Swarovski-Optik Kg v Leica Camera Ag & Anor

A riflescope is a small telescope which is mounted on a rifle to aid the user of the rifle to view his or her target. Such telescopes may have variable magnification or “zoom”. European Patent (UK) No. 1 746 451 (“the patent”) owned by the respondent Swarovski-Optik KG (“Swarovski”) is directed towards improving such telescopes and in particular towards achieving a wide field of view over all magnifications. After the trial of an infringement and revocation action Vos J (as he then was) held that the patent was valid and had been infringed by the appellants, Leica Camera AG and Leica Camera Limited (together “Leica”). On this appeal, Leica challenge that judgment, and the consequent order, contending that the judge ought to have found the patent invalid for lack of inventive step or alternatively lack of novelty. Leica also seek permission from this court to raise additional grounds of objection to the validity of the patent.

On the appeal, as in the court below, Leica were represented by Mr Michael Hicks and Swarovski by Mr Andrew Lykiardopoulos.

The following issues arise for decision on this appeal:

Before turning to the specification of the patent, I will set out some uncontroversial technical background. The basic design of a riflescope is shown in the figure reproduced below taken from the report of Professor Rogers, Leica’s expert. Light entering the telescope from the left (the convention in optical drawings) through the objective lens forms a first (inverted) intermediate image, marked with an X. The lenses labelled “Movable Zoom Relay Elements” provide the variable magnification or zoom. They do so by moving relative to each other and to their position in the telescope in a complex manner which ensures that the image remains in focus whilst the magnification varies. By the time that the light arrives at the second (erect) intermediate image (again marked with an X) the image has been inverted again to make it upright. It is this second intermediate image which is viewed by the eye (at the right hand end in the diagram) through a lens or lenses designated “Eyepiece”.

The range of magnifications provided by the telescope is called the zoom range, and the ratio of the largest to the smallest magnification is called the zoom factor. Thus a riflescope with a magnification range of 1-4 times has a zoom factor of 4. The majority of riflescopes sold before the priority date of the patent (20 July 2005) had a zoom factor of 4 or less.

In the figure reproduced above the beam is shown to focus on the eye at some distance from the eyepiece. This is a feature of some importance in the design of riflescopes, and is known as “eye relief”. A long eye relief is needed in order to allow the rifle to recoil without causing injury to the eye.

The unassisted eye has a very wide angular field of view. The field of view seen by the user through a telescope is much restricted, and is referred to as the apparent or subjective field of view.

The lenses shown in the typical arrangement of telescope shown above are all positive lenses (lenses with at least one convex surface). Such lenses cause light to converge. An undesired effect of the use of a number of positive lenses is field curvature. An image suffering from field curvature, whilst in focus, is not flat, but appears to curve away from the eye of the observer at the edges. Up to a point, the eye can accommodate field curvature in an image, but the image will start to look unnatural if excessively curved. The following diagram reproduced from the report of Professor Rogers shows this effect:

Whilst the curvature of the field is in fact most extreme at high magnifications, it is most apparent to the user at low magnifications. Thus at a magnification of 1x the user is viewing a large portion of the intermediate image, and will see the outer portions where the curvature is most extreme. At higher magnifications the user will view a smaller central portion, where the curvature will be less pronounced and therefore less apparent. If uncorrected, field curvature reduces the usable field of view of the telescope.

A well known means for reducing unacceptable field curvature was the use of a negative lens, that is to say a lens which has at least one concave surface. Negative lenses cause light to diverge. As will be explained, the ability of a negative lens to correct field curvature forms the foundation of Leica’s case for lack of inventive step.

There is a further and independent source of interference with field of view. Mechanical components inside the central tube section of the telescope can cause interference with the outer rays of light passing down the tube, causing the image to dim in brightness at the edges, an effect described as “vignetting”. If nothing is done about vignetting, the user will experience a loss of quality of the image at the edges. Vignetting can in practice be masked by the introduction of a field stop – an apertured disc – at the first intermediate image. This will result in a loss of field of view.

Finally there is an effect known as “the tunnel effect”. A field stop at the first intermediate image (introduced to mask vignetting) may cause a black ring to appear around the image at low magnifications.

The specification of the patent is entitled “Telescope with wide field of view and variable magnification”. Paragraphs [0002] to [0004] discuss a variety of prior art optical devices. Where a zoom factor is indicated, it is four or less. Paragraphs [0005] to [0007] explain the importance of maintaining as wide a field of view as possible when magnifying the image. The objective of the invention is said, at [0008], to be enabling the field of view to be as large as possible across the entire range of magnification.

At [0008] the objective is said to be achieved by an “optical beam deflector device” – in practice a negative lens – which guarantees a subjective field of view of at least 22^º. As a result, it is said:

“… it is now possible to provide a subjective field of view of at least 22^º even at low magnification, in particular at the lowest magnification, of the telescopic device. Until now this has only been possible with the larger magnifications of generic telescopic devices. With the aid of the telescopic device proposed by the invention, even at low magnifications, the observer sees a larger part of the surrounding area than was possible using the prior art systems.”

The specification then goes on to describe a prior art device of the kind I have described above by reference to Professor Rogers’ figure. Building on this description the specification continues at [0017]:

“To enable a subjective field of view of at least 22^º to be ensured even at low magnifications in a telescope or sighting telescope with a maximum magnification or a maximum zoom greater than four times, the invention proposes a beam deflector device 2. An example embodiment of this is illustrated in Figs. 3a to 3c and in this instance it is provided as an additional arrangement integrated in the inverting system 1.”

Figure 3(a) shows the first of these arrangements:

In Figure 3(a) the two crosses on the optical axis (reading from the left) indicate the first and second intermediate image. The numerals 3(a) and 3(b) indicate the movable zoom relay elements. The negative lens – the optical beam deflector device – is shown by numeral 2. It is located between the movable zoom relay elements and the second intermediate image. Although it is not expressly pointed out in the specification, it is to be noticed that the second intermediate image is positioned in the wider part of the tube. Rays of light from the bottom of the first intermediate image are shown, after passing through the field lens and movable zoom relay elements, as diverging from the negative lens 2. As Dr Blandford explained in his first report, this arrangement allowed the use of smaller lenses than would otherwise be necessary to give an equivalent field of view. He explained:

“…without lens 2 the patent’s enhanced field of view could not be achieved in such a compact system – it would require an unacceptably long tube and/or unacceptably wide central tube 6 or eyepiece 5 to house the larger lenses needed.”

To put this another way, the negative lens in the arrangement shown allows a greater field of view for a given diameter of central tube. The use of the negative lens in this way, to give a wider field of view for a given diameter of tube was described in evidence as “the waist effect”.

At [0017] the specification says this about the positioning of the negative lens, in a passage which is echoed later in claims 1 and 3:

“It has proved to be of practical advantage if the optical beam deflector device 2 is disposed on the side of the inverting system 1 facing towards the eyepiece 5. It is also advantageous if it is positioned on the side of the eyepiece-end image plane 10 facing away from the eyepiece 5.”

At [0020] it is explained that the negative lens 2 has a refractive power of between -20 and -40 dioptres, and that with a lens of -27.03 dioptres a subjective field of view of 23.5^o was obtained at all magnifications.

At [0021] the specification explains that Figures 3(a) to 3(c) show the respective arrangements of the zoom relay elements necessary to achieve a magnification of 1x, 3.5x and 6x respectively. It continues:

“The optical beam deflector device 2 deflects the beam in order to enlarge the subjective field of view.”

Finally the patent explains, by reference to Figure 4, the DIN standard method of measuring field of view.

The judge worked from a breakdown of all the claims of the patent, from which I need only extract claims 1, 3 and 8.

Claim 1

Claim 3

Claim 8

We heard the argument on this issue at the outset of the appeal and announced our decision refusing permission to rely on the additional grounds at the conclusion of the argument. Our reasons for doing so are as follows.

The new grounds of appeal relate to integer 11 of claim 1 (“integer 1.11”), namely that the telescope be one:

“with a maximum zoom greater than four times”.

The language of integer 1.11 is undoubtedly sloppy. Although one can logically speak of a zoom factor greater than four times, it makes no sense to speak of a maximum zoom factor greater than four times. A riflescope has only one zoom factor. Viewed acontextually, there are two possibilities to consider. The word “maximum” could simply be ignored as an error. Alternatively the draughtsman may have meant to refer to a maximum magnification(as opposed to zoom factor) greater than four times.

The judge decided (at judgment [169] to [173]) that integer 1.11 meant that the zoom factor was greater than four, thus ignoring the word “maximum”. He said that the phrase was “not good English”, but could only sensibly be referring to zoom factor. He relied on passages in the description as well as the evidence of Dr Blandford. He rejected Leica’s contention that the phrase was so ambiguous that the claim was invalid for lack of clarity or could not be infringed.

In a decision dated 18 April 2013 the Opposition Division of the EPO (“the OD”) decided that a claim which referred only to zoom factor added matter when compared with the application as filed. Swarovski was required by the OD to amend the specification and claims to include within integer 4 of claim 1 a further limitation of a maximum magnification (by the inverting system) of more than four times (in addition to the existing zoom factor limitation). The decision of the OD is subject to appeal, and its effect is for the time being suspended.

Leica contend that if the true permissible scope of the patent is that permitted by the OD, then there has been no finding of infringement by the Leica riflescopes, as it is not self-evident that the magnification achieved by the inverting system in the Leica riflescopes is greater than four times.

Leica wishes to raise the following additional grounds of appeal:

“(1)

The judge should have held that claim 1 was ambiguous in relation to integer 1.11 and was therefore invalid on the ground of insufficiency, and further or alternatively could not be infringed.

(2)

If it means maximum magnification greater than four times then Swarovski has not established infringement (especially if that is to be interpreted to amount to the same disclosure as claim 1 of the application as filed).

(3)

By contrast, if integer 1.11 has the meaning found by the judge it would clearly be invalid on the ground of added matter for the reasons explained by the Opposition Division in its decision of 18 April 2013.” (original emphasis)

The hearing before the OD leading to its 18 April 2013 decision was on 13 and 14 March 2013, a month before the trial commenced in this country. Leica Camera AG (the first appellant) was a party to that decision: we were told that it had raised the added matter point on which they now wish to rely in their grounds of opposition in March 2011. The result of the opposition, and in particular the fact that the OD had acceded to their added matter objection to the extent I have indicated, would have been known to Leica at the end of the hearing. The trial in this country took place on various dates between 11 and 23 April 2013 and judgment was handed down on 10 May 2013. Leica’s application to raise these grounds of appeal was not served until 25 February 2014.

The principles which are to be applied to an application of this sort are well settled. Any ground of appeal must have a realistic as opposed to a fanciful prospect of success, or there must be some other compelling reason for the court to hear an appeal on the new ground. The Court will be slow to allow new points to be taken on appeal which were available to be, but which were not, taken at trial. This is particularly so if further evidence might have been adduced in respect of them. A party who contends that he might wish to call further evidence in consequence of fresh grounds being raised cannot be expected to be very specific about the nature of that evidence: see in general Jones v MBNA International Bank [2000] EWCA Civ 514 and Crane v Sky-in-home [2008] EWCA Civ 978.

It is not in dispute that there can be cases where a patent claim is so truly ambiguous that the court will abandon any attempt to give it a meaning and hold that it cannot be infringed, or alternatively hold the patent to be insufficient: see SmithKline Beecham plc v Apotex Europe [2005] FSR 23 at 115(5) per Jacob LJ. Such cases are, however, not common as the court will usually be able to determine from the specification and claims, and any admissible evidence, the meaning which the skilled person would derive from the language in the claim.

Leica’s point about the ambiguity of integer 1.11 was roundly rejected by the judge and not made the subject of Leica’s Notice of Appeal. Swarovski accepts that the point is simply one of interpretation of the patent, and despite the very late stage at which it is sought to be raised, it would not be unfairly prejudiced by its introduction. Nevertheless, I have come to the conclusion that an appeal on this point would not have a realistic prospect of success. The case comes nowhere near the exacting threshold for showing that a claim is truly ambiguous. Each of paragraphs [0002] to [0004] of the specification, which deal with individual prior art devices, correctly distinguish between zoom factor and magnification. For example at [0003] the specification says in relation to a sighting telescope described in a US specification:

“In this instance, the magnification of the telescope can be varied between 2.5 times and 4 times corresponding to a zoom of 1.6 times.”

In relation to a telescope described in a GB specification, it says that it:

“enables a continuously variable total magnification between a fivefold and a tenfold magnification (zoom 2 times) to be obtained”.

It is true that paragraph [0015] of the specification refers to a telescope with “a maximum magnification or a maximum zoom greater than four times”, but this appears in a general descriptive passage, indicating that maximum magnification and zoom greater than four are alternatives rather than equivalents. These passages, as it seems to me, provide ample basis for the skilled person to conclude that the patentee was intending to refer to a zoom factor greater than 4.

Mr Hicks did not persuade me that there was any realistic basis for challenging the judge’s conclusion on this issue, far less did he show me why this would be one of the relatively rare cases where the court should abandon any attempt at construction because of true ambiguity. I would refuse permission to raise this ground.

I turn therefore to the allegation of added matter. The point made by the OD is that claim 1 of the application as filed did contain a limitation to a magnification of at least four times. The OD pointed out that the present claim extends in scope to telescopes with a magnification less than four times. Thus, for example, if a telescope had a magnification range of 0.5 to 2.5, the zoom factor (5) would be greater than 4 but the maximum magnification (2.5) would be less than 4.

The OD arrived at its decision in reliance on the original German application as filed. The relevant paragraph of that application (corresponding to paragraph [0015] of the granted patent) does not appear to have been treated by the OD as disclosing that the maximum magnification and the zoom factor are alternatives. In particular the English word “or” appearing in the agreed English translation of the application was not given a disjunctive meaning.

Recognising the difficulties that a dispute at this stage about the translation of the German application as filed would give rise to, Mr Hicks indicated that he would advance his point, if permission were granted, based only on the agreed English translation. Whilst that course has its attractions, it sweeps away any suggestion that we should treat the new added matter point as arguable merely because the OD had found there was added matter. The OD’s decision was based on different assumptions to those we must now make as to the disclosure of the application as filed.

Mr Hicks’ acceptance that he must proceed on the basis of the agreed translation of the application as filed also sweeps away such reliance as he might otherwise have placed on the decision of the OD as a reason why this point was not pleaded or argued before the judge. That reason would not in any event have carried much weight, as the decision of the OD was known at the beginning of the trial, even though its reasons were not available until the last day of the trial.

The Grounds of Invalidity in the present action did include a ground of added matter based on feature 1.11. However the ground was expressly abandoned by Leica.

I would not give permission for this point to be raised at this stage. It is a point which could have been raised and pursued at any stage, as is demonstrated by the fact that Leica Germany AG did raise and pursue it before the EPO. Although Leica did plead added matter in relation to integer 1.11, they elected not to pursue it at trial. It is now raised in a slightly different form, extraordinarily late and with no surviving excuse for its lateness. Although added matter points are not generally susceptible to much elaboration in evidence, it is possible that the experts might have been able to shed some light on it, as Mr Lykiardopoulos contends. Applying the Crane v Sky approach we should therefore be particularly slow to commence an examination of the point on appeal in view of the potential prejudice to Swarovski.

The main question which divides the parties on the construction of the claims is the limits which they place on the positioning of lens 2. The relevant features of claim 1 are features 12 and 14. Thus claim 1 requires lens 2 to be both integrated in the inverting system (1) and disposed on the end of the inverting system (1) facing the eyepiece (5). The inverting system is said by feature 6 to be disposed between the first and second intermediate images. Claim 3 requires the lens to be disposed on the side of the second intermediate image pointing away from the eyepiece (5). Claim 8 is obviously surplusage, as it only repeats in slightly different language the requirements of feature 14 of claim 1.

The judge held at [178] of his judgment that features 12 and 14 of claim 1 meant that the negative lens was “positioned at the end of the inverting system but still as part of it, some way to the objective side of the second intermediate image”.

The judge originally contemplated that claim 3 was wider, allowing positioning of the lens 2 right up to the second intermediate image. However that conclusion ignored the fact that claim 3 was expressly dependent on claim 1, so could not be wider than that claim. The judge recognised that fact at a hearing after judgment, but did not consider that it had any material impact on his judgment or order.

Mr Hicks first submitted that claim 1 was broad enough to encompass the positioning of lens 2 even on the eyepiece side of the intermediate image. He further submitted that claim 3 then introduced for the first time a requirement that it should be on the objective side of that image. Finally he submitted that the judge was wrong to say that either claim required the lens to be “some way to the objective side of the second intermediate image”. The lens could be positioned close up against the second intermediate image.

In my judgment, claim 1 does not extend to positioning lens 2 on the eyepiece side of the second intermediate image. The lens is required to be integrated in the inverting system. The inverting system does not extend beyond the second intermediate image in the direction of the eyepiece. Moreover it is clear from the description that lens 2 plays a rôle in the formation of the second intermediate image. It can only do so if it is positioned ahead of the second intermediate image. Mr Hicks did not explain to us how it could perform this function if it were disposed on the eyepiece side.

This approach to the interpretation of claim 1 means that claim 3 does not add anything to claim 1. Mr Hicks deploys claim 3 to argue that claim 1 must be wider: he says that the patentee would scarcely have taken the trouble to include claim 3 if those restrictions were already present in claim 1. This is a common canon of construction of patent claims, but it must be remembered that it is not an inflexible rule of law. It is entirely possible for a draftsman to include claims of identical scope, as he unquestionably appears to have done in the present case by including claim 8. Rigid application of the canon of construction can lead to absurd results. It would do so here.

I do not think that one can spell out of claim 1 an express requirement that lens 2 be placed “some way” to the objective side of the second intermediate image, so as to exclude as a matter of language the positioning of the lens at or very close to the second intermediate image. Such a requirement would be uncertain in scope, and has no basis in the actual language of the claim. In my judgment these features of the claim simply require that the negative lens be placed on the end of the inverting system facing the eyepiece and before the second intermediate image.

The conclusion that the negative lens is not expressly required to be placed at any particular distance from the second intermediate image does not, however, mean that a prior art device with a negative lens placed at or very close to the second intermediate image necessarily falls within claims 1 and 3. The claims contain additional limitations as to the result to be achieved. Thus the optical elements specified by the claim (including lens 2) must be disposed “so that a subjective field of view … of at least 22^ºis guaranteed for all magnifications at which the [first intermediate image] is projected onto the eyepiece-end image plane.”

As the judge pointed out at [175], the patent does not need to explain precisely how far lens 2 is from the second intermediate image. Equipped with the set of parameters given in the patent, the skilled person would be able to calculate the necessary measurements using standard computer-aided design. Thus, viewed as a whole, the claim requires that lens 2 be positioned within the inverting system and before the second intermediate image in such a way as to achieve the functional requirements of the claim.

The judge described this as the key issue in the case. Leica’s case as advanced before the judge and on appeal was attractively simple. Faced with a requirement to produce a telescope with a high zoom factor which maintains its field of view at all magnifications, the skilled person would immediately face the problem of field curvature. It was common general knowledge that one of the ways in which one could counteract field curvature was by the inclusion of a negative lens. The negative lens could, for this specific purpose, be incorporated after (referred to in evidence as “position A”), at (“position B”) or well before (“position C”) the second intermediate image. Each of these positions had something to be said both for and against it. Assuming that position C was that required by the claims, and adopting the judge’s conclusions that the skilled person would be able to obtain the required performance by computer-aided calculation, the skilled person would arrive at a design within the claim without invention. Alternatively the skilled person might place the lens at position B. It was common general knowledge (and common ground) that a wide subjective field of view (at all magnifications and high zoom factors) was desirable.

The judge’s principal answer to this argument is contained at [206] in his judgment:

“Was it common general knowledge to achieve the desired improved zoom factor (over 4) and subjective field of view (over 22 degrees at all magnifications) to integrate a strong negative lens between -20 and -40 dioptres in the inverting system. Nobody had done this before, and I am satisfied that it was not obvious to the skilled person to do so. I accept Dr Blandford’s evidence that he would not have thought of doing it. It would only be obvious if the matter were viewed as Professor Rogers viewed it. In my judgment, as Swarovski submitted, his approach was to ask the wrong question. The question is not whether one might use a negative lens in that position to solve the problem of field curvature. I accept Dr Blandford’s evidence that field curvature would not have been regarded as such a problem by the skilled person. It was well known that the human eye had considerable accommodation of at least 2 dioptres, and Professor Rogers’s idea that the skilled person would have been looking to create a riflescope with field curvature of only 0.5 dioptres is wholly unsupported. In my judgment, it is simply wrong. Optical designers would have accepted an element of discomfort caused by field curvature – knowing that the human eye would be able to re-focus given a short amount of time and accommodate the differences between the sagittal and tangential images.”

The judge regarded that conclusion as confirmed by such secondary evidence as was available. The design of riflescopes had remained the same for many years. Optical designers were a conservative group. He regarded it as probable that high zoom factor riflescopes which maintained a high field of view had not been produced because of the problems of length and width described by the experts.

Mr Hicks attacks the judge’s conclusion principally on the basis that the judge was confusing technical and commercial obviousness. The fact that some designers might be prepared to put up with a degree of field curvature did not mean that it was technically unobvious to decide to do something about it. The skilled person would know that a negative lens in position C would counteract field curvature. Whether he decided to do so was a commercial decision, not a technically inventive one.

So far as technical obviousness was concerned, Mr Hicks drew attention to the judge’s findings that adding a negative lens to a system to reduce field curvature was common general knowledge.

Mr Lykiardopoulos submitted that the judge’s conclusion that it was not obvious to include a strong negative lens in the position specified in the patent so as to achieve a high zoom factor and a wide field of view at all magnifications was justified on the evidence before him. He relied heavily on the fact that the desirable combination of properties delivered by the invention had not been achieved before in a riflescope.

Thus the IOR riflescope relied on by Leica and launched just before the priority date had a zoom factor of 6, and did include a negative lens. On Leica’s case this must have suffered from field curvature. However, the negative lens was positioned after and not before the second intermediate image. In this position it was not capable of delivering all the advantages of the invention, and in particular the waist effect. That was demonstrated by the fact that the field of view fell several degrees below 22^º when the magnification was below 2.7. Moreover, as the judge pointed out at [123] every other high zoom scope that was before the court suffered from the same problem of decay of field of view at low magnifications.

The experts were cross-examined about where they would place the negative lens if field curvature was perceived as a problem. Dr Blandford’s evidence was that he would have placed it in the eyepiece after the second intermediate image as had the designer of the IOR riflescope. To place it at position C was not intuitive because it reduced the room available for zoom motion.

Professor Rogers acknowledged that a negative lens in position C was not used in any of the commercial riflescopes available in 2005. Position C had been used in the 1978 Weaver riflescope, where a weak negative lens had been incorporated a short distance to the left of the second intermediate image. He explained that these riflescopes did not have the same stringent requirements of high zoom and high field of view across the full zoom range.

The judge concluded that “by far the most common position for a negative lens surface in commercial riflescopes by July 2005 was in the eyepiece on the eyepiece side of the second intermediate image”.

Whilst the judge did not put it in quite these terms, I am entirely satisfied that a fair summary of Dr Blandford’s evidence was that he was not convinced that dealing with field curvature had the importance which Professor Rogers attached to it. If, however, the skilled person was motivated to do something about it, he or she would favour positions A or B above C. Position C had never been used before and was counter-intuitive, whereas A and B were tried and tested. Although he accepted that, when presented with a proposition for such a design, a skilled person would appreciate that it would still have an effect on field curvature, that did not make it an obvious choice. I would conclude that position C was not an obvious place for the skilled person to place a negative lens to reduce field curvature.

Professor Rogers’ evidence provided support for the inventiveness of placing the negative lens at a position (such as position C) where it can take advantage of the waist effect shown in the patent. He recognised that placing the lens there solved two problems at the same time, which was not the case if the lens was placed at positions A or B. The first problem was reducing the field curvature and thus increasing the usable field of view. The second problem was to try and get an enhanced subjective field of view at low magnifications down a tube of fixed dimensions. This latter problem was not solved if the lens was placed at positions A or B.

Professor Rogers also recognised that the waist effect provided a concrete benefit which would be recognised by a reader of the patent specification. In stark contrast to that acceptance, he said that on simply being shown an optical design without explanation of its advantages, a designer might notice the presence of a waist effect without understanding what it had been included for.

Leica’s argument proceeded on the basis that the inventive concept of the patent was no more than the placing of the lens anywhere in the region between the zoom relay elements and the second intermediate image. Thus even a decision to place the negative lens at position B would lead to the invention. In my judgment that approach was incorrect. The inventive concept of the patent was to place the negative lens in that region so as to achieve the specified wide field of view across the range of magnifications. It was, therefore, necessary for Leica to prove that the skilled person, proceeding without invention or knowledge of the teaching of the patent, would achieve that performance when he decided to include a negative lens to reduce field curvature at position B. We were not shown any evidence which established that the skilled person would achieve the wide field of view across all magnifications if he started with a negative lens designed to reduce field curvature at position B.

The invention is not rendered obvious by common general knowledge. Despite its attractive simplicity Leica’s case based on correcting for field curvature does not establish what it sets out to prove. The skilled person who was only concerned with field curvature would not be motivated to do anything more than include some correction in the eyepiece. He would be sure that he would be able to achieve any necessary correction for field curvature in that way. That might result, at the most favourable to Leica, in his placing the negative lens just to the objective side of the second intermediate image. At that position it was not established that it would bring the added advantage of the waist effect, allowing the wide field of view across the range of magnifications.

There was no need to explore any other position for the negative lens such as position C. It is only with knowledge of the invention that it becomes attractive to place the negative lens at a position where it can take advantage of the waist effect and achieve a high field of view over the full range of magnifications.

"Elements of optics: pocketbook of technical optics" by Helmutt Naumann described a simple sighting telescope with variable magnification. The telescope provided for two fixed magnification positions, with intermediate positions which required the eyepiece to be re-focused.

Figure 9.3.8 showed a negative lens immediately before the second intermediate image (G2) as follows:-

The judge dealt with the obviousness attack based on Naumann in the following way:

“The simple reason why Naumann does not, in my judgment, render the Patent obvious is that the negative lens in Naumann (albeit that it may be a strong one) is in Professor Rogers’s position B, close to the second intermediate image and forming part of the eyepiece lens system. It is true that the negative lens is on the objective side, but that did not put it in the same category as the positioning of the negative lens taught by the Patent on its proper construction. Naumann’s teaching explains that the negative lens will improve eye relief and field curvature – both of which are anyway common general knowledge of the skilled person.

The difference between the teaching in Naumann and the inventive concept of the Patent is creating a telescope with its central tube containing an inverting system with an integrated negative lens of between -20 and -40 dioptres with a zoom factor greater than 4 and a subjective field of view of at least 22 degrees at all magnifications. Using the Naumann configuration in the design of a telescope would be far from obvious to the skilled person, and would not anyway lead to the invention in the Patent.”

Put even more shortly, the attack based on Naumann leads no further than the attack based on common general knowledge. Naumann would not teach the skilled person that he could solve the problem of maintaining a wide field of view across the full range of magnification. To do so he would have to appreciate that, by moving the negative lens from the position shown in Naumann he could take advantage of the waist effect. This would not have been an obvious step for the skilled person to take.

Betensky’s US Patent 5,500,769 (19^th March 1996) concerns “viewing systems for use with the human eyesuch as monoculars and binoculars”. Figure 1 of Betensky is as follows:-

The summary of the invention includes this passage which makes it clear that Betensky is not at its heart concerned at all with the problem addressed by the patent:

“The present invention takes a completely different approach from the prior art. Specifically, rather than designing binoculars based only on the eye’s aided dynamic field of view, the binoculars of the present invention are designed based on both the eye’s aided dynamic field of view and its aided static field of view. More particularly, in accordance with the invention, it has been determined that the eye’s aided dynamic field of view is not the critical field of view in terms of designing binoculars which can be moved relative to the object ... For binoculars, the user can readily, and prefers to, move the combination of his or her head and the binoculars to follow an object rather than trying to move the binoculars relative to the eyes. This approach is 1) easier since it does not upset the alignment of the binoculars with the eye, 2) does not require reaccommodation of the eye due to uncorrected field curvature, and 3) does not lead to erroneous changes in focus if reaccommodation is not sufficient.”

Leica stress the following passage in Betensky which discusses the eyepiece of the binoculars:

“A further aspect of the invention involves the eyepiece of the binoculars. As the aided static field of view of the binoculars is increased, obtaining a large eye relief becomes difficult. Correcting off-axis aberrations requires the use of negative lens elements which further exacerbates the problem. In accordance with the invention, it has been found that these problems can be addressed by at least partially corrected off-axis aberrations with a negative lens unit placed ahead of the intermediate image. In this way a large eye relief can be readily obtained. ”

Betensky adds that the aspects of the invention relating to the use of a negative lens unit before the intermediate image can be used independently of the other aspects of the invention, that is, it can be used with viewing systems generally.

The negative lens in Betensky “serves to correct off-axis aberrations while still allowing the overall optical system to have a large eye relief, e.g., an eye relief of at least 10 millimetres”.

Leica’s case of obviousness based on this document runs as follows. It is not suggested that the skilled person would take the optical design of Betensky’s binoculars and modify it in such a way as to produce a telescope or riflescope within the claims. Instead it is said that the skilled person would derive from Betensky sufficient general teaching to enable him to design a riflescope within the claims. Thus Leica rely on Betensky’s express encouragement to use the negative lens generally, independently of the other features of the invention. The skilled person would appreciate, say Leica, that the negative lens in Betensky:

Mr Hicks relies on Dr Blandford’s acceptance of these propositions in cross-examination. But Dr Blandford did not travel any further down the road which Leica invited him to take. In particular he did not think that he would take from Betensky an indication that it would be possible to design a viable riflescope using its teaching, given the low quoted figure for eye relief (10 mm). As the judge found, riflescopes require eye relief of some 80 to 90 mm. Dr Blandford also demonstrated that if one scaled the lenses in Betensky so as to achieve that degree of eye relief one did not end up with a lens of negative power as high as that specified in the patent.

Mr Lykiardopoulos also drew our attention to a number of other features of the Betensky disclosure. Thus for variable magnification systems the negative lens in Betensky moves through the intermediate image (of which there is only one in Betensky). This would mean that the reticle could not be placed at the second intermediate image, as it would interfere with the zoom motion. That fact would make the design, in Dr Blandford’s words, inherently unsuitable for a riflescope. The zoom factor in the Betensky binoculars is only 1.7.

The judge rejected Leica’s case of obviousness over Betensky, largely because in his view the negative lens was not integrated into the inverting system.

In my judgment the judge had an ample basis for rejecting the case of obviousness over Betensky. Leica’s case again depends on treating the inventive concept as lying exclusively in the positioning of a negative lens between the zoom relay elements and the second intermediate image, without reference to the other requirements of the claim. Once one has the inventive concept firmly implanted in one’s mind, one can, no doubt, see that similar principles are in play in Betensky’s binoculars. It is quite another matter to conclude that a skilled person reading Bentensky’s disclosure without knowledge of the invention would see how those principles could be applied in the quite different context of a zoom telescope or riflescope.

The judge’s approach displays no error which would justify this court in substituting its own judgment. On the contrary, I would for my part have reached the same conclusion.

Mai’s United States patent No 5 671 088 relates to a sighting scope for a pistol. Figure 1 shows such a pistol sight:

Numeral 34 indicates the second intermediate image. Lens 18 is a negative lens positioned prior to that image. The reticle is positioned at the second intermediate image.

Mai is concerned with the problem of trackout. As Mai explains, the phenomenon of trackout occurs if the optical centres of the erector lenses are not aligned. Trackout constitutes an image shift resulting from misalignment of one lens relative to the other lens.

There was a lengthy disagreement between the experts, extending over several rounds of evidence, as to whether the negative lens disclosed by Mai was a strong negative lens of the kind called for by the patent. The judge appears to have accepted that Mai disclosed a strong negative lens, although the evidential basis for this involved a lengthy analysis, through several rounds of expert reports, of the essentially diagrammatic information in Mai. This involved Professor Rogers making numerous assumptions about what the diagrams in Mai showed in numerical terms. Assumptions had to be made as well about such things as the refractive index of the glass used in the lens. Dr Blandford’s initial view of Mai was that lens 18 “appears to be a weak negative lens element”. His view, maintained in his second report, was that the function of the negative lens was not explained by, or apparent from Mai.

Dr Blandford accepted in cross examination that “within limitations” Mai disclosed all the advantages of “position C” in the patent.

Not surprisingly, the judge considered this an inadequate basis for concluding that the invention was rendered obvious by Mai. Lens 18 in Mai had been subjected to quite unwarranted (I would suggest unrealistic) attention because it was being analysed with the benefit of knowledge of the patent. A far more realistic assessment of the impact of Mai on the skilled person would be that he would not see it as of interest or relevance to the problem addressed by the patent. He would certainly not see that by placing the negative lens in a riflescope between the zoom relay elements and the second intermediate image he could achieve a wide field of view at all magnifications.

There is no cogent explanation in Mai of the purpose of placing the negative lens in the position shown. There was a basis in the evidence for suggesting that it might, for example, have been adopted by Mai in order to provide the level of eye relief which would be necessary for a pistol sight. Unlike a riflescope which is held relatively close to the eye, a pistol is held at arms’ length, and the image must be focused a long way from the eyepiece. Mr Lykiardopoulos relies in this connection on Dr Blandford’s evidence that although one can often recognise the presence of an optical feature, for example the waist effect, one does not always immediately understand the motivation of the designer in incorporating it.

I do not think the judge’s rejection of the obviousness case based on Mai can be faulted. The judge was entitled to hold that, without the benefit of hindsight, Mai would not lead the skilled person to the invention.

The IOR 2-12x32 riflescope is shown in the following drawing

The negative lens is marked with the numeral 124. It is cemented to a flat glass plate 122. It has a power within the range specified in the patent. When the object viewed is at infinity, the second intermediate image is coincident with the interface between the lens 124 and the flat glass plate 122, i.e. just to the left of the negative lens. The negative lens is thus normally in position B. As the distance to the object decreases, the second intermediate image moves towards the eyepiece. Depending on the magnification and the distance to the object, the second intermediate image can be wholly outside the negative lens in the direction of the eyepiece. This will occur at a distance of 96.5 metres or less at 12 times magnification; at a distance of 24 metres or less at 6 times magnification; and at a distance of 2.85 metres or less at 2 times magnification. The apparent field of view is at least 22^º at all magnifications in the range 2.7 to 12 representing a zoom factor in excess of 4. However, at magnifications below 2.7, the apparent field of view falls below 22^º: ultimately to 18.4^o at a magnification of 2 times. Overall the IOR riflescope had a magnification range of 2 to 12 times, i.e. a zoom factor of 6.

The riflescope had a parallax adjustment knob which allows the second intermediate image plane to be brought back into the plane of the reticle, meaning that the negative lens was on the eyepiece side of the second intermediate image.

Leica contend that in certain configurations and in certain conditions of use the IOR riflescope will project an image at the second intermediate image plane in such a way that the riflescope would fall within the claims. Leica accept that these are not conditions that most users of the riflescope would adopt, but contend that they are within the range of adjustments of the riflescope. Thus, if the IOR was used to view a nearby object and its parallax adjustment not used, the second intermediate image would be on the eyepiece side of the negative lens and be covered by claims 1 and 3.

Swarovski’s principal answer to this case is that integer 16 of claim 1 requires that a subjective field of view of at least 22^º is guaranteed for all magnifications at which the second intermediate image is projected into the eyepiece-end image plane. The claim does not require this to happen only over a range of magnifications sufficiently large to provide the zoom factor of 4. Thus the fact that it is common ground that the IOR scope has a subjective field of view below 22^º at a magnification of 2-2.5 times means that the IOR device did not fall within the scope of claim 1. There was accordingly no lack of novelty of any claim.

The judge dealt with the construction of integer 16 of claim 1 at [179] to [180] of his judgment. He said that the feature meant that a subjective field of view above the 22^º threshold was maintained “whatever the magnification at which the device is being used”. He said this gave effect to the teaching of the specification, particularly as it was well known that subjective field of view declines at low magnifications.

Mr Hicks argued that this construction was incorrect. A device in which a field of view of 22^º is maintained over a range of magnifications representing a zoom factor of 4 is all that was required. Provided that was done, one could not avoid infringement (or defeat a novelty attack) by pointing to the fact that there were other magnifications at which the field of view was less extensive.

I have no doubt that the judge was right about the construction of this feature. His construction accords with the teaching of the specification and the way in which the skilled person would understand the patentee to be using the language of the claim. That is a sufficient answer to the lack of novelty attack.

It is not therefore necessary for us to decide whether it is legitimate, when considering novelty in circumstances such as these, to postulate a set of unusual conditions to which a prior art device may be adjusted. I would venture to suggest that the principle that the prior art must provide either a clear disclosure of, or clear and unmistakeable directions to do or make something falling within the claims makes it, to say the least, questionable whether such an approach is permissible.

I am not persuaded that the judge fell into error in any of the ways contended for by Leica. For my part, therefore, I would dismiss this appeal.

I agree.

I also agree.