanned. The output of the television camera can be used be given to a level detector which is set in this way

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is that it only gives an output if the video information the television camera rises above a predetermined standard value. Reflections from such wooden surfaces that show no errors, then generate an output on the television camera that does not exceed this standard value. If, on the other hand, the camera then detects a branch or the like, then the level of this hormone value of the level detected gate rises and this latter gives an output variable se. An actuating device can then use the output variable of this level detector to mark or reject the faulty iuaterial in operation, .us can also use a Number of such detector outputs indicating Pe.zel are counted and the air material can then be sorted accordingly will.

In one embodiment of the invention, the scanner exercises make a first repetitive downstroke over the moving material to find flaws, and then again to produce an output when a perfection is captured. If an imperfection; a second scan is used in parallel to the first scan, to determine whether the detected color mismatch or the detected error in the area between the two scans lies. If this is the case, the material can either be rejected or the additional registration can be added in a counter to the originally recorded color deviation, whereby the material is classified lower which has errors that are larger than the distance between two scans.

In another embodiment of the invention, the scanning device sorts Material due to surface roughness. The material is illuminated with polarized light

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and a polarizer detecting this light is placed between the material and the scanner. Surface roughness changes the .aruchteil the reflected light to the scanning device and thus causes a change in the output signal the scanning device.

Further advantages and details of the invention can also be found in the description of exemplary embodiments which now follows referring to the drawing. In this show:

FIG. 1 shows the block diagram of a first circuit according to the invention;

FIG. 2 is a waveform diagram for explaining the operation of the circuit of FIG. 1;

Pigur 3 shows a further embodiment of the device according to the invention in the block diagram!

Pigur 4 schematically shows a Pernsehraster which can be used in carrying out the invention can;

FIG. 5 schematically shows a mechanical transducer for use in the device according to Pigur 3; and

FIG. 6 shows a further mechanical converter which can be used in the circuit according to Pigur 3 .

In the first embodiment of the invention A circuit block diagram of the Pigur 1 is a television camera which is arranged in such a way that a Strip or a board 14 made of wood is detected, which is moved on a conveyor belt 16. The conveyor belt 16 moves the material 14 in the longitudinal direction perpendicular to the plane of the drawing

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past the camera 1o. In this embodiment, 1o a conventional television camera with an associated amplifier and it generates one or more line scan grids across over the board 14 or its picture and that in the direction of arrow 18 from one side to the other. The scanning movement is repeated quickly and can such a movement of a conventional television grid with 525 lines be, these lines running transversely to the direction of the material 14. Corresponding to one or more of the scanned lines Video information is available at output 2o. This output is shown graphically in FIG. The output signal has sync pulses 22 with a horizontal blanking pulse and horizontal sync pulses on, the signal continuing to carry the video information between the sync pulses. When the camera performs a scanning movement in a direction perpendicular to the direction of movement of the material 14, becomes a lighter colored one or gray background 24 on each side of the video information between each such information 26 and the Synchronization pulse 22 appears. The video signal 26 remains at a relatively constant during each scan Level when no error is detected, i.e. that the light reflected to the television camera is from a normal Wood surface comes that does not show any major defects in this area. Due to the relative movement of the material 14 on the conveyor belt 16 with respect to the television camera 1o as well as the repetitive sampling results in continuous video information for each slightly switched on Areas of the material, so that all of the material 14 is inspected or checked. You can get one or use multiple scans for each raster or even the whole raster if necessary. The material is illuminated in a manner not shown so that it is for the

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TV camera is visible.

The respective output 2o of the camera Io is given as an input to a level discriminator 28. This discriminator does not generate an output variable as long as the video information 26 has a relatively constant value, which is indicative of the fact that the examined surface does not have any significant errors. If, however, a branch or other disturbance is detected by the television camera on the board 14, then a peak 3o appears in the video information (FIG. 2) because such a branch is darker in color than the wooden surface surrounding it, in the exemplary embodiment shown the peak 3o cannot put the level discriminator 28 into operation because it does not reach up to the interference level 32. The next sampling of a further part of the disturbance, ie in this case the assumed branch in the wood, produces a peak 3oa, which in turn reaches the limit level 32 of the level detector 28, which causes an output from the detector 28 to be emitted. In the same way, the tip 3ob produces an output at the discriminator 28.

The level detector 28 is expediently a Schmitt trigger, with a threshold value level 32 at which a continuous Output is generated and a second threshold value 34 at which the output of the circuit is switched off. Of the The area between levels 32 and 34 is called the "hysteresis area" called the Schmitt trigger. When an input signal applied to the Schmitt trigger exceeds level 32 and then remains above this level or within the hysteresis range, then a continuous output is produced. Although such a Schmitt trigger is particularly twofold for the Generation of such waveforms that the subsequent circuit elements can operate, as described below

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will be written, other switching elements can of course also take its place, which then generate an output, if the input applied to the other switching part exceeds a certain value.

The output of the level discriminator 26 formed by a Schmitt trigger in FIG. 1 is sent to a first monostable Circle 34 and placed on an AND gate 35. The mohostable circuit 34 can expediently be formed by a Uni-Vibrator, (one-shot multivibrator), deim applying the output 32 to the In the mono-stable circuit 34, the latter generates an output 36 for a predetermined time, which begins at the end of the output 32 from the level discriminator 2Θ. Triggers in a similar manner the output of the one-shot circuit 34 a second one-shot circuit 38, the output 40 of which continues for a predetermined time after the end of the output 36 from the one-shot circuit 34. The output 4o is applied together with the output variable 32 to the AND gate 35, which itself only then generates an output 42 when signals 32 and 4o coincide. This output signal 4-2 resulting from coincidence triggers a bistable flip-flop 44 * which thereupon from a first State into a second state that generates an output signal transforms. The output of the flip-flop 44 is 46 (see Figure 2) designated. This signal 46 is used to drive an actuating or working device 48, for example a marking device or a display device or, for example, a relay for rejecting or rejecting such a board 14, its Errors go beyond a predetermined standard value. A single such control device is sufficient, for example, if the board 14 is a chipboard or the like, in which when a certain degree of failure or a certain disturbance the plate is sorted out, i.e. no longer to be used.

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In addition to the discrimination with the discriminator 28, the circuit according to FIG. 1 also performs the function of a touch signal only to be supplied while video information is available from camera 1o. When the camera 1o generates a synchronization pulse 22, this synchronization pulse exceeds the hysteresis range of the 'Schmitt trigger' Discriminator 28, whereby an output signal 32 is generated which is used to trigger the monostable circuit 34 at the end of the pulse 32. The signal 36 at the output of the monostable Circle M is an impulse with a relatively short duration, the then ends when the gray background is scanned before the edge of the material reaches 14 from the scan will. At the end of the pulses 36 at the output of the monostable Circuit 34, the monostable circuit 38 is triggered, which in turn generates a signal output 4o, the while a video signal 26 is being applied, the gray area on the other side of the material is scanned 14, which pulse ends before the next synchronization pulse 22 occurs.

x-a the output 4o of the monostable circuit 38 and the Output 32 of the level discriminator 28, both of which are stored at the AND gate 35, must be on these two inputs at the AND gate Signals are present so that it is actuated. The output pulses 32 of the discriminator 28, which with synchronization pulses 22 coincide, do not produce an output 42 at the AND gate 35. However, if a peak 3oa appears in the video signal, causing a Disturbance is indicated in the scanned material, then the output 32 of the discriminator 28 coincides with the gate output signal 4o and the bistable flip-flop 44 is triggered, which in turn is now the continuous output variable 46, which in turn is indicative of the defect in the material being scanned.

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The bistable flip-flop 44 has a memory which stores the detection of a defect in the material 14 to the circuit is reset in a conventional manner via a ground line 5o. This is expedient by causes a micro switch, not shown, with the Line 5o is connected and through the rear ünde of the material 14 is closed when this runs over the switch, so that at this moment the line 5t »is grounded will.

Although a conventional television camera has been described in connection with this embodiment, and although it does a very useful solution, especially because of the possibility the generation of precise signals, especially because no consideration has to be given to stray light, Other optical scanning means can also take their place, for example a light point scanning with a corresponding Find synchronization circuit instead of the television camera 1o application.

the embodiment of Figure 3 also probes a TV camera 1o the strip of material 14 made of plywood or Veneer sheet, which is moved by the conveyor belt 16. The material 14 is directed against the material Light source 52 is illuminated through lens 54. That Light also passes through a first polarizer 56 before it hits the material 14 in order to transmit the light transversely to the Direction of movement of the material 14 and parallel to the scanning direction of the TV camera 1o to polarize. The light is reflected from the material 14 and the mirror 58 and enters the television camera through a second polarizer 6o. The polarizer 6o is aligned in such a way that it is normal

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sometimes the polarized light that lets through from a standard surface of the material 14 passes through. That This means that the polarizer 60 is oriented along the same optical axis as the polarizer 56.

Scanning the television camera 1o results in a Haster 7o, like it is shown in FIG. 4, which consists of "horizontal" individual panels lying parallel to one another at a small distance consists. The third and the fifteenth such individual scan are denoted in FIG. The video output the television camera 1o is fed to the AND gate 62 in Figure 3, while horizontal and vertical trigger signals, those with the horizontal and vertical synchronization pulses from the television camera are applied to the counter 64. These trigger signals are stored in the TV camera preferably by differentiating the horizontal and vertical return stresses are obtained. Daa applied via line 66 vertical trigger signal of the TV camera 10 starts counting in counter 64. The counter 64 then counts the horizontal trigger pulses applied via the line 86 and the numerical content of the counter shows on the yfeise those carried out by the television camera 1o Scans on. When the counter 54 reaches a predetermined content, e.g., a content of the fifteenth count (See Figure 4), then the counter 64 generates an output signal 52 for application to the pulse generator 74. The Pulse generator 74 then generates an output signal 76 which is applied to the AND gate 62 as a switch-on input. The AND gate 62 then reads alao during this particular scan, i. in the selected embodiment example of the fifteenth scan, the video information through.

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The Auajario 76 of the AND gate 72 is optionally available with one of the Pe ^ eI A detecting level detector or discriminator 8o by means of the switch 81 ^ elegt. When the output of the TV camera reaches a predetermined level, the level A discriminator 8o generates one Output on line 82 which is then applied to a counter 84. The counter 84 counts the number of times the video output exceeds the predetermined level in de: a discriminator 6o, So the content of the counter 84 is a measure of the quality (with regard to freedom from mistakes) of the .TV camera seen material.

Further circuit elements beyond the counter 84 are then actuated depending on the number of defects found in the material. Assuming that the counter 84 has a predetermined minimum count, the actuating device is energized by the gate 88. When the counter but a ".to a sere count comprises indicating a _fa Tössere number of Dehlern, then the actuator ^ o dai3 is operated by a second output of the counter 84 via ifis gate 9έ and the latter is connected in such a way it In any case, the gate 88 is locked via a blocking line 94. Even a larger content in the counter Ö4 causes an actuation device 96 to be excited via the gate 98, the latter blocking the gate 92 via the blocking line 100 in such a way that it cannot go into operation. These blocking lines 94 and 100 have the effect that more than one actuator can never be put into operation at any one time.

The actuators 86, 9o and 96 can Itelais or have other corresponding components, with the help of which aan

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the material 14 can sort. For example, a strip of material 14 has a certain minimum number of errors, thus also a certain minimum count in the counter 84 occurs, then the actuator 86 is energized and allows the material 14 to continue on the conveyor 16, waa This means that the material that continues to run has a certain quality "A". But if the actuator 9o 'is excited then the material monitored by the camera or it is classified in such a way that it is revised again. In the same way, at Excitation of the actuator 96 rejected the material and entered another in need of revision Classification.

A second level detecting detector 80b with counter 84b and associated Klaaaifikationaachaltung can be switched on with the switch 81, whereby the output 78 of the AND gate 62 is connected to the level discriminator 80b. The classification or sorting circuit assigned to the discriminator 80b and the counter 84b is essentially identical to the circuit described above, with the exception of an additional actuating device 1o2b, which can be excited via a gate 1o4b at a predetermined count in the counter 84b. Gate 1o4b also receives a blocking signal from line 1o6b from gate 88b when the latter is energized. The circuit with the level discriminator 80b, the counter 64b and the associated circuit elements can be used for further classification of the material 14, if this material has already been classified by using the level discriminator 80, the counter 84 and the circuit elements associated therewith. If ζ.δ. the actuating device 96 returns a piece of material as a category belonging to each "Revise II"

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then this strip can be driven by the same or a similar system in which the switch 81 is in the position in which the level criminator 8ob is switched on. The counter 84b is used to energize the actuator 86b provided that the material strip has the properties that it is classified as B according to a predetermined number of Mistakes are enough. If after rechecking the material appears to have a lower number of errors, the actuator 1o2b is energized and the tape is returned for higher classification.

When the switch 81 is in one of the above-mentioned positions, the operating devices 9o classify or 9ob the strip of material for further checking, with the switch 81 in the same during the next run Position remains. On the other hand, if either actuator 96 or 96b is energized, then the strip of material classified for a lower verification level. Excitation of the actuator 96 classifies, for example the strip of material that is being examined for reintroduction into the system, and then the switch 81 selects the level discriminator 8ob.

In the third position of the switch 81, a level detector 8oo is selected. The output of 82c goes to counter 84c, the appropriately assigned a further classification maintenance which is used to further classify the examined material.

Although a system with the switch 81 to check the material 14, several such systems with several television cameras can of course be used in a suitable manner

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Position along the conveyor track to classify the material can be provided. Such material can also be used two-way within a category with predetermined ones Limits can be classified by using several circuits according to the type of FIG. 3o, for example, two such Circuits arranged along the conveyor belt 16 with successive arrangement of the associated television cameras or it can be a television camera for a circuit on one side of the moving material and a another television camera can be arranged on the other side. Bs can readily be desired, the material which meets criteria B and C, while other materials are rejected. In one circuit According to FIG. 3, the switch 81 is then set in such a way that it activates the discriminator 6ob assigned to classification B. drives and in a second such circuit, the switch 81 is set such that it is the one for the classification C controls the responsible discriminator 8oc. When such a system is operated, the material is let through if either the actuator 86 of the first circuit or the actuator 86b of the second circuit is excited. Of course, other similar combinations are also possible

The counter 64 also generates an output 1o8 when it reaches the counter reading either a little earlier or a little later, which is generated at output 72. In one application, the counter 64 generates an output 1o8 when the TV camera 1o its third scan over the material 14 of the Hasterβ 7ο according to Figure 4 reached. The output 1o8 goes at gate circuits 11o (early look gates). The gate 11o receives a signal from one of the level discriminators 8o, 8ob, 8oc, and the like. corresponding to the position of switch 112, the bit the switch

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bt is coupled in such a way that the same level discriminator included in the circuit by the two switches 81 and 112 is. For example, if the level detector 8o produces an output 82 which indicates the fenlers in the material being examined then a delayed output 114 is provided by the Switch 112 applied to the for 11o. The gate 11o then gives the output 1o8 of the counter 64 through the gate 11o and supplies an input 113 to the pulse generator 74, during the third scan of the next television raster, the third and fifteenth scans of the raster are parallel to each other and a predetermined distance from each other. The output of the pulse generator 74 fades in the video information not only for the fifteenth such scan, but also for the third scan during the next haste time. This further video information from an additional scanning path in parallel to the first scanning path, e.g. from the third scanning line parallel to the usual fifteenth scanning line, is used to find defects in the material 14 which are of such a length that they measure the distance between bridge the defensive lines in the image of the defect. if the fault then bridges this distance becomes an additional one ,; similar to the selected counters 84, 84b, 64c, etc. added. This makes it more likely a rejection in the case in which disturbances or fenlers have a size bridging this distance. Of course, the v * rö3se in question can thereby can be chosen to set the counter 64 to generate an output 1o8 at the time of such a scan, which is closer to or farther from the sample output 72 provided by the pulse generator 74.

The polarizers 56 and 60 are not self-verifying BAD QWCANAkr 0 0 9 8 8 3/0381

necessary to find errors in the material 14 »die can only be recognized by their color. That is so that errors with darker coloring, e.g. a branch or the like in the material 14, with an appropriately set Levels can be registered at the discriminator without the use of polarized light. Polarized Light using polarizers 56 and 6o is useful in finding excessive roughness on the Surface of the material 14. For this purpose, the light is at an angle of incidence of about 37 ° from the vertical steered onto the material 14. A mirror 58 serves to reflect the material 14 through to the television camera 1o the polarizer 6o oriented to let the polarized light pass through. However, if the surface If the material 14 is excessively rough, then it becomes the polarized light disperses and the camera 1o receives less light and generates a signal like this The case is when a dark spot appears. Of course, the dispersed light detection system can be used by a rough spot can be adjusted by changing the angle and the position of the mirror 58 accordingly. The use of polarized light to detect the degree of roughness is also possible in the circuit according to FIG possible.

FIGS. 4 and 5 represent mechanical converters for use in the circuit according to FIG. 3. Each of these converters has a pivotable arm 14 which has a knurled disk 16, preferably made of plastic or the like, which in turn is in physical contact with the surface of the material 14 stands. Each transducer arm has a movable contact 118 of a switch 12o which also has a fixed contact 122. When the fluted

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Disc comes over a rough spot, the contact 118 of the switch 12o moves in the direction of the contact 122 and makes contact. The switch 12o can be provided in FIG To lay level discriminator 8o. Several such transducers arranged above the surface of the moving material 14 are, cause the installation of one or more short input signals to the level discriminator 8o via one of the Switch 12o, whereby an additional count is entered into the counter 84 which is indicative of the physical Roughness of the surface of the material 14.

The invention provides an automatic device for finding faults in the material and for the corresponding Reject or classify the material according to such errors. This working method is carried out automatically, i.e. the economically expensive human labor is not required; It is also important that with it no subjective errors can come in.

All the details shown are important for the invention.

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Claims (1)

PATENTAiiSPH-CHJä 1. Device for detecting errors in a new observation station Passing material, characterized in that the love observationaatation has a converter (1o, Fig. 1) which converts light into electrical signals, the output of which with a is compared with a predetermined level which is set such that it is not in the case of fault-free material exceeded, but exceeded in the case of defective material. 2. Device according to claim 1, characterized in that the converter (1o) is formed by a television camera, which scans the material (14) perpendicularly (18, FIG. 1) to the relative movement between the camera and the material. 3. Apparatus according to claim 2 »characterized in that the television camera makes a first scan across the material on a first path, as an additional Input to the discriminator from the television camera is a path corresponding to a second path parallel to the first path Signal is applied when the second path encounters the image of an error that is at least extends over the distance between the two samples. 4 · Device according to claim 2, characterized by a the material directed light source ·, a polarizing filter (56) between the light source and the material and also between the material and the television camera (1o), so that the television 009883/0381 camera polarized light is received from the material in order to show the roughness of the television camera as an output signal To obtain material (14) representing signal. 0 » Device according to claim 2, characterized by a counter (Pig. 3) for adding up the number of errors according to the registration by the discriminator (8o, 8ob) and switching means responding to the status in the counter for classifying the material for sorting purposes. 6. The device according to claim 2, characterized by responsive gate circuits to the discriminator, for Urzeugung of a signal only during the discharge and through to the Coincidence of the gate signal with the discriminator output signal Responsive switching means, as well as memory operated by the coincidence circuit for displaying the degree of error of the examined material. 7. Apparatus according to claim 2, characterized in that the camera (1o, Fig. 3) scans the image of the material (H) by means of a haster of parallel scans (Fig. A) with mutual spacing between the scans, that a first counter scans the The number of scans counts and an output is generated when a certain number of scans has been reached that a gate circuit is actuated by this counter which fades in the output signal of the television camera, that the output of the discriminator is input to a second counter, which generates an output , when the number of discriminator output signals assumes a predetermined value, and that a plurality of actuating devices (86, 9o, 96) which are responsive to different counter readings in the other counter are provided for classifying and sorting the material, and wherein 009883/0381 - 2ο - between the second counter (ö4) and the various actuation devices (86, 9o, 96) blocking circuits (94, 1oo) are provided, by virtue of which at any point in time only one actuating device can be in operational readiness at a time. 8. Apparatus according to claim 7, characterized by further Switching means for receiving the count of the first counter and for producing an output when the first counter with its output a different scan from the first scan in the scanner is generated, this switching means respond to an output variable of the discriminator, if an error is detected in order to transmit the output information of the television camera to the discriminator during the second scan to put on. 9. Apparatus according to claim 7> characterized by mechanical Transducers that touch the material and add an additional count to the second counter, if one mechanical roughness on the surface of the Material recorded. C 19883/038 1 Blank page