CA1168437A - Process and device for the contact free measurement of a dimension - Google Patents
Process and device for the contact free measurement of a dimensionInfo
- Publication number
- CA1168437A CA1168437A CA000373326A CA373326A CA1168437A CA 1168437 A CA1168437 A CA 1168437A CA 000373326 A CA000373326 A CA 000373326A CA 373326 A CA373326 A CA 373326A CA 1168437 A CA1168437 A CA 1168437A
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- CA
- Canada
- Prior art keywords
- light beam
- data
- dimension
- measurement
- memory
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/08—Measuring arrangements characterised by the use of optical techniques for measuring diameters
- G01B11/10—Measuring arrangements characterised by the use of optical techniques for measuring diameters of objects while moving
- G01B11/105—Measuring arrangements characterised by the use of optical techniques for measuring diameters of objects while moving using photoelectric detection means
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
- G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
- G01B11/0691—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of objects while moving
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Length Measuring Devices By Optical Means (AREA)
- Length Measuring Devices With Unspecified Measuring Means (AREA)
Abstract
ABSTRACT
In a process and apparatus for measuring the dimension of at least one object without physical contact therewith, a fine light beam, for example a laser beam, is deflected across the object in the direction of the dimension to be measured and the instants in time at which the light beam impinges upon and moves off said object are determined and stored as measurement data. These data are then evaluated, together with reference data relating to the speed of deflection of the light beam, to provide a measure of the dimension. In one example a computerised system operates in a continuous cycle wherein the measurement data are recorded and stored in a first memory during a first cycle, the data is transferred to a second memory in the direct memory access mode, and then during the next circle the data in the second memory is processed whilst new data is being read into the first memory. A chopper circuit linked to the means for deflection of the light beam, for example a rotary mirror, serves both to control the operating cycle and to provide the reference data.
In a process and apparatus for measuring the dimension of at least one object without physical contact therewith, a fine light beam, for example a laser beam, is deflected across the object in the direction of the dimension to be measured and the instants in time at which the light beam impinges upon and moves off said object are determined and stored as measurement data. These data are then evaluated, together with reference data relating to the speed of deflection of the light beam, to provide a measure of the dimension. In one example a computerised system operates in a continuous cycle wherein the measurement data are recorded and stored in a first memory during a first cycle, the data is transferred to a second memory in the direct memory access mode, and then during the next circle the data in the second memory is processed whilst new data is being read into the first memory. A chopper circuit linked to the means for deflection of the light beam, for example a rotary mirror, serves both to control the operating cycle and to provide the reference data.
Description
1~ 37 BACKGROU~D 0~ ~HE INVE~I0~
~he present invention concerns a process for the contact-free measuremen-t o~ a dimension of at least one object, wherein a ~ine light beam, more especially a laser beam, is deflected across the object, within a measuring field, in the direction o~ the dimension to be measured, and the period of interruption of the light beam by the object is compared with a reference period, and wherein the dimension of the object is ascertained from these periods.
In a known measuring process of this kind the period of interruption of the light beam by the object is compared with the period of the transition of the light beam across a window de~ining the mea~
~5 suring field (US - PS 4,082,L~63). ~he dimension of the object -to be determined thus has the same relation-ship to the dimen.sion of the window opening as -the period of the in-terruption of the light beam b~ the : object has to the period of the transition of the light beam across the measuring field, that is -to say ~rom window edge to window edge. Errors which can occur in this method of measurement due to a non constant velocity of transi-tion of -the light beam across the measuring field are compensa-ted b-~
providing a coarse grid in the measuring field during the manufacture of the measuring app æ atus, b~ means , ~
~61~437 -- 3 ~
of which calibration values can be stored. An inter-polation is necess æy to obtain measurement values between the calibration values. ~his known measuring process of~ers only limited possibilities ~or the determination and processing of measuremen-t values, because data can be collected and processed only at each transition o~ the light beam through predeter-mined points. ~he time available ~or the processing of data is correspondingly short. As stated only a rela-tivel~ coarse calibration is possible ~or which a special program unit is necessary, which is such that a recalibra-tion o~ an installed apparatus during servicing is very di~icult. ~he comparison o~ the dimension to be measured with the dimension o~ a window opening re~uires that this window opening be very accurately measured and does not alter, a condition which is dif~icult to maintain, ~or example, with variations in temperature.
SUMMARY 0~ ~E INVE~I0~
It is the object o~ the present invention -to provide a versatile measuring process which has a min-imum o~ sources o~ error.
~he invention accordingl~ provides a process for measuring a dimension o~ a-t least one object without physicall~ contacting said objec-t, wherein a fine ~_ 4 _ light beam is deflected across the object in the direc-tion of the dimension to be measured, The instants at which the light beam is blocked and unblocked by the object are recorded and stored as measurement data.
The measurement data are evaluated to provide a measure of the dimension by comparison of the period of time defined between the recorded instants with a predeter-mined reference period of time related to the speed of deflection of the light beam. In accordance with the invention, the instants recorded during a plurality of consecutive deflections of the light beam across the object to be measured are stored as measurement data and the evaluation of the corresponding measurement data is effected subsequently and collectively while new data are detected and stored, The invention, in accordance with a further embodiment, provides a process for measuring a dimen sion of at least one object without physically con-tacting said object, wherein a fine light beam is def-lected across the object in the direction of the dimen-sion to be measured. The instants at which the light beam is blocked and unblocked by the object are recor-ded and stored as measurement data, The measurement data are evaluated to provide a measure of the dimen-sion by comparison of the period of time defined bet-ween the recorded instants with a predetermined refer-ence period of time related to the speed of deflection of the light beam, In accordance with the invention, there is provided memory means. The process includes storing in the memory means at time addresses position values corresponding each to one predetermined position of the light beam during its deflection, The values are detected from the memories at the instants at which the light beam is blocked and unblocked by the object.
The process also includes the further step of detecting reference time data and evaluating the dimension and/or position of the object from the position values.
,~., .... . . ..
a -In accordance with a still further embodiment of the invention, there is provided a process for mea-suring a dimension and/or position of at least one object without physically contacting the object. A
fine light beam is deflected across the object in the direction of the dimension to be measured, and the instants at which the light beam is blocked and unblocked by the object are recorded and stored as measurement data.
The measurement data are evaluated to provide a measure of the dimension by comparison of the period of time defined between the recorded instants with a predeter-mined reference period of time related to the speed of deflection of the light beam. In accordance with the invention, there is provided the improvement comprising deflecting the light beam across an optical window having edges defining an instant of entering of the light beam into the window and an instant of the light beam leaving the window. The object is placed in the window, and a periodicity of scanning cycles of the light beam is detected. There is also included the step of storing all data indicative of the instants at which the light beam is blocked and unblocked by the object and by the window respectively and indicative of the scanning cycles.
Calibrated data is stored in accordance with alinearities of the scanning movement of the light beam through the window, and the dimension and/or position of the object is selectively evaluated from the data.
From a different aspect, and in accordance with the invention, there is provided a device for the contact free measurement of a dimension of at least one object.
The device includes a light source for providing a fine light beam, and means for deflecting the light beam across an object to be measured in the direction of the dimension which is to be measured. Means are provided for determining the instants of time at which the light beam respectively impinges upon and moves off the object.
, - 4b -Means are also provided for dynamically storing measure-ment data corresponding respectively to the instants of time, and means are further provided for calculating from the meas~rement data and from a reference value corresponding to the rate of deflection of the light beam the value of the dimension. This value is deter-mined in accordance with the time differences between the instants of time, MeanS are provided for displaying the resulting measurement value, the calculating means having a computer-controlled system including a central processor unit. A first memory is provided for receiving the measurement data during each of a plurality of con-secutive measurement cycles, and a second memory is pro-vided for receiving data from the first memory~ The arrangement is such that between each two consecutive measurement cycles the system operates in the direct memory access mode to transfer data from the first memory to the second memory, and that during each measurement cycle the data contained in the second memory is pro-cessed by the central processor unit whilst the data in the first memory is being updated.
BRIEF DESCRIPTION OF IHE DRAWINGS
Figure 1 is a diagrammatic view of a measuring .
3~7 device, ~igure 2 is a circuit diagram of the device shown in Figure 1, ~igure 3 is a diagram illustrating waveforms occurring in the circuit o~ ~igure 2, and ~igure ~ is a diagram explaining the measure-ment of a transparent object.
DESCRIPIION 0~ ~HE PRE~ERRED EMBODIMEN~
~he device according to ~igure 1 comprises an optical s~stem which partly consists of known ele-ments. A fine laser beam 2 is directed from a dia-grammatically illustra-ted source 1 onto an octagonal mirror 3 driven at a constant rotary speed. ~he re-flected laser beam passes through an objective com-prising a lens 5 and thence passes across a measuring field which is defined by a shutter or a window with boundaries 6. ~he optical system is so arranged that, be~ond the lens 5, the ligh-t beam constantly extends parallel to the optical axis, and is moved from the upper to the lower edge of the window 6-6 as the mirror 3 rotates in the clockwise direction indicated by the arrow in Figure 1. Each facet of the mirror 3 causes one transition of the light beam across the window to effect a corresponding measurement.
In the illustrated example an object 8 to be measured is arranged in the measuring region, and may, for example, be a cable, a wire, a pipe or the like, which runs transversely to the optical axis of the measuring device and o:~ which the outer diameter is to be determined. Beyond the measuring position there is arranged a condenser lens 9 which focuses the laser beam onto a photocell 10. ~he photocell produces an output signal ~ as shown in Figure 3, which is 0 or low when the beam is screened by the window elements 6 or by -the object 8 and which is I or high when the laser beam is unobstructed. As shown in Figure 3, two impulses occur periodically, the impulses begin-ning with the entry of the light beam into the window 6-6 and ending with its exit therefrom, and the gap between the two impulses corresponding to the screen-ing of the beam by the object 8. ~he embodiment o~
Figures 1 and 2 comprises a digital evalua-tion circuit with a microprocessor. A single photocell 22 is ar-ranged on one side o~ the window 6-6, namely the side ~rom which the ligh-t beam enters the window.
As shown in Figure 2 the microprocessor 23 is connected by way of a data bus 24 and an address bus 25 with further circuit parts.
~he input signal ~ from the photocell 10 is applied to a logic circuit 36 incorporating a dif~er-entiator which responds to the rising and falling ~168~37 flanks of impulses of -the input signal, an address counter control arrangement and further control cir-cuits. A signal from a transmitter 3" is also fed to this logic circuit, said signal being produced by a chopper rotating with the mirror 3 and consist-ing of a too-thed disc 3' with 8 -teeth corresponding to the 8 faces of the mirror. The output of an os-cillator 30 is continuously applied to a counter 29 which is thus cons-tan-tly incremented, and -the output of the counter is applied to a memory 27 by way of a buffer latch 28. The oscillator operates, for example, at a frequency of 18 MHz and the counter 29 has a high counting capacity of, for example, 24 bits. The transfer of the output from the counter to the memory 27 is con-trolled by the logic circuit 36 in a manner to be described below. The circuit further comprises an address counter 35 which is connected to the memory 27 and, by way of circuits 37 and 38, wi-th the data bus 24 and the address bus ` 20 25.
A permanent read-only memory 31 defines the progr~m rou-tine and also serves for the storage of correcting data at defined addresses. A dynamic memo~y 32 serves the processor as a working memory for all data -to be processed. An input-output unit 33 applies the measurement values to a display 34.
.
:~16~437 ~ he control of -the memo~y 32 is effected by way of an OR gate 39 either in the direc-t memory access mode by way of the logic circuit 36 or during the pro-cessing of measurement values by the microprocessor (CPU) 23.
~igure 3 shows the inpu-t signals, namely the measurement signal E, which, at the instant No eorres ponding to the entry of the ligh-t beam into the window 6, changes from O to I, -then, during a first transition of the light beam across -the objeet 8 corresponding to the period P1, returns to 0, and again changes to I, when the light beam illuminates the photocell 10 in its transition between the object 8 and the exit from the window 6. A plurality of measurement periods are repea-ted in this manner, eight sueh measurement periods producing the measurement impulses P1 to P8 and corresponding to one measurement cycle or one re~olution of the mirror 3. ~igure 3 also shows the signal C of the chopper as well as a signal C' trans-mit-ted from the logic circuit 36 to the microprocessor (CPU) 23 and formed by di~iding the chopper signal by the factor of eight. At each occurrence of an impulse flank in the signal E, corresponding to each blocking or unblocking of the light beam, the instan-taneous coun-t of the counter 29 is stored in the memory 27 and remains a~ailable there as a measuring value.
~hortly after the occurrence of the flank C" after each cycle of eight measurements, the microprocessor is interrup-ted and the circuit continues to operate in the DMA (direct memory access) mode. All of the values in the memory 27 are thus transferred to the memory 32. When this transfer is complete, the logie circuit is switched to the measurement mode and the microprocessor 23 is caused to run the program. ~ince the DMA~logic has direct access to both memories 27 and 32, the -transfer of the values can be effected in a ma-tter of mil]iseconds, and in the present embodiment i-t can be effected in the time space between -two con-secu-tive measurement cycles, as illustrated in ~igure 3. As the new measuring cycle begins, and new data is read in-to the memory 23, the evaluation of the previously recorded data, in aeeordance with the pro-gram contained in the memory 31, is effected as a separate opera-tion, and the result is then indicated on the display by way of the output circuit 33.
~he program can be changed, and can thus be adapted -to desired re~uiremen-ts, for example to enable the measurement of a plurality of objects located in the measuring field, in which case the evaluation can easily be so programmed that one or more time spans or periods can be ascertained, during which the light beam is screened by a corresponding object, and the dimension of the or each of these objects 8~37 is ascertained in the previously described manner by comp æison of each period, or of a sum of the periods, with the period of the measurement cycle.
Figure 4 shows a possibility for the measure-men-t of cylindrical, transparent objec-ts, for exam-ple plastics tubes for surgical purposes. ~he signal E comprises the rising flank No upon entry of the light beam into -the window 6, as already described.
When the ligh-t beam impinges upon the transparent object total reflection of the light beam occurs so that ligh-t no longer reaches the photocell 10 and a firs-t falling flank N1 occurs in the signal.
Especially with hollow objects, several phases of transmission and reflection of light then occur, which result in the occurrence of a corresponding plurality of signal flanks. At the instant Nx the ligh-t beam moves off the object. A special circuit in the logic elemen-t 36 is effective to ensure that the data for the instants No and N1 alike are trans-ferred to the memory 27. ~he data for the following instants N2 to N(x-1? only reach the buffer latch 28 and are constantly updated in the buffer. ~hat is to say that only the data from the last occurring in-stant is stored. Upon the occurrence of the ~alling flank of the chopper signal the last value which has been read into the buffer 28, which corresponds to ' .
the instant ~x, is transferred to the store 27 and remains available -there for fur-ther processing.
In the preceding case it is assumed -that one measurement is e~fected during each measurement cycle, tha-t is to say that the dimension of the object to be ascertained can be derived ~rom the following periods:
D = K . P1 + P2 + ... P8 No' - ~o in other words the desired dimension D of the object can be derived from the relationship between the sum of the periods of transition of the light beam across the object and the period of one rotation of the mirror . A mean value of eight individual measurements can also be established. lhus the measurement is indepen-dent both of the rotary speed of the mirror and of any variation in its ro-tary speed, and any lack of geometrical accuracy of the mirror is of no effeet, since a plurality of individual measurements are averaged. ~he continuous determination of individual measurement values can be achieved, however, as well as any other evaluation or additional mode of opera-tion, by means of the microprocessor program. Single measuremen-ts can be ascer-tained and evaluated indi-vidually. ~t is thus possible to ascertain the dif-ference between a maximum and a minimum meas~remen-t value and to eliminate a measurement when this in-creases the maximum value or reduces the minimum value by, for example, more than 10%. Measurements which ha~e been de-termined during a cycle of measure-ment can furthermore be eliminated when the number of flanks occurring in the signal ~ during the cycle is not a whole multiple of eight. A counter may be provided to register each measurement rejected as invalid as well as each valid measuremen-t and -there-by to allow a diagnosis of the measuring device. It is further possible to effect a linearisa-tion in a simple manner. If the lens 5 is not corrected in such a manner that wi-th a constant rotary speed o~
the mirror 3 a constant velocity of transition of the ligh-t beam -through the measurement field between the edges of the window 6 is ef~ected, then a correction or calibration is necessary. ~his calibra-tion can be effected in a manner such that there are coord-inated to all measurement values which exist in the memory 27 in the form of counted impulses of the oscillator 30, corresponding corrected values which are contained in a special memory. ~he provision of these coordinated counts or calibration values can be effected in various ways. lThe impulse counts cor-responding to various posi-tions within the measuring field can be determined experimentally and stored.
~ ~L6~3437 _ 13 -Preferably however a calibration or correction is effected on the basis of a known mathematical corres-pondence between the angle of incidence of the light beam on the lens 5 and the distance of the light beam within the measuring field from the optical a~is. For a given op-tical system and a given deflection mirror there exists a given mathematical function which can be taken into a consideration. For similar lenses, to which the same function basically corresponds, only one valuation is necessary -through the input of characteristic values or constants K to -take into considera-tion the curvature of the function or the variation from a linear course. According to this mathematical relationship a calibration memory can be set up, or a calculating program can be effected by the microprocessor which continuously converts the determined measurement value in accordance with the mathematical relationship. ~his kind of calibra-tion or correction on the basis of mathematical relation-ship can also be matched to existing apparatus in a simple manner during servicing. If, for example, an optical system has to be changed, the corresponding characteristic values can be fed in. In the case of the initially described, known arrangement with a calibration grid, a suitable calibration logic is necessary which is not integrated into the measuring 116~4~7 apparatus and makes ver~ much more di~ficult a cali-bration outside the factory.
~he present invention concerns a process for the contact-free measuremen-t o~ a dimension of at least one object, wherein a ~ine light beam, more especially a laser beam, is deflected across the object, within a measuring field, in the direction o~ the dimension to be measured, and the period of interruption of the light beam by the object is compared with a reference period, and wherein the dimension of the object is ascertained from these periods.
In a known measuring process of this kind the period of interruption of the light beam by the object is compared with the period of the transition of the light beam across a window de~ining the mea~
~5 suring field (US - PS 4,082,L~63). ~he dimension of the object -to be determined thus has the same relation-ship to the dimen.sion of the window opening as -the period of the in-terruption of the light beam b~ the : object has to the period of the transition of the light beam across the measuring field, that is -to say ~rom window edge to window edge. Errors which can occur in this method of measurement due to a non constant velocity of transi-tion of -the light beam across the measuring field are compensa-ted b-~
providing a coarse grid in the measuring field during the manufacture of the measuring app æ atus, b~ means , ~
~61~437 -- 3 ~
of which calibration values can be stored. An inter-polation is necess æy to obtain measurement values between the calibration values. ~his known measuring process of~ers only limited possibilities ~or the determination and processing of measuremen-t values, because data can be collected and processed only at each transition o~ the light beam through predeter-mined points. ~he time available ~or the processing of data is correspondingly short. As stated only a rela-tivel~ coarse calibration is possible ~or which a special program unit is necessary, which is such that a recalibra-tion o~ an installed apparatus during servicing is very di~icult. ~he comparison o~ the dimension to be measured with the dimension o~ a window opening re~uires that this window opening be very accurately measured and does not alter, a condition which is dif~icult to maintain, ~or example, with variations in temperature.
SUMMARY 0~ ~E INVE~I0~
It is the object o~ the present invention -to provide a versatile measuring process which has a min-imum o~ sources o~ error.
~he invention accordingl~ provides a process for measuring a dimension o~ a-t least one object without physicall~ contacting said objec-t, wherein a fine ~_ 4 _ light beam is deflected across the object in the direc-tion of the dimension to be measured, The instants at which the light beam is blocked and unblocked by the object are recorded and stored as measurement data.
The measurement data are evaluated to provide a measure of the dimension by comparison of the period of time defined between the recorded instants with a predeter-mined reference period of time related to the speed of deflection of the light beam. In accordance with the invention, the instants recorded during a plurality of consecutive deflections of the light beam across the object to be measured are stored as measurement data and the evaluation of the corresponding measurement data is effected subsequently and collectively while new data are detected and stored, The invention, in accordance with a further embodiment, provides a process for measuring a dimen sion of at least one object without physically con-tacting said object, wherein a fine light beam is def-lected across the object in the direction of the dimen-sion to be measured. The instants at which the light beam is blocked and unblocked by the object are recor-ded and stored as measurement data, The measurement data are evaluated to provide a measure of the dimen-sion by comparison of the period of time defined bet-ween the recorded instants with a predetermined refer-ence period of time related to the speed of deflection of the light beam, In accordance with the invention, there is provided memory means. The process includes storing in the memory means at time addresses position values corresponding each to one predetermined position of the light beam during its deflection, The values are detected from the memories at the instants at which the light beam is blocked and unblocked by the object.
The process also includes the further step of detecting reference time data and evaluating the dimension and/or position of the object from the position values.
,~., .... . . ..
a -In accordance with a still further embodiment of the invention, there is provided a process for mea-suring a dimension and/or position of at least one object without physically contacting the object. A
fine light beam is deflected across the object in the direction of the dimension to be measured, and the instants at which the light beam is blocked and unblocked by the object are recorded and stored as measurement data.
The measurement data are evaluated to provide a measure of the dimension by comparison of the period of time defined between the recorded instants with a predeter-mined reference period of time related to the speed of deflection of the light beam. In accordance with the invention, there is provided the improvement comprising deflecting the light beam across an optical window having edges defining an instant of entering of the light beam into the window and an instant of the light beam leaving the window. The object is placed in the window, and a periodicity of scanning cycles of the light beam is detected. There is also included the step of storing all data indicative of the instants at which the light beam is blocked and unblocked by the object and by the window respectively and indicative of the scanning cycles.
Calibrated data is stored in accordance with alinearities of the scanning movement of the light beam through the window, and the dimension and/or position of the object is selectively evaluated from the data.
From a different aspect, and in accordance with the invention, there is provided a device for the contact free measurement of a dimension of at least one object.
The device includes a light source for providing a fine light beam, and means for deflecting the light beam across an object to be measured in the direction of the dimension which is to be measured. Means are provided for determining the instants of time at which the light beam respectively impinges upon and moves off the object.
, - 4b -Means are also provided for dynamically storing measure-ment data corresponding respectively to the instants of time, and means are further provided for calculating from the meas~rement data and from a reference value corresponding to the rate of deflection of the light beam the value of the dimension. This value is deter-mined in accordance with the time differences between the instants of time, MeanS are provided for displaying the resulting measurement value, the calculating means having a computer-controlled system including a central processor unit. A first memory is provided for receiving the measurement data during each of a plurality of con-secutive measurement cycles, and a second memory is pro-vided for receiving data from the first memory~ The arrangement is such that between each two consecutive measurement cycles the system operates in the direct memory access mode to transfer data from the first memory to the second memory, and that during each measurement cycle the data contained in the second memory is pro-cessed by the central processor unit whilst the data in the first memory is being updated.
BRIEF DESCRIPTION OF IHE DRAWINGS
Figure 1 is a diagrammatic view of a measuring .
3~7 device, ~igure 2 is a circuit diagram of the device shown in Figure 1, ~igure 3 is a diagram illustrating waveforms occurring in the circuit o~ ~igure 2, and ~igure ~ is a diagram explaining the measure-ment of a transparent object.
DESCRIPIION 0~ ~HE PRE~ERRED EMBODIMEN~
~he device according to ~igure 1 comprises an optical s~stem which partly consists of known ele-ments. A fine laser beam 2 is directed from a dia-grammatically illustra-ted source 1 onto an octagonal mirror 3 driven at a constant rotary speed. ~he re-flected laser beam passes through an objective com-prising a lens 5 and thence passes across a measuring field which is defined by a shutter or a window with boundaries 6. ~he optical system is so arranged that, be~ond the lens 5, the ligh-t beam constantly extends parallel to the optical axis, and is moved from the upper to the lower edge of the window 6-6 as the mirror 3 rotates in the clockwise direction indicated by the arrow in Figure 1. Each facet of the mirror 3 causes one transition of the light beam across the window to effect a corresponding measurement.
In the illustrated example an object 8 to be measured is arranged in the measuring region, and may, for example, be a cable, a wire, a pipe or the like, which runs transversely to the optical axis of the measuring device and o:~ which the outer diameter is to be determined. Beyond the measuring position there is arranged a condenser lens 9 which focuses the laser beam onto a photocell 10. ~he photocell produces an output signal ~ as shown in Figure 3, which is 0 or low when the beam is screened by the window elements 6 or by -the object 8 and which is I or high when the laser beam is unobstructed. As shown in Figure 3, two impulses occur periodically, the impulses begin-ning with the entry of the light beam into the window 6-6 and ending with its exit therefrom, and the gap between the two impulses corresponding to the screen-ing of the beam by the object 8. ~he embodiment o~
Figures 1 and 2 comprises a digital evalua-tion circuit with a microprocessor. A single photocell 22 is ar-ranged on one side o~ the window 6-6, namely the side ~rom which the ligh-t beam enters the window.
As shown in Figure 2 the microprocessor 23 is connected by way of a data bus 24 and an address bus 25 with further circuit parts.
~he input signal ~ from the photocell 10 is applied to a logic circuit 36 incorporating a dif~er-entiator which responds to the rising and falling ~168~37 flanks of impulses of -the input signal, an address counter control arrangement and further control cir-cuits. A signal from a transmitter 3" is also fed to this logic circuit, said signal being produced by a chopper rotating with the mirror 3 and consist-ing of a too-thed disc 3' with 8 -teeth corresponding to the 8 faces of the mirror. The output of an os-cillator 30 is continuously applied to a counter 29 which is thus cons-tan-tly incremented, and -the output of the counter is applied to a memory 27 by way of a buffer latch 28. The oscillator operates, for example, at a frequency of 18 MHz and the counter 29 has a high counting capacity of, for example, 24 bits. The transfer of the output from the counter to the memory 27 is con-trolled by the logic circuit 36 in a manner to be described below. The circuit further comprises an address counter 35 which is connected to the memory 27 and, by way of circuits 37 and 38, wi-th the data bus 24 and the address bus ` 20 25.
A permanent read-only memory 31 defines the progr~m rou-tine and also serves for the storage of correcting data at defined addresses. A dynamic memo~y 32 serves the processor as a working memory for all data -to be processed. An input-output unit 33 applies the measurement values to a display 34.
.
:~16~437 ~ he control of -the memo~y 32 is effected by way of an OR gate 39 either in the direc-t memory access mode by way of the logic circuit 36 or during the pro-cessing of measurement values by the microprocessor (CPU) 23.
~igure 3 shows the inpu-t signals, namely the measurement signal E, which, at the instant No eorres ponding to the entry of the ligh-t beam into the window 6, changes from O to I, -then, during a first transition of the light beam across -the objeet 8 corresponding to the period P1, returns to 0, and again changes to I, when the light beam illuminates the photocell 10 in its transition between the object 8 and the exit from the window 6. A plurality of measurement periods are repea-ted in this manner, eight sueh measurement periods producing the measurement impulses P1 to P8 and corresponding to one measurement cycle or one re~olution of the mirror 3. ~igure 3 also shows the signal C of the chopper as well as a signal C' trans-mit-ted from the logic circuit 36 to the microprocessor (CPU) 23 and formed by di~iding the chopper signal by the factor of eight. At each occurrence of an impulse flank in the signal E, corresponding to each blocking or unblocking of the light beam, the instan-taneous coun-t of the counter 29 is stored in the memory 27 and remains a~ailable there as a measuring value.
~hortly after the occurrence of the flank C" after each cycle of eight measurements, the microprocessor is interrup-ted and the circuit continues to operate in the DMA (direct memory access) mode. All of the values in the memory 27 are thus transferred to the memory 32. When this transfer is complete, the logie circuit is switched to the measurement mode and the microprocessor 23 is caused to run the program. ~ince the DMA~logic has direct access to both memories 27 and 32, the -transfer of the values can be effected in a ma-tter of mil]iseconds, and in the present embodiment i-t can be effected in the time space between -two con-secu-tive measurement cycles, as illustrated in ~igure 3. As the new measuring cycle begins, and new data is read in-to the memory 23, the evaluation of the previously recorded data, in aeeordance with the pro-gram contained in the memory 31, is effected as a separate opera-tion, and the result is then indicated on the display by way of the output circuit 33.
~he program can be changed, and can thus be adapted -to desired re~uiremen-ts, for example to enable the measurement of a plurality of objects located in the measuring field, in which case the evaluation can easily be so programmed that one or more time spans or periods can be ascertained, during which the light beam is screened by a corresponding object, and the dimension of the or each of these objects 8~37 is ascertained in the previously described manner by comp æison of each period, or of a sum of the periods, with the period of the measurement cycle.
Figure 4 shows a possibility for the measure-men-t of cylindrical, transparent objec-ts, for exam-ple plastics tubes for surgical purposes. ~he signal E comprises the rising flank No upon entry of the light beam into -the window 6, as already described.
When the ligh-t beam impinges upon the transparent object total reflection of the light beam occurs so that ligh-t no longer reaches the photocell 10 and a firs-t falling flank N1 occurs in the signal.
Especially with hollow objects, several phases of transmission and reflection of light then occur, which result in the occurrence of a corresponding plurality of signal flanks. At the instant Nx the ligh-t beam moves off the object. A special circuit in the logic elemen-t 36 is effective to ensure that the data for the instants No and N1 alike are trans-ferred to the memory 27. ~he data for the following instants N2 to N(x-1? only reach the buffer latch 28 and are constantly updated in the buffer. ~hat is to say that only the data from the last occurring in-stant is stored. Upon the occurrence of the ~alling flank of the chopper signal the last value which has been read into the buffer 28, which corresponds to ' .
the instant ~x, is transferred to the store 27 and remains available -there for fur-ther processing.
In the preceding case it is assumed -that one measurement is e~fected during each measurement cycle, tha-t is to say that the dimension of the object to be ascertained can be derived ~rom the following periods:
D = K . P1 + P2 + ... P8 No' - ~o in other words the desired dimension D of the object can be derived from the relationship between the sum of the periods of transition of the light beam across the object and the period of one rotation of the mirror . A mean value of eight individual measurements can also be established. lhus the measurement is indepen-dent both of the rotary speed of the mirror and of any variation in its ro-tary speed, and any lack of geometrical accuracy of the mirror is of no effeet, since a plurality of individual measurements are averaged. ~he continuous determination of individual measurement values can be achieved, however, as well as any other evaluation or additional mode of opera-tion, by means of the microprocessor program. Single measuremen-ts can be ascer-tained and evaluated indi-vidually. ~t is thus possible to ascertain the dif-ference between a maximum and a minimum meas~remen-t value and to eliminate a measurement when this in-creases the maximum value or reduces the minimum value by, for example, more than 10%. Measurements which ha~e been de-termined during a cycle of measure-ment can furthermore be eliminated when the number of flanks occurring in the signal ~ during the cycle is not a whole multiple of eight. A counter may be provided to register each measurement rejected as invalid as well as each valid measuremen-t and -there-by to allow a diagnosis of the measuring device. It is further possible to effect a linearisa-tion in a simple manner. If the lens 5 is not corrected in such a manner that wi-th a constant rotary speed o~
the mirror 3 a constant velocity of transition of the ligh-t beam -through the measurement field between the edges of the window 6 is ef~ected, then a correction or calibration is necessary. ~his calibra-tion can be effected in a manner such that there are coord-inated to all measurement values which exist in the memory 27 in the form of counted impulses of the oscillator 30, corresponding corrected values which are contained in a special memory. ~he provision of these coordinated counts or calibration values can be effected in various ways. lThe impulse counts cor-responding to various posi-tions within the measuring field can be determined experimentally and stored.
~ ~L6~3437 _ 13 -Preferably however a calibration or correction is effected on the basis of a known mathematical corres-pondence between the angle of incidence of the light beam on the lens 5 and the distance of the light beam within the measuring field from the optical a~is. For a given op-tical system and a given deflection mirror there exists a given mathematical function which can be taken into a consideration. For similar lenses, to which the same function basically corresponds, only one valuation is necessary -through the input of characteristic values or constants K to -take into considera-tion the curvature of the function or the variation from a linear course. According to this mathematical relationship a calibration memory can be set up, or a calculating program can be effected by the microprocessor which continuously converts the determined measurement value in accordance with the mathematical relationship. ~his kind of calibra-tion or correction on the basis of mathematical relation-ship can also be matched to existing apparatus in a simple manner during servicing. If, for example, an optical system has to be changed, the corresponding characteristic values can be fed in. In the case of the initially described, known arrangement with a calibration grid, a suitable calibration logic is necessary which is not integrated into the measuring 116~4~7 apparatus and makes ver~ much more di~ficult a cali-bration outside the factory.
Claims (17)
1. In a process for measuring at least one without physically contacting said object, wherein a fine light beam is deflected across said object in the dir-section of a dimension to be measured, the instants at which the light beam is blocked and unblocked by said object are recorded and stored as measurement data, and said measurement data are evaluated to provide a measure of the said dimension by comparison of the period of time defined between said recorded instants with a predetermined reference period of time related to the speed of deflection of said light beam, the improvement comprising deflecting said light beam across an optical window having edges defining an instant of entering of said light beam into the window and an instant of said light beam leaving the window, said object being placed in said window, de-tecting the periodicity of scanning cycles of said light beam, storing individually each data indica-tive of said instants at which the light beam is blocked and unblocked by said object and by said window respectively and indicative of said scanning cycles, storing calibrated data in accordance with alinearities of the scanning movement of said light beam through said window, and selectively evaluating by microprocessor means from said data the dimension and or position of said object.
2. In a process for measuring a dimension and or position of at least one object without physically contacting said object, wherein a fine light beam is deflected across said object in the direction of the dimension to be measured, the instants at which the light beam is blocked and unblocked by said object are detected and stored as measuring data, and said measuring data are evaluated to provide a measure of said dimension, the improvement comprising providing memory means, storing in said memory means separate values each corresponding to one predetermined posi-tion of said light beam during its deflection, detect-ing stored values from said memories defining the instants at which the light beam is blocked and un-blocked by said object, detecting further reference time data and evaluating said dimension and or posi-tion of said object from said values and reference time data.
3. In a process for measuring a dimension of at least one object without physically contacting said object, wherein a fine light beam is deflected across said object in the direction of the dimension to be measured, the instants at which the light beam is blocked and unblocked by said object are recorded and stored as measurement data, and said measurement data are evaluated to provide a measure of the said dimension by comparison of the period of time defined between said recorded instants with a predetermined reference period of time related to the speed of de-flection of said light beam, the improvement wherein said instants recorded during a plurality of consecu-tive deflections of the light beam across the object to be measured are stored as measurement data, and the evaluation of the corresponding measurement data is effected subsequently and collectively while new data are detected and stored.
4. A process according to Claim 1 or Claim 3, wherein the deflection of the light beam is effected by means of a polygonal rotating mirror, and the time period between two consecutive transitions of the light beam through a defined position is used as a basis for the reference period.
5. A process according to Claim 1 or Claim 3, wherein the deflection of the light beam is effected by means of a polygonal rotating mirror, and the period of rotation of the mirror is used as a basis for the reference period.
6. A process according to Claims 1, 2 or 3, wherein the deflection of the light beam is effected by means of a polygonal rotating mirror, the said evaluation is effected by means of a micro-processor system arranged to receive said measurement data together with a chopper signal generated by a mechanism rotating with said mirror.
7. A process according to Claims 1, 2 or 3, wherein individual measurement results which differ substantially from a ascertained means value from a number of results are rejected.
8. A process according to Claims 1, 2 or 3, wherein a number of individual measurement results which differ sub-stantially from an ascertained mean value from a number of results is registered and utilized to check the operation of the apparatus.
9. A process according to Claims 1, 2 or 3, wherein those measuring results are rejected which yield a number of measurement data which is not a whole multiple of the number of mirror faces of a polygonal mirror provided for effecting the deflection of the light beam.
10. A process according to Claims 1, 2 or 3, wherein those measuring results are rejected which yield a number of measurement data which is not a whole multiple of the number of mirror faces of a polygonal rotating mirror provided for effecting the deflection of the light beam, and wherein the number of rejected measurements is registered and utilized for checking the operation of the apparatus.
11. A process according to Claim 1, wherein a calibra-tion or correction of the measurement is carried out on the basis of the mathematical correlation between the angle of incidence of the light beam upon an optical system for di-recting the light beam onto said object and the distance of the light beam from the optical axis of said system when emitted from said system towards the object.
12. A process according to Claim 11, wherein the said calibration or correction is effected continuously by means of a computer.
13. A process according to Claim 11, wherein cali-bration or correction data corresponding to the measure-ment data are stored and are read out of the store during the measurement.
14. A device for the contact free measurement of a dimension of at least one object, comprising a light source for providing a fine light beam, means for de-flecting said light beam across an object to be measur-ed in the direction of the said dimension which is to be measured, means for determining the instants of time at which said light beam respectively impinges upon and moves off said object, means for dynamically stor-ing measurement data corresponding respectively to said instants of time, means for calculating from said measurement data and from a reference value correspond-ing to the rate of deflection of said light beam the value of said dimension, determined in accordance with the time difference between said instants of time, and means for displaying the resulting measurement value, said calculating means having a computer-controlled system including a central processor unit, a first memory for individually receiving each of said measure-ment data during each of a plurality of consecutive measurement cycles, and a second memory for receiving data from said first memory, the arrangement being such that between each two consecutive measurement cycles the system operates in the DMA (direct memory access) mode to transfer data from the first memory to the second memory, and that during each measurement cycle the data contained in the second memory is processed by said central processor unit whilst the data in the first memory is being updated.
15. A device according to Claim 14, wherein the said means for deflecting said light beam comprises a rotary poly-gonal mirror, and said device further comprises means for producing an output signal corresponding to the periodic de-flection of the light beam by said mirror, the said means for calculating the value of said dimension being arranged to re-spond to said output signal to provide the said reference value.
16. A device as claimed in Claim 15, including a logic circuit arranged to respond to the said output signal corre-sponding to the periodic deflection of the light beam and to control in accordance with said signal the cycle of storage and processing of measurement data.
17. A device as claimed in Claim 16, wherein said means for producing said output signal comprises a chopper device arranged to cooperate with said rotary mirror.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH231480A CH645462A5 (en) | 1980-03-25 | 1980-03-25 | METHOD AND DEVICE FOR THE CONTACTLESS MEASUREMENT OF A DIMENSION OF AT LEAST ONE OBJECT. |
| CH2'314/80-5 | 1980-03-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1168437A true CA1168437A (en) | 1984-06-05 |
Family
ID=4230897
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000373326A Expired CA1168437A (en) | 1980-03-25 | 1981-03-18 | Process and device for the contact free measurement of a dimension |
Country Status (11)
| Country | Link |
|---|---|
| JP (1) | JPS56150302A (en) |
| AU (1) | AU538202B2 (en) |
| BE (1) | BE888013A (en) |
| CA (1) | CA1168437A (en) |
| CH (1) | CH645462A5 (en) |
| DE (1) | DE3111356A1 (en) |
| ES (1) | ES8203150A1 (en) |
| FR (1) | FR2479447B1 (en) |
| GB (1) | GB2072840B (en) |
| IT (1) | IT1135714B (en) |
| ZA (1) | ZA811935B (en) |
Families Citing this family (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5937405A (en) * | 1982-08-26 | 1984-02-29 | Mitsutoyo Mfg Co Ltd | Photoelectric type measuring device |
| JPS6134410A (en) * | 1984-07-26 | 1986-02-18 | Mitsutoyo Mfg Co Ltd | Optical measuring apparatus |
| US4730116A (en) * | 1985-08-06 | 1988-03-08 | Mitsubishi Denki Kabushiki Kaisha | Sheet thickness measuring apparatus by optical scanning |
| JPS6249202A (en) * | 1985-08-28 | 1987-03-03 | Mitsutoyo Mfg Corp | Optical measuring apparatus |
| CH672184A5 (en) * | 1985-12-17 | 1989-10-31 | Manfred Meyer | |
| CH674774A5 (en) * | 1986-04-03 | 1990-07-13 | Zumbach Electronic Ag | |
| DE3713109A1 (en) * | 1987-04-16 | 1988-11-03 | Limess Licht Messtechnik Gmbh | Device for measuring workpieces |
| KR920004750B1 (en) * | 1988-01-19 | 1992-06-15 | 미쓰비시전기 주식회사 | Thickness measuring method |
| DE3815011A1 (en) * | 1988-04-30 | 1989-11-16 | Leybold Ag | DEVICE FOR NON-DESTRUCTION-FREE MEASUREMENT OF THE RESISTANT THIN LAYERS |
| DE3816322A1 (en) * | 1988-05-13 | 1989-11-23 | Udo Dr Ing Tutschke | Method and device for the contactless measurement of the external dimensions of bodies |
| GB8816346D0 (en) * | 1988-07-08 | 1988-08-10 | Kyriakis J | Apparatus for monitoring product in hostile environment |
| DE3824820A1 (en) * | 1988-07-21 | 1990-01-25 | Gebhard Birkle | DEVICE FOR CONTACTLESS OPTICAL DETERMINATION OF GEOMETRIC DIMENSIONS OF AN OBJECT |
| DE4024849A1 (en) * | 1990-08-06 | 1992-02-13 | Horn Hannes Dr Schulze | Object dimension digital measurement - uses pulsed laser beam passed across pulse detection path in repeated, pref. oscillatory, manner |
| DE9013559U1 (en) * | 1990-09-27 | 1990-12-06 | Mesacon Gesellschaft für Meßtechnik mbH, 4600 Dortmund | Optical device for measuring the speed or length of a moving surface |
| FR2678727A1 (en) * | 1991-07-04 | 1993-01-08 | Tabacs & Allumettes Ind | CALIBRATION METHOD AND DEVICE, IN PARTICULAR FOR CIGARETTES, USING THE DETERMINATION OF THE INTERCEPTION TIME OF A LASER BEAM. |
| DE4201385A1 (en) * | 1992-01-21 | 1993-07-22 | Peter Dipl Ing Renner | Optical measurement system with light curtain, photoelectric receiver - contains null point, linearity error correction circuit for digitised receiver signal |
| DE19516154A1 (en) * | 1995-05-03 | 1996-11-14 | Hell Ag Linotype | Optical position determining arrangement for rotating objects |
| EP3047232B1 (en) * | 2013-09-16 | 2022-04-06 | Steinfurth Mess-Systeme GmbH | Method and device for establishing a geometry of a container for packaging a flowable medium |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1191591B (en) * | 1958-01-17 | 1965-04-22 | Licentia Gmbh | Method for photoelectrically determining the relative position of at least one edge of an object |
| JPS5335569A (en) * | 1976-09-14 | 1978-04-03 | Asahi Glass Co Ltd | Method of measuring outer diameter of transparent substance |
| US4097849A (en) * | 1976-09-27 | 1978-06-27 | Systems Research Laboratories, Inc. | Electronic comparator for process control |
| US4082463A (en) * | 1977-01-06 | 1978-04-04 | Systems Research Laboratories, Inc. | Calibrated optical micrometer |
| JPS53119079A (en) * | 1977-03-26 | 1978-10-18 | Tatsu Akutsu | Measuring method of diameter of running filamentous articles |
| US4168126A (en) * | 1977-07-05 | 1979-09-18 | Altman Associates, Inc. | Electro-optical measuring system using precision light translator |
-
1980
- 1980-03-25 CH CH231480A patent/CH645462A5/en not_active IP Right Cessation
-
1981
- 1981-03-18 CA CA000373326A patent/CA1168437A/en not_active Expired
- 1981-03-18 FR FR8105566A patent/FR2479447B1/en not_active Expired
- 1981-03-19 BE BE1/10179A patent/BE888013A/en not_active IP Right Cessation
- 1981-03-20 AU AU68585/81A patent/AU538202B2/en not_active Ceased
- 1981-03-23 GB GB8108947A patent/GB2072840B/en not_active Expired
- 1981-03-23 DE DE19813111356 patent/DE3111356A1/en active Granted
- 1981-03-23 ZA ZA00811935A patent/ZA811935B/en unknown
- 1981-03-24 IT IT20686/81A patent/IT1135714B/en active
- 1981-03-25 JP JP4258181A patent/JPS56150302A/en active Pending
- 1981-03-25 ES ES500695A patent/ES8203150A1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| ES500695A0 (en) | 1982-03-01 |
| AU6858581A (en) | 1981-10-01 |
| GB2072840A (en) | 1981-10-07 |
| JPS56150302A (en) | 1981-11-20 |
| AU538202B2 (en) | 1984-08-02 |
| GB2072840B (en) | 1983-11-09 |
| DE3111356A1 (en) | 1982-03-25 |
| FR2479447A1 (en) | 1981-10-02 |
| FR2479447B1 (en) | 1986-06-27 |
| CH645462A5 (en) | 1984-09-28 |
| ZA811935B (en) | 1982-04-28 |
| DE3111356C2 (en) | 1988-05-11 |
| BE888013A (en) | 1981-07-16 |
| ES8203150A1 (en) | 1982-03-01 |
| IT1135714B (en) | 1986-08-27 |
| IT8120686A0 (en) | 1981-03-24 |
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