T 2168/19 28-09-2022

1. Patent as granted (main request) - ground for opposition of lack of inventive step

The subject-matter of granted claim 1 does not involve an inventive step in view of D1 and common general knowledge.

1.1 Closest prior art and distinguishing feature

It is undisputed that the embodiment of D1, shown in figures 4 and 5, represents the closest prior art and that the subject-matter of claim 1 differs from this embodiment of D1 in that the effective diameter of the second filter is larger than the effective diameter of the first filter. Indeed, D1 is silent about the relative size of the first filter (33) and the second filter (54).

1.2 Objective technical problem

The board agrees with the opponent's submission during the oral proceedings before the board that the objective technical problem solved by the distinguishing feature of claim 1 is to make optimum use of the space available in the microscope, to use as little material as possible and to proceed in a cost-saving manner. This is a task that the skilled person basically always faces in the development of every microscope.

1.3 Obvious solution defined by the distinguishing feature

As explained by the opponent during the oral proceedings before the board, it is common general knowledge that the light emitted from an object (3), positioned in the focal plane of the objective lens (29), emanates from the objective lens (29) in the form of parallel rays propagating in a diverging manner towards the tube lens (37). This common general knowledge is exemplified by the disclosure of D10, figure 3B, page 352, second paragraph. As a consequence, the section of light in the plane of the first filter (33) closest to the objective lens (29) has a smaller diameter as compared to the section of light in the plane of the second filter (54) closest to the tube lens (37). In other words, the effective optical diameter of the first optical filter (33) is smaller than the effective optical diameter of the second optical filter 54). The reference signs mentioned above refer to those of figures 4 and 5 of D1.

Furthermore, it is undisputed "that the skilled person knows that microscopes, in particular the microscope of D1, are designed with specific aperture stops and axial distances to provide that no vignetting occurs" (see patent proprietor's letter dated 9 July 2021, page 5, second paragraph; highlighted in the original).

Starting from the microscope shown in figures 4 and 5 of D1 and confronted with the objective technical problem, namely making optimum use of the available space, the skilled person would have designed a microscope in which the diameter of the optical filters is as small as possible. This means, taking account of the fact that the section of light in the plane of the first filter (33) is smaller than the section of light in the plane of the second filter (54), that the skilled person would have selected a first filter having an effective diameter which is smaller than the effective diameter of the second filter. At the same time, by choosing filter sizes as small as possible, the skilled person solves the further tasks of using as little material as possible and proceeding in a cost-saving manner.

Moreover, since the skilled person knows that vignetting has to be generally suppressed in microscopes, the skilled person would have selected filters being sufficiently large, namely a second filter whose effective diameter is larger than the effective diameter of the first filter. The option of selecting optical filters having large but identical effective optical diameters would mean that either the first filter is too large, thereby not using the available space in an optimum manner, or the second filter is too small, thereby vignetting the light beam.

In conclusion, when solving the objective technical problem, the skilled person would obviously have chosen the effective diameter of the second filter (54) to be larger than the effective diameter of the first filter (33), thereby arriving at a microscope falling under the scope of granted claim 1 without exercising any inventive skills.

1.4 Patent proprietor's counter-arguments

1.4.1 The patent proprietor, referring to paragraphs [0020] to [0022] of the patent and to the documents T1 to T3, was of the view that the optical filters disclosed in D1 were not filter blocks as defined in claim 1. As argued in its letter dated 9 July 2021, page 3, third paragraph, a filter block had to be block shaped and to have a filter block frame to remove the optical filter either together with the filter frame or without it. Therefore, the subject-matter of claim 1 further differed from the embodiment of D1 in that it comprised filter blocks.

The board is not convinced by this argument. Contrary to the patent proprietor's view, the description of the patent, paragraphs [0020] to [0022], describing specific features of a filter block, cannot limit the scope of claim 1. The subject-matter of a claim is only defined by the features which are actually present in the claim. The claim wording has to be interpreted as broadly as reasonable. In the present case, the expression "filter block" defines a general item comprising at least a filter. In particular, nothing speaks against considering the "upper illumination reflecting member 33" and the "second upper illumination reflecting member 54" of document D1 (see figures 4 and 5 of D1) as being filter blocks. Moreover, in the board's view, a filter block in general is not restricted to an item comprising the specific technical properties described by the patent proprietor in its letter dated 9 July 2021. The general words "block" or "filter block", as such, have a broader meaning in the field of optical microscopes. Documents T1 to T3 merely disclose properties of specific optical filter blocks which cannot be considered to represent a generally valid definition of a filter block.

1.4.2 During the oral proceedings before the board, the patent proprietor argued that the objective technical problem relating to the distinguishing feature of claim 1 was not merely about mechanical positioning of optical filters inside an optical microscope. See also its letter dated 9 July 2021, pages 4 to 7. Further tasks of the skilled person had to be considered, namely how to cost-effectively facilitate the addition of further optical filters between the objective lens and tube lens, and how to efficiently suppress the occurrence of vignetting.

The board acknowledges that cost-effectiveness and vignetting play a role in the design of a microscope. However, these aspects have already been taken into account in the above reasoning why the skilled person would have arrived at the claimed microscope in an obvious manner. As explained in point 1.3 above, by providing a second optical filter (54) having a larger effective diameter than the first optical filter (33), cost-effectiveness and suppression of vignetting are automatically fulfilled by the solution implemented by the skilled person. Indeed, using a first optical filter having a smaller effective diameter than the second optical filter is cost-effective in comparison to using a first optical filter having an unnecessarily large effective diameter. Moreover, using a second optical filter having a larger effective diameter than the first optical filter avoids vignetting of the parallel light beam propagating in a divergent manner from the first optical filter towards the second optical filter.

1.4.3 Accordingly, the ground for opposition under Article 100(a) EPC in combination with Article 56 EPC prejudices the maintenance of the patent as granted.

2. Remittal of the case

As requested by the patent proprietor, the board considers it appropriate to make use of its discretion under Article 111(1), second sentence, EPC and Article 11 RPBA 2020 in remitting the case to the opposition division for further prosecution.

2.1 For the reasons provided in point 1. above, the board came to the conclusion that the subject-matter of claim 1 of the patent as granted (main request) lacked an inventive step and that, therefore, the appealed decision rejecting the opposition had to be set aside.

2.2 The board notes that the patent proprietor filed a total of eight auxiliary requests during the appeal-opposition proceedings and that currently it maintained all these requests. The board further notes that five of these requests are identical to the requests filed by the patent proprietor during the first-instance opposition proceedings so that there is no reason for not admitting at least some of these requests into the appeal-opposition proceedings. Claim 1 of each of these auxiliary requests comprises additional features compared to claim 1 of the patent as granted in order to overcome the objection of lack of inventive step. The decision under appeal did not deal with the subject-matter claimed in any of these auxiliary requests. The patentability of the subject-matter of claim 1 of the auxiliary requests would therefore have to be assessed for the first time in the appeal proceedings.

In addition, in view of the numerous objections of lack of inventive step, lack of clarity and added subject-matter raised by the opponent throughout the appeal proceedings the board considers that the assessment of the patentability of claim 1 of the auxiliary requests comprises a complexity in terms of the number of new issues which is not compatible with the primary object of the appeal proceedings to review the decision under appeal in a judicial manner (Article 12(2) RPBA 2020).

2.3 The opponent requested that the case not be remitted but that the board decide on the objection of lack of inventive step to the subject-matter of claim 1 of the auxiliary requests on file. In the opponent's view, a review of inventive step would be possible within the framework of Article 12(2) RPBA 2020 defining the primary object of the appeal proceedings to be a review of the decision under appeal in a judicial manner. The opponent recalled that there is no right of a party to have the case remitted to the department of first instance. Moreover, the opponent submitted that remitting the case would delay the proceedings, increase the costs and maintain legal uncertainty.

The board is not convinced by the opponent's arguments. As submitted by the patent proprietor during the oral proceedings before the board, the appealed decision only dealt with the objection of lack of inventive step of the feature relating to the relative sizes of the filters' effective diameters. In the case at hand, examining new features for the first time and deciding whether they comply with all the requirements of the EPC goes beyond the task of an appellate instance. Moreover, the board concurs with the patent proprietor that the negative consequences of a remittal (delay, cost, legal uncertainty) are to be considered acceptable under the circumstances of the present case.

2.4 In view of the above, there are special reasons within the meaning of Article 11 RPBA 2020 in the case at hand which justify remitting the case to the opposition division for further prosecution.