Optics: measuring and testing – Lamp beam direction or pattern
Patent
1999-11-04
2000-11-21
Pham, Hoa Q.
Optics: measuring and testing
Lamp beam direction or pattern
356123, 356375, 2502012, 21912183, G01J 100
Patent
active
061511099
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a device for detecting and calculating focus point position, shape and power distribution of a laser beam after a focussing lens, and which at least incorporates a laser source, the focussing lens, a light affecting body, a light sensor, and means for calculation.
BACKGROUND OF THE INVENTION
As automation increases in industry and increased complexity when choosing materials lasers become increasingly important. Especially promising is the Nd:YAG laser, which is very well suited to be integrated with a robot, but also carbon dioxide and excimer lasers are important for industry. There are also other lasers, which industrial applicability is high.
In this kind of inventions, there is often a lens having the purpose of focussing the laser beam in desired way. A consequence of the presence of the lens is that the laser beam appears with a waist, i.e. a shape which in the direction of the beam first presents a narrowing feature, which thereafter becomes wider. The processing effect of the laser beam is naturally at maximum where the beam presents its smallest surface. Therefore, it is interesting to be able to position the laser simply and effectively in order to accomplish this.
Today, one way of measuring the position of the focus point position, which should be the same as the tool center point of the robot, is based on the assistance of a visual assisting laser and manually moving the robot in order to position the focus point position in a well-defined position in space. This is normally time-consuming and gives an obvious lack of precision.
In SE-447 972 a method for detecting a focus point position for a device processing with a laser is presented. It is characterized by a light shielding element, which can shield a fraction of the laser beams and a light sensor, produces an output signal. The output signal is proportional to the amount of laser light having passed through the light shielding element. The searching for focus is arranged so that at least the light shielding element or the light sensor is moved in direction of the optical axis for detection of the position, at which the output signal of the light sensor is at its maximum or at its minimum. Based on the minimum or maximum output signal of the light sensor the focus point position is detected. It should be noted that the invention described in this document only detects the focus point position and does not deal with the shape or power distribution of the laser beam.
PURPOSE OF THE INVENTION AND ITS MOST CHARACTERISING FEATURES
An area within which the present invention can be used is processing of various materials (e.g. metals and plastics) such as welding, cutting, soldering and hardening with a laser. In these cases a high power laser is used. It should be noted that the invention preferably also can be used in connection with low power lasers, for instance when positioning of robots intended for automatized spray painting. In this case a previously known low power laser and a focussing lens are arranged to the robot, or robots at machines with multiple axes, so that the focus point position of the laser always coincides with the tool center point, also known as TCP, if this has been chosen in a free point in the vicinity of the machine. Thus, the present invention can here be used to determine the tool center point of a robot or another machine, even if the tool is of another kind than a laser.
The present invention is constituted by that a focussing lens, the light affecting body and the light sensor are arranged so that their relative distances are adjustable, that the laser beam and the light affecting body are arranged to perform a relative movement consisting of one or more tracing movements through the beam path, preferably in at least one plane and with different relative distances, that the light sensor is arranged to measure at least a fraction of the laser light emitted by the light affecting body, and that the light sensor is arranged to produce an output signal which is arrang
REFERENCES:
patent: 3555280 (1971-01-01), Richards
patent: 3571598 (1971-03-01), Lombard
patent: 4008965 (1977-02-01), Nobusawa
patent: 4009392 (1977-02-01), Hanley
patent: 4472055 (1984-09-01), Tsutsumi
patent: 4772772 (1988-09-01), Juptner et al.
Bromssen Bernt von
Nilsson Thomas
Institutet for Verkstadsteknisk Forskning
Pham Hoa Q.
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