US 6,208,445 B1Granted

Apparatus for wireless optical transmission of video and/or audio information

AssigneeNokia Corporation

InventorGerd Reime

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Abstract

The invention relates to an apparatus for wireless optical transmission of video and/or audio information, such as television broadcasts or video recordings, with IR radiation radiated into the surrounding free space by an optical transmitter and received by one or more photo receivers. It is the object of the invention to provide means for extending the transmission range of wireless optical transmission systems and for simplifying signal processing, so that television broadcasts or video recordings can be reliably transmitted under ambient light conditions typical in residential buildings while requiring only limited additional circuitry for matching the optical transmission channel and a small number of luminescent diodes. This object is solved in that at least for the upper frequency spectrum of the video and/or audio information, the optical transmission is based on a pulse-shaped source signal, with the information represented by the temporal position of the signal edges between pulses and non-pulse periods. A simple edge detector converts the source signal into a channel pulse signal which includes a short spike-shaped channel pulse synchronous with each signal edge in the source signal. The optical receiver includes a 1:2 frequency divider for restoring from the received channel pulse signal the original shape of the pulse-shaped source signal.

Claims11

Dependent claims

An apparatus for wireless optical transmission of video and/or audio information with a signal source (1,4) which supplies at least one pulse-shaped source signal (Se) denoting the video and/or audio information through the temporal position of rising and falling signal edges (H/L, L/H) between pulses and non-pulse periods, wherein the source signal (Se) is converted by a signal processor (24, 34, 37, 38) which is specific to the type of the signal source (1, 4) into a playback signal (CV, L, R) for a video and/or audio playback unit (2, 3),

with a source signal converter for converting the source signal (Se) into a channel pulse signal (Sk),
with at least one luminescent diode (16) for radiating a signal radiation (Sl) which is at least modulated with the channel pulse signal (Sk), into the surrounding free space,
and with at least one photo receiver (20, 30) comprising means (23, 24, 33, 34, 37, 38) for recovering the video and/or audio information contained in the received signal radiation (Sl), characterized in
that the source signal converter includes an edge detector (14) for generating a channel pulse signal (Sk) provided at each rising and falling signal edge (H/L, L/H) of the source signal (Se) with a channel pulse (Pk) which is several times shorter than the duration of the pulses and the non-pulse periods of the source signal (Se),
and that the means for recovering the video and/or audio information comprises at least a 1:2 frequency divider (23, 33) in a photo receiver (20, 30) and the signal processor (24, 34, 37, 38) specific to the type of the signal source (1,4).

2 more elements

Dependencies are inferred from the claim text.