Method and device for intensity-dependent light modulation

An intensity-dependent attenuation device for light, having a polarizer (P1, STI, ST2), which allows linearly polarized light to propagate through in one input polarization direction (EPR1, EPR2), and having an analyzer (P2, ST1, ST2, ST3) which is crossed relatively thereto by a substantial number of degrees or by 90 degrees,

• characterized by a first λ/2 phase-retardation plate (1), a second optically addressable, spatially resolving light modulator (4) designed as a λ/4 phase-retardation plate, and a mirror (5), incident light (10a, 10b) propagating, in turn, through the polarizer (P1, ST1, ST2, ST3), the first λ/2 phase-retardation plate (1), and the second light modulator (4), and, from there, impinging on the mirror (5), and, subsequently, in the reverse direction, again propagating through the second light modulator (4) and the first λ/2 phase-retardation plate (1) and, from there, impinging on the analyzer (P2, ST1, ST2, ST3),
• a) the first λ/2 phase-retardation plate (1) having a first indicatrix which
• without an external electric field, runs in a first rest-position direction (R1);
• in response to the application of a first external electric field (+E1), runs in a first deflection direction (A), which is rotated with respect to the first rest-position direction (R1) by a first angle (+α) that is independent of the light intensity, about the direction of the first external electric field (+E1);
• and
• in response to the application of a second external electric field (−E1), equal and opposite to the first external electric field (+E1), runs in a second deflection direction (B), which is rotated with respect to the first rest-position direction (R1) by a second angle (−α), which is equal and opposite to the first angle (+α);
• b) the second light modulator (4) having a fourth indicatrix, which
• without an external electric field, runs in a second rest-position direction (R2);
• in response to the application of a seventh external electric field (+E4), runs in a third deflection direction (C), which is rotated with respect to the second rest-position direction (R2) by a third angle (+β), about the direction of the seventh external electric field (+E4);
• in response to the application of an eighth external electric field (−E4), equal and opposite to the seventh external electric field (+E4), runs in a fourth deflection direction (D), which is rotated with respect to the second rest-position direction (R2) by a fourth angle (−β), equal and opposite to the third angle (+β);
• the magnitude of the third and of the fourth angle (+β, −β) increasing in response to increasing light intensity, up to a specific maximum value (βmax), not however beyond this, and the third and fourth deflection directions (C, D) reaching a first and second limiting deflection direction (Cmax, Dmax), respectively, in the case that the magnitude of the third or fourth angle (+β, −β) reaches the maximum value (βmax );
• c) the first and the second phase-retardation plates (1, 2) and the first light modulator (3) being so oriented to one another and with respect to the polarizer (P11, ST1, ST2, ST3) that
• the first deflection direction (A) and the first limiting deflection direction (Cmax) run in parallel to one another and in parallel or perpendicularly to the input polarization direction (EPR1, EPR2), or
• the second deflection direction (B) and the second limiting deflection direction (Dmax) run in parallel to one another and in parallel or perpendicularly to the input polarization direction (EPR1, EPR2);
• d) the first or second external electric field (+E1, −E1) being applied to the first phase-retardation plate (1), and the seventh or eighth external electric field (+E4, −E4) being applied to the second light modulator (4);
• and
• e) the first and second, and the seventh and eighth external electric fields (+E1, −E1, +E4, −E4), respectively, being selected in such a way that the first angle (a) and the maximum value (βmax ) fulfill the condition 2α−βmax=n·45°+T, n being equal to 0,1,2,3, . . . and T being a tolerance of ±5°.

A method for attenuating light as a function of intensity, which passes through a polarizer (P1), which allows linearly polarized light to propagate through in one input polarization direction (EPR1, EPR2) and strike an analyzer (P2) that is crossed thereto by a substantial number of degrees or by 90 degrees,

• wherein the light propagates, in turn, through the polarizer (P1), a first λ/2 phase-retardation plate (1),
• a first optically addressable, spatially resolving light modulator (3) designed as λ/2 phase-retardation plate, and a second λ/2 phase-retardation plate (3), and, from there, impinging on the analyzer (P2),
• a) the first λ/2 phase-retardation plate (1) having a first indicatrix which
• runs without an external electric field in a first rest-position direction (R1);
• in response to the application of a first external electric field (+E1), runs in a first deflection direction (A), which is rotated with respect to the first rest-position direction (R1) by a first angle (+α) that is independent of the light intensity, about the direction of the first external electric field (+E1);
• and
• in response to the application of a second external electric field (−E1), equal and opposite to the first external electric field (+E1), runs in a second deflection direction (B), which is rotated with respect to the first rest-position direction (R1) by a second angle (−α), equal and opposite to the first angle (+α);
• b) the first light modulator (2) having a second indicatrix which, without an external electric field, runs in a second rest-position direction (R2);
• in response to the application of a third external electric field (+E2), runs in a third deflection direction (C), which is rotated with respect to the second rest-position direction (R2) by a third angle (+β), about the direction of the third external electric field (+E2);
• in response to the application of a fourth external electric field (−E2), equal and opposite to the third external electric field (+E2), runs in a fourth deflection direction (D), which is rotated with respect to the second rest-position direction (R2) by a fourth angle (−β), equal and opposite to the third angle (+β);
• the magnitude of the third and of the fourth angle (+β, −β) increasing in response to increasing light intensity, up to a specific maximum value (βmax ), not however beyond this, and the third and fourth deflection directions (C, D) reaching a first and second limiting deflection direction (Cmax, Dmax), respectively, in the case that the magnitude of the third or fourth angle (+β, −β) reaches the maximum value (βmax );
• c) the second λ/2 phase-retardation plate (3) having a third indicatrix which, without an external electric field, runs in the first rest-position direction (R1);
• in response to the application of a fifth external electric field (+E3), runs in the first deflection direction (A);
• and
• in response to the application of an external sixth electric field (−E3), equal and opposite to the fifth external electric field (+E3), runs in the second deflection direction (B);
• d) the first and the second phase-retardation plates (1, 3) and the first light modulator (2) being so oriented to one another and with respect to the polarizer (P1) that
• the first deflection direction (A) and the first 1 imiting deflection direction (Cmax) run in parallel to one another and in parallel or perpendicularly to the input polarization direction (EPR1, EPR2), or
• the second deflection direction (B) and the second limiting deflection direction (Dmax) run in parallel to one another and in parallel or perpendicularly to the input polarization direction (EPR1, EPR2);
• e) the first or second external electric field (+E1, −E1) being applied to the first phase-retardation plate (1), the third or fourth external electric field (+E2 −E2) being applied to the first light modulator (2), and the fifth or sixth external electric field (+E3, −E3) being applied to the second phase-retardation plate (3);
• and f) the first and second, the third and fourth, and the fifth and sixth external electric fields (+E1, −E1, +E2, −E2, +E3, −E3), respectively, being selected in such a way that the first angle (a) and the maximum value (βmax fulfill the condition 2α−βmax=n·45°+T, n being equal to 0,1,2,3, . . . and T being a tolerance of ±5°.

A method for attenuating light as a function of intensity, which passes through a polarizer (P1), which allows linearly polarized light to propagate through in one input polarization direction (EPR1, EPR2) and strike an analyzer (P2, ST1, ST2, ST3) that is crossed thereto by a substantial number of degrees or by 90 degrees, characterized by a first λ/2 phase-retardation plate (1), a second optically addressable, spatially resolving light modulator (4) designed as λ/4 phase-retardation plate, and a mirror (5), incident light (10a, 10b) propagating, in turn, through the polarizer (P1, ST1, ST2, ST3), the first λ/2 phase-retardation plate (1), and the second light modulator (4), and, from there, impinging on the mirror (5), and, subsequently, in the reverse direction, again propagating through the second light modulator (4) and the first λ/2 phase-retardation plate (1) and, from there, impinging on the analyzer (P2, ST1, ST2, ST3),

• a) the first λ/2 phase-retardation plate (1) having a first indicatrix which
• without an external electric field, runs in a first rest-position direction (R1);
• in response to the application of a first external electric field (+E1), runs in a first deflection direction (A), which is rotated with respect to the first rest-position direction (R1) by a first angle (+α) that is independent of the light intensity, about the direction of the first external electric field (+E1);
• and
• in response to the application of a second external electric field (−E1), equal and opposite to the first external electric field (+E1), runs in a second deflection direction (B), which is rotated with respect to the first rest-position direction (R1) by a second angle (−α), equal and opposite to the first angle (+α);
• b) the second light modulator (4) having a fourth indicatrix, which
• without an external electric field, runs in a second rest-position direction (R2);
• in response to the application of a seventh external electric field (+E4), runs in a third deflection direction (C), which is rotated with respect to the second rest-position direction (R2) by a third angle (+β), about the direction of the seventh external electric field (+E4);
• in response to the application of an eighth external electric field (−E4), equal and opposite to the seventh external electric field (+E4), runs in a fourth deflection direction (D), which is rotated with respect to the second rest-position direction (R2) by a fourth angle (−β), equal and opposite to the third angle (+β);
• the magnitude of the third and of the fourth angle (+β, −β) increasing in response to increasing light intensity, up to a specific maximum value (βmax), not however beyond this, and the third and fourth deflection directions (C, D) reaching a first and second limiting deflection direction (Cmax, Dmax), respectively, in the case that the magnitude of the third or fourth angle (+β, −β) reaches the maximum value (βmax );
• c) the first and the second phase-retardation plates (1, 2) and the first light modulator (3) being so oriented to one another and with respect to the polarizer (P11, ST1, ST2, ST3) that
• the first deflection direction (A) and the first limiting deflection direction (Cmax) run in parallel to one another and in parallel or perpendicularly to the input polarization direction (EPR1, EPR2), or
• the second deflection direction (B) and the second limiting deflection direction (Dmax) run in parallel to one another and in parallel or perpendicularly to the input polarization direction (EPR1, EPR2);
• d) the first or the second external electric field (+E1, −E1) being applied to the first phase-retardation plate (1), and the seventh or eighth external electric field (+E4, −E4) being applied to the second light modulator (4);
• and
• e) the first and the second, and the seventh and the eighth external electric fields (+E1, −E1, +E4, −E4), respectively, being selected in such a way that the first angle (a) and the maximum value (βmax) fulfill the condition 2α−βmax=n·45°+T, n being equal to 0,1,2,3, . . . and T being a tolerance of ±5°.