Note: Descriptions are shown in the official language in which they were submitted.
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OPTIC SENSOR DESIGNED TO SUPPLY INFORMATION REPRESENTATIVE OF
THE STATE OF A SURFACE
BACKGROUND OF THE INVENTION
The present invention relates to an optic sensor designed to
supply information, either visual or not, representative of the
state existing on at least a defined portion of the surface of
an object.
To supervise the state of the surface of an object, for example
to check the surface condition of a pipe manufactured and
running continuously, it is at present necessary to position a
sufficient number of optic cameras around the pipe to be able to
cover the whole circular cross-section. A minimum of three optic
cameras are required placed 120 degrees with respect to one
another, but this number may be more than three if a very good
definition is required, in which case high-precision cameras
have to be used, comprising an extremely carefully designed and
sophisticated lens system. Although state-of-the-art devices
give satisfactory technical results, they have the drawbacks of
being extremely heavy, complex, and therefore costly, and of
often being excessively space-consuming.
The drawbacks exist for most devices, industrial or not, which
make use of optic representation of the existing state at a set
point of the surface of an object. For example, to align a large
microelectronics mask with the layer it has to cover with very
great precision, for manufacture of semi-conductor integrated
circuits, four high-definition optic cameras can be used, which
is naturally also very heavy in terms of both cost price and
space requirements.
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SUMMARY OF THE INVENTION
The object of the present invention is to overcome these
drawbacks. It is based for this. purpose on an optic sensor
capable of supplying information representative of the state
existing on at least a defined portion of the surface of an
object, the sensor comprising at least one optic head comprising
optic microguides achieved in a substrate, a substrate edge,
which bears the departure points of the microguides, having a
shape in correlation with the portion of object surface to be
examined, whereas the arrival points of the microguides converge
on a photodetector line array, the photodetector line array
being connected to an electronic processing unit.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be better understood and its advantages and
other features will become more clearly apparent from the
following description of several.non-restrictive examples of
embodiment and use of the optic sensor, referring to the
accompanying schematic drawings, in which
Figure 1 is a schematic diagram of an optic supervision
installation of the surface state of a continuously running
tube, the installation using two optic sensors according to the
invention;
Figure 2 shows an alternative embodiment of the sensor used for
the installation in figure 1;
Figure 3 shows an application of the invention to alignment of
plates, in particular masks for manufacture of semi-conductor
integrated circuits;
Figure 4 likewise illustrates the application of the invention
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to centering of a cylindrical part;
Figure 5 shows how the invention is applicable to optic
examination of the surface state of a drilled hole, either
cylindrical or not; and
Figure 6 shows an application of the invention to supervision of
manufacture of plates whose edge has a predetermined crooked
shape.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to figure l, reference 1 designates a tube or pipe,
seen in transverse section, which is manufactured continuously
in a conventional manner and whose surface state is to be
checked.
For this purpose two adjoined optic heads 2 and 3 are used, each
made up of a substrate formed for example by a glass plate,
respectively 4 and 5, on the surface of which a bundle of light
microguides, respectively 6 and 7, is fitted. The microguides
can be achieved by any suitable integrated optic technology, for
example by ion exchange, by layers deposited on silicon, by
doping on lithium niobate, or by diffusion. To give an
indication, the thickness of the substrate may be about one
millimeter.
Each of these bundles starts off from a semi-circular portion 8,
9 of a first edge 10, 11 of the corresponding substrate 4, 5,
and ends on the opposite edge 12, 13 on a conventional photo-
detector line array, respectively 14 and 15. Such a line array
comprises a set of photodetectors electronically tested by
scanning or by multiplexing. According to a preferred
embodiment, CCD line arrays tested by electronic scanning are
used.
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By building up the microguide bundles 6, 7. each of the
microguides terminates on at least one associated photodetector
point of the corresponding line array, which can currently be
achieved (with accuracy) by photolithography processes, each
line array 14, 15 being fixed to the corresponding edge 12, 13
of the substrate 4, 5 which is associated with it.
The tube 1 being uniformally lighted by an external device
(conventional, not shown), each microguide of the bundle 6, 7
transmits to the photodetector points of the line array 14, 15
which are associated with it a light intensity level which is
representative of the reflectivity, and therefore of the surface
state and shape of the small element of the tube 1 which is
situated opposite the departure end (located on the above-
mentioned semi-circular portion 8, 9) of this microguide.
Each line array 14 and 15 has associated with it in conventional
manner an electrical connector, respectively 16 and 17,
electrically connected to a printed circuit board 18, 19
performing scanning control, power supply, and data collection
and shaping, the board and connector normally being supplied by
the manufacturer.
The data is transmitted via bidirectional links 20 and 21 to a
central processing unit 22, for example microprocessor-based,
which may be connected to display means, formed for example by a
screen 23 and/or alphanumeric readout 24.
The characteristics of a standard tube in good condition having
been previously recorded in a memory of the microprocessor
contained in the processing unit 22, any surface defect of the
tube 1, which runs continuously through the circle 8, 9 formed
by abutment of the two edges 10, 11 of the substrates 4 and 5,
will be detected by the microguide(s) located opposite it and
will be able, by comparison, to be displayed, at least as far as
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position is concerned, on the display means 23 and/or 24.
In the embodiment which has just been described, the line array
and its associated connector and board are quite close to the
optic head and the object it'is checking. This may be
inconvenient in some cases, and in this respect figure 2 shows
an alternative embodiment wherein the photodetector line array
is located farther away by means of a flat optic fiber
connector.
As can be seen in figure 2, each optic head with microguides,
such as head 5 in figure 1, is separated into two substrates 5'
and 5", each bearing a bundle of microguides, respectively
bundle 7' and bundle 7" each comprising the same number n of
microguides.
These two substrates 5' and 5" are made up of n optic fibers
placed between the departure edge 13' of substrate 5' and the
departure edge 11" of substrate 5".
As can be seen in the drawing, the bundle 7' connects the n
light-sensing points located on the semi-circle 9 to the
departure ends of the n corresponding optic fibers 25, whereas
the bundle 7" connects the n downstream ends of these n optic
fibers 25 to the n photodetectors of line array 15.
The bundles ?' and 7" have a suitable shape enabling them to be
connected to the connecting optic fibers 25. The diameter and
spacing of the optic fibers is generally much greater than the
distance between the microguides at their connection with the
line array or on the detection section 9. The bundles 7' and 7"
therefore have a diverging shape in the direction of the
connecting optic fibers 25. An optic result is finally obtained
equivalent to that of the circuit according to figure 1, with an
offset location of the electronic processing part formed by the
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photodetector line array and the associated printed circuit
board.
Figure 3 shows an application of the invention to precise
positioning of a plate 26, which may for example be an
integrated circuit manufacturing mask, with respect to a fixed
guide mark formed here by four crosses 27A to 27D.
To achieve this kind of alignment, four linear optic heads 28A
to 28D with microguides are used, all the microguides being
identical, similar to those described above, and naturally each
associated with a photodetector line array (not shown).
Each of the optic heads is positioned in a judiciously chosen,
well-defined manner, for example as represented in the drawing,
above the cross, respectively 27A to 27D, which corresponds to
it. Each of these crosses therefore corresponds, on the optic
head which is associated with it, to a well-determined
graduation (and therefore to a microguide) of this optic head.
As each edge of the plate 26 also gives, when the plate is slid
under the optic heads 28A to 28D, an optic indication which
corresponds to the corresponding graduation of each head, it can
easily be understood that the plate will be correctly centered
when the distances between the graduations recorded by the line
arrays 28A, 28C and respectively 28B, 28D are identical. A very
precise alignment is thus obtained at low cost.
The same kind of device is applicable, as is shown in figure 4,
to centering of the axis O of a cylindrical part 29, for example
a tubular part, with respect to a set point C. Three linear
optic heads 30A to 30C with microguides are then used,
positioned as shown, for example 120 degrees from one another
and all three directed towards the point C, at a distance
therefrom appreciably equal to the radius R of the straight
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cross-section of the circular cylindrical part 29 (assumed to be
seen from the end in the drawing). Centering will then be
achieved when the graduations (each given by the circular edge
of the part 29) of the three heads,30A to 30C are equal.
It should be noted that the device is of appreciable
flexibility, since it is independent from the radius R of the
part 29 to be centered : for a more or less large radius, the
three optic heads 30A to 30C merely have to be moved closer or
farther away.
Another application of the invention is represented in schematic
farm in figure 5. This then involves inspecting the surface
condition of a drilled hole 31, cylindrical or not, and closed
or not. For this an optic head with microguides 32 is used,
built on the same principle as before, but whose glass substrate
33 has an elongated flat shape, of smaller transverse dimensions
than those of the hole 31. The departure terminations 34 of the
microguides 35 are then regularly distributed over the two side
edges 36, 37 of the elongated glass plate 33.
In order to illuminate the inside of the hole 31, one microguide
35 out of two can be supplied with lighting intensity for
illumination, and is therefore not used for optic sensing (a
system not represented in figure 5). It should naturally be
noted that the alternate "lighting microguide - optic detection
microguide" arrangement of the bundle can also be used in all
the embodiments described hitherto. In a general manner, some of
the microguides of the bundle can be assigned to lighting of the
surface to be examined whereas the others are assigned to
detection.
Finally, figure 6 shows the use of an optic sensing head,
comprising an appreciably rectangular glass plate 38 with a
bundle of microguides 39, for supervision of the predefined
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profile 41 of the edge of a part 40 manufactured in large or
small series. In this case, the information transmitted by the
microguides is compared to reference information, corresponding
to the profile, stored in the central processing unit memory.
It should be noted that to execute certain embodiments according
to the invention, the departure edge of the glass substrate
which contains the departure microguide terminations, i.e. the
sensing points of the optic head which forms part of the present
invention, should be cut and polished. Advantageously, cutting
can be achieved by a water jet charged with abrasive micro-
particles, for example diamond microparticles . a clean, well-
polished edge is thus obtained, which may notably be curved.
The invention is in no way limited to the particular embodiments
which have just been described. Quite on the contrary, other
alternative embodiments and forms of execution are envisageable,
within the scope of similar or different applications. Micro-
guides can, for example, be formed on the top and bottom faces
of a sensing head substrate, the microguides of one of the faces
being assigned to lighting the surface to be examined and the
microguides of the other face being assigned to detection.
