WO1980002873A1

WO1980002873A1 - A method of determining the shape and position of an object and an apparatus to perform the method

Info

Publication number: WO1980002873A1
Application number: PCT/SE1980/000099
Authority: WO
Inventors: C Palmers
Original assignee: Inst Verkstadstek Forsk Ivf; C Palmers
Priority date: 1979-06-14
Filing date: 1980-04-08
Publication date: 1980-12-24
Also published as: SE7903116L

Abstract

A method of determining the shape and position of an object (F). This aim is accomplished by means of an apparatus comprising an emitter (1) emitting a beam (S) which in a specific manner scans an area, thus falling on the surface of the object (F) from which it is reflected back to a receiver (2), whereby the angles of emission and of reception ((Alpha) and (Alpha), respectively) as well as the scanning angle ((Beta)) of the beams (S and S', respectively) are determined such that with the aid of these angles and on the basis of knowledge of the distance (L) between the emitter (1) and the receiver (2) it becomes possible to determine the position and shape of the object (F) and to use it for various kinds of control purposes.

Description

A Method of Determining the Shape and Position of an Object and an Apparatus to Perform the Method.

The invention concerns a method of determining the shape and position of an object. The requirements that the information is correct and complete are high. This is a considerable problem in hitherto known systems and limits the methods with regard to precision, speed and flexibility.

The purpose of the invention is to make it possible to measure in an efficient manner the shape and position of an object for the purpose of e.g. controlling various processes, such as control of robots of various kinds, the operation of spray-painting equipment and the like. To achieve this purpose the method in accordance with the invention is characterized in that a beam, performing a scanning movement, is emitted at a known angle to the X-axis of a coordinate system from a stationary emitter onto the object in question, said beam scanning movement being effected by means of a rotating mirror,whereby the beam is reflected by said object onto a receiver which determines the angle of reception of the beam, thus making it possible to compute the data necessary to cetermine the shape and position of the object on the basis o f the angle of beam emission, the beam scanning angle and the angle of beam reception as well as on the basis of the distance between the emitter and the receiver. The invention also concerns an apparatus designed to perform the method, said apparatus being characterized by a stationary emitter emitting a scanning beam in the manner defined and arranged to cooperate with a rotating mirror, and by a receiver which is positioned at a known distance from the emitter to receive the beam reflected from the object, said receiver arranged to indicate the desired data through determination on the basis of the angle of beam emission, the beam scanning angle and the angle of beam reception as well as the distance between the emitter and the receiver. In accordance with the dependent claim a lens or equivalent means is arranged ahead of the receiver to filter or polarize the beam of light. The invention will be described in closer detail in the following with reference to the accompanying drawings, wherein

Fig. 1 illustrates a three-axes coordinate system for use in connection with an apparatus designed to perform the method in accordance with the invention. Fig. 2 illustrates an application of the method in accordance with the invention in the direction of arrow II of Fig. 3, and

Fig. 3 illustrates the apparatus in accordance with Fig. 2 in a view in the direction of arrow III in Fig. 2. As illustrated in Fig. 1 a beam S is emitted by an emitter 1 at an angle α to the X-axis towards the object P. The beam S is reflected by the object F towards a receiver 2 in the form of a beam S' forming an angle δ to the X-axis. The beam 5 is also emitted in a plane forming angle β ( ɣ) to the plane defined by axes X and Z , this angle being denominated herein the scanning angle. The distance between the emitter 1 and the receiver 2 is denominated L. Through knowledge of the angles α and a and by determining the angle β and the distance L, it is possible to determine exactly the position of the point of reflection R in space and because the beam S performs a scanning movement, it therefore becomes possible to obtain a point-by-point determination of the position of the object F and of its shape.

In Fig. 2 the emitter 1 is a rotating source of light emitting the beam S towards an object F which in this case could be a tin intended to be spray-painted, The beam S forms an angle α to the X-axis. Fig. 3 illustrates the same thing but in a view from above, and ahead of the receiver 2 a lens 3 is arranged, since in some cases it may be desirable to give a specific wave length to the beam of light S' failing on the receiver 2.

The emitter 1 may be a light-emitting diode or a laser diode. The emitter could be stationary, in which case the scanning movement of the beam is achieved with the aid of a rotating mirror. If the object F is stationary the beam of light must perform a scanning movement in one more direction in order to scan the entire object, but in case the object F moves along a definite path the angle α may be fixed. The invention permits scanning of the surface of an object at a very high speed with the aid of an apparatus comprising very few parts, which provides for reliable examination results and low apparatus costs. The invention is not limited to the example described and illustrated in the drawings but a number of modifications are possible within the scope of the appended claims. This is particularly true as concerns the application of the system for various measuring purposes.

Claims

C l a i m s

1, A method of determining the shape and position of an object (F), c h a r a c t e r i z e d i n t h a t a beam (S), performing a scanning movement, is emitted at a known angle ( α) to the X-axis of a coordinate system from a stationary emitter (1) onto the object (F) in question, said beam scanning movement being effected by means of a rotating mirror, whereby the beam (S) is reflected by said object onto a receiver (2) which determines the angle of reception ( δ ) of the beam, thus making it possible to compute the data necessary to determine the shape and position of the object (F) on the basis of the angle of beam emission ( α ) the beam scanning angle (β ) and the angle of beam reception ( δ ) as well as on the basis of the distance (L) between the emitter (1) and the receiver (2).

2. Apparatus designed to perform the method defined in claim 1 to determine the shape and position of an object (F), c h a r a c t e r i z e d by a stationary emitter (1) emitting a scanning beam (2) in a specific manner defined and arranged to cooperate with a rotating mirror, and by a receiver (2) which is positioned at a known distance (L) from the emitter (1) to receive the beam (S') after its reflection by the object (F), said receiver araanged to indicate the αasired data through determination on the basis of the ancle of beam emission ( α), the beam scanning angle (β ), and the angle of beam reception ( δ) as well as on the basis of the cistancc (L) between theemitter (1) and the receiver (2).

3. An apparatus as claimed in claim 2, c h a r a ct e r i z e d by a lens (3) or similar means which is arranged ahead of the receiver (2) to filtrate or polarize the beam of light (S').