Abstract: Method and apparatus (16) for projecting infrared or near infrared or low intensity visible light from a pen, pointer or other guiding object in the form of a coded pattern image, detectable by a camera and recognition system but invisible, or hardly visible to the user and audience, thus controlling and interacting with a computer (19) during a presentation, computer supported work and/or other interactive use of a computer, including pointing, selecting, drawing and writing, both distantly (11) and closely (10) to the front or rear projection screen or possible other type of display screen, without any distracting visual patterns or spots, while the possible visual feedback to the user and audience can be generated by the computer and display system onto the display screen in a controlled and context-sensitive way.

Abstract: Apparatus for detecting proximity between a first object (target object) and a second object (reference object), comprising a light source and a light detector adapted to receive resulting back-scattered light from the reference object when illuminated from the light source, whereby the intensity of back-scattered light to the light detector is utilized as a measure of said proximity. The target object comprises an optical device having a focal plane and being adapted to be illuminated by the light source. The axes of the light rays from the light source and the back-scattering to the light detector have mutually closely adjacent and substantially parallel or coincident portions. Said proximity corresponds to a distance (relative position) between the target object and the reference object wherein the reference object is located substantially at the focal plane.

Abstract: Apparatus for detecting proximity between a first object (target object) and a second object (reference object), comprising a light source and a light detector adapted to receive resulting back-scattered light from the reference object when illuminated from the light source, whereby the intensity of back-scattered light to the light detector is utilized as a measure of said proximity. The target object comprises an optical device having a focal plane and being adapted to be illuminated by the light source. The axes of the light rays from the light source and the back-scattering to the light detector have mutually closely adjacent and substantially parallel or coincident portions. Said proximity corresponds to a distance (relative position) between the target object and the reference object wherein the reference object is located substantially at the focal plane.