Abstract: The invention relates to an optical device (FILT) for filtering light received, by polarisation or mechanically, from a medium presenting a graphic and/or textual content, characterized in that cycles of opening and closing a vision space, in a visible light spectrum, are realized periodically using the optical device (FILT) at a preset frequency Fd and in that the successive open periods each have a duration (T1) comprised in an interval of values ranging from 15 to 35% of the duration (T) of the realized cycles.

Abstract: A method for displaying graphical content in a playback device (DISP), the graphical content being displayed and erased periodically on the display device according to successive cycles that take place at a predetermined frequency (Fd) and in that the successive display periods each have a duration (T1) comprised in an interval of values ranging from 15 to 30% of the duration (T) of the cycles that have taken place.

Abstract: The invention relates to a device (LIGHT) for lighting a graphic and/or textual content present on any medium and in particular on a paper medium. The lighting device (LIGHT) is configured to periodically activate and deactivate said lighting beam in successive cycles carried out at a preset frequency Fd. Each cycle has a duration T and comprises a period of activation of the light beam of duration T1 followed by a period of deactivation of the light beam of duration T2 or vice versa. The frequency Fd is comprised in an interval of values ranging from 60 to 90 Hz and the duration T1 of the periods of activation of the light beam is comprised in an interval of values ranging from 15 to 30% of the duration T of the cycles.

Abstract: A method for displaying graphical content in a playback device, the graphical content being displayed and erased periodically on the display device according to successive cycles that take place at a predetermined frequency (Fd) and in that the successive display periods each have a duration (T1) comprised in an interval of values ranging from 15 to 30% of the duration (T) of the cycles that have taken place.

Abstract: The invention relates to a device (LIGHT) for lighting a graphic and/or textual content present on any medium and in particular on a paper medium. The lighting device (LIGHT) is configured to periodically activate and deactivate said lighting beam in successive cycles carried out at a preset frequency Fd. Each cycle has a duration T and comprises a period of activation of the light beam of duration T1 followed by a period of deactivation of the light beam of duration T2 or vice versa. The frequency Fd is comprised in an interval of values ranging from 60 to 90 Hz and the duration T1 of the periods of activation of the light beam is comprised in an interval of values ranging from 15 to 30% of the duration T of the cycles.

Abstract: The invention relates to an optical device (FILT) for filtering light received, by polarisation or mechanically, from a medium presenting a graphic and/or textual content, characterized in that cycles of opening and closing a vision space, in a visible light spectrum, are realized periodically using the optical device (FILT) at a preset frequency Fd and in that the successive open periods each have a duration (T1) comprised in an interval of values ranging from 15 to 35% of the duration (T) of the realized cycles.

Abstract: The invention relates to a lighting device (LIGHT) of a graphic and/or textual content represented on any support and in particular of the paper type, characterized in that a light beam generated in a visible light spectrum is activated and periodically deactivated from the lighting device (LIGHT) according to successive cycles operated at a predetermined frequency (Fd) and in that the successive illumination periods each have a duration (T1) within a range of values from 15 to 30% of the duration (T) of the operated cycles.

Abstract: The invention relates to a lighting device (LIGHT) of a graphic and/or textual content represented on any support and in particular of the paper type, characterized in that a light beam generated in a visible light spectrum is activated and periodically deactivated from the lighting device (LIGHT) according to successive cycles operated at a predetermined frequency (Fd) and in that the successive illumination periods each have a duration (T1) within a range of values from 15 to 30% of the duration (T) of the operated cycles.

Abstract: A laser for use in all fields of measurement using a heterodyne effect delivers two waves at different frequencies, having mutually orthogonal linear polarizations. It comprises a lasing medium placed in a laser resonating cavity defined by mirrors and a birefringent crystal placed on the path of the two waves. The lasing medium is located in the resonating cavity in a zone where the two waves are separated spatially. Two quarter wave plates, one of which has neutral lines at substantially 45.degree. from the polarization axes of the birefringent means, are placed in the common path of the two waves so as to give a helical polarization to the two waves between the plates.

Abstract: Selective optical resonator comprising at least two mirrors and a selective means disposed between two of these mirrors, said means being constituted by:an at least partial linear polarization means for the light in a direction P,a first birefringent plate having two neutral lines, one forming an angle .alpha..sub.1 =0 with direction P,an optically active substance having a birefringence with dispersion and which rotates the light polarization direction by an angle .theta. dependent on the wavelength of the .lambda. light,a second plate which is identical to the first having two neutral lines, one forming the angle .alpha..sub.2 =.theta. with the direction P, whereby the resonator is then selective for said wavelength .lambda..

Abstract: In a method for stabilizing the frequency of the stimulated radiation emitted by a laser, the radiation is subjected to a first rotation of its direction of polarization by applying a magnetic field to a material which exhibits the phenomenon of magnetic rotatory polarization and is placed in a two-mirror resonator. Anisotropic losses are introduced in the resonator so as to produce a second rotation of the direction of polarization, part of the radiation contained in the resonator is extracted and its direction of polarization D is measured. The direction D is held in a reference direction D.sub.O by measuring the difference between the two directions, by reducing this difference to zero and by modifying the value of the resonant frequency of the resonator.