Optical element with variable transmission and screen comprising such an optical element

An optical element, comprising:

• an essentially planar substrate comprising a first large surface adapted to function as a light entrance surface, and a second large surface adapted to function as a light exit surface,
• a multiplicity of chambers embedded in the substrate, which, depending on their sizes, either each forming a separate louver or gathered in groups with each group forming a louver, each louver having longitudinal sides and narrow sides that extend between the first large surface and the second large surface, wherein the narrow sides of each louver are arranged within the area of the large surfaces and the longitudinal sides connect these, and wherein spaces between the louvers contain at least one opaque material,
• a liquid or a skeleton matrix with which the chambers, are filled, wherein the liquid or the skeleton matrix contains up to 50 volume percent of electrophoretically or magnetophoretically movable further particles which reflect and/or scatter light of one or several wavelengths or wavelength ranges in the region visible to a human eye,
• and electromagnetic switching structure configured in planar fashion in the substrate on the narrow sides of the louvers, wherein the switching structure in a switched-on state generates an electromagnetic field effective in the louvers, whereby the further particles are moved in the liquid or in the skeleton matrix, thus causing a change of an angle-dependent transmission, by the optical element, of light of the wavelengths or wavelength ranges that enters the substrate through the light entrance surface at angles at which it hits the louvers, and is reflected and/or scattered by the further particles.

An optical element, comprising:

• a planar substrate having a first large surface adapted to function as a light entrance surface and a second large surface adapted to function as a light exit surface,
• a liquid or a skeleton matrix that is arranged between the first and the second large surface and contains up to 60 volume percent of electrophoretically or magnetophoretically movable particles, wherein there is a multiplicity of particles that absorb or scatter light of one or several wavelengths or wavelength ranges,
• electromagnetic switching structure that is configured in planar fashion on one or both large surfaces and/or in the substrate between the large surfaces, and, in a switched-on state, generates an electromagnetic field effective between the large surfaces, whereby the particles are moved in the liquid or in the skeleton matrix,
• so that the transmission by the optical element of light of the wavelengths or wavelength ranges absorbed by the particles changes, wherein, in a first operating state B1, the transmission amounts to more than 50%, and, in a second operating state B2, to less than 50%, referred to the direction of the normal to the second large surface of the substrate.

An optical element, comprising:

• a planar substrate with a first large surface adapted to function as a light entrance surface and a second large surface adapted to function as a light exit surface,
• a multiplicity of chambers embedded in the substrate, each with one or several surfaces,
• a liquid with which the chambers are filled, wherein the liquid contains up to 20 volume percent of electrophoretically or magnetophoretically movable particles, which absorb or scatter light of one or several wavelengths or wavelength ranges,
• electromagnetic switching structure that is configured in planar fashion on one or both surfaces of the chambers, and, in a switched-on state, generate an electromagnetic field effective inside the chambers, whereby the particles are moved in the liquid, so that the transmission, by the optical element, of light of the wavelengths or wavelength ranges absorbed by the particles changes, wherein, in a first operating state B1, the transmission amounts to more than 50%, and, in a second operating state B2, to less than 50%, with respect to a direction of a normal to the second large surface of the substrate.