CA1195426A

CA1195426A - Photoelectric apparatus for monitoring a dimension

Info

Publication number: CA1195426A
Application number: CA000417681A
Authority: CA
Inventors: Gunther Krippner; Franz Postlbauer; Karl Kletzmaier
Original assignee: Elektronikbau Krippner & Kletzaier & Co GmbH
Current assignee: Elektronikbau Krippner & Kletzaier & Co GmbH
Priority date: 1981-12-31
Filing date: 1982-12-14
Publication date: 1985-10-15
Also published as: DE3238883C2; CZ925082A3; DE3238883A1; CZ278541B6; ATA565981A; AT396036B

Abstract

ABSTRACT OF THE DISCLOSURE

A photoelectric apparatus for monitoring a dimension and the position of an object placed in a space defined between two substantially parallel measuring planes, which comprises a light emitter arrangement including a sequence of light emitters arranged in one of the measuring planes, a light receiver arrangement including a like sequence of light receivers arranged in the other measuring plane, each of the light emitters being arranged to emit a light beam into the space towards a respective one of the light receivers, and an electronic processor unit for determining an interruption of the light beam by the object placed in the space, the processor unit including a timed control for sequentially operating each light emitter with at least two light receivers.

Description

c~

The present invention relates to a photoelectric measuring appara~us or indicating or monitoring a dimension or pos.ition of an object, which may be moving, such as the dimension of a log. The object is placed in a space defined between two substantially parallel measuring planes, a light emitter arrangement including a sequence of light emitters is arranged in one of the measuring planes and a light receiver arrangement including a like sequence of light receivers is arranged in ~he other measuring plane, each of the light emitters being arranged to emit a light beam into the space towards a respective one of the light receivers~ An electronic processor uni~ determines an interruption of the light beam by the object placed in the space.
Accepted German patent application ~o. 2,555,975 of Karl Klet~maier and Gunther Krippner, published ~uly 19, 1979 discloses a photoelectric apparatus for i.ndicating and monitoring the dimension of a log with a sensing device including a plurality of light-sensitlve elements arranged on A measuring plane and ass3ciated with a light source for generating a shadow image o:E the object on the measuring plane~ To obtain an exact measur1ng result indepPnden~ oF
the distance or position of the log in relation to the rneasuring plane and the light source, a dist.-nce measuring device is arranged in a plane extending perpendicularly to the measuring plane or at a pre-adjustable distance from the meas~ring plane to indicate the distance between the measuring plane and the log. In this manner, changes in the distance be~ween the log, the measuring plane or the light source may be determined and very accurate measuring results may be obtained~ While this apparatus has been succe~sfully used, it has been found that such high accuracy is not always required.
Published German paten~ application No. 2,920,804 of Gunter Link~ laid open November 27~ 1980, discloses an apparatus fox measuring the diameter of logs by use of a llght curtain. This light curtain is constitu~ed by vertically superimposed rows of photoelectric emitters and receivers, infrared-sensitive semi-conductor elements being used as light receivers and light emittersO To obtaln sufficien~ accuracy with the use of such a parallel-light light curtain~ the vertically superimposed light emitter and receiver rows are so obliquely inclined to the horizontal that the centers of neighboring elements have a predetermined distance from each other in the vertical direction, i.e. the same dis~ance as that of the uppermost elemen~ in a row from the next adjacent elemellt. This measurillg apparatus also includes an electronic processing unit and a control for cyclically operating the light emitters and the opposite light receivers associated therewith in pairs. ~his measuring apparatus requires a very comple~ electronic an~ r therefore, is often too expensive to buy and maintain.
U. S. patent No. 3~806,253 of Eric B. Denton, dated April 23, 1974 also uses a light curtain ~o determine ~he diameter of a log and comprises -two measuring devices positioned at an angle of about 90 for determining the center llne of the log by triangulation. This apparatus is not very accurate while requiring a great number o~ structural components and, therefore, being quite expensive.
It is the primary object of this invention to provide an apparatus of the first-described type which is simple in structure and is capable of dependz~ly monitoring a dimension oE an object at a favorable cost.
This and other objects are accomplished according to the invention with an electronic processor uni~ which includes a timed control for sequentially operating each light emitter with at least two light receivers. This improvement has the advantage that the timed and sequentia~ sensing of the light beam between one light emitter and several light receivers makes it possible to determine whether or not the object whose dimension is to be monitored also ex-tends into the range between two measuring groups consisting of a light emitter and a light receiver opposite and associated wi-th each o-therO

In this connection~ it is advantageous that a considerable increase in the measuring accuracy is obtained at little extra cost by using the existing light emitters several times in conjunction wi-th the consecutive connection of the light receivers with at least two different light emittersO This makes lt possible to provide a cost~effective manufacture and maintenance of the apparatus while, at the same time, providing measurements accurate enough for calibration.
The above and other objects, ad~antages and features of the present invention will become more apparent from the following detailed description of certain now preEerred embodiments thereof, taken in conjunction ~i~h the accompanying, generally schematic drawlng wherein FIG~ l is a simplified dlagram of a photoelectric apparatus for monitoriny a dimension and the positlon of an object, in side elevation, including a diagram oE the control circuit;
FIG. 2 is a like view of another embodiment of the apparatus;
FIG~ 3 is an end view seen in the direction oE arrow III of F~G. 2, showing the receiver arrangement of the apparatus;
FIG. 4 is a perspective view o another embodiment of the apparatus, including the control circuit connecting the emitter and receiver arrangements to the electronic processor unit.
Referring now to the drawing and first to FIGo 1~

photoelectric apparatus l for monitoring dimension 2 of ob~ect 3, for example the diameter o~ a log 4, is shown -to comprise measuring device 5 and electronic processor unit 6. Object 3 is placed in a space definecl between two substantially parallel measuring planes 9 and 10.
Measuring device 5 comprises light emit-ter arrangemen-t 7 including a sequence of light emitters 11 to 21 arranged in measuring plane 9, and light receiver arrangement 8 including a like sequence of light receivers 22 to 32 in other measuring plane 10. Each light emitter is arranged to emit a light beam into the space towards a respective one of the light receivers~

The light emitters may be semi-conductor elements capable of emitting infrared light beams. A control circuit connects electronic processing and programming 5~
unit 6 to the light emitter and light receiver arrangements for determining an interruption of the light beam ~y the object placed in the space. The control circuit includes transmission line 33 connec.ing light emitter arrangement 7 with switching element 34O
Central energy supply unit 35 and control 36 are connected to switching element 34. ~he control is connected to the electronic processor and programming unit to receive control pulses therefrom. In response to the received control pulses, control 36 actuates switching element 34 to connect a respective one of light emitters 11 to 21 to energy source 35 and thereby to activate the connected light emitter. Light receiver arrangement 10 is connected tc switching element 37 by transmission line 38 and, in response to the control pulses from control 36 connected to switching element 37, a respective one of light receivers 22 to 32 is connected by 3Wi tching element 37 to one of the coun-~ers 39 of processing unit 6. Each counter 39 serves to time the control so that dimension

2 of log 4 is measured along different por-tions oE the log along the length thereoE. Respective ones of the light emitters and receivers are paired and arranged opposite each other in alignment, the emitters and receivers defining identical distance 40 between each other in the sensing direction indicated by arrow 41.
The monitoring of dimensiQn 2 proceeds in the following manner in the direction of arrow 41:

A control pulse from control 36 actuates switching elements 34 and 37 to connect light emitter 11 to energy source 35 whereby the emitter is activated and to connect light receiver 22 -to the lnput of one of counters 39. If light beam 42 received from emitter 11 by receiver 22 is not interrupted, as shown in FlG. 1, connected counter 39 is not switched on. Immediatel~

successive Light emitter 12 ls then sequen~i.ally operated by switching element 34, instead o~ emi~ter 11, to de-termine whether liqht beam 43 between emitter 12 and receiver 32 is interrup~ed. Since, as shown in the drawing, this is not the case, switching element 37 will now connect light receiver 23 to the input of the one counter 39, instead of receiver 22. This is repeated sequentially and since light beam 44 also is not interrupted by object 3, switching element 34 wi]l simuLtaneously operate light emltter 13 and light receiver 23 and, subsequently, light emit~er 13 and light receiver 24. Since the light beam between emitter 13 and receiver 24 also ~e~l uninterrupted, coun-ter 39 is still not s~itched on. Se~uential operation of light emitter 14 together with receiver 24 generates light beam 45 which is .interrupted by log 4. This will cause a timing pulse to be transmitted to counter 39 by swit~hing element 37. In the subsequent sequential operation proceeding as hereinabove described, each light emitter 14, 15, 16, 17, 18 and 19 will be opera-ted with light receivers 25, 26l 27, 28 and 29. Since the beams between these light emitters and receivers are ~5~

interrupted hy log 4, each switching step will transmit a timing pulse to counter 39.
As the sensing cycle proceeds in the direction of arrow 41 and reaches the simultaneous operation of ligh-t emitter 19 and light receiver 30, light beam 46 therebetween is Eound not to be interrupted by log 43 This also interrupts the operation of counter 39 and, there~ore, the measuring procedure. However, to avoid any faulty measurements and provide an extra margin of safety~ control 36 may be arranged to continue operation oE light emitters 20, 21 and light receivers 31, 32 to ascertain that the light beams therebetween are not interrupted, iOe. that no portion of the log extends :into the space therebetweenO
The number of control pulses received by counter 39 is directly proportional to dimension 2. Since distance 40 between the emltters and receivers in the sensing direction 41 is exactly the same, this distance need only be multiplied by the number appearing on counter 39 to determine the length of dimension 2. However, it must be noted that each light receiver 22 to 32 is always operated with two successlve light emitters 11 12; 12, 13; 13, 14, and so forth so that the multiplication factor does not correspond -to distance 40 but to the half of this distance. In Lhls particular arrangement, each light emitter is associated with an aligned light receiver, and ~imed control 36 is arranged for common operatiorl of the light emitter and light receiver aligned therewith and, in a further, indepelldent object sensing cycle, for operation of q~
another light receiver aligned with a neighboring one of the light emi~,ters. In this manner and without increasing the number of light emitters and receivers, the measuring accuracy of apparatus 1 is doubled because, in sensing direction 41, each trailing light emitter is operated simultaneously with a light receiver aligned with the immediately preceding light emitter and thus obtains an interpolation between light beams 42, 44t for example, of two pairs of aliyned light emitters and receivers 11, 22 and 12, 23, A plural:ity of counters 39 is provided to enable diameter 2 of log 4 to be measured several times over the length of the log so that the volume thereof may be calcu].ated. The results determined by counters 39 may be transmitted to further electronic processor units and combined therein with the length measurement to compute the volume of log 4, ~hus enabling a series of logs to be calibrated accordingly. It is important in this .respect that a result is obtained Eor dimension 2 which is accurate enough or calibrat;.on, the accuracy of the monitoring apparatus being increased because two receivers are sensed by each emitter.
In photoelectric monitoring apparatus 47 of FIG. 2 for moni~oring dimension 48 of object 49, two neighboring light emitters 50 and 51 of light emitter arrangement 52 are associated with two aligned light receivers 56 and 59 of light receiver arrangement Ç3.

At least one fur-ther light receiver 57 and 58 is arranged in -the sequence between the two light receivers 56, 59 aligned with neighboring light emitters 50~ 51~

Object 49 may be, for example, a rolled work piece, a tree trunk or a paper web or the like~ For a better understanding o~ this embodiment, the measuring procedure is illustrated and described only in connection with emitters 50 and 51 of li.ght emitter arrangement 52 and receivers 53 to 62 of l.ight receiver arrangement 63. As will be understood from the arrangements of FIG~ 1 and as partly indicated in FIG~
2, apparatus 47 comprises a larger number of light emitters and receivers to enable it to be used :Eor monitoring larger dimensions 48.

In this embocliment, the timed control is arranged for simultaneously operating at least one of nei.ghboring light emitters 50~ 51 with Eurther light receivers 57 and 58 in sequential object sensing cycles. Thus~ light em.itter 50 is operated simultaneously with light receiver 53, then 54, then 55, and so forth in the sensing direction indicated by arrow 64. As shown, llght beam 65 between emitter 50 and rece.iver 53 is no-t interrupted while object 49 interrupts the beams between the emitter and sequelltial receivers 54 to 58. For a clearer understanding, the beams are shown by differently configurated linesl the beams between aligned emitters and receivers 50, 56 and 51~ 59 being shown in full lines, and the beams between the emitters and further receivers being shown in broken and differently chain-dotted lines. To obtain the b~st possible measuring resolutiorl or interpolatiorl of distance 66 between the two neighboring light emitters in sensing direction 64, light receivers 56 to 58 sequen'cially receive the light beams ~rom b~ ~h~rT~~

emitter 51, too, as the sensing cyc]e proceeds, and it ,. ~..
is determ.ined at each measuring step whether the beam between this light emitter and 'che light receivers associated therewith is lnterrupted or not. In the illustrated examp].e, beam 67 between light emitter 51 and light receiver 59 is the first beam which i.s not interrupted as sensing oE object 49 proceeds in the direction of arrow 64, and this signals the end of the measurement of dimension 48. This timed control of the sequential operation of the same light receiver with different light emitters produces an enhanced degree of interpolation and better resolution in indicating the position of the object or its dimension between neighboring lig~t emitters without subs-tantially increasing the cost of the installation.
The end view of light receivers 56~ 59 in FIG. 3 shows them al.igned with ligh-t emitters 50~ 51 arrayed in f.irst row 6B, further light receivers 55~ 53 arrayed in second row b9 and further light receivers 54, 57 arrayed in third row 70, the rows of the arrayed further light receivers be~ng spaced from, and being substantially paral.lel to, the first row. Nelghboring l.ight emitters 50 and 51 of ligh'c emitter arrangement 52 defi.ne predetermined distance 66 ~he~ebetween in the direc-cion of the measuring planes and light receivers 53 to 59 in rows 68, 69, 70 de~ine predetermined portion 71 oE

distance 66 therebe'cween. In the illus-tra-ted embodiment, distance 71 is a third of dist,ance 66. For a better understanding, the light emit~er arrangement ~5~

has been shown in the same plane as light receiver arrangement 63, i7e. in side view, while the end view of the receiver areangement is~ ln fact, in the same position as shown in FIG. 2.
This embodiment has the advantage of reducing the resolution capability to below that of the minimal distance between two neighboring light receivers in one row determined by the physical dimensions thereoE, without re~uiring a complex control circuit. The timed control of the present invention achieves a greatly increased accuracy simply by the special arrangement of the receivers and the same number of emitters, a multiple control being required only in association with light receiver arrangement 63 for receivers 53 to 59 and not for light emitter arrangement 52 9 as sensing proceeds in the direction of arrow 64.
According to this invention, the timed control is arranged for sequentially operating successive light emitters in an object sensing direction extending substantially parallel to the measuring planes, each light emitter being operated with the light receiver trailing the operated light emitters in this direction and then with the light receiver ali~ned with the operated light emitter. This makes it possible to start sensing with several light emitters at the same time, which subs-tantially reduces the required time Eor sensing the entire space in which the object is located.
In the embodiment o FIG. 3, negligible measurement deviations are produced because of the angular path of , ", e: ~ ~ ~
the individual beams~ the maximum error Q~ with ~9~

beam 65 when light emitter 50 and light receiver 53 are operated simultaneously. However, i:E the diskance perpendicular to the direction of sensing is not too large, this measuring error is negligible or may be simply corrected by a compensatory circuit, for instance in a microprocessor or the like, on the ~asis of the known distancesO At any rate, the required devices :Eor correctlon of the minor measurement errors are much simpler and less expensive than a multiple contro] Eor the 7.ight emitters corresponding in number to the light receivers to obtain in each instance an exactly perpendicular path of the sensing beam to the sensing direction indicated by arrow 64, i.e. to measuriny planes 72 and 73.
FIG. 4 illustrates an embodiment in which light emitters 79 to 81 and ligh-t receivers 88 to 96 are arrayed over respective measuring planes 75 and 76 at predetermined vertical distance 97 and horizontal distance 98. Monitoring apparatus 74 is shown in perspective v.iew to enhance an understanding o:E the structure and operation thereof. I,ight emltter arrangement 77 is arranged in measuring plane 75 and light receiver arrangement 78 is arranged in measuring plane 76. As shown in connection with light emitters 8l and 84, each light receiver is arranged to receive the light beams from at least these two emit-ters. Processor unit ~9 of apparatus 74 :Eurther comprises receiver coupling stage 102 sequentially connectlng each light receiver with the light emitters whose 1igh-t beams are received thereh~ to computer 103 which includes indicating and operating unit 104.
Monitoring apparatus 74 operates in the following manner:
Emitter coupling stage 101 of electronic processor unit 99 transmits a contro]. pulse to one of the light emitters, i.e. emitte.r 81. ~eceiver coupling stage 102 of the processor unit now scans light receivers 88 to 96 sequentlally to ascertain whether the beam emittecl by light emitter 81 and the scanned light receiver is interrupted by object 100 or not. The corresponding signals from the sequentially scanned receivers are stored in computer 103. After this sequence ascertaining the state of the beam from light emi-tter 81 to light receivers 88 to 96, light emitter 84 is operated by transmi-tting a control pulse thereto Erom the electronic processor unit~ Receiver coupling stage 102 now again scans light receivers 88 to 96 in sequence to ascertain whe~her or no~ the beam emitted by light emitter 84 is interrupted by object 100. This procedure is repeated until ~he state o:E the beams between all the light emitters and receivers has been ascertainecl in the indicated manner. As schematlcally shown in FIGo 4 this produces an indication o~ the posi~ion and dimension of object 100 placed in the space between measuring planes 75 and 76 since the indicated interruption o~ the beam between light emitter 81 and light receivers 94, 95 and 96 as well as that of the beam between emitter 84 and receivers 88, ~9, 90, 91 and 92 produces a spa~ial image and the peripheral shape o-f object 100~ For a better understandingr the portions of the in~errupted beams between the light emitter and object have been shown in heavy lines.
The measuring values or indications of interruptions of beams in the space holding the object are stored in computer 103 and, since the exact position of the light emitters and receivers is known, the position oE object 100 may be accurately computed and, assuming the light receivers are sufficiently close together in their array in measuring plane 76, the dimensions, such as length, width and height, of object 100 may be accurately computed in the computer. l~he reason for the high accuracy of the computation is the operation of a plurality of receivers with the operation of each emitter. In this manner, a relatively small number of light emitters can be used to produce an extremely high scanning density for the object, thus reducing ~he cost of the apparatus while assuring its high accuracy. This ~canning density may be further enhanced by arranging additional light receivers 105 in measuring plane 76.

The output signals corresponding to the desired dimension and/or position monitored in the indicated manner in apparatus 74 may be digitally indicated and/or recorded by connecting indicating and service unit 104 to the output oE computer 103.
The light emitter and receiver arrangements of FIG.

4 enable object 100 to be sensed three-dimensionally so tha-t a single measuring step at the same time indicates measurements in two dimensions~ For example~ the length o~ the object as well as the height thereof in the sensing direction may be ascertained simultaneously.

Of course, the use of computer 103 in electronic processor unit 99 makes it possible to utilize any number of light emitters and receivers to obtain any measuring accuracy desired. Whatever these numbers may be, the system has the advantage that several light receivers are operated with each light emitter. In this manner, all the receivers can be utilized with a much smaller number of emitters to obtain highest measuring accuracy at lower cost.
Emitter coupling stage 101 and receiver coupling stage 102 may be constituted by suitable electronic control units, such as shifting registers, integrated circuits and the like. Similarly, computer 103 may be consti~uted by any suitable memory and computer circuit. Preferably, computer 103 is a microprocessor so that the computer may simultaneously be used or programminy the control of the respective ligh-t emitters and receivers as wel] as processing the signals derived there-from, particularly for the computation oE the coordinate points determining the dimension or position oE the object.
Spacings 97 and 93 between the light emitters and receivers of the embodiment of FIG. 4 may be se]ected according to requirements and the spacings between the light receivers may differ completely f om those selected for the light emittersO

It will be obvious for those skilled in ~he art that monitoring appara~us 74 of FIG. 4 may also be used to secure a space and/or an ob~ect therein, i.e. on interruption of a beam, device 104 may emit an audible and/or visual alarm signal.
The light emitters and receivers in the herein described and illustrated monitoring apparatus may preferably be constituted by semi-conductor elements, it being preEerred to make these elements sensi~ive only to infrared light so that they cannot be influenced by other light sources.
The accuracy of ~he measuring results obtained by ~y.
the monitoring apparatus of the present invention ~T~
be further enhanced by additionally providing a distance measur:ing device enabling the distance between objects

3, 49 or 100 and measuring planes 9 and 10, 52 and 53, and 75 and 76 to be measured, for example mechanical sensors, reflected light barriers, ultrasonic devices and the like. This makes it possible to measure a ~hird dimension and also enables the electronic processor unit to correct for differing distances between the measuring plane and the object when the beam paths are oblique.

~ 16

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A photoelectric apparatus for monitoring a dimension and the position of an object placed in a space defined between two substantially parallel measuring planes, which comprises (a) a light emitter arrangement including (1) a sequence of light emitters arranged in one of the measuring planes, (b) a light receiver arrangement including (1) a like sequence of light receivers arranged in the other measuring plane, each of the light emitters being arranged to emit a light beam into the space towards a respective one of the light receivers, (c) an electronic processor unit for determining an interruption of the light beam by the object placed in the space, the processor unit including (1) a timed control for sequentially operating each light emitter with at least two light receivers.

2. The photoelectric apparatus of claim 1, wherein each light emitter is associated with an aligned light receiver, and the timed control is arranged for common operation of the light emitter and light receiver aligned therewith and, in a further, independent object sensing cycle, for operation of another light receiver aligned with a neighboring one of the light emitters.

3. The photoelectric apparatus of claim 1, wherein two neighboring ones of the light emitters are associated with two aligned ones of the light receivers, at least one further light receiver is arranged in the sequence between the two light receivers aligned with the neighboring light emitters, and the timed control is arranged for simultaneously operating at least one of the neighboring light emitters with the further light receiver in sequential object sensing cycles.

4. The photoelectric apparatus of claim 3, wherein the light receivers aligned with the light emitters are arrayed in a first row, the further light receiver is arrayed in at least one further row spaced from, and substantially parallel to, the first row.

5. The photoelectric apparatus of claim 4, wherein the neighboring light emitters define a predetermined distance therebetween in the direction of the measuring planes and the light receivers in said rows define a predetermined portion of said distance therebetween.

6. The photoelectric apparatus of claim 1, wherein the timed control is arranged for sequentially operating successive ones of the light emitters in an object sensing direction extending substantially parallel to the measuring planes, each of the light emitters being operated with the light receiver trailing the operated light emitter in said direction and then with the light receiver aligned with the operated light emitter.

7. The photoelectric apparatus of claim 1, wherein the light emitters and light receivers are arrayed over the respective measuring planes at predetermined distances, each of the light receivers being arranged for receiving the light beams from at least two of said light emitters, and the electronic processor unit further comprising a receiver coupling stage sequentially connecting each light receiver with the light emitters whose light beams are received thereby.