Title of Invention

AN APPARATUS FOR NON INVASIVE MEASUREMENT OF SPATIAL PARAMETERS OF A DISTANT OBJECT

Abstract

The invention provides an apparatus for non-invasive Measurement of spatial parameters of a distant object comprising a camera (3) and two light sources (1,2), positioned in one plane for creating two images or spots with their respective power sources (14,12,13). The outputs of the camera (3) can be connected to a processing unit (15) for processing the spot images captured by the camera and producing two distant spots (18,19) for computation of the parameters. In the case of measurement of parameters under dynamic conditions, a speed transducer (16) can be provided for measuring the relative speed of the apparatus and the object, the speed transducer (16) also being connected to the processing unit (15).

Full Text

The present invention relates to an apparatus for measurement of spatial parameters of a distant object under static or dynamic condition. More specifically, the invention relates to an apparatus for non-invasive or contactless measurement of spatial parameters of a distantly located rod like long object under static for dynamic conditions. Measurement under dynamic conditions means that either the object or the measuring device or both are in motion having a relative' speed between them. The current practice for measurement of spatial parameters of a distant object like its height (from a base like the ground) or distance (from another object), stagger (in a horizontal plane) or deviation (in a vertical plane), horizontal inclination or vertical gradient, and size or diameter (in case of rod or wire shaped objects) ranges from manual to automatic methods. However there is no single apparatus for specific technique that can accommmodate measurement of so many parameters from a single operation. Amongst the automatic methods, there are invasive or contact type and non-invasive or contactless measurement techniques. Height or distance can be measured using a light source and one two cameras as in the triangulation technique. Gradient or inclination can also be determined from the same, if measurements are made at known intervals of spacings. Height from a base or distance of an object from another object can - 3 - also be determined in a limited way using ultrasonic and microwave techniques. These are also non-invasive techniques. Invasive techniques may use various displacement transducers like linear potentiometer LVDT. However contactless method of measurement of stagger and size or diameter of a rod like object through a single operation is not known. Manual and invasive (contact type) measurements are suitable for static measurements. For moving objects they are not suitable. Invasive techniques of measurements in hazardous, corrosive and inaccessible environments are unfit for consideration. On the other hand, the optical triangulation method used in height or distance (range) measurement from a distance from the object cannot be adopted for moving objects. The method uses two cameras and one light source. The cameras are required to be focused on the object. In case of vibrating objectds and out door environment optical triangulation method appears to be unsuitable. The invasive methods are limited to short ranges, under normal environmental conditions and for static or at best for slowly moving objects. For very large distances, the time of flight measuremen6t technique using lasers is very accurate but expensive and involves complex hardwere. Thus,one object of the invention is to provide an apparatus which can determine simultaneously from one measurement all - 4 - four spatial parameters, namely height or distance, gradient or inclination,stagger or deviation,and object size or diameter. Another object of the invention is to provide an apparatus for on line measurement of above spatial parameters of static as well as dynamic (moving) objects. Yet another object of the invention is to provide an apparatus for non-invasive or contactless technique of measurement which makes it suitable for hazardous and corrosive environments and inaccessible areas. A further object of the. invention is to provide an apparatus for measurement of spatial parameters of an object that is not affected by electromagnetic interference (EMI) or radio frequency interference (RFI). One more object of the invention is to provide expanded laser beam line which ensures two images (spots) on the moving object even when the latter is swinging on both sides of its initial position. A still further object of the invention is to provide an apparatus that uses fast and effective noise filtering, compensation and corrections to measurements made for giving accurate and faster results. - 5 - One more object of the invention is to provide an apparatus, where by suitable choice of laser sources and camera it is possible to use the apparatus in day light. However, for measurements in the night or dark environment, visible lasers or light sources with focusing arrangements are sufficient. Yet one more object of the invention is to provide an apparatus, where different combinations of one laser source and one light source with focusing arrangement or two light sources with focussing arrangements, and with or without beam expanders, and with, one CCD camera or vide camera to make the measurements possible depending on cost and accuracy desired. In the present invention, two light sources with focusing arrangement or two laser sources or one laser source and one light source with focusing arrangement create two images or spots on the object with a camera. The camera can be a video camera. It can also be a charge coupled device which can provide digital images using array of detectors. The camera is focused on the images and connected to a processing unit or a PC through a video card. The technique adopted is a modified active triangulation method. Though it is not essential, the light beams or the lasers are expanded through two cylindrical lens systems and the spot images created by the light stripes are captured in the camera - 6 - and processed to obtain two distinct spots out of the images corrupted with ambient and other noise. This can also be done in specific cases without using beam expanders. Using the modified triangulation method, distance (for horizontal focusing) or height (for vertical focusing) is computed. Gradient of the object is determined by moving the apparatus through a known distance along the length of the object and by computing the difference in height at the two extreme locations with respect to the distance moved. Similarly, the deviation from an axis in a horizontal plane can be determined. The stagger or movement of the object on either side of a predetermined axis (horizontal or vertical) is computed from the movement of the line joining the two spots as captured by the CCD camera in terms of pixels (picture cells) or it can be imaged by the video camera. The spot size as detected by the camera (in terms of pixels or spatial distance) is used to determine the diameter of a rod or wire type object. The measurements are accomplished through an integrated system by creation of two images on the object by using two laser sources or one laser source and one light source or two light sources. A video camera or a CCD is used for grabbing these two images created on the object by the two laser sources or two light sources or one laser source and one light source. The - 7 - images are processed including filtering of environmental noise. Difference between the two images (or spots) in terms of pixels or spatial distance is used to compute height or distance. Distance between measured values of height of distance at two known intervals of length along the object axis is used to compute gradient or inclination. The shift of the line joining the two images on either side of a predetermined axis is used for determination of stagger or deviation of the object. The number of pixels occupied by each of the images or the spatial length of each image is used to determine size or diameter of a rod or wire shaped object. According to this invention, there is provided an apparatus for non-invasive measurement of spatial parameters of a distant object under static or dynamic conditions comprising a camera and two light sources for creating two images or spots with their respective power sources; said camera and said light sources being positioned in one plane so that their axis is parallel to the object or fixed in position with respect to a reference line; output of said camera being connected to a processing unit for processing said spot images captured by the camera to produce two distinct spots for computation of parameters. The invention will now be described with reference to the accompanying drawings where : - 8 - Figure 1 shows, in schematic view, the apparatus of the present invention; Figure 2 shows the method of measuring stagger of an object. Referring to Figure 1, the two light sources with focusing arrangement 1,2 or two laser sources or one laser source and one light source with focusing arrangement and a video camera 3 or a CCD camera are rigidly positioned and aligned in such a manner that their axis 4 is parallel to the linear object 5 or fixed in position with respect to a reference line. The laser sources or the. light sources or the laser source and the light sources 1,2 are fitted with beam expanders (cylindrical lenses) 6,7 at their apertures or they are without the beam expanders. The beam expanders when fitted, produce parallel light stripes 8,9 which intersect the object 5 at 10,11 producing spot images. If the beam expanders are not fitted by focusing 1,2 on the object 5 two spot images will be obtained. In the figure 12,13 and 14 are the power supplies to the laser sources or light sources or laser source and light source and the camera. The output of the video or CCD camera 3 is interfaced with a PC 15. A speed transducer 16 measures the speed of the apparatus (or the relative speed between the apparatus and object) and its output is fed to the PC 15. Knowing the distance travelled between two consecutive - 9 - measurements, the gradient or slope of the object 5. can be determined. The shifting of the spot-pair 18,19 (Fig.2) obtained from the images created on the object 10,11 (Fig.l) along x-direction in the array of detectors 17 (in terms of pixels) (Fig.2) of the CCD camera 3 is a measurement of stagger of the object 5. The shifting in case of video image in terms of spatial distance will give the same measurement. The spot size imaged in the camera detectors (each spot may occupy more than one pixel of the CCD camera or spatial length in case of a video camera)gives the diameter or size of the line object 5. The distance D between the image 18 and image 19 (Fig.2) along y-direction provides the measure of height using polynomial expressions. Gradient is calculated from the heights computed at two different positions and the distance travelled between these two positions as given by processed output of the speed transducer 16. The apparatus is useful for measurement of height,gradient,stagger and diameter of a contact wire in railway electric traction where the contact wire is kept at high voltage potential and not convenient for invasive technique of - 10 - measurement. It can also be used for monitoring sag of a high voltage transmission line. In addition the system can be used for erection of high rising structures. The apparatus is applicable with ease for measurement of spatial parameters of an object irrespective of how the object is located or in which direction it is moving. A prototype of the apparatus was developed which was mounted inside a 8-wheeler railway tower wagon (inspection car) along the width of the viewing window of the test car. Test runs between two stations about 40 kms apart were conducted for measurement of spatial parameters of the contact wire of the electric traction, which was at 25 KV potential, under dynamic conditions (with various speeds of the inspection car between 20 kmph and 60kmph). The following test results were obtained, which are found to be better from accuracy point of view, than the requirements of the Indian Railways. Similar experiments in the laboratory under static conditions were performed and measured values were found to be in conformity - 11 - with the values measured manually. It is therefore, inferred that the accuracy in measurment under static and dynamic conditions or under vibration remains unaltered. 1. Height of the contact 4.8 to 5.85m ± 2 cm wire from the rail 2. Stagger of the contact -35 to 35 cm ± 1 cm wire from the central axis of the tower wagon 3. Gradient of the contact wire 3mm/m ± 10% computed from measured heights at intervals of known distances 4. Diameter of the contact wire 9 mm caution dia indicating wear and tear due to friction with the pantograph 12 WE CLAIM: 1. An apparatus for non-invasive Measurement of spatial parameters of a distant abject (5) comprising : a camera (3) and two light sources (1,2) for creating two images or spots with their respective power sources (14,12, 13): said camera (3) and said light sources (1,2) being positioned in one plane so that their axis (4) is parallel to the object (5) or fixed in position with respect to a reference line; outputs of said camera (3) being connected to a processing unit (15) for processing said spot images captured by the camera to produce two distinct spots (18,19) for computation of parameters 2. The apparatus as claimed in claim 1, wherein a speed transducer (16) is provided with its output connected to said processing unit (15) for measuring the relative speed between the apparatus and the object. 3. The apparatus as claimed in claim 1, wherein said camera (3) is a video camera. 4. The apparatus as claimed in claim 1, wherein said camera (3) is a charge coupled device (CCD). 3. -13- 5. The apparatus as claimed in claim 1, wherein said light sources (1, 2) are fitted with focusing arrangement. A. The apparatus as claimed in claim 1, wherein said light sources (1, 2) are lasers. 7. The apparatus as claimed in claim 1, wherein said light sources (1,2) comprise one laser source and one light source fitted with focusing arrangement. 8. The apparatus as claimed in claim 5, wherein said laser sources (1, 2) are each fitted with one beam expander (6,7) for producing parallel light stripes (8,9) which intersect the object (5) at (10,11) to produce spot images on the moving object. 9- The apparatus for non-invasive measurement of spatial parameters of a distinct object under static or dynamic conditions substantially as herein described and illustrated in the accompanying drawings. Dated this 10th day of May, 2000 The invention provides an apparatus for non-invasive Measurement of spatial parameters of a distant object comprising a camera (3) and two light sources (1,2), positioned in one plane for creating two images or spots with their respective power sources (14,12,13). The outputs of the camera (3) can be connected to a processing unit (15) for processing the spot images captured by the camera and producing two distant spots (18,19) for computation of the parameters. In the case of measurement of parameters under dynamic conditions, a speed transducer (16) can be provided for measuring the relative speed of the apparatus and the object, the speed transducer (16) also being connected to the processing unit (15).

Documents:

00280-cal-2000 abstract.pdf

00280-cal-2000 claims.pdf

00280-cal-2000 correspondence-1.1.pdf

00280-cal-2000 correspondence-1.2.pdf

00280-cal-2000 correspondence.pdf

00280-cal-2000 description (complete).pdf

00280-cal-2000 drawings.pdf

00280-cal-2000 form-1.pdf

00280-cal-2000 form-19.pdf

00280-cal-2000 form-2.pdf

00280-cal-2000 form-3.pdf

00280-cal-2000 p.a.pdf

280-CAL-2000-FORM 27.pdf