http://www.techradar.com/news/apple-patent-points-to-pencil-that-writes-on-any-surface-including-air
origin - https://www.pipiscrew.com/2018/02/apple-patent-points-to-a-pencil-that-writes-on-any-surface-including-air/ apple-patent-points-to-a-pencil-that-writes-on-any-surface-including-air