T 0037/99 09-11-2000

I. The appellant (= proprietor of the patent) lodged an appeal against the decision of the Opposition Division revoking European patent No. 0 544 002.

II. Two oppositions against the patent as a whole had been filed by the respondents (= opponents 01 and 02, respectively) and based on the grounds of lack of novelty and/or inventive step (Article 100(a) EPC).

III. The oppositions inter alia referred to the following documents (using the numbering of the opposition proceedings):

E1: JP-B-58-8627 (and English translation E1* thereof furnished by opponent 01)

E3: Extended Abstracts of the 51th Autumn Meeting of The Japan Society of Applied Physics, published on 26. September 1990, 29p-R-6 (and English translation E3* thereof furnished by opponent 01)

E4: K. Iga et al.: "Surface Emitting Laser", Ohm Co., Ltd, 1990, pages 246 to 247 (and English translation E4* thereof furnished by opponent 01)

E6: JP-A-63-1147 (and English translation E6* thereof furnished by opponent 01), and

E7: JP-A-1-185513 (and English translation E7* thereof furnished by opponent 01),

which documents were again cited by the parties in the present appeal proceedings.

In addition, the following documents:

A: Optics, vol. 15, No. 6, December 1986, pages 504(38) to 505(39) (and partial English translation thereof furnished by the appellant)

B: Optics, vol. 19, No. 6, June 1990, pages 350(2) to 355(7) (and partial English translation thereof furnished by the appellant)

C: "Search Report on Trends in Optical Technology VIII / Development Trend and Prospects of Optical Technology", March 1991, pages 246 to 251 (and partial English translation thereof furnished by the appellant)

D24: US-A-4 956 844

D25: US-A-4 813 762

D26: Electronics Letters, 28 February 1991, vol. 27, No. 6; pages 437 to 438

E8: JP-B-3-30843, and

E9: JP-A-62-58214

have been submitted by the parties for the first time in the appeal proceedings.

IV. In its revocation of the patent in suit, the Opposition Division held that the subject matter of amended independent claims 1 and 11, respectively, was not inventive with respect to a combination of the teachings of documents E1 and E3.

V. With the statement of grounds of appeal, the appellant filed a main request and a first auxiliary request, the independent claims of the former being identical to those considered in the impugned decision.

VI. Oral proceedings were arranged by the summons dated 21. August 2000 in accordance with the respective auxiliary requests of the parties. In a communication of 28 September 2000, the Board expressed its provisional non-binding opinion that the independent claims of the main request were not anticipated by the prior art. Moreover, in accordance with the case law of the boards of appeal, document E1 should be regarded as closest prior art from which the subject matter of the main request mainly differed by the use of a monolithic two-dimensional surface emitting laser array. The technical effects achieved and the presence of an inventive step were to be assessed at the oral proceedings. An analogous discussion should take place with respect to the subject matter of the first auxiliary request once its admissibility under Article 123(2) EPC had been established.

VII. With a letter dated 9 October 2000, the appellant filed independent claims for a second auxiliary request based on features derived from the description.

VIII. As a reaction to said letter, respondent 01 requested rejection of the second auxiliary request as inadmissible because of having been filed too late.

IX. Oral proceedings took place on 9 November 2000. During the oral proceedings, the appellant replaced all previous auxiliary requests by new auxiliary requests 1 to 8, and respondent 02 submitted new document D26. At the end of the oral proceedings, the decision of the Board was given.

X. The appellant requested that the decision under appeal be set aside and that the patent be maintained as amended according to the main request filed with the letter of 5 February 1998 or alternatively on the basis of auxiliary requests 1 to 8 submitted at the oral proceedings.

XI. The respondents requested that the appeal be dismissed.

XII. The wording of the independent claims according to the appellant's requests reads as follows:

Main request

"1. An image forming apparatus, comprising:

an image bearing member (5) for forming a static latent image thereon;

a charging unit (52) for charging the surface of said image bearing member (5);

a laser beam scanning unit (53) for scanning, with a plurality of laser beams, a surface of said image bearing member (5) which is charged; and

a developing unit (55) for causing a developing agent to adhere on the surface of said image bearing member (5) scanned with the laser beams;

wherein said laser beam scanning unit (53) comprises:

a monolithic semiconductor laser array (21) having a plurality of light emitting portions (21a) for emitting laser beams, said light emitting portions (21a) being formed on a single device substrate (22); and

a deflecting unit (3) for deflecting laser beams emitted from said light emitting portions (21a) to the surface of said image bearing member (5);

a scanning optical system for two-dimensionally forming spots on a surface of said image bearing member with the laser beams deflected by said deflecting unit (3), said image bearing member being moved in a direction substantially perpendicular to a scanning direction of said laser beams so that the spots are two-dimensionally formed;

characterized in that: each of said light emitting portions (21a) has an optical oscillator with an optical axis substantially perpendicular to the surface of said single device substrate;

the lighting and the amount of light of each of said light emitting portions (21a) are discretely controlled; and

said light emitting portions (21a) are so two-dimensionally disposed on said single device substrate that said two-dimensionally formed spots on the surface of said image bearing member form their own separate scanning lines.

11. A laser beam scanning unit, comprising: a monolithic semiconductor laser array (21) having a plurality of light emitting portions (21a) for emitting laser beams, said light emitting portions (21a) being formed on a single device substrate; and

a deflecting unit (3) for deflecting the laser beams emitted from said light emitting portions (21a);

a scanning optical system for two-dimensionally forming spots on a surface of a member to be scanned with the laser beams deflected by said deflecting unit (3), said member to be scanned being moved in a direction substantially perpendicular to a scanning direction of said laser beams so that the spots are two-dimensionally formed;

characterized in that: each of said light emitting portions (21a) has an optical oscillator with an optical axis substantially perpendicular to the surface of said single device substrate;

the lighting and the amount of light of each of said light emitting portions (21a) are discretely controlled; and

said light emitting portions (21a) are so two-dimensionally disposed on said single device substrate that said two-dimensionally formed spots on the surface of said member to be scanned form their own separate scanning lines."

First auxiliary request

The first auxiliary request differs from the main request in that claim 11 of the main request has been deleted.

Second auxiliary request

Claims 1 and 11 of the second auxiliary request in substance differ from those claims of the main request in that the additional feature

"and the distance apart of each adjacent laser beam emitted from the semiconductor laser array being 100 µm or less"

has been inserted at the end of the clause beginning with "a monolithic semiconductor laser array (21)".

Third auxiliary request

The third auxiliary request differs from the second auxiliary request in that claim 11 of the second auxiliary request has been deleted.

Fourth auxiliary request

The fourth auxiliary request corresponds to the third auxiliary request, the additional feature however reading

"and the distance apart of each adjacent laser beam emitted from the semiconductor laser array being 50 µm to 100 µm".

Fifth auxiliary request The fifth auxiliary request corresponds to the third auxiliary request, the additional feature however reading

"and the distance apart of each adjacent laser beam emitted from the semiconductor laser array being 50 µm or 100 µm".

Sixth auxiliary request The sixth auxiliary request corresponds to the third auxiliary request, the additional feature however reading

"and the distance apart of each adjacent laser beam emitted from the semiconductor laser array being 100 µm".

Seventh auxiliary request The seventh auxiliary request differs from the main request in that the additional feature

"and each laser beam emitted from the semiconductor laser array has a cross section of an elliptical shape having its major axis according with the scanning direction of the laser beam"

has been inserted at the end of claims 1 and 11.

Eighth auxiliary request The eighth auxiliary request corresponds to the seventh auxiliary request, claim 11 of the seventh auxiliary request having, however, been deleted.

XIII. The appellant's arguments in support of its requests can be summarised as follows:

Document E1 may be accepted as closest prior art. This document is, however, vague in some respect and rather old - 16 years between its date of filing and the priority dates of the patent in suit being a long time in a highly commercial field. Although the prior art deals with high speed printing, it relies on expensive optics so that an objective remains of producing a commercial product at reasonable price and robustness.

It is admitted that claims 1 and 11 of the respective requests relate to the same invention. Hence, if one claim falls, the other claim will also fall. The subject matter of the main request differs from the prior art in that a monolithic two-dimensional laser array of Vertical Cavity Surface Emitting Laser (= VCSEL) diodes is employed. This difference results in the following effects:

(1) A smaller spread angle with respect to that of Edge Emitting Laser (= EEL) diodes.

This has important advantageous consequences for a laser printer since a high requires a powerful collimating lens, which is expensive, and very precise adjustment so that any movements will effect the image quality. The collimating lens of the claimed invention is cheaper and easier to position due to its greater focal length.

(2) A reduced spot spacing.

Owing to the larger spread angle and the smaller focal length, there is a large spacing of spots in the prior art so that one either has to accept a bad resolution or to angle the linear array to the scanning direction. However, when doing so in the prior art, a tiny angle results which is difficult to adjust. Hence, a smaller spot spacing leads to realistic angles, cheaper optics and a better and more stable adjustment.

(3) A more compact array.

VCSELs have a more uniform spread angle as compared to EELs. In addition, there is a low threshold current and, accordingly, less heat, and each spot forms its own scanning line.

Document E1 discloses a monolithic linear EEL array (see Figure 4) arranged perpendicular to the scanning direction and having a big spacing between the lines because of the spread angle. Figure 5 of E1, which shows only two lines of discrete lasers, can hardly be considered a full and detailed disclosure. The respondents' interpretation of E1 is based on a great deal of hindsight since this prior art only schematically shows a series of boxes in Figure 5 and cannot anticipate VCSELs, simply because they did not exist in 1975.

Newly submitted documents D24 and D25 correspond to other documents discussed before the first instance and disclose nothing more than Figure 6 of the patent in suit: a combination of individual lasers to form a high power light source. The only example of a discretely controlled VCSEL is described in document E3. However, a skilled person would not have taken E3 into consideration since there is no use disclosed and no other pointer which might encourage a skilled person in this direction. On the contrary, a large spacing and a low power output guide away from the requirements of the present invention, and the existence of a smaller spread angle which gives a host of advantages for laser printers is even not mentioned in E3.

Starting from E1, there is no one-way street situation since the VCSEL structure is not the only version of a monolithic two-dimensional array, but only one option among at least three, as can be seen from document D24. Therefore, the use of VCSELS in the present context involves an inventive step.

Although no further time is required to study document D26 submitted at the oral proceedings, it should not be admitted to the proceedings since it could have been filed earlier and the patentee is now denied any possibility of being consulted. This document may also relate to a combination of laser beamlets for power purposes, the meaning of "addressable" is unclear and the spread angle problem is not discussed.

Since some of the above arguments actually do not relate to a scanning unit but to a printer, claim 11 has been cancelled in the first, third to sixth and eighth auxiliary request, respectively.

Having regard to the second auxiliary request, it is accepted that the specific phrase "100 µm or less" has not been explicitly disclosed apart from the upper limit 100 µm (see column 11, equation (3) of the patent in suit). However, looking at the disclosure as a whole there is no reason to be limited to 100 µm since the desirability of a small spacing is clearly apparent from the contested patent (see also decision T 187/91 which can be applied here). Moreover, this view is supported by the application as published, which is not limited to the contents of the patent as granted, and has also lead to a number of divisional applications. At various places of the A-publication, a beam spacing of less than 100 µm has been disclosed (see in particular page 22, line 24 and page 29, line 25: "as narrow as 50 µm"; page 37, line 14: "0.05 mm or less"). The full original disclosure must be available for amendments after grant, and an extent of protection by shifting the subject matter of a claim would only be possible if the new feature were not inserted into the preamble, but into the characterising portion of said claim.

Nevertheless, to safeguard the appellant's last chance the third to sixth auxiliary requests have been restricted to spacing values more specifically disclosed. In any case, the reason for defining the spacing in the preamble of said claims was not to make a substantive limitation, but to make explicit what is already implicit from suitability for laser printing, and thus to highlight the full width of the above argument with respect to document E3. The appellant acknowledges that such spacing values belong to the prior art.

The seventh and eighth auxiliary requests rely on the previous second auxiliary request filed in reasonable time before the oral proceedings and thus should be admissible. As regards Article 123(2) EPC, the elliptical cross-section of the laser beam is directly derived from the description indicating that on the imaging member the minor axis is in the scanning direction to have a more square-like pixel shape. However, it has to be taken into account that the laser beam is processed by normal optical components which - due to spherical aberration as generally known from textbooks - cause a rotation of the ellipse. Therefore, in view of common general knowledge, the claimed subject matter is sufficiently clear. This is also true for the meaning of "scanning direction" and where the shape of the cross-section is defined. Before the beam gets to the optics, it has the claimed shape and ends up rotated at the scanning plane.

The prior art is silent on a specific shaping of the laser beam which is particularly simple if VCSELs are used. Figure 6 of document E8 relates to EELs and does not show the claimed beam shape. Document E9 is unclear with respect to the beam shape emitted by the laser. Document E7 shows the desired effect and thus confirms the fact that the claimed shape is conventional. However, the question is how to achieve this shape.

XIV. The respondents advanced the following counterarguments:

Respondent 01:

Apparently, all parties agree that document E1, which shows the basic configuration for simultaneous scanning, comes closest to the subject matter of the patent in suit. Document E1, which relates to an up-to-date technical concept, discloses an alternative two-dimensional arrangement in Figure 5, where the laser emitting points of adjacent rows are staggered to achieve a closer spacing. Page 6, last paragraph of the English translation, which deals with the preference of monolithic laser arrays, applies to the entire teaching of E1, i.e. to the structure of Figure 5 as well. For a skilled reader, this directly implies the use of SEL type lasers which were known at the priority dates of the patent in suit. If a skilled person were to check the availability of such laser type he would come across document E3 or newly filed document D26 describing the SEL structure claimed, the use of which inherently leads to all effects and advantages referred to by the appellant. In particular, an individual addressability is clearly disclosed in these documents.

The appellant's arguments with respect to E3 are not persuasive since an output power of 0.3 W or more is sufficient, and no lower limit has been disclosed for the laser spacing, 600 µm being merely a particular example. Although E3 does not refer to a printer, it should be born in mind that claim 11 is also not restricted to a printer. Therefore, the subject matter of the main request lacks novelty or at least inventive step since no hindsight is necessary to arrive at the claimed invention by a straightforward application of E3.

With respect to the subject matter of the second to fifth auxiliary requests, the objection under Article 123(2) EPC is maintained in view of the fact that the only spacing value disclosed in the patent specification is 100 µm in the context of highlighting the influence of the collimator focal length. However, this is not an upper limit value, and it is also inadmissible to claim a range without lower limit or to refer to passages and figures no longer included in the contested patent as a basis of disclosure. Furthermore, the fact that the new feature has been inserted in the first part of claim 1 does not make any difference with respect to admissibility since an invention is defined by the whole set of features contained in a claim.

In any case, the spacing values claimed in the second to sixth auxiliary requests are conventional (see e.g. E4) and amount to a mere clarification which cannot support patentability. If, on the contrary, such values were considered relevant, it would be necessary to arrange for an additional search which at this very late stage of the proceedings should also not be admissible.

The same argument holds for the subject matter of the seventh and eighth auxiliary requests comprising a new unsearched feature which never formed part of any claim, but was derived from the description, and thus should also be inadmissible at this late stage. Moreover, this amendment offends against Article 123(2) EPC since the new feature is taken out of its context and based on an unclear relationship: a "scanning plane" is defined by two directions, i.e. a scanning direction and a subscanning direction. Moreover, "emitted" being an inherent property of any laser beam, this term does not impose any limitations on the laser beam status. It is also unclear at which location the claimed orientation exists, i.e. when emitted or just before impinging on the scanning plane?

The effect to be achieved in accordance with the appellant's explanations is not apparent from the claims which do not include any optics causing the alleged rotation of the elliptical cross-section. A provisional search carried out by respondent 01 has, nevertheless, lead to documents E8 and E9 disclosing the new feature per se.

Respondent 02:

The focus of argument has changed in the present discussion since most of the appellant's allegations are now directed to the importance of vertical cavity lasers, whereas document E1 allegedly relates to the EEL type. While document E1 does not explicitly define the type of lasers employed, it is the view of respondent 02 that VC laser arrays are widespread for two-dimensional scanning purposes as can be seen not only from document E3, but also from document D26 disclosing a VCSEL matrix architecture for optical scanners. Hence, when starting from document E1 only basic knowledge would be involved to arrive at the subject matter of the main request in a genuine one-way street situation. In consequence, there should be lack of novelty or at least of inventive step.

With respect to the numerical spacing values claimed in accordance with the second to fifth auxiliary requests, no such disclosure is derivable from the patent specification. The original application documents are to be disregarded in this context because the patent specification has been restricted in the eyes of the public so that spacing values below 100 µm are no longer relevant to the invention as granted. If the amended claims were to be allowed, Rule 86(4) EPC should apply since the respective new features have never been searched and are not linked by a unitary concept with the original claims. In any case, the claimed spacing would not be inventive because a spacing of not much more than 100 µm can be derived from document D26 and a design as compact as possible is clearly desirable.

Finally, as regards the seventh and eighth auxiliary requests, respondent 02 concurs with respondent 01 in that these requests should not be admissible because they contain unsearched subject matter filed at a very late stage of the proceedings. Moreover, the teaching imparted is technically incorrect in that a laser beam has no relationship to the scanning direction. In fact, all of the appellant's arguments relate to the image formed on the scanning plane. Thus, the new feature is unclear and has only been disclosed in combination with an appropriate ratio of the ellipse axes. There are also serious doubts as to the rotation referred to by the appellant since no such influence of lenses has been reported in the patent.