WO1986005268A1

WO1986005268A1 - An apparatus for converting a radiation profile line into electrical signals corresponding thereto

Info

Publication number: WO1986005268A1
Application number: PCT/NL1986/000007
Authority: WO
Inventors: Pieter Wilhelmus Verbeek
Original assignee: Stichting Centrum Voor Micro-Elektronica
Priority date: 1985-03-04
Filing date: 1986-03-04
Publication date: 1986-09-12
Also published as: NL8500600A; EP0248811A1; NL190460C; NL190460B; JPS62502703A

Abstract

An apparatus for determining the shape of an object (18) by converting a radiation profile line (1, 2) into electrical signals corresponding thereto, comprising a flat composite transducer (3) on which a radiation profile line (1, 2) to be processed can be incident, and adapted for converting in a two-dimensional way said radiation into electrical signals, said transducer (3) being provided with transducing regions (4) arranged in a fixed two-dimensional pattern, and being connected to means (6, 7) for delivering and processing the electrical signals thus produced in a corresponding sequence. In particular said transducer (3) comprises a plurality of juxtaposed rectilinear transducing regions (4) for producing electrical signals correlated to the location of radiation incidence on the region in question, and connected, at least at one extremity (5), to means (6) for delivering the produced signals. These rectilinear transducing regions (4) can be formed by rectilinear transducers (9) with lateral photo-effect.

Description

An apparatus for converting a radiation profile line into electrical signals corresponding thereto.

The invention relates to an apparatus fox converting a radiation profile line into electrical signals corresponding thereto. A radiation profile line is here understood to be radiation incident on a surface in the form of a line, the shape of said line 5 having a meaning, and, in particular, being related to the result of a measurement. Such a profile line can be produced either by directly incident radiation or by means of an image forming system, whether or not after deflection or scattering by a body to be examined. The plane of incidence is, eventually, the surface of a 10 transducer, by means of which the radiation can be converted into electrical currents.

This profile line can, for instance, be related to a distance measurement by means of radiation remitted or transmitted by a body to be examined, and said line can be a picture of the 15 line of intersection of a radiation plane and the outer surface of said body, or a measure for variations in the superficial shape or the transparency of said body, so that, for instance, said profile line can be used for checking whether said body satisfies require¬ ments made thereon. 20 In both mentioned, and possibly also in other cases, there exists a need for an apparatus by means of which such a line can be converted into electrical signals which are suitable for further processing, or which can be used for obtaining, by means of a curren display screen, a suitable display of said line, which apparatus 25 should, in particular, require as little space as possible, and should be able to follow relatively fast changes of a profile line.

It is an object of the invention to provide such an apparatus. The apparatus of the invention is characterised by a flat composite transducer on which radiation in the form of a radiation profile line to be processed can be incident, said transducer being adapted to convert said radiation in a two-dimensional way into electrical signals, said transducer being provided, to that end, with transducing regions arranged in a fixed two-dimensional pattern, and being, furthermore, connected to means for delivering and pro¬ cessing the produced electrical signals in a manner which is un¬ ambiguously related to corresponding transducer regions.

Generally speaking for such a transducer a matrix of dis¬ crete photo-electric transducers might be used, in which the in- dividual points can be optionally scanned in order to obtain, for instance, a signal series suitable for being displayed or being processed in an other manner, for which purpose one should not be bound to the current television apparatuses. However, because of practical considerations such as availability, it is, according to the invention, preferred to use a composite transducer comprising a plurality of juxtaposed and substantially rectilinear transducing regions, each being adapted to produce electrical signals unam¬ biguously related to the point of radiation incidence on the trans¬ ducer regions in question, said regions being connected, at least at one extremity thereof, to output means for delivering the pro¬ duced signals, said means, furthermore, being connected to means for processing the signals produced by the various regions in an inter¬ related manner.

In particular said signal output means are realised as electronic series/parallel converters by means of which the signals, appearing simultaneously at the outputsof the various transducing regions, can be derived as serial signal series, and, in particular, said output means can be formed by an analogue shift register.

In a first main embodiment of the apparatus according to the invention the rectilinear transducer regions are formed by recti¬ linear transducers with lateral photo-effect, the longitudinal axes thereof intersecting the profile line to be transformed in different points, and being connected, at both extremities, to an output means adapted to produce a signal corresponding to the current intensity at the respective extremity, said output means being synchronised in such a manner that the signals appearing at both extremities of a transducer are simultaneously delivered, and the processing means are adapted to determine the ratio between the signals simultaneous¬ ly appearing at both extremities of the same transducer.

Such lateral photo-effect transducers are known, and reference can be made to the thesis of D.J.W. Noorlag, "Lateral Photo-Effect Position-Sensitive Detectors", Delft (1982). The curren derived at the extremities of such a rectilinear transducer when irradiating in an intermediate point have an intensity which is in¬ versely proportional to the distances of the point of incidence of the radiation and the respective extremities. In- the subject appara¬ tus the various portions of the profile line corresponding to the various juxtaposed transducers can be accurately derived from the ratio measurement.

In particular the corresponding outputs of the various • transducers are each connected to a corresponding parallel/series converter, and the outputs of both converters are connected to a stage for determining the ratio between the simultaneously arriving signals.

In a second main embodiment of the apparatus of the in¬ vention the rectilinear transducer regions are each formed by a series of photo-cells each connected to a respective cell of an analogue shift register. Determining the location of the profile line takes place step-wise then, in contrast to the first-mentioned main embodiment.

In order to obtain a more accurate determination of the shape of the profile line, in said second main embodiment means can be used for widening said profile line transversely to its main direction of extension up to a width which is at least equal to the centre-line distance between photo-cells which are juxtaposed transversely to said direction of extension, the processing means being adapted for measuring the ratio between the intensities of signals originating from photo-cells each irradiated by a portion of the widened profile line. From this ratio of overlapping the accurate location of the profile line can be derived. If, then, the axes of the analogue shift registers con¬ nected to said photo-cell series are directed transversely to the main direction of extension of the profile line, the signal series originating from the output means can be transferred towards a series/parallel converter by means of which the various signal series can be brought into the parallel form, the processing means then being adapted for determining the intensity ratio between pairs of corresponding signals of adjoining signal series.

If, on the contrary, the axes of the analogue shift regist connected to said photo-cell series are directed parallel to the direction of the profile line, the output means can be connected to a processing means which is adapted to determine the ratio between successive'signals of the same signal series.

In particular the radiation profile line can be originatin from an apparatus for determining the shape or shape or composition deviationsof a body to be examined, said apparatus consisting of a source of a narrow light beam, in particular a laser beam, and an optical system for forming, on the transducer surface, image points of the radiation diffused or deflected by said body, said apparatus being characterised in that the source is adapted to form at least one radiation plane which is directed in such a manner that the radiation diffused or deflected by the body is focussed by said optical system on the composite transducer as a radiation profile line of the afore-mentioned kind.

In this respect radiation rediffused from the body surface and using the latter for determining the outer shape or shape finishing of said body, as well as radiation diffused or refracted and transmitted by said body and using the latter for determining thereby structure deviations thereof, are being considered here. In particular a fan of radiation surfaces can be used Tor producing a corresponding member of profile lines, and then either one single radiation plane is moved step-wise, or, in the case of the composite transducers of the second main embodiment, a plurality of planes is simultaneously used.

The invention will now be elucidated below in more detail by reference to a drawing, showing in:

Fig. 1 a highly simplified diagrammatical representation of an apparatus of the invention for elucidating the general prin- ciple of operation thereof;

Figs. 2A and B a simplified -diagrammatical representation of a first embodiment of the apparatus of Fig. 1 and the signals occurring therein respectively;

Figs.3A and B and Figs. 4A and B corresponding represen- tations of two other embodiments and associated signals respectively; and

Figs. 5 and 6 a diagrammatical representation of a known depth measuring apparatus and a modification thereof according to the invention respectively. Fig. 1 shows an example of a simple profile line 1 with a projecting portion 2 incident on a transducer surface 3. This profile line has a rectilinear main extension direction, but this should not necessarily always be the case. The shown profile line shape, however, simplifies the description of the apparatus of the invention to be given below.

The transducer 3 should be adapted to produce electrical signals corresponding to the radiation distribution according to the line 1, which transducer, for practical reasons, should be as thin as possible. To that end a matrix of transducer points would be suitable as such, which points, for instance, might be arbitrari¬ ly scanned, but, according to the invention and for practical reason use is made of transducers manufactured by available techniques, and in the following, some examples of realisation thereof will be des- cribed.

As diαgrαmmαticαlly shown in Fig. 1, the transducer 3 consists of parallel juxtaposed strip-like transducer regions 4, and the longitudinal direction thereof is, in the case shown, trans- versely directed to the direction of extension of the profile line 1. The latter is not strictly necessary if the shape of the profile line 1 and the operation of the transducer regions 4 allow a different direction of said transducer regions, as will be des¬ cribed below. Moreover it is not always necessary to use rectilinear or mutually parallel transducer regions 4. This depends, of course, on the location and shape of a profile line 1 to be converted. For many applications, however, the parallel structure of Fig. 1 will be unaintly suitable. For the sake of simplicity the description will be restricted to this embodiment. The transducer regions 4 are so that at the signal outputs

5 thereof signals will appear which correspond to the location of the profile line 1 in respect of the various regions 4. The actual ^* . structure of these regions will be described in more detail.

The signal outputs 5 are connected to a stage 6 for de- livering the obtained signals. It would, as such, be feasible to construct this stage as a memory in which the signals in corres¬ pondence with the location of the profile line 1-are stored in an analogue or digital form, and this memory can be read out in the most suitable way for further processing these signals. In practice stage 6 will, however, generally be formed by a parallel/series converter by means of which the signals simultaneously appearing at the various outputs 5 can be brought in the series form, and then signals series are produced which can be processed further or can be used for picture display. At 7 an additional processing stage is shown in which operations still to be described in more detail can be performed, either on signals in parallel form, or in signals in series form. The operation results and/or signal series can be taken off at an output 8.

For stage 6 known electronic circuits can be used. Below analogue parallel/series converters or analogue shift registers (also called CCD, "Charge Coupled Device") will particularly men- tioned, but the invention is not restricted to such converters; as mentioned above, stage 6 can also be adapted for processing the signals in parallel 'if this is desired.

Fig. 2 shows a first embodiment of such a device. The regions 4 are formed by rectilinear transducers 9 with lateral photo-effect of the kind described in the thesis of D.J.W. Noorlag, "Lateral Photo-Effect Position-Sensitive Detectors", Delft (1982). Such a transducer has two terminal connections 5a and 5b, and the intensities of the currents in said connections, when irradiating an intermediate point, are inversely proportional to the distances between said point and the connections in question. For simplcity's sake the means for applying the required voltages are not indicated.

Each connection 5 is connected to a current integrator, shown as a capacitor.10. These^' connections are, furthermore, each connected to an associated cell 11 of an output transducer 6a or 6b resp. constructed as a parallel/series converter. These cells obtain a charge state corresponding to that of the associated capacitor 10. The various charges can be transferred towards adjacent cells by means of a suitable control signal, so that, at the outputs 12a and 12b resp., signal series will appear corresponding to the current intensities at the various connections 5a and 5b resp. In Fig. 2B the signals appearing at the outputs 12a and 12b for the profile line shape shown are represented.

The outputs 12a and 12b are connected to a corresponding input of a processing circuit 7 which is adapted to determine the ratio between the signal intensities simultaneously appearing at both inputs. At the output 8 signal series will then appear which corresponds to the location of the profile line 1 and its deviation in respect of the extremities of the transducers 9. The number of the rectilinear transducers 9 depends on the desired resolution and on th^'e length of the profile line 1. Sampling by means of the parallel/series converters or analogue shift registers 6a and 6b can take place very quickly, and can, in particular, be adapted to the signal frequency in a current video display apparatus. An advantage of such lateral photo-effect transducers is that the location of an irradiated point can be determined continuous¬ ly and with a high accuracy, so that a similar accuracy in deter¬ mining the deviations 2 can be obtained. It will be clear that, in this case, the direction of the transducers 9 should be transversely to the main extension of the profile line 1 if this profile line, as shown, mainly comprises rectilinear portions.

Figs. 3A and B show, in a similar way, an other embodiment of a composite two-dimensional transducer 3 according to the in- vention, which composite transducer has a known structure such as developed for video camera's. This composite transducer comprises a series of analogue parallel/series converters or shift registers 13 corresponding to the strips 4 of Fig. 1. The individual cells 14 thereof are each connected to an associated photo-cell not shown, this in such a manner that the charge state of a cell depends on the irradiation state of the associated photo-cell. The outputs 5 at one extremity of the various transducers 13 are connected again to respective cells 11 of an analogue parallel/series converter or shift register 6. The various converters are simultaneously control- led so as to transfer the charge state of the various cells step- wise towards the respective outputs 5. Then the charge states of a series of corresponding cells of the various transducers 13 will appear in the cells 11 of the transducer 6, which, again, are to be shifted onwards before the next series arrives. At the output 12 a composite signal series will appear, from which the shape of the profile line 1 can be derived.

Such a composite transducer has, in respect of the trans¬ ducer of Fig. 2A, the disadvantage that the accuracy of the location determination of the profile line 1 is restricted by the dimensions and the centre-line distances of the cells 14.

In order to improve the location determination the pro¬ file line is, as shown, widened to such an extent that its width 5 is at least equal to the centre-line distance of two adjacent cells 14. So etines the profile line to be processed is already wide enough; if this is not the case, the line can be widened by means of an optical system or by defocussing a focussing lens.

If the widened profile line 1 is incident on two adjacent 0 cells 14, both will produce a signal depending on the radiation distribution over both cells, so that by measuring the intensity ratio between the signals originating from the adjacent cells of the same transducer 13, the correct location of the centre of gravit of the profile line 1 can be determined. 5 However, as appears from Fig. 3B, the signals between whic said ratio is to be determined, are situated at some mutual distance in the output signal series. For. executing the ratio measurement, the output line 12^"is, now, connected to a series/parallel converter 15 in which the various partial signal series are brought in the 0 parallel form, and this in such a manner that the signals originatin from corresponding cells 14 of adjacent transducers 13 will again be juxtaposed, the processing stage 7 then being adapted to determin the ratio between adjacent signal pairs.

Measuring the intensity ratio between signal pairs in this

25 manner is, however, rather complicated. Figs. 4A and B show a diffe¬ rent embodiment in which this measurement is simpler. Now the trans¬ ducers 13 are parallel to the main direction of extension of the profile line 1. As appears from the signal shape shown in Fig. 4 B, the signals in the output signal series relating to adjacent cells

30 14 of different transducers 13 are juxtaposed so that the ratio measurement is considerably simplified without the necessity of an additional series/parallel converter.

Another advantage of the embodiment of Fig. 4 is that, if the profile line 1 is widened in such α manner that more than two adjacent cells can be covered, finding the centre of gravity is simpler, since the signals in question are, as such, succeeding one another; in the case of parallel-forming according to Fig. 3 this 5 would lead to a substantially more complex processing.

A profile line of the afore-mentioned shape is, in parti¬ cular, obtained in a special depth measuring apparatus of the in¬ vention, by means of which the outer shape of a body can be de¬ termined.

10 Fig. 5 shows the principle on which this apparatus is based.

A source 1ό of a very narrow beam 17, in particular a lase beam, is directed towards a surface 18 to be examined, said surface comprising, for instance, a recessed part 18a and a protruding part

15 18b. This surface is, for instance, movable in the x-direction, and it is desired to determine the distance in the z-direction between the portions 18a and 18b. By means of. a lens 20 the radiation 19a and 19b remitted by said surfaces 18a and 18b resp. is focussed on a surface 21 in the form of discrete image points 22a and 22b resp.

20 In a known apparatus the surface 21 is formed by a rectilinear trans ducer, e.g. a transducer 13 according to Fig. 3, and from the loca¬ tion of the image point 22 varying in time when displacing the surface 18 the shape of the latter can be derived.

A drc -back of this apparatus is that, even with opto-

25 mechanical means such as a rotating mirror, a complete profile line cannot be quickly recorded. Fig. 6 shows a modified embodiment of such an apparatus in which, by means of a suitable optical system 23, a radiation plane 17' is produced, intersecting the surface 18 to be examined according to a profile line, the remitted radiation 19

30 being directed by means of a lens 20 towards a transducer surface 3 of the above-mentioned kind, on which a profile line 1 is focussed corresponding to the line of intersection of the surface 18 and the radiation plane 17' If the surface 18 is moved in the x-direction, - li ¬ the whole surface 18 can be scanned in order to obtain a complete picture of'the shape of this surface. As a matter of fact also the radiation plane 17' can be moved along the surface 18.

When using the transducers of the kind shown in Figs. 3 and 4, it is possible to use, instead of a single radiation plane 17', a fan of mutually separated planes, and then the various pro¬ file lines 1 are formed in a juxtaposed manner. In Fig. 3 an additi¬ onal profile line 1' is indicated. Then care should be taken, of course, that a sufficient distance between adjacent profile lines is present so as to avoid disturbances.

Instead of examining a surface, in the case of transparent objects the structure thereof can be examined in this manner if structure variations give rise to a deflection of the radiation. As already mentioned, the transducers described before can also be used in the case of radiation profile lines obtained in a different manner, e.g. luminous lines formed on an oscillograph screen. Generally speaking such transducers can be used in all cases wherein such a profile line can be formed on the transducer surface. For the rest it will be cJ ^*ar that any composite trans- ducer having a uniform matrix structure is suitable for this purpose, and the signal output is, then, to be adapted to the display and processing requirements. In particular matrix transducers having individually addressable matrix points are contemplated, in which case only those portions are to be addressed in which points of interest 2 of such profile lines are situated, which can give rise to a substantial acceleration of the measurement. This may be impor¬ tant, for instance, if quickly moving surface portions of an object are to be examined. For the time being only the composite trans¬ ducers shown in Figs. 2, 3 and 4 are very suitable as they can be manufactured by means of available techniques.

It is also conceivable to store the signals originating from such a transducer in a matrix memory, and to read out only the portions of interest.

Claims

C l a i s

1. An apparatus for converting a radiation profile line into electrical signals corresponding thereto, characterised by a flat composite transducer (3), on which radiation in the form of a radiation profile line (1, 2) to be processed is incident, and adapted to convert said radiation into electrical signals in a two- dimensional way, said transducer (3) being provided, to that end, with transducing region^'s (4) arranged in a fixed two-dimensional pattern, and, furthermore, being connected to means (ό, 7) for delivering and processing the produced electrical signals in a manner which is unambiguously related to corresponding transducer regions.

2. The apparatus of claim 1, charcterised in that the composite transducer (3) comprises a plurality of juxtaposed and substantially rectilinear transducing regions (4), each being adapted to produce electrical signals unambiguously related to the point of radiation incidence on the region in question, and being connected, at leastat one extremity (5) thereof, to output means (6) for delivering the produced signals, said means, furthermore, being connected to means (7) for processing the signals produced by the various regions (4) in an interrelated .nanner.

3. The apparatus of claim 2, characterised in that the signal output means (ό) are realised as electronic series/parallel converters, by means of which the signals appearing simultaneously at the outputs (5) of the various transducing regions (4) can be derived as a serial signal series.

4. The apparatus of claim 3, characterised in that the signal output means (6) are formed by at least one analogue shift register.

5. The apparatus of any one of claims 2..4, characterise in that the rectilinear transducing regions (4) are formed by recti- linear lateral photo-effect transducers (9), the longitudinal axes thereof intersecting the profile line (1, 2) to be converted in different points, and being connected, at both "extremities (5a,5b) , with an output means (6a, 6b) adapted to produce a signal corres¬ ponding to the current intensity at the respective extremity (5a, 5b), said output means (6a, 6b) being synchronised in such a manner that the signals appearing at both extremities (5a, 5b) of a trans¬ ducer (9) are simultaneously delivered, the processing means (7) being adapted to determine the ratio between the signals simultane¬ ously appearing at both extremities (5a, 5b) of the same transducer (9).

6. The apparatus of claim 5, characterised in that the corresponding outputs (5a, 5b) of the various transducers (9) are each connected to a corresponding parallel/series converter (6a, 6b), and the outputs of both converters being connected to a stage (7) for determining the ratio between the simultaneously arrived signals.

7. The apparatus of any one of claims 2..4, characterise in that rectilinear transducer regions (4) are each formed .by a series of photo-cells each connected to a respective cell (14) of an analogue shift register (13).

8. The apparatus of claim 7, characterised in that means are present for widening the profile line (1, 2) transversely to its main direction of extension up to a width which is at least equal to the centre-line distance between cells (14) which are juxtaposed transversely to said direction of extension, the pro- cessing means (7) being adapted for measuring the intensities of signals originating from cells (14) each irradiated by a portion of the widened profile line (1, 2).

9. The apparatus of claim 8, characterised in that the axes of the analogue shift register (13) each connected to a photo- cell series are directed transversely to the main direction of ex¬ tension of the profile line (1, 2), and in that the output of the output means (6) is connected to a series/parallel converter (15), the processing means (7) being adapted for determining the intensity ratio between pairs of corresponding signals of adjoining signals series.

10. The apparatus of claim 8, characterised in that the axes of the analogue shift registers (13) each connected to a photo¬ cell series are directed parallel to the direction of the profile line (1, 2), and in that the output means (6) is connected to a processing means (7) adapted to determine the ratio between successi signals of the same signal series.

11. The apparatus of any one of claims 1..10, intended for determining the the shape or shape or composition deviations of a body to be examined, comprising a source of a narrow radiation beam, in particular a laser beam, and an optical system for forming on the transducer surface image points of the radiation diffused or de- fleeted by said body, characterised in that the source (16) is adapted to form at least one radiation plane (17') which is di¬ rected in such a manner that the radiation diffused or deflected by the body (18) is focussed by the optical system (20) on the composit transducer (3) as a radiation profile line (1, 2).

12. The apparatus of claim 11, ch aracterised in that it is adapted for producing a fan of radiation planes in order to form a corresponding member of profile lines (1,2; 1').

13. The apparatus of claim 12, characterised by means for moving a single radiation plane (17') step-wise.

14, The apparatus of claim 12 and any one of claims 7..10, charac terised by means for simultaneously forming a plurality of radiation planes (17*).