GB1575054A

GB1575054A - Method of and apparatus for laser-beam processing of a workpiece

Info

Publication number: GB1575054A
Application number: GB22392/77A
Authority: GB
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1976-05-28
Filing date: 1977-05-27
Publication date: 1980-09-17
Also published as: CH616357A5; JPS5653470B2; FR2352624A1; IT1079230B; SE411717B; BE855155A; AT355140B; FR2352624B1; NL7705878A; DE2624121A1; JPS52145898A; SE7706257L

Abstract

The invention relates to a method for the precision machining of a workpiece (3) arranged in the working zone (1) of a machining laser (2), a laser measuring beam (10) being blended into the beam path of the laser machining beam (5), and the laser beams being deflectable in two orthogonal directions by means of controlled galvanometer mirrors (7). The invention consists in the fact that the workpiece surface, the shape and size of which are known, is scanned by means of the laser measuring beam (10), and the light of the laser measuring beam (10) reflected from the workpiece surface is utilised for detecting the position of the workpiece (3) inside the working zone (1) of the machining laser (2). <IMAGE>

Description

(54) IMPROVEMENTS IN OR RELATING TO A METHOD OF AND APPARATUS FOR LASER-BEAM PROCESSING OF A WORKPIECE (71) We, SIEMENS AKTIENGESELL SCHAFT, a German Company of Berlin and Munich, German Federal Republic, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - The invention relates to methods of and appartus for high-precision laser-beam processing of a workpiece arranged in the operating field of a processing laser, wherein a measuring-laser beam is gated into the beam path of the processing laser beam, and wherein at least the measuring-laser beam can be deflected in at least one direction by means of one or more controlled reflectors.

Processing lasers may be used to adjust the value of components, such as thin or thick film resistances or capacitances, and to adjust the natural frequency of components such as steel bending oscillators of the type used to maintain a specific channel frequency constant in telephone systems.

Furthermore, in small-structure and microstructure elements, processing lasers may be employed to produce photo-masks for integrated circuits, for example, to divide ceramic or glass substrates, or to remove metal layers applied to glass plates, amongst other applications.

The United States Patent Specification No. 3,902,036 describes and illustrates a control unit for a processing laser, into whose beam path a measuring-laser beam is gated in. A pulsed processing laser, e.g.

a YAG-laser beam having a wavelength of 1.06 microns, is projected onto a workpiece via suitable deflecting devices. A He-Ne laser team having a wavelength of approximately 0.63 microns is gated into the beam path of the processing laser by means of a reflector, a beam splitter and a phase shift device, being employed to divide the measuring-laser beam into two individual beam components that are mutually displaced in phase by 90 , which individual beam components- are each fed to respective axial detectors via a diffraction screen. A control circuit for an optical switch located in the beam path of - the processing laser is driven via a control logic circuit which is connected to the axial detectors. This measure serves to provide for control of a constant advancement of the pulsed processing laser beam in accordance with a given programme, whilst avoiding the danger of over-working or overload at the coordinate deflection points. However a prerequisite of this known control system for a processing laser is that prior to the beam treatment the location of the workpiece should be precisely aligned to the optical axis, namely the zero axis of the processing laser beam. However, such alignment of a work-piece requires a considerable outlay in time and expertise. If a plurality of like-shaped workpieces are to be treated, generally it is sufficient to perform one setting up alignment assuming it is possible to use a carrier which accurately fixes the position of each workpiece. However, frequently conditions are such that the workpiece cannot be directly and positively held in the carrier mounting, but must be supported by clamps, pins or strips joined to the workpiece. For example, these clamps or pins can consist of current supply lines on the component which is to be adjusted.

In the case of frequency adjustments, such as on steel bending oscillators, it is not possible to hold the oscillating element firmly in a mounting, as this would alter its oscillatory behaviour. Therefore, the component's terminal elements are used to support it in the workpiece mounting, in a position relative to the laser. Particularly in the case of small components, terminal elements of this type can become slightly bent out of their theoretical position. This results in the central point coordinates of the component which is to be processed coming to lie outside the theoretical position relative to the optical zero axis within the operating field of the processing laser beam.

One object of the present invention is to provide a method of and apparatus for high-precision processing of a workpiece which is arranged in an operating field of a processing laser, in which said workpiece surface contour is known. According to one aspect the invention consists in a method of working a a workpiece by the beam of a processing laser, in which a measuringlaser is provided whose beam is gated into the beam path of the laser processing beam, in which the laser beams are deflected in at least one direction by means of one or more controlled reflectors to produce a reflection of said measuring beam from the surface of a workpiece mounted for processing, said workpiece being of known shape and size, in which the light from the measuring-laser beam which has been reflected by the workpiece surface, is utilised to produce an output signal that serves to detect the position of the workpiece within the operating field of the processing laser, in which a programmed process computer controls the processing laser beam, and in which the response produced by scanning the known processing surface of the workpiece by means of the measuringlaser beam which has been gated into the beam path of the processing laser is used to determine the position coordinates of the workpiece surface relative to the centrepoint coordinates of the operating field of the processing laser by converting the optically measured intensities of the light reflected by the workpiece surface into signal which are fed to the process computer, calculating from these signals the centrepoint coordinates of the workpiece surface in the operating field by the computer, and using the result to transform the control programme for the laser processing beam to the centrepoint coordinates of the workpiece surface.

This mode of procedure enables the position of the workpiece to be detected within the operating field of the processing laser, and thus allows the coordinates of the operative surface -to be transfrmed to the centrM point co-ordinates of the known workpiece surface which is to be processed Ïn this way it is possible to avoid any faults which are only of a trivial nature, but which nevertheless affedt a precision processing of the workpiece surface without manually re-aligning the workpiece. The process is implemented by a programmed process computer which controls the laser processing beam. Advantageously, by scanning the known processing surface of the workpiece with the measuring-laser beam which has been gated into the beam path of the processing laser, the position co-ordinates of the workpiece surface are determined relative to the central point co-ordinates of the operative surface of the processing laser, in that the optically measured intensities of the light reflected by the workpiece surface are converted into analogue voltage values, the latter being fed to the process computer, which caluculate from the signals the central point co-ordinates of the workpiece surface in the operating field, and transforms the control programme for the laser processing beam to the central point coordinates of the workpiece surface. The control values which serve to guide the processing beam and which are emitted by the programmer of the process computer are modified by the transformation values.

The light reflected by the workpiece is detected by light sensors, and the measured signals are fed to an analysis logic circuit. It is particularly advantageous to eliminate alien light components, in order to achieve a clearer recognition of the reflection signal produced by the measuringlaser beam on the workpiece surface. Many workpieces do not have an entirely flat surface. Therefore the laser light is diffracted on the surface of the workpiece. In this case the alien light acts as an interference to the production of a clearly defined reflection signal. By eliminating alien light components, a clear reflection signal is obtained which is sufficient to determine the position of the scanned surface within the operating field.

According to another aspect the invention consists in an apparatus for laser beam processing of a workpiece, including a mounting to hold a workpiece having a surface of known shape and size in the path of a processing laser beam, a measuring laser to project a beam for measuring the workpiece position relative to said processing beam, means for gating said measuring beam into the processing beam path, means for deflecting said measuring beam in at least one direction to scan the surface of said workpiece, detector means for receiving measuring beam components reflected from the workpiece, means for converting the optically measured intensities of the light reflected by the workpiece surface into signals which are fed to a programmed process computer controlling the processing laser beam said computer calculating from these signals the centrepoint coordinates of the worktiece surface in the operating field, and using the result to transform the control programme for the processing laser beam to the centrepoint coordinates of the workpiece surface.

Advantageously the detector is in the form of a ring of light-conducting fibres, the ends of which are directed towards the surface of the workpiece.

The light of the measuring-laser beam which has been reflected by the workpiece is fed via the light conducting fibres to photo-electric detectors which convert the light intensity into a voltage value. By designing the sensors in the form of a ring which contains light conducting fibres, even when the workpiece surface is rough or contains grooves for example, it is still possible to achieve a good adaptation of the reflected light, independently of the course or direction of the grooves within the operating field of the processing laser.

The light conductor fibres contained in the sensor are preferably divided into two groups. All light conducting fibres of each group are coupled to a respective detector via a respective interposed interference filter. Within the ring, the light conducting fibres of one group are interleaved with those of the other group. The interference filter assigned to the first group is permeable to be a light wave length corresponding to daylight, and the other interference filter assigned to the second group is permeable only to the light wave length of the measuring-laser beam. In this way the daymeasuring signal by means of a discriminlight component is eliminated from the ator circuit arranged following the detectors, the signal obtained being fed to a coordinate computer.

The invention will now be described with reference to the drawings, in which Figure 1 schematically illustrates one exemplary embodiment of the construction of a processing laser with a laser-measuring beam gated into the beam path of the processing laser in accordance with the invention; Figure 2 is an explanatory schematic plan view of a workpiede; Figure 3 is an explanatory schematic plan view of another workpiece; Figure 4 is a sectional view of a preferred detector system; Figure 5 is a plan view of the detector system shown in Figure 4; Figure 6 is an explanatory graph; Figure 7 is a schematic representation of the sensing and- detecting system; and Figure 8 is a circuit diagram of the circuitry for~ dealing with the output of the detector system.

~ The arrangement shown in - Figure 1 is for processing a workpiece 3 arranged in the operating field 1 - of a processing laser 2. The -- procesting laser 2, which in this example- - is- - a- pulsed YAG-laser, is connected to a voltage source 4, and the wavelength of its output laser beam 5 amounts to 1.06 microns. The processing laser beam is projected via a focussing optical system 6, a beam-splitter 7 and a laser beam deflection control optical system 8, to cover the operating field 1 of the processing laser. In the represented zero position, the laser beam cuts the co-ordinate zero point 0 of the operating field plane vertically. A further voltage source 9 is connected to a He Ne measuring laser 19, which supplies a measuring beam 10 that is gated into the path of the laser beam 5 by the beamsplitter 7 via a focussing optical system 11, therefore the measuring beam likewise cuts the co-ordinate zero point 0 of the operating field plane 1. Deflection of the laser beams in two mutually orthogonal coordinate directions X and Y of the operating field plane can be effected by means of electric motors 8x and 8y. Any light of the measuring-laser beam reflected by the workpiece is fed via a sensor 12 to photoelectric detectors 13 and 14 which each supply a signal proportional to the received light to a discriminator 15 whose output signal 16 is connected to a process computer 17. The process computer analyses the reflection signal in comparison with a stored programme, and controls the electric motors 8x and 8y. Furthermore, when the processing of the work-piece 3 is completed, through the intermediary of an adjusting-measuring device (not shown) a signal via line 18 sends control commands governing the input or discharge of a workpiece from the operating field 1.

The He-Ne-laser 19 supplies a laser beam 10, the wavelength of which amounts to 0.63 microns. The power of this laser is low, and amounts in this example to a value between 10 and 20 mW.

If the operating field 1 of the processing laser is equipped with a workpiece 3, in many cases it cannot be ruled out that the surface central point M of the workpiece 3 will lie outside the centre 0 of the operating field 1. If the workpiece is to be processed in accordance with a stored programme via a process computer 17, this is only possible when the central point coordination M of the workpiece coincides with the central point co-ordinates 0 of the operating field 1. However, as the position of the workpiece 3 is not precisely defined in the operating field 1, it is necessary to determine the position of the work-piece 3 within the operating field 1. If the position of the work-piece 3 within the operating field 1 of the processing laser 2 is known, then by means of a co-ordinate transformation carried put by the process computer 17, the control co-ordinates read out from the stored programme of the pro cess computer 17 can be transformed to the workpiece central point and fed to the electric motors 8x and 8y. In order to obtain these correction values, it is firstly necessary to determine the position of the workpiece 3 within the operating field 1.

To this end, in a first operative step, the measuring beam 10 scans the workpiece surface, and the scanned values are compared in the process computer with stored, known values of the workpiece shape and size. From these scanned values it is then possible to calculate the processing central point or co-ordinate central point M of the workpiece within the co-ordinates of the operating field 1.

Figure 2 shows a workpiece surface 3 which is located in the plane of the operating field 1, and which here is in the form of a circular disc. In order to detect the position of a workpiece surface whose shape and size is known, relative to the operating field of the processing laser, firstly the measuring laser beam is moved from the 0-position of the operating field along the X-axis ~ to the co-ordinate field edge Ryl. Along a path Sxl there is formed a reflection signal, which ceases at a point P1. Now the measuring laser beam is returned along the X-axis of the operating field to the operating field edge Ry2; so that a reflection signal Sx2 is formel. If the reflection signal Sxl is greater than Sx2, the circle central point M lies to the left by the value of the -Ax, and otherwise lies on the right hand side of the Y-axis. If, in the case of a circular surface, the size is known, the central point of the circle M is also known.

However, this establishment is not sufficient to determine the position of the circle central point within the operating surface, as the path value Sx can lie above or below the central point. Therefore, it is necessary to deflect the measuring beam by a path value Y' and to again conduct it in parallel to the path Sx. In this way a second signal Sx' is obtained and in the present example the path value Sx' is greater than the path value Sx so that the circle central point M must lie above the X-axis of the co-ordinate central point 0 of the operating field. By halving the path Sx, when the area of the circle is known, it is now possible to calculate the central point co-ordinates M of the area of the circle and of the workpiece within the operating field. If the central point co-ordinates of the workpiece surface M are known the correction values Ax and Ay can also be determined. If the processing laser beam is to produce a circular groove 20 in the workpiece surface, it is necessary to correct the control co-ordinates for the electric motors in order to deflect-the laser beam by the aforementioned correction values.

In Figure 3 a different workpiece, having a known, rectangular operating surface 3 is located within the operating field 1 of the processing laser 2. This workpiece can also be rotated about its Z-axis which leads through the workpiece central point M.

Again one proceeds in the manner described above. Firstly, the measuring beam is moved in the X-direction along the Xaxis over the workpiece surface, so that the points P1 and P2 and the path lengths represented by signal duration ASx and Sx are determined. Then the laser beam is deflected by a path value Y' and is again guided in parallel to the X-axis over the workpiece surface to obtain the points P1' and P2' and the signal Sx', although the position of the workpiece is not yet clearly defined within the operating field. These values Sx and Sx' can obviously occur above and/or below the central point M of the workpiece. In order to precisely determine the position of the workpiece in the operating field, it is therefore advantageous to determine the path values Syl and Sy2 by de flecting the laser measuring beam in the direction of the Y-axis. This clearly and unambiguously defines the position of the workpiece within the operating field. From the measured values it is now possible to determine the precise position of the work piece within the operating field. One can also proceed correspondingly with other known surface shapes, in order to deter mine the position of a workpiece in the operating field. It is also possible to clearly determine the position of the workpiece within the operating field by multiple scanning row-by-row in only one co-ordinate direction, e.g. in the X-direction.

Figures 4 and 5 illustrate the sensor 12 shown in Figure 1, Figure 4 giving a longitudinal section and Figure 5 a view of that end surface which faces towards the workpiece. The sensor 12 possesses a central channel 21 through which the laser beams pass to the workpiece surface. It consists of a tube having inlet light conducting fibres 23, the ends 23' of which are flush with the end surface 24 of the sensor 12.

As can be seen in particular from Figure 5, the light conducting fibres are arranged in the form of a ring around the channel 21. In Figure 5, the light conducting fibre end faces are separately represented either as a point A23' or a cross B23' to identify those of two groups A and B. The ends B23' marked with a cross belong to group B, and the ends A23' designated by a point belong to group A, and the ends are interleaved in such manner that the light conducting fibres belonging to group A are arranged in a sequence 1, 3, 5 etc. and those belonging to group B are arranged in a graduation sequence 2, 4, 6 etc., around the ring.

Figure 6 shows how a work piece surface 3 that is not absolutely flat but, in dependence upon the method by which it is produced, has a surface which is more or less rough, e.g. possesses grooves, may interfere with measurements because when the workpiece is scanned by the measuring beam, the reflection light is diffracted or differently deflected at the surface. This gives rise to a diffraction figure 26 which is dependent upon the structure and position of the surface within the operating field. This effect becomes particularly manifest when the surface F possesses grooves 25 or the like, which generally run parallel to one another, as shown in Figure 6. Alignment of the workpiece 3 in the operating field 1, e.g. in such manner that the grooves run parallel to the X-axis can be achieved only with difficulty. If, as shown in - Figure 6, the grooves form an angle to the X-axis, a diffraction image 'sin?ilar to that shown as 26 is formed. In order to be able to detect this diffraction image, the light conducting fibres are arranged in the form of a ring around the treatment location, as illustrated in Figure 4 and 5. The influence of daylight is particularly disturbing in the case of surfaces which are not flat, and in the case of operating surfaces which are not uniformly illuminated. In order to precisely detect the reflection signal, it is therefore advisable to eliminate any daylight influence. For this reason the light conducting fibres are arranged in two groups A and B in the sensor 12.

Figure 7 shows the arrangement of the bunches of light conducting fibres in the groups A and B. The light reflected by the workpiece surface is transferred from each group of light conducting fibres to a respective photo-electric detector, 27 and 28.

By providing a preceding interference filter, 29 and 30 respectively the photo-electric detector 27 can be caused to detect the He-Ne-laser light and a band of the surrounding light of 633 nm, and the photoelectric detector--28 can b caused to detect simply a band of the surrounding light at 601 nm. The component due to surrounding light produces virtually the same voltage range in each of the two detectors 27 and 28.

The construction of the discriminator circuit for the elimination of daylight influence is illustrated in Figure 8. Inputs 27' and 28' of the amplifiers 31 and 32 are connected to the outputs of the photoelectric detectors 27 and 28 respectively.

Potentiometers 33 and 34 are set in such manner that when the He-Ne-laser is switched off, zero potential prevails at the output of a measuring value amplifier 37.

During a measurement cycle, only the fil ter 29 is permeable to the wavelength of the measuring-laser beam, so that the volt age range produced by the measuring beam appears, as a measured value, at output 35 of a measured value amplifier 37, and is now fed to a terminal amplifier 38, whose output is connected to a Schmitt trigger stage 39, which converts the measured sig nal into analysable measured signals 40, to be fed via output 41 to the process com puter.

The process computer is advantageously designed as a micro-processor comprising 16 byte-stores having random access (RAM) and 1.5 kbyte-read-out stores (RPROM) and having a monitoring cir cuit (control hardware). On account of the high interference level in pulsed laser sys tems, the monitoring circuits and stores are preferably constructed in the CMOS-tech nique.

The digital output of the micro-processor leads to a 12-bit-digital-analogue converter, the analogue output of which controls a power amplifier and the subsequently con nected electric motors (Figure 1). The ac tual calculation of the central point is ef fected by the software, where the known surface image of the workpiece is stored in the read-out store (RPROM). By means of a programmed overswing, the hysteresis of the electric motors 8x and 8y is maintained within narrow limits. The freely program mable control has the advantage - that by modifying the software it is possible to determine the position of different surface shapes or simple figures using the same hardware. Using this device it is possible to determine the position of the work piece within the operating field with an accuracy of 1.3% with areas of 15 mm2.

This accuracy is not dependent upon the micro-processor but upon the deflector elements and upon the focussing optical systems.

WHAT WE CLAIM IS: - 1. A method of working a workpiece by the beam of a processing laser, in which - a measuring-laser is provided, Whose beaih-- is gated into the bearn path of the laser processing beam in which the laser beams are deflected in at least one direction by means of one or more controlled reflectors to produce a reflection of said measuring beam from the surface of a workpiece mounted for processing, said workpiece being of known shape and size, in which the light from the measuring-laser beam which has been reflected by the workpiece surface, is utilised to produce an output signal that serves to detect the position of the workpiece within the operating field of the processing laser, in which a pro

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

graduation sequence 2, 4, 6 etc., around the ring.

Figure 6 shows how a work piece surface 3 that is not absolutely flat but, in dependence upon the method by which it is produced, has a surface which is more or less rough, e.g. possesses grooves, may interfere with measurements because when the workpiece is scanned by the measuring beam, the reflection light is diffracted or differently deflected at the surface. This gives rise to a diffraction figure 26 which is dependent upon the structure and position of the surface within the operating field. This effect becomes particularly manifest when the surface F possesses grooves 25 or the like, which generally run parallel to one another, as shown in Figure 6. Alignment of the workpiece 3 in the operating field 1, e.g. in such manner that the grooves run parallel to the X-axis can be achieved only with difficulty. If, as shown in - Figure 6, the grooves form an angle to the X-axis, a diffraction image 'sin?ilar to that shown as 26 is formed. In order to be able to detect this diffraction image, the light conducting fibres are arranged in the form of a ring around the treatment location, as illustrated in Figure 4 and 5. The influence of daylight is particularly disturbing in the case of surfaces which are not flat, and in the case of operating surfaces which are not uniformly illuminated. In order to precisely detect the reflection signal, it is therefore advisable to eliminate any daylight influence. For this reason the light conducting fibres are arranged in two groups A and B in the sensor 12.

Figure 7 shows the arrangement of the bunches of light conducting fibres in the groups A and B. The light reflected by the workpiece surface is transferred from each group of light conducting fibres to a respective photo-electric detector, 27 and 28.

By providing a preceding interference filter, 29 and 30 respectively the photo-electric detector 27 can be caused to detect the He-Ne-laser light and a band of the surrounding light of 633 nm, and the photoelectric detector--28 can bé caused to detect simply a band of the surrounding light at 601 nm. The component due to surrounding light produces virtually the same voltage range in each of the two detectors 27 and 28.

The construction of the discriminator circuit for the elimination of daylight influence is illustrated in Figure 8. Inputs 27' and 28' of the amplifiers 31 and 32 are connected to the outputs of the photoelectric detectors 27 and 28 respectively.

Potentiometers 33 and 34 are set in such manner that when the He-Ne-laser is switched off, zero potential prevails at the output of a measuring value amplifier 37.

During a measurement cycle, only the fil ter 29 is permeable to the wavelength of the measuring-laser beam, so that the volt age range produced by the measuring beam appears, as a measured value, at output

35 of a measured value amplifier 37, and is now fed to a terminal amplifier 38, whose output is connected to a Schmitt trigger stage 39, which converts the measured sig nal into analysable measured signals 40, to be fed via output 41 to the process com puter.

The process computer is advantageously designed as a micro-processor comprising

16 byte-stores having random access (RAM) and 1.5 kbyte-read-out stores (RPROM) and having a monitoring cir cuit (control hardware). On account of the high interference level in pulsed laser sys tems, the monitoring circuits and stores are preferably constructed in the CMOS-tech nique.

The digital output of the micro-processor leads to a 12-bit-digital-analogue converter, the analogue output of which controls a power amplifier and the subsequently con nected electric motors (Figure 1). The ac tual calculation of the central point is ef fected by the software, where the known surface image of the workpiece is stored in the read-out store (RPROM). By means of a programmed overswing, the hysteresis of the electric motors 8x and 8y is maintained within narrow limits. The freely program mable control has the advantage - that by modifying the software it is possible to determine the position of different surface shapes or simple figures using the same hardware. Using this device it is possible to determine the position of the work piece within the operating field with an accuracy of 1.3% with areas of 15 mm2.

This accuracy is not dependent upon the micro-processor but upon the deflector elements and upon the focussing optical systems.

WHAT WE CLAIM IS: - 1. A method of working a workpiece by the beam of a processing laser, in which - a measuring-laser is provided, Whose beaih-- is gated into the bearn path of the laser processing beam in which the laser beams are deflected in at least one direction by means of one or more controlled reflectors to produce a reflection of said measuring beam from the surface of a workpiece mounted for processing, said workpiece being of known shape and size, in which the light from the measuring-laser beam which has been reflected by the workpiece surface, is utilised to produce an output signal that serves to detect the position of the workpiece within the operating field of the processing laser, in which a pro

grammed process computer controls the processing laser beam, and in which the response produced by scanning the known processing surface of the workpiece by means of the measuring-laser beam which has been gated into the beam path of the processing laser is used to determine the position coordinates of the workpiece surface relative to the centrepoint coordinates of the operating field of the processing laser by converting the optically measured intensities of the light reflected by the workpiece surface into signals which are fed to the process computer, calculating from these signals the centrepoint coordinates of the workpiece surface in the operating field by the computer, and using the result to transform the control programme for the laser processing beam to the centrepoint coordinates of the workpiece surface.
2. A method as claimed in Claim 1, in which said signals are analogue voltage values.
3. A method as claimed in Claim 1 or Claim 2, in which positive recognition of the reflection signal produced by the lasermeasuring beam on the workpiece surface is ensured by eliminating ambient light components.
4. A method as claimed in Claim 1, substantially as described with reference to Figures 1 to 8.
5. Apparatus for laser beam processing of a workpiece, including a mounting to hold a workpiece having a surface of known shape and size in the path of a processing laser beam, a measuring laser to project a beam for measuring the workpiece position relative to said processing beam, means for gating said measuring beam into the processing beam path, means for deflecting said measuring beam in at least one direction to scan the surface of said workpiece, detector means for receiving measured beam components reflected from the workpiece, means for converting the optionally measured intensities of the light reflected by the workpiece surface into signals which are fed to a programmed process computer controlling the processing laser beam, said computer calculating from these signals the centrepoint coordinates of the workpiece surface in the operating field, and using the result to transform the control programme for the processing laser beam to the centrepoint coordinates of the workpiece surface.
6. Apparatus as claimed in Claim 5, in which said detector is in the form of a ring surrounding the beam path and containing light-conducting fibres, the ends of which are directed towards the operating surface positioned in the path of the processing laser beam.
7. Apparatus as claimed in Claim 6, in which said light conducting fibres are divided into two groups, all the light conducting fibres of each group being coupled to a respective photo-electric element detector via an interposed interference filter.
8. Apparatus as claimed in Claim 7, in which the light conducting fibres of one group are interleaved with the light conducting fibres of the other group, each with the same graduated spacing about the cir cumference of the sensor ring.
9. Apparatus as claimed in Claim 8, in which one said photo-sensitive detector receives only light from said measuring laser via its filter, which has a pass band to 633 nm., and the other detects only a band of the surrounding light of 601 nm.
10. Apparatus as claimed in Claim 9, in which the photo-sensitive detectors are followed by a discriminator serving to eliminate the daylight influence.
11. Apparatus for working a workpiece by the beam of a processing laser, substantially as described with reference to Figures 1, 4, 5, 7 and 8.