This decision concerns an invention that relates to foldable display devices and compensating for distortion. The Board agreed with the applicant that mathematically determining compensation based on distortion experienced by a view at an assumed viewing angle is technical, since it solves the problem of using the entirety of the flexible screen for a display and improves the readability in the deformation zone. Here are the practical takeaways from the decision T 1678/19 of July 26, 2022, of the Technical Board of Appeal 3.4.03.
In a foldable display, the displayed content in a distorted region of the screen (when the screen is in part folded state) has to be adapted to compensate for the impairments or distortions of the content displayed in the folded region.
The invention aims to improve the compensation of the distortion. This is solved by determining the kinds and degrees of distortion that may be experienced by a viewer – i.e. assuming that the display device is viewed from a particular / typical viewing angle – and mathematically determining the compensation.
Apparatus claim 1 of the Sole Request (labelling (A), (B), ... introduced by the Board)
(A) A display system (10), comprising:
(B) a foldable display unit (11) to display visual information, the visual information based at least in part on display data; and
(C) a display control unit (14) configured for receiving the display data and at least one fold signal indicative of a fold in at least a portion of the display unit,
(D) and outputting one or more display control signals (20) operative to cause the display unit to display the visual information,
(E) the display control signals being output at least in part in response to the at least one fold signal to adapt the one or more display control signals to change a format of the visual information,
(F) wherein the fold in the display unit creates a deformation area (17) along a fold axis of the display unit,
(G) and wherein the format change compensates for impairment of the visual information in the deformation area by displaying the visual information in compensated format in the deformation area, the compensation being mathematically determined based on distortion experienced by a viewer at an assumed viewing angle.
Is it patentable?
In the first instance, the Examining Division alleged that the subject-matter of the claims (Auxiliary Request in the first instance) lacked inventive step starting from document D2 (UP 2006 243621 A).
The Board summarized the cited document and identified the three distinguishing features, and the technical effect of these features:
3.2 Disclosure of D2
3.2.1 D2 discloses a foldable screen. The screen is an electronic paper within a plastic frame which contains several parts (Fig. 12, reference signs 904, 905). The frame together with the electronic paper screen can be folded like a paper sheet as is shown in Fig. 12. Sensors, such as Hall sensors 918, 920 and magnets 917, 919 detect which parts of the screen are folded out. A control circuit receives the sensor signals and adapts the displayed content, which can be text or an image.
3.2.2 D2 discloses in Fig. 12 that displayed content is adapted in the fold region in the area between sub-screen 912 and 913. The sub-region with the reference sign 908 in Fig. 12 is kept free of text, because in this constellation the electronic paper is too much deformed such that it is not suitable for displaying text. The same is shown in Fig. 17 for regions 907 and 908 (see paragraph ).
The Board then identified the distinguishing features and the technical effect and problem solved and feature:
3.3.1 D2 therefore discloses Features (A) to (F). D2 discloses (paragraphs -) that the format change compensates for impairment of the visual information in the deformation area by displaying the visual information in compensated format in the formation area by means of
(a) adapted text spacing / positioning,
(b) adapted text font size or
(c) scaling an image.
D2 does not disclose that the compensation is mathematically determined based on distortion experienced by a viewer at an assumed viewing angle.
The effect of this difference is that the entirety of the flexible screen is used even after deformation and that the readability in the deformation zone is improved.
The objective technical problem can therefore be formulated as to use the entirety of the flexible screen for display and to improve the readability in the deformation zone.
The Board then decided that the subject-matter was not obvious:
3.6.1 The Examining Division referred to document D4, arguing that compensation based on the assumed position of the observer is disclosed in paragraphs  to  of D4. D4 taught in this passage to adapt the projected content to the curved surface of the screen.
3.6.2 The Appellant argued that the skilled person would not have turned to document D4 from a consideration of the objective technical problem. D4 clearly related to a fixed surface with no flexibility, and contained no teaching in relation to identification of a fold region, let alone any compensation for impairment of visual information in a deformation area caused by folding. The skilled person would therefore not have turned to D4 based on the objective technical problem.
As the geometry of the display was already known in D4, the key point was purely understanding the field of view. This was equated to the observer but in a way that was different from the claim feature according which the compensation was mathematically determined based on distortion experienced by a view at an assumed viewing angle. In D4 the field of view was presented as a rigid mathematical element irrespective of any assumed viewing angle.
3.6.3 The Board agrees with the Appellant that even if the skilled person had turned to document D4 and by combining the teachings of D2 and D4, it would not have arrived at the combination of Features (A) to (G). D2 teaches only the adaptation to the viewer by scaling the image/text or by introducing blank spaces. D2 discloses inclination sensors to detect which part of the electronic book is opened, but not in order to determine a viewing angle. Nothing in D2 and D4 teaches for a foldable screen to first determine a viewing angle of the reader and then to adapt the distortion of the image / text according to the viewing angle.
Therefore, the Board agreed that the subject-matter of claims involves an inventive step, and the application was granted.
You can read the full decision here: T 1678/19 of July 26, 2022, of the Technical Board of Appeal 3.4.03