GB2166236A

GB2166236A - A method and apparatus for contactlessly determining the diameter of material to be measured

Info

Publication number: GB2166236A
Application number: GB08519681A
Authority: GB
Inventors: Franz Pozimski; Jorg Krieger; Hans Hocke; Gerhard Grellmann
Original assignee: Schwermaschinenbau Kombinat Ernst Thalmann VEB
Current assignee: Schwermaschinenbau Kombinat Ernst Thalmann VEB
Priority date: 1984-10-29
Filing date: 1985-08-06
Publication date: 1986-04-30
Also published as: GB8519681D0; GB2166236B; DD248035A3; DE3520758A1

Abstract

The invention relates to a method and an apparatus for contactlessly determining the diameter of elongate or bar-like material to be measured, preferably for the rolled material and cable, in which the image of the material 3 to be measured is divided by a semi-transparent mirror 5 into two images 10, 11 of equal size, each with half the brightness or brightness of the same magnitude, and the optical axes 21, 22 are at an angle of from 10 to 170 DEG , preferably 90 DEG , relative to each other. Each image portion is scanned by a respective CCD sensor 6, 9 arranged to view a region of the image portion corresponding to a different region of the object 3, the regions being separated from a centre-line by spaces 12, 13. <IMAGE>

Description

SPECIFICATION A method and apparatus for contactlessly determining the diameter of material to be measured This invention relates to a method and apparatus for contactlessly determining the diameter of elongate or bar-like material to be measured, particularly, but not exclusively, rolled material and cable.

German laid-open application (DE-OS) No 27 50 109 discloses a laser scanning method and an apparatus for carrying it into effect, wherein a laser beam is deflected by way of a rotary polygonal mirror. The divergent beams are put into a parallel condition by an optical means. The object to be measured is disposed in the parallel beam of the measuring field. The parallel beam is then focussed on to a photoreceiver by an optical means.

By way of synchronisation of the beam transit time through the measuring field, the diameter of the material to be measured is ascertained from the dark time, while the laser beam is cut off or shaded by the material to be measured. The disadvantage in that connection is the high level of manufacturing and adjustment expenditure in regard to the individual optical components. Furthermore, with a large measuring field, the optical means for putting the beam into a parallel condition and for focussing the beam suffers from severe image defects or aberrations.

DD patent specification No. 152 988 discloses a method and an apparatus wherein the size of the shadow of an object to be measured, which is projected through an objective lens, is measured by a line of diodes. The size of the object to the measured is obtained from the image-forming scale of the objective lens, in conjunction with the spacing of the sensors in the line. That method and apparatus suffer from limitations in regard to the measuring field and systematic measurement errors when dealing with oscillating objects to the measured.

The aim of the invention is to provide an increase in the size of the object field with the same degree of resolution, and to provide for oscillation error compensation.

The invention is based on the problem of providing a method and an apparatus which measures material to be measured, of an elongate or bar-like or strand-like configuration, which is freely movable in the measuring field, with a diameter > 5 millimetres, with a degree of resolution c 10 ijm, without using mechanically moved components.

According to the present invention in one aspect there is provided a method for contactlessly determining the diameter of elongate or bar-like material to be measured, wherein the material to be measured is irradiated in a rearward mode by a light source by way of a condenser and evaluated with an electronic grid, said material to be measured being divided by a semi-transparent mirror into two images of equal size, each with half the brightness or brightness of the same magnitude, which is scanned by a respective charge-coupled device, wherein one CCD scans the lower half of the image and the other COD scans the upper half of the image, and a fixed intermediate space is provided.

In the method, the material to be measured is irradiated in a rearward mode by a light source, by way of a condensor, and evaluated with an electronic grid.

It is in accordance with the invention that the material to be measured is divided by a semitransparent mirror into two images of equal size, each with half the brightness or brightness of equal magnitude. The image is scanned by a respective charge-coupled device (CCD line). In that connection, the one COD line scans the lower half of the image and the other COD line scans the upper half of the image, with a respective intermediate space in each case.

It is also in accordance with the method of the invention that the COD lines are scanned jointly with a shift of half a cycle, but in opposition in regard to their direction, and the fixed intermediate space is given prior or subsequently thereto.

According to the present invention in another aspect there is provided apparatus for carrying out the method, wherein disposed in succession on the optical axis thereof is a light source, a condenser, an objective lens and an electronic grid, and that there are provided two optical axes which are at an angle of 10 to 1700, relative to each other, and COD lines provided at the end of the optical axes are disposed at the same spacing relative to a semi-transparent mirror provided between the objective lens and the COD line.

An embodiment of the invention will now be described, by way of an example, with reference to the accompanying drawings, in which: Figure 1 shows diagrammatically the measuring apparatus according to the present invention; and Figure 2 shows the timing or cycle regime.

Referring to Figure 1, disposed in succession on an optical axis 21 is a light source 1, a condenser 2, the material 3 to be measured, an objective lens 4, a semi-transparent mirror 5 and the image plane 6 with a COD line 8 arranged above the optical axis 21. Between the COD line 8 and the optical axis 21 is an intermediate space 12. A further optical axis 22 extends through the mirror 5 and includes an image plane 7 with a COD line 9 and an intermediate space 13 between the COD line 9 and the optical axis 22. The spacing between the COD line 8 and the mirror 5 is equal to the spacing between the COD line 9 and the mirror 5. The lines 8 and 9 are disposed in different planes. In other words, the optical axes 21 and 22 are disposed at and an angle a of from 10 to 1700, preferably 90 , relative to each other.

As shown in Figure 1, the light beam emitted by the light source 1 is put into a parallel condition by the condenser 2. The material 3 is divided by the objective lens 4 and the semi-transparent mirror 5 into two images of equal magnitude, each with half the brightness or brightness of the same magnitude, on the two image planes 6 and 7. The COD line 9 scans the upper half 10 of the image while the COD line 8 scans the lower half 11 of the im age. The intermediate spaces 12 and 13 respectively are equal to or greater than zero and serve to increase the field of the material being measured. In addition, that eliminates partial adjustment of the COD lines 8 and 9 relative to each other as the intermediate spaces 12 and 13 are determined electrically.The value in respect of the intermediate space 12 or 13 respectively is determined once and non-erasably introduced into a memory means 14. A logic means 15 controls the operating sequence in respect of time so that the line signals are read into a counter 18 by way of a signal processing means 16 and 17 in accordance with the zip closure principle in accordance with Figure 2, in parallel mode, but shifted by half a cycle, and then the intermediate spaces 12 and 13 are read into the counter 18, from the memory means 14. In the case of the group of digits shown in Figures 2, the first digit - 1 or 2 - denotes the COD line 8 or 9 and the second digit - 1 to n - denotes the corresponding image point. The counter content is fed to a display unit 20 by way of an interim memory 19.

Relative to the optical axis 21, the COD lines 8 and 9 operate from the inside outwardly or from the outside inwardly. That mode of operation permits oscillation error compensation. A controller 23 provides for a uniform strength of illumination.

The invention makes it possible to increase the size of measuring field to be ascertained, with the same degree of resolution.

Oscillation error compensation is provided as a result of the mutually opposite scanning procedure.

Claims

1. A method for contactlessly determining the diameter of elongate or bar-like material to be measured, wherein the material to be measured is irradiated in a rearward mode by a light source by way of a condenser and evaluated with an electronic grid, said material to be measured being divided by a semi-transparent mirror into two images of equal size, each with half the brightness or brightness of the same magnitude, which is scanned by a respective charge-coupled device, wherein one COD scans the lower half of the image and the other COD scans the upper half of the image, and a fixed intermediate space is provided.

2. A method as claimed in claim 1, in which the COD lines are scanned jointly with a shift of half a cycle but in opposition in regard to their directions, and the fixed intermediate space is provided previously or subsequently thereto.

3. Apparatus for carrying out the method claimed in claim 1, wherein disposed in succession on the optical axis thereof is a light source, a condenser, an objective lens and an electronic grid, and there are provided two optical axes which are at an angle of 10 to 1700, relative to each other, and COD lines provided at the end of the optical axes are disposed at the same spacing relative to a semi-transparent mirror provided between the objective lens and the COD line.

4. Apparatus as claimed in claim 3, in which the two optical axes are at an angle of 90" relative to each other.

5. A method of contactlessly determining the diameter of elongate or bar-like material to be measured, substantially as hereinbefore described.

6. Apparatus for contactlessly determining the diameter of elongate or bar-like material to be measured, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.