EP1309886A2

EP1309886A2 - 3d motion distant measuring device from a single reference point

Info

Publication number: EP1309886A2
Application number: EP00988998A
Authority: EP
Inventors: Guido A. Danieli
Original assignee: LUISE NADIA SILVANA
Current assignee: Calabrian High Tech Srl
Priority date: 1999-12-15
Filing date: 2000-12-15
Publication date: 2003-05-14
Also published as: ITCS990021A1; WO2001044834A3; WO2001044834A2

Abstract

The present invention is relative to a measuring device of the components of the displacement of one point in three perpendicular directions. Base of the instrument, a Laser distance measuring system, that, measuring the phase shift of the ray refracted by a refracting element placed on the point of measure, supplies with millimetric precision the variation of the distance between laser source and refractive element. The conventional instrument is not however able to measure displacements in a plane perpendicular to the laser ray. The present invention instead, adding to the refractive element a video camera, mounted with the refractive element on a plate motorised by two step motors, and a second light source parallel to the first laser to generate on the video camera sensor a light spot, allows, analysing the digital image, to maintain always the refractive element centred with respect to the ray, acting on the step motors. Since the displacements necessary to maintain the image centred are exactly opposite to those of which the instrument is displaced, the simple recording of the movements supplies the two perpendicular components. A second possible configuration is also presented, characterised by an inferior sensitivity to x, y displacements.

Description

Description 3D motion distant measuring device from a single reference point- Brief description of the state of the art.

Displacement's distant optical measurements are of fundamental utility in modern technique. For these measurements the LASER is becoming increasingly important.

However the simpler systems supplies only distance, thus, if one needs a three dimensional measurement, one needs using three interferometric lasers in three directions bearing a sufficient mutual inclination. This however imposes to choose three fixed reference points, which is not always simple to obtain. The present invention allows instead to obtain all components of the motion of a point starting from a single reference point, simply motorising the refractive element of a Laser, that must reflect the Laser ray to allow the measurement of the phase shift and hence of the distance, adding on the side of the first laser, a second laser or a light source whose ray must be focused to generate a light dot in proximity of the refractor element, on a CCD sensor (CCD, Charge Coupled Device) of a digital video camera, whose optic has been replaced by a black tube to reduce natural light interference. In this way, the spot of light generates an image on the CCD. Alternatively, reducing the instrument sensitivity, the entire video camera complete with optical system is placed inside a container presenting a dark screen in front of the camera to cut the natural light, while the bright spot generates once again an image on the video camera sensor. All these elements have then to be mounted on a device able to move on a plane approximately perpendicular to the Laser ray. The image so generated is transmitted to a computer or digital processor, that, with a programme in Visual Basic or in any other language, analyses the image to detect position modifications, and moves the device with the help of step motors to newly centre the image.

It is hence enough to register the commands supplied to the step motors to newly centre the image, since these movements are equal and opposite to the displacement of the spot. The Figure 1 illustrates the system in its completeness, with the two lasers placed in parallel and fixed to the reference system, and with refractor and video camera mounted on the system of which the displacement must be measured.

In Figure 2 is schematised the distal portion of the measuring device, containing the step motors, video camera and refractors.

As a further alternative, it is possible to utilise only one laser of the interferometric type, placing the video sensor behind the refracting plane, in correspondence to a small hole made on the same refracting plane, and using a tube long as much as the space between refracting plane and video sensor to eliminate light coming from any other source than the hole. In order however to have a fair sensitivity, to motion in the x, y plane, the tube must be rather long, since the measurement sensitivity to the beam displacement is reduced by the factor b / a (tube length) / (distance of the measuring plane from the laser source). This is schematically shown in Fig. 3.

Claims

Claims.

1) 3D Displacements measuring system using laser technology, able to supply at one time the x, y and z components, starting from a single reference point, composed by an interferometric laser system complete with refractive element, and by a light source, eventually completed by an optical system, used to generate a light spot on a video camera deprived of the optic, or provided by a protective screen, and by a pair of electronically controlled motors, used to reposition the image on the video sensor in the original position moving the sensor on a plane perpendicular to the impinging ray. 2) 3D Displacements measuring system using laser technology, as per claim 1, but in which the second light source is also a laser.

3) 3D Displacements measuring system using laser technology, as per claim 1, but in which the video camera is solid state (CCD sensor).

4) 3D Displacements measuring system using laser technology, as per claim 1, but in which the image is formed directly on the video sensor without any optical system, protecting the sensor with a black tube and a filter to eliminate natural light interference.

5) 3D Displacements measuring system using laser technology, as per claim 1, but in which the image is formed on a dark screen, while the video camera is kept inside a water and light proof container, holding the dark screen in front of the camera, complete with optical lenses, which sees a luminescent spot on the dark screen.

6) 3D Displacements measuring system using laser technology, as per claims 1 - 5, in which a second pair of motors has been added, used to correct also the orientation of the refractive element, keeping it always perpendicular to the impinging ray.

7) 3D Displacements measuring system using laser technology, able to supply at one time the x, y and z components, starting from a single reference point, composed by an interferometric laser system complete with refractive element, on whose centre a small hole has been made, by a video sensor (a CCD camera without optical system) held at the end of a black tube placed on the other side of the refractive element and centred with the hole, and by a couple of step motors (or any other motor in which the angle is controlled), used to newly centre the image on the video sensor, moving the same on a plane perpendicular to the impinging ray.