T 0092/93 31-07-1995

A. Main request

(i) State of the art

1. Document (D1) relates to non-destructive methods of measuring and monitoring such parameters of clad optical fibres as the diameter, the circularity and the eccentricity of the core - see column 1, lines 8 to 22. With reference to Figure 28, this document describes an apparatus for examining the structure of a clad optical fibre (10), which apparatus comprises a spectrometer base (12), a holder (11) fastened to the base (12) for securing the fibre (10) to be measured, a radiant energy source (18) directing a light beam (19) at the fibre (10), and a spectrometer (16) mounted on a rotatable table (13) coaxial with the fibre and the base (12). In operation, the table (13) is driven by a motor (22) and a slit detector (17) of the spectrometer (16) views the scattering pattern produced by the clad fibre (10) - see from line 52 of column 15 to line 12 of column 16.

The fact that the light beam (19) is perpendicular to the axis of the optical fibre (10) is not stated expressis verbis in document (D1). However, the theoretical considerations developed in document (D1) are based on this assumption - see column 3, lines 59 to 63. - and none of the formulae disclosed there would be valid if such were not the case, since they do not include any symbol denoting the angle formed by the light beam and the axis of the fibre - see also Claim 2.

The Appellant contested that the optical axis of the measuring means comprising the light source (18) and the "pickup system", formed by the spectrometer (16), the slit detector (17) and the rotatable table (13) would extend from said light source to said pickup system. However, document (D1) states that, in operation, the spectrometer (16) is rotated to the 0 position and that the table (13) is subsequently rotated so that the detector (17) views the entire scattering pattern after one complete revolution (360 ) has been accomplished - see column 16, lines 3 to 8. For reasons of symmetry, it is thus clear that the axis of the spectrometer (16) at the 0 position - i.e. that of light scattered in the forward direction, as defined in column 4, lines 33 to 35. - and the light beam (19), of which said axis of the spectrometer forms the prolongation at that position, constitute the optical axis of the optical measuring means described in document (D1). This is even more clear in the alternative embodiment of Figure 29 to which the Appellant drew attention, where a circular array of photodiodes (30) and a scanner (31) are substituted for the spectrometer (16), the rotatable table (13) and the motor (22) - column 16, lines 24 to 28. Therefore, keeping to the formulation and terminology of Claim 1, as apparatus according to Figure 28 of document (D1) comprises:

- optical measuring means comprising a light source for irradiating the side wall of an optical fibre with an observing light and a pickup system for detecting said observing light traversing said optical fibre, the optical axis of said optical measuring means extending from said light source to said pickup system, and

- an optical fibre mounting member for mounting said optical fibre thereon, the axis of said optical fibre and the optical axis of said optical measuring means being set perpendicular to one another.

Furthermore, in said apparatus,

"the measuring means including the pickup system is capable of measuring a luminance distribution of the light passing through the optical fibre".

2. Besides the light source (18) and the spectrometer (16), the Figure 28 of document (D1) shows a control circuit (24), a lock-in amplifier (26) and a pen recorder (27). Obviously, the amplifier and the pen recorder may not be considered as a calculation means, whereas the control circuit is just said to drive the motor (22) rotating the spectrometer and to energize the light source - see from line 65 of column 15 to line 5 of column 16. Nevertheless, the cited passage of the description states that the amplifier (26) receives the output of the slit detector (17) and that, "in an on-line process, the output of amplifier (26), would be connected to suitable logic circuitry such that, if the parameter being measured ... exceeded or fell below some priorly established tolerance limit, a feed-back loop could make appropriate changes to the process". Furthermore, as stated in independent Claims 1 and 4 of document (D1), the core diameter and the cladding thickness are computed. Therefore, despite the lack of explicit disclosure, it appears that Figure 28 of document (D1) is only a partial representation of an apparatus which necessarily comprises

"means for calculating structural parameters (of a clad optical fibre) on the basis of the measured light having traversed the optical fibre".

3. The notion of "lens effect" is not clearly defined in the patent application. Nevertheless, the outer surface of an optical fibre's cladding being a cylindrical dioptre, the fringe pattern which can be observed from the outside is necessarily an image of the actual fringe pattern produced by light diffraction at the boarder between core and cladding. Furthermore, a cylindrical dioptre is a poor imaging device, and with increasing distance to the plane containing the light source and the axis of the fibre, said image becomes more and more distorted. Therefore, the lens effect mentioned in Claim 1 cannot be anything other than the distortion and/or magnification of the observed fringe pattern resulting from the convexity of the fibre's outer surface. As a matter of fact, in a reply dated 4. December 1991 to the first communication of the Examining Division, the Appellant made submissions which are in agreement with this conclusion.

Now, the "lens effect" of any dioptre or optical system is a consequence of the refraction of light by the dioptre and, therefore, is related to the deviation ( ) of the rays exiting the dioptre or the system. Furthermore, the formulae of document (D1) take this angle into account, in particular those numbered 13 to 19, of which the validity is readily apparent. Therefore, the calculating means provided according to document (D1) for determining structural parameters of an optical fibre on the basis of said formulae necessarily "correct the lens effect on the luminance distribution of the light passing through the optical fibre". The Appellant did not raise any objection regarding this point. On the contrary, it acknowledged that a person skilled in the art is well aware of the lens effect and submitted that including method steps for correcting this effect would result in unduly restricting the invention - see page 10 of the Statement of Grounds of Appeal.

4. With respect to an apparatus embodying the teachings of document (D1), the subject-matter of Claim 1 is thus novel in that

- either the optical fibre mounting member or the optical measuring means is rotatable relative to the other, and in that

- the pickup system includes a focusing means having its "observing plane" set at a position within or close to the diameter of the optical fibre.

The latter feature actually means that, with respect to the focusing means, the luminance detecting member of the pickup system - typically, the target of a television pickup tube as may be inferred from Claim 2 - is located in a plane conjugate of an object plane which is at a position "within or close to the diameter of the optical fibre".

(ii) Inventive step

5. The methods of determining structural parameters of clad optical fibres or rods disclosed in the present application, in document (D1) and in document (D2) are based on measurements of distances between maxima and/or minima of a luminance distribution produced by the passage of a light beam through such an optical fibre or rod. Therefore, the requirement to be met in order to achieve an accurate determination of such parameters is either that the primary fringe pattern produced by the core-cladding interface be accessible to the measuring means or that a sharp image of said pattern be formed at some accessible place.

The Appellant did not contest that the primary fringes are produced within the bulk of the clad fibre or rod. In document (D2), which was considered by the Appellant to be the most relevant for assessing inventiveness, it is indeed stated that, between those rays that traverse only the cladding and those rays that traverse both the cladding and the core, there is a particular group of rays which are incident at a grazing angle and are totally reflected - see column 3, lines 14 to 20. Two dark regions are thus present within the bulk of the optical fibre or rod, which regions are part of the primary fringe pattern.

Therefore, when designing an apparatus of the kind covered by the pre-characterising clause of Claim 1, no exercise of inventive ingenuity is required from the skilled person to provide, in order to determine more accurately structural parameters of clad optical fibres, a focussing means such that an object plane located within or close to the diameter of the fibre to be examined and a plane coinciding with the target of a suitable pickup device be conjugate - see also column 5 of document (D2), lines 1 to 6. Besides, anyone having practical or theoretical knowledge of optics is well aware of the subsidiary advantage offered by such a measure, to wit a possible reduction in size of the apparatus.

6. Rotating the optical fibre relative to the pickup system of the claimed apparatus aims obviously at determining whether, and if so in which direction, the axis of the core is shifted with respect to the axis of the cladding's outer surface. However, both this measure and the result expected therefrom are known in the art - see column 4 of document (D2), lines 21 to 23 - and the Appellant did not contend that, taken alone, any of them might be considered as evidence of an inventive step.

7. In the Board's judgment, therefore, Claim 1 according to the Appellant's main request lacks an inventive step. Mutatis mutandis, the same reasons and the same conclusion apply to the independent method Claim 11.

8. Therefore, the Appellant's main request is not allowable having regard to, Article 52(1) EPC in conjunction with Article 56 EPC.

B. Auxiliary request

Admissibility

1. The first part of the headnote of Decision T 153/85 reads as follows:

I. If an Appellant desires that the allowability of alternative sets of claims should be considered in an appeal, such alternative claims should normally be filed with the Statement of Grounds of Appeal or as soon as possible thereafter.

II. When deciding an appeal during oral proceedings, a Board of Appeal may refuse to consider alternative claims which have been filed at a late stage, e.g. during the oral proceedings, if such claims are not clearly allowable.

In the present case, the subject-matter of the characterising portion of Claim 1 of the auxiliary request (see paragraph V above) was not previously the subject-matter of any of the claims of the application, and has been derived from the description. Although it appears that no objection to this amended claim arises under Article 123(2) EPC, nevertheless the subject- matter of this claim has not been specifically considered by the Examining Division, and may not have been specifically searched by the Search Division.

As pointed out in paragraph 2.1 of Decision T 153/85:

"In relation to appeal proceedings, the normal rule is as follows: if an appellant wishes that the allowability of the alternative set of claims, which differ in subject-matter from those considered at first instance, should be considered (both in relation to Article 123 EPC and otherwise) by the Board of Appeal when deciding on the appeal, such alternative sets of claims should be filed with the grounds of appeal, or as soon as possible thereafter."

Furthermore:

"In all normal circumstances, an appellant has ample time and opportunity, both during the proceedings at first instance and during the appeal proceedings, to consider and formulate the full range of claims that he may desire, well prior to the oral hearing (in the appeal proceedings). This is especially applicable to the present case. During the proceedings before the Examining Division, following a first communication issued on 25 July 1991, in a second communication issued on 17 February 1992 the Examining Division specifically considered the inventiveness of Claim 11 (a method claim), being the narrower of the two independent Claims 1 and 11, and stated not only that Claim 11 did not involve an inventive step having regard to documents (D1) and (D2), but also that "the description does not provide any method steps which could render Claim 11 inventive" (paragraph 2.7), and that "The Applicant should be aware that there appears to be no inventive material in the application and continuation of the examination procedure appears likely, at this stage, to result in a refusal".

Thus the Appellant has had at least three years since receipt of such communication, and before receipt of the Board's communication dated 9 March 1995, in which to propose the set of claims which was first filed on 25. April 1995, the evening before oral proceedings before the Board of Appeal, as an auxiliary request. The Board's communication dated 9 March 1995, which the Appellant received on 13 March 1995, merely developed the reasoning of the Examining Division for a possible finding of lack of inventive step with respect to the set of claims filed with the Statement of Grounds of Appeal, on the basis of documents (D1) and (D2).

In the Board's view, an alternative set of claims such as the auxiliary request which was filed on 25 April 1995, including new claims with subject-matter which had not previously been included in the claims, should have been filed with the Statement of Grounds of Appeal, or at least soon after, if the Appellant wished such claims to be fully considered in these proceedings.

2. In the circumstances that this auxiliary request was only filed the evening before oral proceedings before the Board of Appeal, the Board would only admit this auxiliary request into the proceedings if the claims were "clearly allowable", in the sense that they can quickly be seen by the Board both to introduce no objections under the EPC and to meet all outstanding objections under the EPC.

In this connection the Board observes as follows:

(i) All transparent substances have a refractive index which varies as a function of the wave length of light. The use of a non-monochromatic light, therefore, would be detrimental to the sharpness of the luminance distribution detected by the pickup system.

(ii) That the measuring means be capable of measuring the luminance distribution of the light passing through the optical fibre at the position (Px) - in fact: capable of determining said distribution - is a condition sine qua non to be met for determining structural parameters of said fibre.

(iii) The distances (Zn, Z*n) are also dependent on the diameters of the core and the cladding, which diameters are not previously known. How the calculating means could determine the distance ( X) from these data is consequently unclear.

(iv) Stating that a calculating means measures distances is unclear. This lack of clarity is the more showing as it is further stated that the calculating means is capable of "correcting the measured distances ..." In fact: the position of the "focussing plane" - i.e. the object plane, as may be inferred from Figure 13A - is dependent upon the convergence of the focussing means, its distances to the centre of the fibre and the target of the pickup tube (14), the diameter and the refractive index of the cladding. Said focussing plane is the one of which the image formed by the cylindrical dioptre is conjugate of said target with respect to the focussing means (18). This remark strengthens the conclusion under 3.

(v) Claim 1 according to the Appellant's auxiliary request is unclear and fails to define completely and correctly its subject-matter. As appears from the preceding, removing these drawbacks reveals that the claim lacks an inventive step, because as indicated generally by the Examining Division in its communication dated 17 February 1992 (see paragraph B(1) above), the claimed features are trivial to any one knowing the elementary laws of geometrical optics.

3. In these circumstances, in the Board's judgment the subject-matter of the claims of the auxiliary request filed on 25 April 1995 is not clearly allowable in the sense set out in paragraph B(2) above, and this auxiliary request is therefore inadmissible.