DE102020008055A1 - Optical element with variable transmission and screen with such an optical element - Google Patents

Abstract

The invention relates to an optical element (1), comprising at least one, preferably more than five, layers (S1, S2, ...), each layer (S1, S2, ...) material with a multiplicity of light-absorbing electrical Includes absorption dipoles which, at least in a first state, are aligned parallel to a selectable preferred direction or fluctuate around it, said preferred direction enclosing an angle between 0° and 45° to the surface normal of layer S1, so that light which penetrates the optical element , depending on its direction of incidence relative to the layers (S1, S2, ...) and its polarization properties, is transmitted or partially or completely absorbed. Optionally, the light-absorbing electrical absorption dipoles in each layer (S1, S2, ...) can be in their orientation and/or their absolute value and/or their density can be varied in order to split the respective layer (S1, S2, ...) into at least two different ones In interaction with at least one polarization filter (P) and/or means for varying the polarization properties of light, such as liquid crystals, the optical element (1) can be further developed in order to, in combination with an image display device, have a switchable to enable a protective effect.

Description

field of invention

In recent years, great advances have been made in widening the viewing angle of LCDs. However, there are often situations in which this very large viewing area of a screen can be a disadvantage. Information is also increasingly available on mobile devices such as notebooks and tablet PCs, such as bank details or other personal details and sensitive data. Accordingly, people need control over who can see this sensitive data; they must be able to choose between a wide viewing angle in order to share information on their display with others, e.g. when looking at holiday photos or for advertising purposes. On the other hand, they need a small viewing angle if they want to keep the image information confidential.

A similar problem arises in vehicle construction: the driver must not be distracted by image content such as digital entertainment programs when the engine is switched on, while the passenger would like to consume the same while driving. A screen is therefore required which can switch between the corresponding display modes.

State of the art

Additional films based on micro-lamellas have already been used for mobile displays in order to achieve visual data protection. However, these foils were not switchable, they always had to be applied by hand and then removed again. You also have to transport them separately to the display when you don't need them. A significant disadvantage of the use of such lamellar foils is also associated with the associated loss of light.

the U.S. 6,765,550 B2 describes such a privacy screen using micro-slats. The biggest disadvantage here is the mechanical removal or mechanical attachment of the filter and the loss of light in protected mode.

In the US 5,993,940A describes the use of a film that has small prism strips evenly arranged on its surface in order to achieve a privacy mode. Development and production are quite complex.

In the WO 2012/033583 A1 switching between free and restricted vision is generated by driving liquid crystals between so-called "chromonic" layers. This results in a loss of light and the effort is quite high.

the US 2012/0235891 A1 describes a very complex backlight in a screen. There come according to 1 and 15 not only several light guides are used, but also other complex optical elements such as microlens elements 40 and prism structures 50, which transform the light from the rear lighting on the way to the front lighting. This is expensive and complex to implement and also associated with light loss. According to the variant after 17 in the US2012/0235891 Both the light sources 4R and 18 produce light with a narrow illumination angle, and the light from the rear light source 18 is first converted into light with a large illumination angle with great effort. This complex conversion is - as already mentioned above - strongly reducing the brightness.

According to the JP 2007-155783 A special optical surfaces 19 that are complex to calculate and produce are used, which then deflect light into different narrow or wide areas depending on the angle of incidence of the light. These structures resemble Fresnel lenses. There are also interference edges that deflect light in undesirable directions. It therefore remains unclear whether sensible light distributions can actually be achieved.

In the U.S. 2013/0308185 A1 describes a special light guide designed with steps, which emits light over a large area in different directions, depending on the direction from which it is illuminated from a narrow side. In interaction with a transmissive image display device, for example an LC display, a screen that can be switched between free and restricted viewing modes can thus be produced. One of the disadvantages here is that the limited visual effect is generated simultaneously either only for left/right or for up/down, but not for left/right/up/down as is necessary for certain payment transactions. In addition, a residual light is still visible even in restricted viewing mode from blocked viewing angles.

the WO 2015/121398 A1 the Applicant describes a screen with two modes of operation in which scattering particles are present in the volume of the corresponding light guide for the switching of the modes of operation. However, the scattering particles selected there from a polymer usually have the disadvantage that light is decoupled from both large areas, which means that about half of the useful light is emitted in the wrong direction, namely towards the backlight, and not to a sufficient extent there due to the structure can be recycled. In addition, the scattering particles made of polymer distributed in the volume of the light guide can, under certain circumstances, particularly at higher concentrations, lead to scattering effects which reduce the visual protection effect in the protected operating mode.

The approach of the technology of "Electrical Birefringence (EDB)" is based on the idea of using the switchable liquid crystals of an additionally applied LC panel to "filter" all light rays that do not emerge from the imaging layer at a specific emission angle. Disadvantages of this technology are high additional energy and cost expenditure and the difficult to change +/-40° sweet spot. The degree of absorption of the LC structures is also insufficient, since the attenuation of the light intensity increases again for viewing angles greater than the sweet spot, so that the light intensity for viewing angles greater than +/-40° is up to 3% of the maximum light intensity.

The aforementioned methods and arrangements usually have the disadvantage in common that they significantly reduce the brightness of the basic screen and/or require a complex and expensive optical element for mode switching and/or reduce the resolution in the freely viewable mode and/or visual artifacts with very high-resolution displays.

Description of the invention

It is therefore the object of the invention to describe an optical element in which light which is incident on the optical element is transmitted or partially or completely absorbed depending on its direction of incidence and its polarization properties, but not depending on its position. Furthermore, the transmission of light should be influenced by the optical element as a function of the angle (optionally perpendicular), it being possible here to switch between at least two operating states. In particular, angular restrictions in the transmission should be switchable in certain directions.

The optical element or systems based on it should be inexpensive to implement and, in particular, universally usable with different types of screens in order to enable switching between a privacy screen - existing at least in the horizontal direction - and a free viewing mode, with the resolution of such a screen essentially not should be reduced.

• - mindestens eine, bevorzugt mehr als fünf, Schichten S1, S2, ..., (eine Schicht S1, S2, ... kann im Rahmen der Erfindung beispielsweise einer Moleküllage entsprechen; es kann sich aber auch um eine mechanisch separate Lage eines geeigneten Materials handeln),
• - wobei jede Schicht S1, S2, ... Material mit einer Vielzahl Licht absorbierender elektrischer Absorptionsdipole umfasst, welche mindestens in einem ersten Zustand parallel zu einer wählbaren Vorzugsrichtung ausgerichtet sind oder um diese herum fluktuieren, wobei die besagte Vorzugsrichtung einen Winkel zwischen 0° und 45° zur Flächennormale der Schicht S1 einschließt,
• - so dass Licht, welches in das optische Element einfällt, in Abhängigkeit von seiner Einfallsrichtung gegenüber den Schichten S1, S2, ... und seinen Polarisationseigenschaften transmittiert oder teilweise oder ganz absorbiert wird.

This object is achieved according to the invention by an optical element comprising

• - At least one, preferably more than five, layers S1, S2, ..., (a layer S1, S2, ... can correspond, for example, to a molecular layer within the scope of the invention; but it can also be a mechanically separate layer of a suitable trade materials),
• - wherein each layer S1, S2, ... comprises material with a plurality of light-absorbing electric absorption dipoles which, in at least a first state, are aligned parallel to or fluctuate around a selectable preferential direction, said preferential direction having an angle between 0° and 45° to the surface normal of layer S1,
• - so that light which is incident on the optical element is transmitted or partially or completely absorbed depending on its direction of incidence with respect to the layers S1, S2, ... and its polarization properties.

The extinction (i.e. the absorption) of the light depends on the absolute number of absorption dipoles (and thus inherently also on the layer thickness of the absorption dipoles) and the mutual alignment between the absorption dipole and the electric field of the incident light. Depending on the implementation, the density of said electric absorption dipoles, their strength or the refractive index in the layers S1, S2, ... can vary. In the case of a passive, ie non-switchable, optical element, the volume density of the absorption dipoles can approach 100%.

For modeling the transmission it is assumed that the absorbing absorption dipoles are oriented parallel to the plane of incidence. The filter only absorbs the polarization that is polarized in the plane of incidence of the light -p-polarized light-. Light that is polarized perpendicular to the plane of incidence -s-polarized light- is completely transmitted. This property is essential in all configurations of the invention and represents an essential inventive means-effect relationship. The transmission of p-polarized light with an incident intensity I ₀ (α) is modeled below. The transmission of light through an absorbing layer is described by the Lambert-Beer law: $$I\left(a\right)=I_0\left(a\right)e^{-\mathrm{i.e}\left(a\right)N{\sigma }_{abs}\left(a\right)}$$

Here α is the direction of propagation relative to the surface normal, d(α) is the optical path length depending on the direction of propagation, N is the number of absorbing molecules and σ _abs (α) is the absorption cross section depending on the angle of incidence. With the help of Snell's law of refraction, the angle of propagation in the medium α can be calculated from the angle of incidence β. This then results from the equation of the dipole and the change in the optical path: $$I\left(a\right)=I_0\left(a\right)e^{-\mathrm{i.e}/N{\sigma }_{abs}\text{sin}{\left(a\right)}^2}$$

Depending on the application, each of the layers (S1, S2, ...) has a periodic or non-periodic structure.

Furthermore, an optical element according to the invention can be produced by lamination of a plurality of polymer film polarizers and/or by photoalignment of molecules or particles, which then each form one or more layers S1, S2, . However, other manufacturing options are within the realms of possibility.

The micro-lamella filters described in the prior art (also called “View Control Filter - VCF” or “Light Control Filter - LCF”) make use of geometric optics. Due to the alternating periodic arrangement of transparent and absorbing layers, (almost) all incident light that propagates at large angles relative to a defined direction is absorbed here. The position of the absorbers is checked there.

In contrast, in the case of the optical elements according to the invention, the transmission of light with different directions of propagation changes, since the absorption cross section of the molecules changes with the direction of propagation. In the case of the invention, therefore, it is not the position that is controlled, but rather the orientation (orientation) of the absorbers.

In other words: the invention is based on a direction-dependent absorption of the light beams when passing through an optical element according to the invention, specifically independently of the position of the light beams.

This applies both to non-switchable optical elements according to the invention, as described above, and to switchable configurations described below.

For switchability of the optical effect of the optical element according to the invention, i.e. for a switchable optical element, the light-absorbing electrical absorption dipoles in each layer (S1, S2, ...) can have their orientation (orientation) and/or their absolute value and/or their density can be varied in order to be able to put the respective layer (S1, S2, ...) into at least two different states.

Possible configurations of a switchable optical element or each layer S1, S2, ... in it are based, for example, on liquid crystals or fluorophores, which are arranged in a so-called "vertical alignment cell" or in a liquid crystal cell with homogeneous alignment on the surfaces and therein between at least two States can be rotated. In this case, the light-absorbing electrical absorption dipoles are also rotated and can thus assume at least two states of action. It is particularly conceivable in such configurations that more than two states, e.g. three or eight states, each with different optical effects, are achieved. Other configurations of the liquid crystal cells are also conceivable.

With such active, i.e. switchable, optical elements, volume densities of the absorption dipoles between 0.1% and 90% based on liquid crystals are conceivable.

Alternatively, configurations of a switchable optical element or of each layer S1, S2, . In this way, in particular, but not solely, the density of the absorption dipoles can be varied.

In general, a polarization filter can advantageously be located in front of or behind the optical element in the viewing direction.

• - zwei nicht-schaltbare erfindungsgemäße optische Elemente, bei denen die Vorzugsrichtungen der Absorptionsdipole sich um weniger als 10° voneinander unterscheiden,
• - eine zwischen den optischen Elementen angeordnete schaltbare Flüssigkristallschicht, die in Abhängigkeit von einem auf sie wirkenden elektrischen Feld EF1 oder EF2 die Polarisationseigenschaften durch sie hindurchdringenden Lichtes beeinflusst,
• - optional einen oberhalb oder unterhalb der optischen Elemente angeordneten Polarisationsfilter P,
• - Mittel zum wahlweisen Erzeugen der besagten elektrischen Felder EF1 und EF2, beispielsweise durch transparente ITO-Elektroden E1 und E2,
• - so dass bei Vorhandensein des besagten Polarisationsfilters P in einer ersten Betriebsart B1H oder B1V bei einem elektrischen Feld EF1 unpolarisiertes Licht, welches senkrecht zum schaltbaren Lichtfilter in diesen einfällt, zu mindestens 24% transmittiert und so dass unpolarisiertes Licht, welches in einem Winkel von über 30 Grad zur Mittelsenkrechten des schaltbaren Lichtfilters in diesen einfällt, zu mindestens 85% absorbiert wird, wobei diese Absorption ausschließlich in horizontaler (Betriebsart B1H) oder in vertikaler (Betriebsart B1V) Richtung gilt und parallel zur Polarisationsrichtung des Polarisationsfilters P liegt, wenn die Horizontale parallel zur Unterkante und die Vertikale parallel zur linken oder rechten Seitenkante der Schicht S1 orientiert ist,
• - so dass bei Abwesenheit eines Polarisationsfilters P in einer zweiten Betriebsart B3 bei einem elektrischen Feld EF1 unpolarisiertes Licht, welches in einem beliebigen Winkel in den schaltbaren Lichtfilter einfällt, zu mindestens 24% transmittiert wird,
• - und so dass schließlich in einer weiteren Betriebsart B2 bei einem elektrischen Feld EF2 unpolarisiertes Licht, welches senkrecht zum schaltbaren Lichtfilter in diesen einfällt, zu mindestens 24% transmittiert und so dass unpolarisiertes Licht, welches in einem Winkel von über 30 Grad zur Mittelsenkrechten des schaltbaren Lichtfilters in diesen einfällt, zu mindestens 85% absorbiert wird, wobei dies gleichzeitig sowohl in horizontaler als auch in vertikaler Richtung gilt, wenn die Horizontale parallel zur Unterkante und die Vertikale parallel zur linken oder rechten Seitenkante der Schicht S1 orientiert ist.

The invention acquires particular significance by being implemented in a switchable light filter. In a first embodiment, this includes:

• - two non-switchable optical elements according to the invention, in which the preferred directions of the absorption dipoles differ from one another by less than 10°,
• - a switchable liquid crystal layer arranged between the optical elements, which influences the polarization properties of light penetrating through it depending on an electric field EF1 or EF2 acting on it,
• - optionally a polarization filter P arranged above or below the optical elements,
• - means for selectively generating said electric fields EF1 and EF2, for example by means of transparent ITO electrodes E1 and E2,
• - so that in the presence of said polarization filter P in a first operating mode B1H or B1V in an electric field EF1 unpolarized light, which is incident perpendicular to the switchable light filter in this, at least 24% is transmitted and so that unpolarized light, which is at an angle of over 30 degrees to the perpendicular bisector of the switchable light filter, is absorbed by at least 85%, whereby this absorption applies exclusively in the horizontal (B1H operating mode) or in the vertical (B1V operating mode) direction and is parallel to the polarization direction of the polarization filter P if the horizontal is parallel to the bottom edge and the vertical is oriented parallel to the left or right side edge of layer S1,
• - so that in the absence of a polarization filter P in a second operating mode B3 in an electric field EF1 unpolarized light, which is incident at any angle in the switchable light filter, is transmitted to at least 24%,
• - and so that finally in a further operating mode B2 in an electric field EF2 unpolarized light, which is incident perpendicularly to the switchable light filter, is transmitted to at least 24% and so that unpolarized light, which is at an angle of more than 30 degrees to the perpendicular bisector of the switchable Light filter incident in this, is absorbed by at least 85%, this also applies both in the horizontal and in the vertical direction when the horizontal is oriented parallel to the bottom edge and the vertical parallel to the left or right side edge of the layer S1.

Thus, the switchable light filter of the first embodiment, in conjunction with an image display unit, allows switching between either a two-sided or a four-sided privacy screen (e.g. top/bottom B1V vs. top/bottom/left/right protected B2), if a polarization filter P is present, or , if no polarization filter P is present, switching either between free viewing in all directions and four-sided privacy protection (e.g. free vision B3 vs. above/below/left/right protected B2).

It is possible that, for example, either the electric field EF1 or the electric field EF2 describes a field-free state, with the respective other electric field EF2 or EF1 having an absolute field strength greater than zero, e.g. 0.5 MV/m.

Depending on the configuration of the two optical elements, the field-free state can mean that operating mode B2 is present. However, it is also possible that one of the operating modes B1H, B1V or B3 is present in the field-free state.

• - zwei schaltbare optische Elemente, wobei für jedes der optischen Elemente die beiden besagten Zustände durch an beide optische Elemente anliegende elektrische Felder EF1 oder EF2 erzeugt werden (d.h., EF1 und EF2 liegen gleichzeitig an beiden optischen Elementen an),
• - optional einen oberhalb oder unterhalb der optischen Elemente angeordneten Polarisationsfilter P (Dieser ist nicht notwendig, kann aber die Leistungsfähigkeit des schaltbaren Lichtfilters verbessern. Die Polarisation des Polarisationsfilters P und die des einfallenden Lichtes müssen kongruent sein.),
• - eine zwischen den optischen Elementen angeordnete Schicht zur Rotation der Polarisationsrichtung des die besagte Schicht durchdringenden Lichts um 90 Grad, z.B. bestehend aus uniaxial-gedrehtem (analog zu einer TN-Zelle im feldfreien Zustand) und/oder aus optisch aktivem Material,
• - Mittel zum Erzeugen besagter elektrischer Felder EF1 oder EF2 (typischerweise stellt eines der Felder EF1 oder EF2 einen feldfreien Zustand dar),
• - so dass in einer Betriebsart B3 bei Anliegen des elektrischen Feldes EF1 unpolarisiertes Licht, welches in einem beliebigen Winkel zum schaltbaren Lichtfilter in diesen einfällt, zu mindestens 24% transmittiert wird, wobei in dieser Betriebsart B3 die Absorptionsdipole der beiden optischen Elemente senkrecht zueinander ausgerichtet sind, und die Absorptionsdipole des Polarisators P, wenn vorhanden, parallel zu dem ihm nächstliegenden schaltbaren optischen Element zueinander ausgerichtet sind,
• - und so dass in einer zweiten Betriebsart B2 bei Anliegen des elektrischen Feldes EF2 unpolarisiertes Licht, welches senkrecht zum schaltbaren Lichtfilter in diesen einfällt, zu mindestens 24% transmittiert und so dass unpolarisiertes Licht, welches in einem Winkel von über 30 Grad zur Mittelsenkrechten des schaltbaren Lichtfilters in diesen einfällt, zu mindestens 85% absorbiert wird, wobei dies gleichzeitig sowohl in horizontaler als auch in vertikaler Richtung gilt, wenn die Horizontale parallel zur Unterkante und die Vertikale parallel zur linken oder rechten Seitenkante der Schicht S1 orientiert ist, wobei in dieser Betriebsart B2 die Absorptionsdipole von Polarisator P, wenn vorhanden, und zu dem ihm nächstliegenden schaltbaren optischen Element senkrecht und von den beiden optischen Elementen jeweils parallel zueinander ausgerichtet sind.

A second embodiment includes a switchable light filter

• - two switchable optical elements, the two said states being generated for each of the optical elements by electric fields EF1 or EF2 applied to both optical elements (ie, EF1 and EF2 are applied to both optical elements at the same time),
• - optionally a polarization filter P arranged above or below the optical elements (this is not necessary, but can improve the performance of the switchable light filter. The polarization of the polarization filter P and that of the incident light must be congruent.),
• - a layer arranged between the optical elements for rotating the direction of polarization of the light penetrating said layer by 90 degrees, e.g. consisting of uniaxially rotated (similar to a TN cell in the field-free state) and/or of optically active material,
• - means for generating said electric fields EF1 or EF2 (typically one of the fields EF1 or EF2 represents a field-free state),
• - so that in an operating mode B3, when the electric field EF1 is present, at least 24% of unpolarized light incident on the switchable light filter at any angle is transmitted, with the absorption dipoles of the two optical elements being aligned perpendicular to one another in this operating mode B3 , and the absorption dipoles of the polarizer P, if present, are aligned parallel to the switchable optical element closest to it,
• - and so that in a second operating mode B2 when the electric field EF2 is present, unpolarized light, which is incident perpendicularly to the switchable light filter, is transmitted to at least 24% and so that unpolarized light, which is at an angle of more than 30 degrees to the perpendicular bisector of the switchable At least 85% of the light filter incident on it is absorbed, whereby this applies both in the horizontal and in the vertical direction at the same time, if the horizontal is oriented parallel to the lower edge and the vertical is oriented parallel to the left or right side edge of the layer S1, with this operating mode B2 the absorption dipoles of polarizer P, if present, and are aligned perpendicularly to the switchable optical element closest to it and parallel to one another by the two optical elements.

The switchable light filter of this second embodiment, in combination with an image reproduction unit, thus allows switching between free viewing in all directions and four-sided privacy protection (free view B3 vs. top/bottom/left/right protected B2).

• - ein nicht schaltbares, erfindungsgemäßes optisches Element,
• - einen Polarisationsfilter P der dem optischen Element vor oder nachgeordnet ist,
• - eine zwischen dem optischen Element und dem Polarisationsfilter P angeordnete Flüssigkristallschicht, die in Abhängigkeit von einem auf sie wirkenden elektrischen Feld EF1 oder EF2 die Polarisationseigenschaften des durch sie hindurchdringenden Lichtes beeinflusst,
• - Mittel zum wahlweisen Erzeugen der besagten elektrischen Felder EF1 und EF2,
• - so dass in einer Betriebsart B1V oder B1H bei Anliegen des elektrischen Feldes EF1 unpolarisiertes Licht, welches senkrecht zum schaltbaren Lichtfilter in diesen einfällt, zu mindestens 24% transmittiert und so dass unpolarisiertes Licht, welches in einem Winkel von über 30 Grad zur Mittelsenkrechten des schaltbaren Lichtfilters in diesen einfällt, zu mindestens 85% absorbiert wird, wobei diese Absorption ausschließlich in horizontaler (Betriebsart B1H) oder ausschließlich in vertikaler Richtung (Betriebsart B1V) gilt, wenn die Horizontale parallel zur Unterkante und die Vertikale parallel zur linken oder rechten Seitenkante der Schicht S1 orientiert ist,
• - und so dass in einer zweiten Betriebsart B1H oder B1V bei Anliegen des elektrischen Feldes EF2 unpolarisiertes Licht, welches senkrecht zum schaltbaren Lichtfilter in diesen einfällt, zu mindestens 24% transmittiert und so dass unpolarisiertes Licht, welches in einem Winkel von über 30 Grad zur Mittelsenkrechten des schaltbaren Lichtfilters in diesen einfällt, zu mindestens 85% absorbiert wird, wobei dies entweder ausschließlich in vertikaler (Betriebsart B1V) oder ausschließlich in horizontaler Richtung (Betriebsart B1 H) gilt, so dass die Absorptionsrichtung zwischen der ersten und der zweiten Betriebsart B1 jeweils um 90 Grad gedreht ist, wenn die Horizontale parallel zur Unterkante und die Vertikale parallel zur linken oder rechten Seitenkante der Schicht S1 orientiert ist.

A third embodiment includes a switchable light filter

• - a non-switchable optical element according to the invention,
• - a polarization filter P which is arranged before or after the optical element,
• - a liquid crystal layer arranged between the optical element and the polarization filter P, which influences the polarization properties of the light passing through it depending on an electric field EF1 or EF2 acting on it,
• - means for selectively generating said electric fields EF1 and EF2,
• - so that in an operating mode B1V or B1H when the electric field EF1 is present, at least 24% of unpolarized light, which is incident perpendicular to the switchable light filter, is transmitted and so that unpolarized light, which is at an angle of more than 30 degrees to the median perpendicular to the switchable At least 85% of the light filter incident on it is absorbed, whereby this absorption applies exclusively in the horizontal direction (operating mode B1H) or exclusively in the vertical direction (operating mode B1V), if the horizontal line is parallel to the bottom edge and the vertical line is parallel to the left or right side edge of the layer S1 oriented
• - and so that in a second operating mode B1H or B1V when the electric field EF2 is present, at least 24% of unpolarized light, which is incident perpendicular to the switchable light filter, is transmitted and so that unpolarized light, which is at an angle of more than 30 degrees to the perpendicular bisector of the switchable light filter incident on it is absorbed by at least 85%, whereby this applies either exclusively in the vertical direction (operating mode B1V) or exclusively in the horizontal direction (operating mode B1 H), so that the absorption direction between the first and the second operating mode B1 changes by rotated 90 degrees when the horizontal is oriented parallel to the bottom edge and the vertical is oriented parallel to the left or right side edge of layer S1.

The configuration of this third embodiment of a switchable light filter can be switched between B1V and B1H modes by rotating the polarizing filter P by 90 degrees.

It is also possible here that, for example, either the electric field EF1 or the electric field EF2 describes a field-free state, with the respective other electric field EF2 or EF1 having an absolute field strength greater than zero, eg 0.5 MV/m.
Depending on the configuration of the optical element and the polarization filter P, the field-free state can mean that the B1H operating mode is present. However, it is also possible that the B1V operating mode is present in the field-free state.
Thus, the switchable light filter of this third embodiment, in combination with an image reproduction unit, allows switching between vertical privacy protection and horizontal privacy protection (top/bottom protected B1V vs. left/right protected B1H). In a laptop, for example, this would mean that a user can view the content in B1V mode together with other people who are next to the user and who are essentially at the same eye level, while in B1H mode the people next to the side view the image content can't see.

The switchable light filter of this third embodiment can be varied in its construction.
Table 1 below shows some essential construction variants. In each case, the first-mentioned component is on top in the viewing direction and the others follow below. In this case, the abbreviation "L/R" means that the optical effect is active in horizontal effect (with the horizontal direction already defined above). For the polarization filter P, this means that it transmits horizontally (linearly) polarized light and (essentially) absorbs vertical light. Correspondingly, “O/U” for the polarization filter P means that it transmits vertically (linearly) polarized light and horizontally (essentially) absorbs light
For the resulting effect of this switchable filter in combination with an image display unit, which can be arranged in front of or behind the switchable filter, the abbreviation "L/R" means that the privacy screen effect works horizontally, i.e. that a view from the left and right is prevented . This finally corresponds to the operating mode B1H of the switchable filter.
Analogously, "O/U" for the switchable filter in conjunction with an image display unit means that the visual protection effect works vertically, i.e. that a view from above and below is prevented. This corresponds to the operating mode B1V of the switchable filter. Table 1: construction Field-free (e.g. EF1 means no electrical field is present): Effect in conjunction with an image display unit Field attached (e.g. EF2 means an electric field is attached): Effect in conjunction with an image display unit polarization filter P (L/R) liquid crystal layer 3 optical element 1 Privacy Effect (L/R) - B1H Privacy Effect (O/U) - B1V polarization filter P (O/U) liquid crystal layer 3 optical element 1 Privacy Effect (O/U) - B1V Privacy Effect (L/R) - B1H optical element 1 liquid crystal layer 3 polarization filter P (L/R) Privacy Effect (O/U) - B1V Privacy Effect (L/R) - B1H optical element 1 liquid crystal layer 3 polarization filter P (O/U) Privacy Effect (L/R) - B1H Privacy Effect (O/U) - B1V

It should be pointed out once again that the “O/U” privacy screen effect allows normal viewing for several viewers in many practical cases if they are looking at the image display unit from the side from approximately the same height.

• - ein schaltbares optisches Element,
• - einen oberhalb oder unterhalb des optischen Elementes angeordneten Polarisationsfilter P,
• - Mittel zum Erzeugen elektrischer Felder EF1 oder EF2, wobei für das optische Element mindestens zwei Zustände durch das jeweils anliegende elektrische Feld EF1 oder EF2 erzeugt werden,
• - so dass in einer Betriebsart B3, bei welcher die Absorptionsdipole der Schichten (S1, S2, ..) des schaltbaren optischen Elements parallel zur Substratoberfläche des schaltbaren optischen Elements und senkrecht zur Transmissionsrichtung des Polarisators ausgerichtet sind, unpolarisiertes Licht, welches in einem beliebigen Winkel zum optischen Element in dieses einfällt, zu mindestens 25% transmittiert wird,
• - und so dass in einer Betriebsart B1H oder B1V, bei welcher die Absorptionsdipole der Schichten (S1, S2, ..) des schaltbaren optischen Elements entlang der besagten Vorzugsrichtung ausgerichtet sind, unpolarisiertes Licht, welches senkrecht zum schaltbaren Lichtfilter in diesen einfällt, zu mindestens 24% transmittiert und so dass unpolarisiertes Licht, welches in einem Winkel von über 30 Grad zur Mittelsenkrechten des schaltbaren Lichtfilters in diesen einfällt, zu mindestens 85% absorbiert wird, wobei dies entweder in vertikaler (Betriebsart B1V) oder horizontaler in Richtung (Betriebsart B1H) gilt, wenn die Horizontale parallel zur Unterkante und die Vertikale parallel zur linken oder rechten Seitenkante der Schicht S1 orientiert ist.

A fourth embodiment also includes a switchable light filter

• - a switchable optical element,
• - a polarization filter P arranged above or below the optical element,
• - Means for generating electrical fields EF1 or EF2, wherein at least two states are generated for the optical element by the respective applied electrical field EF1 or EF2,
• - so that in an operating mode B3, in which the absorption dipoles of the layers (S1, S2, ..) of the switchable optical element are aligned parallel to the substrate surface of the switchable optical element and perpendicular to the transmission direction of the polarizer, unpolarized light which is at any angle incident on the optical element, at least 25% is transmitted,
• - and so that in an operating mode B1H or B1V, in which the absorption dipoles of the layers (S1, S2, ..) of the switchable optical element are aligned along said preferred direction, unpolarized light, which is incident perpendicular to the switchable light filter in this, at least 24% is transmitted and so that unpolarized light that strikes the switchable light filter at an angle of more than 30 degrees to the perpendicular bisector is absorbed by at least 85%, with this either in a vertical (operating mode B1V) or horizontal direction (operating mode B1H) applies when the horizontal line is oriented parallel to the bottom edge and the vertical line is oriented parallel to the left or right side edge of layer S1.

It is also possible here that either the electric field EF1 or the electric field EF2 describes a field-free state, with the respective other electric field EF2 or EF1 having an absolute field strength greater than zero, eg 0.5 V/m .

Depending on the configuration of the optical element and the polarization filter P, the field-free state can mean that the B3 operating mode is present. However, it is also possible that one of the operating modes B1H or B1V is present in the field-free state.

Thus, the switchable light filter of this fourth embodiment, in combination with an image reproduction unit, allows switching between visual protection in the vertical or horizontal direction and no visual protection effect (top/bottom protected B1V or left/right protected B1H vs. no visual protection B3).

For special applications, a switchable light filter--regardless of the aforementioned embodiment--can be subdivided into a plurality of separately switchable segments, so that it is possible to switch over locally between the respective possible operating states. In conjunction with an image display unit, this would mean that, for example, only a part of the image area can be switched between a visual protection (e.g. operating mode B1H or B2) and no visual protection effect (e.g. operating mode B3, possibly also B1V) for a clear view, while the complementary Part of the screen is permanently in a privacy mode (e.g. operating mode B1H or B2) or in no privacy mode (e.g. mode B3, possibly also B1V).

There can even be several such segments that are geometrically separate from one another and can be switched between the operating modes separately or together.

As already noted above, the invention acquires particular importance through the combination of a switchable light filter as described above with an image display unit to form a screen.

• - einen wie vorstehend beschriebenen schaltbaren Lichtfilter einer der vier genannten Ausgestaltungen, und
• - eine dem schaltbaren Lichtfilter von einem Betrachter aus gesehen nach- oder vorgeordnete Bildwiedergabeeinheit.

Such a screen, which can be operated in at least a first operating state B1V and/or B3 for a horizontally free viewing mode and in at least a second operating state B1H and/or B2 for a horizontally restricted viewing mode

• - a switchable light filter as described above, one of the four configurations mentioned, and
• - an image reproduction unit which is arranged upstream or downstream of the switchable light filter as seen from the perspective of an observer.

The image display unit advantageously corresponds to an LCD panel, one polarization filter of which corresponds to the polarization filter P. This can be the front or rear polarizer in the LCD assembly.

In addition, the switchable light filter can advantageously be arranged between the LCD panel and its backlight in order to switch between a first operating state B3 (or B1V) for a clear view mode and a second operating state B1H or B2 for a restricted view mode, because the light from the backlight due to the switchable light filter in the horizontal direction once focused (B2 or B1H) and once not focused (B3 or B1V). With "Focusing" This does not mean focusing in the manner of lenses, but rather a narrowing of the emission range or transmission range over the angles.

Alternatively, the image display unit can be an OLED, an SED display, an FED display, a microLED display or a VFD display, in front of which a switchable light filter is arranged. Since the switchable light filter is effective regardless of the type of image display unit, any other type of screen can also be used.

Such a screen is advantageously used in a mobile device, a motor vehicle, aircraft or watercraft, in a payment terminal or in an access system.

It is possible to switch between the above-mentioned operating modes in order to protect sensitive data, i.e. to display them perceptibly for only one viewer, or alternatively to display image content for several viewers at the same time.

Furthermore, a switchable or non-switchable optical element can be used in the configurations described above together with a static image or a dynamic image display unit such as an LCD panel, for example to make advertising content visible only in a restricted field of view.

However, the variety of applications for the optical element according to the invention does not end with applications for displaying image content with or without visual protection effects. On the contrary, other applications are possible, for example when special properties of a lighting device are desired. Configurations of the optical element in which defined polarization contrasts are generated are conceivable. These in turn can be used in the context of optical sensors.

• - mindestens ein Modul M1, M2, .. bestehend in dieser Reihenfolge aus einer ersten Linse oder einem ersten Linsenraster L1 mit Mikrolinsen, einem schaltbaren oder nicht schaltbaren erfindungsgemäßen optischen Element wie weiter oben beschrieben, und einer zweiten Linse oder einem zweiten Linsenraster L2,
• - eine Lichtquelle LS,
• - einen optischen Detektor D,
• - optional einen Strahlteiler ST,
• - optional abbildende Optiken L3 und L4,
• - optional polarisationsrotierende Schichten 4,
• - wobei in einer ersten Alternative für eine optische Detektion in Transmission das Messgerät in der Reihenfolge Lichtquelle LS, erstes Modul M1, Objekt O, zweites Modul M2 sowie optischer Detektor D aufgebaut ist, und
• - wobei in einer zweiten Alternative für eine optische Detektion in Reflektion das Messgerät in der Reihenfolge Lichtquelle LS, Strahlteiler ST, erstes Modul M1 sowie Objekt O, aufgebaut ist, wobei hier der optische Detektor D zum Empfang von durch den Strahlteiler ST ausgekoppelten optischen Signalen geeignet neben den vorgenannten Komponenten angeordnet ist,
• - so dass der optische Detektor D polarisationsmaskierte optische Informationen detektieren kann, wobei für die Linse oder jede Mikrolinse des dem jeweils dem optischen Detektor D zugewandten Linsenrasters L1 des entsprechenden Moduls M1 oder M2 eine Polarisationsinformation vorliegt.

In this respect, the invention also includes a measuring device for the optical detection of properties of the surface and/or the volume of an object O, including

• - at least one module M1, M2, .. consisting in this order of a first lens or a first lens array L1 with microlenses, a switchable or non-switchable optical element according to the invention as described above, and a second lens or a second lens array L2,
• - a light source LS,
• - an optical detector D,
• - optionally a beam splitter ST,
• - optional imaging optics L3 and L4,
• - optional polarization-rotating layers 4,
• - In a first alternative for optical detection in transmission, the measuring device is constructed in the order of light source LS, first module M1, object O, second module M2 and optical detector D, and
• - In a second alternative for optical detection in reflection, the measuring device is constructed in the order of light source LS, beam splitter ST, first module M1 and object O, with the optical detector D being suitable here for receiving optical signals coupled out by the beam splitter ST is arranged next to the aforementioned components,
• - So that the optical detector D can detect polarization-masked optical information, polarization information being present for the lens or each microlens of the respective optical detector D facing lens array L1 of the corresponding module M1 or M2.

Such a measuring device allows versatile applications for measuring surfaces, roughness, curvature, depolarization or also in the field of "machine vision". Other applications are conceivable. In principle, the direction and/or polarization-dependent weakening of the light is used to make optical differences visible.

Optionally, the measurement can also be carried out confocally with the measuring device according to the invention, for example in order to determine the scattering properties of particles.

In principle, the performance of the invention is retained if the parameters described above are varied within certain limits.

It goes without saying that the features mentioned above and those still to be explained below can be used not only in the specified combinations, but also in other combinations or on their own, without departing from the scope of the present invention.

• 1a die Prinzipskizze eines nicht schaltbaren optischen Elements,
• 1 b die Prinzipskizze eines schaltbaren optischen Elements in einem ersten Zustand,
• 1c die Prinzipskizze eines schaltbaren optischen Elements in einem zweiten Zustand,
• 2 die Prinzipskizze eines schaltbaren Lichtfilters in einer ersten Ausgestaltung mit einem Polarisationsfilter P,
• 3 die Prinzipskizze eines schaltbaren Lichtfilters in einer ersten Ausgestaltung ohne Polarisationsfilter,
• 4a bis 4c Skizzen zur Beeinflussung des Lichtes aufgrund eines schaltbaren Lichtfilters gemäß der 3,
• 5 die Prinzipskizze eines schaltbaren Lichtfilters in einer zweiten Ausgestaltung,
• 6 die Prinzipskizze eines schaltbaren Lichtfilters in einer dritten Ausgestaltung,
• 7 die Prinzipskizze eines schaltbaren Lichtfilters in einer vierten Ausgestaltung,
• 8 die Prinzipskizze eines Messgerätes, das in Durchlicht arbeitet, unter Nutzung eines optischen Elements,
• 9 die Prinzipskizze eines Messgerätes, das in Reflektion arbeitet, unter Nutzung eines optischen Elements,
• 10 die Prinzipskizze eines Messgerätes, das in Durchlicht arbeitet, in einer zweiten Ausgestaltung unter Nutzung eines optischen Elements, sowie
• 11-15 optische Simulationen zur Veranschaulichung der optischen Wirkung eines optischen Elements.

The invention is explained in more detail below with reference to drawings, which also show features that are essential to the invention. It shows

• 1a the principle sketch of a non-switchable optical element,
• 1 b the schematic diagram of a switchable optical element in a first state,
• 1c the schematic diagram of a switchable optical element in a second state,
• 2 the schematic diagram of a switchable light filter in a first embodiment with a polarization filter P,
• 3 the schematic diagram of a switchable light filter in a first embodiment without a polarization filter,
• 4a until 4c Sketches for influencing the light due to a switchable light filter according to the 3 ,
• 5 the schematic diagram of a switchable light filter in a second embodiment,
• 6 the schematic diagram of a switchable light filter in a third embodiment,
• 7 the schematic diagram of a switchable light filter in a fourth embodiment,
• 8th the basic sketch of a measuring device that works in transmitted light using an optical element,
• 9 the basic sketch of a measuring device that works in reflection, using an optical element,
• 10 the basic sketch of a measuring device that works in transmitted light, in a second embodiment using an optical element, and
• 11-15 optical simulations to illustrate the optical effect of an optical element.

The drawings are not true to scale and merely provide schematic representations.

• - mindestens eine Schicht S1,
• - wobei diese Schicht S1 Material mit einer Vielzahl Licht absorbierender elektrischer Absorptionsdipole (die hier vereinfacht als kleine vertikale Striche dargestellt sind) umfasst, welche mindestens in einem ersten Zustand parallel zu einer wählbaren Vorzugsrichtung ausgerichtet sind (hier senkrecht zur Oberfläche der Schicht S1) oder um diese herum fluktuieren, wodurch die besagte Vorzugsrichtung einen Winkel zwischen 0° und 45° zur Flächennormale der Schicht S1 einschließt,
• - so dass Licht, welches in das optische Element einfällt, in Abhängigkeit von seiner Einfallsrichtung gegenüber der Schicht S1 und seinen Polarisationseigenschaften transmittiert oder teilweise oder ganz absorbiert wird.

the 1a shows the schematic diagram of an exemplary non-switchable optical element 1, which is within the scope of the invention. The same includes

• - at least one layer S1,
• - wherein this layer S1 material with a multiplicity of light-absorbing electrical absorption dipoles (which are shown here in simplified form as small vertical lines) which, at least in a first state, are aligned parallel to a selectable preferred direction (here perpendicular to the surface of layer S1) or around these fluctuate around, as a result of which said preferred direction encloses an angle between 0° and 45° to the surface normal of layer S1,
• - so that light which is incident on the optical element is transmitted or partially or completely absorbed depending on its direction of incidence with respect to the layer S1 and its polarization properties.

An optical element 1 according to the invention can be produced, for example, by lamination of a large number of polymer film polarizers and/or by photoalignment of molecules or particles. Depending on the implementation, the density of said electric absorption dipoles in layer S1 can vary. With a passive polarizer, the volume density can approach 100%.

The optical element 1 according to the invention represents a privacy filter for linearly polarized light. A polarizer P is therefore provided here, which polarizes light incident from below linearly parallel to the drawing surface. However, the polarizer P does not change the directions of light propagation. Two possible light propagation directions are indicated by the two thick arrows. Due to the effect of the absorption dipoles, the light is now absorbed by the optical element 1, which has an (oblique) direction of approximately more than 30 degrees with respect to the bisector on the layer S1. Finally, essentially only the light incident perpendicularly onto the optical element 1 remains after passing through the same, as illustrated by the single arrow at the top of the drawing.

Depending on the application, each of the layers (S1, S2, ...) has a periodic or non-periodic structure.

The extinction (i.e. the absorption) of the light depends on the layer thickness of the absorption dipoles. The drawings show this 11 until 15 optical simulations to illustrate the optical effect of an optical element 1.

the 11 FIG. 1 shows a diagram of the normalized transmission of the light as it passes through an optical element 1 according to FIG 1 , plotted here over horizontal measuring angles from -90° to +90°. The strong absorption effect at angles above +/-25° is clearly visible. The simulations are based on an assumed layer thickness of an optical element 1 of d=0.5mm, a refractive index of the material of n=1.5, the molarity M=0.01 mol m ^-3 and an exemplary molar extinction of ε=12700 m ² mol ^-1 .

In 12 are the circumstances 11 plotted logarithmically on the ordinate for the value range essential for use. It can be seen that with such parameters at +/-25° the transmission is already reduced to around one percent and at +/-40° to only around 0.001 percent. In 13 were the for 11 assumed assumptions regarding the refractive index n for values n=1.0; 1.3; 1.5 and n=1.7 calculated. It can be seen that the transmission becomes more restricted at the angle, the lower the refractive index of the material of layer S1.

Furthermore, the 14 a variation of the normalized transmission through an optical element 1 according to the ratios 11 with regard to the thickness of an optical element 1. Layer thicknesses of d=0.1 mm; 0.2mm; 0.3mm; 0.4 mm and 0.5 mm calculated. As expected, a larger layer thickness results in a stronger limitation of the transmission over the angles.

Finally shows 15 the angle-dependent, normalized transmission for three selected parameter sets (1. n=1.0 and d=0.2 mm; 2. n=1.5 and d=0.5 mm; 3. n=1.7 and d= 0.65mm). All three sets of parameters produce very similar optical effects.

In contrast, the micro-lamellar filters known in the state of the art (also called “View Control Filters - VCF” or “Light Control Filters - LCF”) make use of the geometric optics. The alternating periodic arrangement of transparent and absorbing layers absorbs (almost) all light that propagates at large angles relative to a defined direction. The position of the absorbers is checked there.

In contrast, in the case of the optical elements according to the invention, the transmission of light with different directions of propagation changes, since the absorption cross section of the molecules changes with the direction of propagation. In the case of the invention, therefore, it is not the position that is checked, but rather the orientation of the absorbers in particular.

In other words: the invention is based on a direction-dependent absorption of the light beams when passing through an optical element according to the invention, and in fact is fundamentally independent of the position of the light beams.

This applies both to non-switchable optical elements according to the invention, as described above, and to switchable configurations described below.

For a switchability of the optical effect of the optical element 1, so for a switchable optical element 1, the light-absorbing electrical absorption dipoles in each layer (S1, S2, ...) can be varied in their alignment and / or their absolute value to the respective layer (S1, S2, ...) in at least two different states.

Possible configurations of a switchable optical element or each layer S1, S2, ment cell" or in a liquid crystal cell with homogeneous alignment on the surfaces and can be rotated between at least two states. In this case, the light-absorbing electrical absorption dipoles are also rotated and can thus assume at least two states of action. It is particularly conceivable in such configurations that more than two states, for example three or eight states, each with different optical effects, are achieved. Other configurations of the liquid crystal cells are also conceivable.

For this shows 1b the schematic diagram of a switchable optical element in a first state and 1c the schematic diagram of a switchable optical element in a second state.

For this exemplary case, it should be assumed that the incident light is p-polarized, i.e. polarized parallel to the plane of incidence (see Fig 1b) is. If the transparent electrodes E1, E2 are uncharged, ie they generate the electric field EF1 with 0 V/m (field-free), then the liquid crystal molecules shown here as dots (which are formed here, for example, as layers S1, S2 and S3) are aligned along the Surface of the electrodes E1, E2. This can be achieved by appropriate combination of surface functionalization and liquid crystals and is known in the prior art. For light that propagates in the plane of the drawing and is s-polarized, the polarization of the light and the absorption dipoles of the liquid crystals are always oriented perpendicular to one another. Therefore, no absorption takes place, so that the light propagation directions shown above and below the substrates S with s-polarization penetrate the switchable optical element 1 unhindered.

will, as in 1c shown, the electrodes E1 and E2 are charged, ie they generate the electric field EF2 > 0 V/m, so the liquid crystals in the layers S1, S2 and S3 rotate. If the voltage, and thus the field strength EF2, exceeds a certain threshold value, the liquid crystal molecules and thus—if present—also the dye molecules are aligned parallel to the field lines of the electric field EF2. As a result, light is absorbed as a function of the angle α, the angle between the direction of propagation of the light and the normal to the surface of the layer S1. The absorption increases with the angle α. The extinction of the electric field of light is proportional to sin(α).

In principle, it is advantageous to control the alignment of the dye molecules in order to control the axis of the privacy screen or to carry out a defined beam steering.

In condition according to 1b the dipoles are oriented perpendicular to the polarization of the incident light and are in the state of 1c parallel to the vertical incidence of light.

With such switchable optical elements, volume densities between 0.1% and 90% based on liquid crystals are conceivable.

• - zwei nicht-schaltbare erfindungsgemäße optische Elemente 1, 2, bei denen die Vorzugsrichtungen der Absorptionsdipole sich um weniger als 10° voneinander unterscheiden,
• - eine zwischen den optischen Elementen 1, 2 angeordnete schaltbare Flüssigkristallschicht 3, die in Abhängigkeit von einem auf sie wirkenden elektrischen Feld EF1 oder EF2 die Polarisationseigenschaften des durch sie hindurchdringenden Lichtes beeinflusst,
• - einen unterhalb der optischen Elemente 1, 2 angeordneten Polarisationsfilter P (oberhalb wäre auch möglich),
• - zeichnerisch nicht dargestellte Mittel zum wahlweisen Erzeugen der besagten elektrischen Felder EF1 und EF2, beispielsweise oberhalb und unterhalb der Flüssigkristallschicht 3 angeordnete Elektroden,
• - so dass in einer ersten Betriebsart B1H oder B1V bei einem elektrischen Feld EF1 unpolarisiertes Licht, welches senkrecht zum schaltbaren Lichtfilter 5 in diesen einfällt, zu mindestens 24% transmittiert und so dass unpolarisiertes Licht, welches in einem Winkel von über 30 Grad zur Mittelsenkrechten des schaltbaren Lichtfilters 5 in diesen einfällt, zu mindestens 85% absorbiert wird, wobei diese Absorption ausschließlich in horizontaler (Betriebsart B1H) oder in vertikaler (Betriebsart B1V) Richtung gilt, wenn die Horizontale parallel zur Unterkante und die Vertikale parallel zur linken oder rechten Seitenkante der Schicht S1 orientiert ist,
• - und so dass schließlich in einer weiteren Betriebsart B2 bei einem elektrischen Feld EF2 unpolarisiertes Licht, welches senkrecht zum schaltbaren Lichtfilter 5 in diesen einfällt, zu mindestens 24% transmittiert und so dass unpolarisiertes Licht, welches in einem Winkel von über 30 Grad zur Mittelsenkrechten des schaltbaren Lichtfilters 5 in diesen einfällt, zu mindestens 85% absorbiert wird, wobei dies gleichzeitig sowohl in horizontaler als auch in vertikaler Richtung gilt, wenn die Horizontale parallel zur Unterkante und die Vertikale parallel zur linken oder rechten Seitenkante der Schicht S1 orientiert ist.

The invention acquires particular importance in that it is implemented in a light filter 5 that can be switched. Such a switchable light filter 5 is in a first embodiment 2 shown. It includes:

• - two non-switchable optical elements 1, 2 according to the invention, in which the preferred directions of the absorption dipoles differ from one another by less than 10°,
• - a switchable liquid crystal layer 3 arranged between the optical elements 1, 2, which influences the polarization properties of the light penetrating through it depending on an electric field EF1 or EF2 acting on it,
• - A polarization filter P arranged below the optical elements 1, 2 (above would also be possible),
• - Means, not shown in the drawing, for selectively generating said electric fields EF1 and EF2, for example electrodes arranged above and below liquid crystal layer 3,
• - so that in a first operating mode B1H or B1V in an electric field EF1 unpolarized light, which is incident perpendicularly to the switchable light filter 5, is at least 24% transmitted and so that unpolarized light, which is at an angle of more than 30 degrees to the perpendicular bisector of the switchable light filter 5 incident on it, is absorbed by at least 85%, whereby this absorption only applies in the horizontal (B1H operating mode) or vertical (B1V operating mode) direction if the horizontal is parallel to the lower edge and the vertical is parallel to the left or right side edge of the layer S1 is oriented,
• - and so that finally in a further operating mode B2 with an electric field EF2 unpolarized light, which is incident perpendicularly to the switchable light filter 5, is transmitted to at least 24% and so that unpolarized light, which is at an angle of more than 30 degrees to the perpendicular bisector of switchable light filter 5 incident on it, is absorbed by at least 85%, whereby this applies both in the horizontal and in the vertical direction at the same time, when the horizontal is oriented parallel to the lower edge and the vertical is oriented parallel to the left or right side edge of the layer S1.

• - in einer zweiten Betriebsart B3 bei einem elektrischen Feld EF1 unpolarisiertes Licht, welches in einem beliebigen Winkel in den schaltbaren Lichtfilter 5 einfällt, zu mindestens 24% transmittiert wird,
• - und so dass schließlich in einer weiteren Betriebsart B2 bei einem elektrischen Feld EF2 unpolarisiertes Licht, welches senkrecht zum schaltbaren Lichtfilter 5 in diesen einfällt, zu mindestens 24% transmittiert und so dass unpolarisiertes Licht, welches in einem Winkel von über 30 Grad zur Mittelsenkrechten des schaltbaren Lichtfilters 5 in diesen einfällt, zu mindestens 85% absorbiert wird, wobei dies gleichzeitig sowohl in horizontaler als auch in vertikaler Richtung gilt, wenn die Horizontale parallel zur Unterkante und die Vertikale parallel zur linken oder rechten Seitenkante der Schicht S1 orientiert ist.

Furthermore, the 3 in modification of 2 the schematic diagram of a switchable light filter 5 in a first embodiment, but this time without a polarization filter. This design serves to

• - in a second operating mode B3, at least 24% of unpolarized light, which is incident on the switchable light filter 5 at any angle, is transmitted in an electric field EF1,
• - and so that finally in a further operating mode B2 with an electric field EF2 unpolarized light, which is incident perpendicularly to the switchable light filter 5, is transmitted to at least 24% and so that unpolarized light, which is at an angle of more than 30 degrees to the perpendicular bisector of switchable light filter 5 incident on it, is absorbed by at least 85%, whereby this applies both in the horizontal and in the vertical direction at the same time, when the horizontal is oriented parallel to the lower edge and the vertical is oriented parallel to the left or right side edge of the layer S1.

Thus, the switchable light filter 5 of the first embodiment, in conjunction with an image display unit, allows switching between a two-sided and a four-sided privacy screen (e.g. top/bottom B1V vs. top/bottom/left/right protected B2), if a polarization filter P is present, or, if no polarization filter P is present, switching either between free viewing in all directions and four-sided privacy protection (e.g. free vision B3 vs. above/below/left/right protected B2).

It is possible that, for example, either the electric field EF1 or the electric field EF2 describes a field-free state, with the respective other electric field EF2 or EF1 having an absolute field strength greater than zero, e.g. 0.5 MV/m.

Depending on the configuration of the optical elements 1 and 2, the field-free state can mean that the B2 operating mode is present. However, it is also possible that one of the operating modes B1H, B1V or B3 is present in the field-free state.

the 4a until 4c show a sketch of the state of polarization of the light due to a switchable light filter according to 3 . the 4a shows the polarization state of the public mode, in which the light is tangentially polarized for viewing angles greater than 30° and normal incidence light is linearly polarized. the 4c shows the polarization state in reduced view mode. Here, light for an angle of incidence of, for example, greater than 30° is very strongly attenuated, while light with vertical incidence is transmitted unpolarized.

Due to the alignment or orientation of the absorption dipoles, the light is polarized for the angle of incidence, ie the linear polarization of the light is always aligned perpendicularly to the direction of origin. This state is in 4a shown and applies after the light has passed through the non-switchable optical element 1. The light with small angles is only weakly polarized. Ideally, light that is emitted perpendicularly is not absorbed, ie it is polarized.

If the light now passes from the optical element 2 into the liquid crystal layer 3, it depends on the state of the liquid crystal layer 3 whether and how the state of polarization of the light is changed or remains unchanged. If, for example in the field-free state EF1, the polarization rotation in the liquid crystal layer 3 is switched off, nothing changes in the state described above. After passing through the liquid crystal layer 3 and further through the non-switchable optical element 1, the transmission remains essentially unchanged. If a polarizer P is present above the optical element 1 or below the optical element 2, an operating mode B1H or B1V, depending on the design, is achieved. If this polarizer does not exist, the operating mode B3 is implemented.

If, in contrast, the polarization rotation in the liquid crystal layer 3 is switched on by applying an electric field EF2>0 V/m, then the polarization is rotated by 90° everywhere. The polarization state is in 4b shown: the polarization state after passage through the optical element 2 and the polarization-rotating liquid crystal layer 3 is shown there. This will be in the context of further Light propagation due to the optical element 1 extinguishes all light that propagates at an angle greater than 25° or about 30°. This corresponds to operating mode B2 and is in 4c shown.

• - zwei schaltbare optische Elemente 1, 2, wobei für jedes der optischen Elemente 1, 2 die beiden besagten Zustände durch an beide optische Elemente 1, 2 anliegende elektrische Felder EF1 oder EF2 erzeugt werden (EF1 liegt am Element 1 und EF2 am Element 2 an),
• - optional einen oberhalb oder unterhalb der optischen Elemente 1, 2 angeordneten Polarisationsfilter P (Dieser ist nicht notwendig, kann aber die Leistungsfähigkeit des schaltbaren Lichtfilters verbessern. Die Polarisation des Polarisationsfilters P und die des einfallenden Lichtes müssen kongruent sein.),
• - eine zwischen den schaltbaren optischen Elementen 1, 2 angeordnete Schicht 4 zur Rotation der Polarisationsrichtung (z.B. Flüssigkristalle oder eine schaltbare Halbwellenplatte) des die besagte Schicht 4 durch-dringenden Lichts um 90 Grad,
• - zeichnerisch nicht dargestellte Mittel zum Erzeugen besagter elektrischer Felder EF1 oder EF2 (typischerweise stellt eines der Felder EF1 oder EF2 einen feldfreien Zustand dar),
• - so dass in einer Betriebsart B3 bei Anliegen des elektrischen Feldes EF1 unpolarisiertes Licht, welches in einem beliebigen Winkel zum schaltbaren Lichtfilter 5 in diesen einfällt, zu mindestens 24% transmittiert wird, wobei in dieser Betriebsart B3 die Absorptionsdipole der beiden schaltbaren optischen Elemente 1, 2 senkrecht zueinander ausgerichtet sind und die Absorptionsdipole des Polarisators P, wenn vorhanden, parallel zu den Absorptionsdipolen des dem Polarisator P nächstliegenden schaltbaren optischen Elements 1 oder 2 zueinander ausgerichtet sind,
• - und so dass in einer zweiten Betriebsart B2 bei Anliegen des elektrischen Feldes EF2 unpolarisiertes Licht, welches senkrecht zum schaltbaren Lichtfilter 5 in diesen einfällt, zu mindestens 24% transmittiert und so dass unpolarisiertes Licht, welches in einem Winkel von über 30 Grad zur Mittelsenkrechten des schaltbaren Lichtfilters 5 in diesen einfällt, zu mindestens 85% absorbiert wird, wobei dies gleichzeitig sowohl in horizontaler als auch in vertikaler Richtung gilt, wenn die Horizontale parallel zur Unterkante und die Vertikale parallel zur linken oder rechten Seitenkante der Schicht S1 orientiert ist, wobei in dieser Betriebsart B2 die Absorptionsdipole von Polarisator P, wenn vorhanden, und zu dem ihm nächstliegenden schaltbaren optischenElement 1 senkrecht und von den beiden optischen Elementen 1 und 2 jeweils parallel zueinander ausgerichtet sind.

Furthermore shows 5 the schematic diagram of a switchable light filter 5 in a second embodiment. This includes

• - Two switchable optical elements 1, 2, with the two said states being generated for each of the optical elements 1, 2 by electrical fields EF1 or EF2 applied to both optical elements 1, 2 (EF1 is applied to element 1 and EF2 to element 2 ),
• - optionally a polarization filter P arranged above or below the optical elements 1, 2 (this is not necessary, but can improve the performance of the switchable light filter. The polarization of the polarization filter P and that of the incident light must be congruent.),
• - a layer 4 arranged between the switchable optical elements 1, 2 for rotating the direction of polarization (e.g. liquid crystals or a switchable half-wave plate) of the light penetrating said layer 4 by 90 degrees,
• - Means, not shown in the drawing, for generating said electric fields EF1 or EF2 (typically one of the fields EF1 or EF2 represents a field-free state),
• - so that in an operating mode B3, when the electric field EF1 is present, at least 24% of unpolarized light incident on the switchable light filter 5 at any angle is transmitted, with the absorption dipoles of the two switchable optical elements 1 in this operating mode B3 2 are aligned perpendicular to one another and the absorption dipoles of the polarizer P, if present, are aligned parallel to the absorption dipoles of the switchable optical element 1 or 2 closest to the polarizer P,
• - and so that in a second operating mode B2 when the electric field EF2 is present, at least 24% of unpolarized light, which is incident perpendicularly to the switchable light filter 5, is transmitted and so that unpolarized light, which is at an angle of more than 30 degrees to the perpendicular bisector of the switchable light filter 5 incident on it, is absorbed by at least 85%, whereby this applies both in the horizontal and in the vertical direction at the same time, if the horizontal is oriented parallel to the lower edge and the vertical is oriented parallel to the left or right side edge of the layer S1, with in In this operating mode B2, the absorption dipoles of polarizer P, if present, and of the switchable optical element 1 closest to it are aligned perpendicularly and of the two optical elements 1 and 2, in each case parallel to one another.

Thus, the switchable light filter 5 of this second embodiment, in conjunction with an image display unit, allows switching between free viewing in all directions and four-sided privacy protection (free vision B3 vs. top/bottom/left/right protected B2).

• - ein nicht schaltbares, erfindungsgemäßes optisches Element 1,
• - einen Polarisationsfilter P der dem optischen Element 1 vor oder nachgeordnet ist,
• - eine zwischen dem optischen Element 1 und dem Polarisationsfilter P angeordnete Flüssigkristallschicht 3, die in Abhängigkeit von einem auf sie wirkenden elektrischen Feld EF1 oder EF2 die Polarisationseigenschaften des durch sie hindurchdringenden Lichtes beeinflusst,
• - zeichnerisch nicht dargestellte Mittel zum wahlweisen Erzeugen der besagten elektrischen Felder EF1 und EF2,
• - so dass in einer Betriebsart B1V oder B1H bei Anliegen des elektrischen Feldes EF1 unpolarisiertes Licht, welches senkrecht zum schaltbaren Lichtfilter 5 in diesen einfällt, zu mindestens 24% transmittiert und so dass unpolarisiertes Licht, welches in einem Winkel von über 30 Grad zur Mittelsenkrechten des schaltbaren Lichtfilters 5 in diesen einfällt, zu mindestens 85% absorbiert wird, wobei diese Absorption ausschließlich in horizontaler (Betriebsart B1H) oder ausschließlich in vertikaler Richtung (Betriebsart B1V) gilt, wenn die Horizontale parallel zur Unterkante und die Vertikale parallel zur linken oder rechten Seitenkante der Schicht S1 orientiert ist,
• - und so dass in einer zweiten Betriebsart B1H oder B1V bei Anliegen des elektrischen Feldes EF2 unpolarisiertes Licht, welches senkrecht zum schaltbaren Lichtfilter 5 in diesen einfällt, zu mindestens 24% transmittiert und so dass unpolarisiertes Licht, welches in einem Winkel von über 30 Grad zur Mittelsenkrechten des schaltbaren Lichtfilter 5 in diesen einfällt, zu mindestens 85% absorbiert wird, wobei dies entweder ausschließlich in vertikaler (Betriebsart B1V) oder ausschließlich in horizontaler Richtung (Betriebsart B1H) gilt, so dass die Absorptionsrichtung zwischen der ersten und der zweiten Betriebsart B1 jeweils um 90 Grad gedreht ist, wenn die Horizontale parallel zur Unterkante und die Vertikale parallel zur linken oder rechten Seitenkante der Schicht S1 orientiert ist.

A third embodiment of a switchable light filter 5, which is shown as a schematic diagram in 6 shown includes

• - a non-switchable optical element 1 according to the invention,
• - a polarization filter P which is arranged before or after the optical element 1,
• - a liquid crystal layer 3 arranged between the optical element 1 and the polarization filter P, which influences the polarization properties of the light passing through it depending on an electric field EF1 or EF2 acting on it,
• - Means, not shown in the drawing, for selectively generating said electric fields EF1 and EF2,
• - so that in an operating mode B1V or B1H when the electric field EF1 is present, at least 24% of unpolarized light, which is incident perpendicular to the switchable light filter 5, is transmitted and so that unpolarized light, which is at an angle of more than 30 degrees to the perpendicular bisector of the switchable light filter 5 incident on it, is absorbed by at least 85%, this absorption being valid exclusively in the horizontal (operating mode B1H) or exclusively in the vertical direction (operating mode B1V) if the horizontal is parallel to the bottom edge and the vertical is parallel to the left or right side edge the layer S1 is oriented,
• - And so that in a second operating mode B1H or B1V when the electric field EF2 is present, unpolarized light, which is incident perpendicularly to the switchable light filter 5, at least 24% is transmitted and so that unpolarized light, which is incident on the switchable light filter 5 at an angle of more than 30 degrees to the median perpendicular to the switchable light filter 5, is absorbed by at least 85%, with this either exclusively in the vertical direction (operating mode B1V) or exclusively in the horizontal direction ( Operating mode B1H) applies, so that the absorption direction is rotated by 90 degrees between the first and the second operating mode B1 when the horizontal is oriented parallel to the lower edge and the vertical is oriented parallel to the left or right side edge of layer S1.

The configuration of this third embodiment of a switchable light filter 5 can be switched between the operating modes B1V and B1H by rotating the polarization filter P by 90 degrees.

It is also possible here that, for example, either the electric field EF1 or the electric field EF2 describes a field-free state, with the respective other electric field EF2 or EF1 having an absolute field strength greater than zero, e.g. 0.5 MV/m.

Depending on the configuration of the optical element 1 and the polarization filter P, the field-free state can mean that the B1H operating mode is present. However, it is also possible that the B1V operating mode is present in the field-free state.

Thus, the switchable light filter 5 of this third embodiment, in conjunction with an image display unit, allows switching between vertical privacy protection and horizontal privacy protection (top/bottom protected B1V vs. left/right protected B1H). In a laptop, for example, this would mean that a user can view the content in B1V mode together with other people who are next to the user and who are essentially at the same eye level, while in B1H mode the people next to the side view the image content can't see.

The switchable light filter 5 of this third embodiment can be varied in its construction, as has been described above.

• - ein schaltbares optisches Element 1,
• - einen oberhalb oder unterhalb des optischen Elementes 1 angeordneten Polarisationsfilter P,
• - zeichnerisch nicht dargestellte Mittel zum Erzeugen elektrischer Felder EF1 oder EF2, wobei für das optische Element 1 mindestens zwei Zustände durch das jeweils anliegende elektrische Feld EF1 oder EF2 erzeugt werden,
• - so dass in einer Betriebsart B3, bei welcher die Absorptionsdipole der Schichten (S1, S2, ..) des optischen Elements 1 parallel zur Substratoberfläche des optischen Elements 1 und senkrecht zur Transmissionsrichtung des Polarisators ausgerichtet sind, unpolarisiertes Licht, welches in einem beliebigen Winkel zum schaltbaren Lichtfilter 5 in diesen einfällt, zu mindestens 25% transmittiert wird,
• - und so dass in einer Betriebsart B1H oder B1V, bei welcher die Absorptionsdipole der Schichten S1, S2, .. des optischen Elements 1 entlang der besagten Vorzugsrichtung ausgerichtet sind, unpolarisiertes Licht, welches senkrecht zum schaltbaren Lichtfilter 5 in diesen einfällt, zu mindestens 24% transmittiert und so dass unpolarisiertes Licht, welches in einem Winkel von über 30 Grad zur Mittelsenkrechten des schaltbaren Lichtfilters 5 in diesen einfällt, zu mindestens 85% absorbiert wird, wobei dies entweder in vertikaler (Betriebsart B1V) oder horizontaler in Richtung (Betriebsart B1H) gilt, wenn die Horizontale parallel zur Unterkante und die Vertikale parallel zur linken oder rechten Seitenkante der Schicht S1 orientiert ist.

Furthermore, a fourth, as a basic sketch in 7 shown embodiment of a switchable light filter 5

• - a switchable optical element 1,
• - a polarization filter P arranged above or below the optical element 1,
• - Means, not shown in the drawing, for generating electric fields EF1 or EF2, with at least two states being generated for the optical element 1 by the electric field EF1 or EF2 applied in each case,
• - So that in an operating mode B3, in which the absorption dipoles of the layers (S1, S2, ..) of the optical element 1 are aligned parallel to the substrate surface of the optical element 1 and perpendicular to the transmission direction of the polarizer, unpolarized light which is at any angle incident on the switchable light filter 5, is transmitted to at least 25%,
• - and so that in an operating mode B1H or B1V, in which the absorption dipoles of the layers S1, S2, .. of the optical element 1 are aligned along said preferred direction, unpolarized light, which is incident perpendicularly to the switchable light filter 5, to at least 24 % transmitted and so that unpolarized light, which is incident at an angle of more than 30 degrees to the perpendicular bisector of the switchable light filter 5, is absorbed by at least 85%, this being either in a vertical (operating mode B1V) or in a horizontal direction (operating mode B1H) applies when the horizontal line is oriented parallel to the bottom edge and the vertical line is oriented parallel to the left or right side edge of layer S1.

It is also possible here that, for example, either the electric field EF1 or the electric field EF2 describes a field-free state, with the respective other electric field EF2 or EF1 having an absolute field strength greater than zero, e.g. 0.5 MV/m.

Depending on the configuration of the optical element 1 and the polarization filter P, the field-free state can mean that the B3 operating mode is present. However, it is also possible that one of the operating modes B1H or B1V is present in the field-free state.

Thus, the switchable light filter 5 of this fourth embodiment, in conjunction with an image display unit, allows switching between visual protection in the vertical or horizontal direction and no visual protection effect (top/bottom protected B1V or left/right protected B1H vs. no visual protection B3).

For special applications, a switchable light filter 5--regardless of the aforementioned embodiment--can be divided into several separately switchable segments, so that it is possible to switch over locally between the respective possible operating states. In conjunction with an image display unit, this would mean that, for example, only a part of the image area can be switched between a visual protection (e.g. operating mode B1H or B2) and no visual protection effect (e.g. operating mode B3, possibly also B1V) for a clear view, while the complementary Part of the screen is permanently in a privacy mode (e.g. operating mode B1H or B2) or in no privacy mode (e.g. mode B3, possibly also B1V).

There can even be several such segments that are geometrically separate from one another and can be switched between the operating modes separately or together.

As already noted above, the invention acquires particular importance through the combination of a switchable light filter as described above with an image display unit to form a screen.

• - einen wie vorstehend beschriebenen schaltbaren Lichtfilter einer der vier genannten Ausgestaltungen, und
• - eine dem schaltbaren Lichtfilter von einem Betrachter aus gesehen nach- oder vorgeordnete Bildwiedergabeeinheit.

Such a screen, which can be operated in at least a first operating state B1V and/or B3 for a horizontally free viewing mode and in at least a second operating state B1H and/or B2 for a horizontally restricted viewing mode

• - a switchable light filter as described above, one of the four configurations mentioned, and
• - an image reproduction unit which is arranged upstream or downstream of the switchable light filter as seen from the perspective of an observer.

The image display unit advantageously corresponds to an LCD panel, one polarization filter of which corresponds to the polarization filter P. This can be the front or rear polarizer in the LCD assembly.

In addition, the switchable light filter can advantageously be arranged between the LCD panel and its backlight in order to switch between a first operating state B3 (or B1V) for a clear view mode and a second operating state B1H or B2 for a restricted view mode, because the light from the backlight due to the switchable light filter in the horizontal direction once focused (B2 or B1H) and once not focused (B3 or B1V). "Focusing" does not mean focusing in the manner of lenses, but a narrowing of the emission area or transmission depending on the angle of incidence.

Such a screen is advantageously used in a mobile device, a motor vehicle, aircraft or watercraft, in a payment terminal or in an access system.

It is possible to switch between the above-mentioned operating modes in order to protect sensitive data, i.e. to display them perceptibly for only one viewer, or alternatively to display image content for several viewers at the same time.

In principle, additional retardation films can also be used within the scope of the invention in order to be able to further adapt the polarization states. This applies to the aforementioned as well as to the embodiment of the invention described below.

However, the variety of applications for the optical element according to the invention does not end with applications for displaying image content with or without visual protection effects. Rather, other applications are possible if special properties of a lighting device are desired. Configurations of the optical element 1 in which defined polarization contrasts are generated are conceivable. These in turn can be used in the context of optical sensors.

• - mindestens ein Modul M1, M2, .. bestehend in dieser Reihenfolge aus einer ersten Linse oder einem ersten Linsenraster L1 mit Mikrolinsen, einem schaltbaren oder nicht schaltbaren erfindungsgemäßen optischen Element 1 wie weiter oben beschrieben, und einer zweiten Linse oder einem zweiten Linsenraster L2,
• - eine Lichtquelle LS,
• - einen optischen Detektor D,
• - optional einen Strahlteiler ST,
• - optional abbildende Optiken L3 und L4,
• - optional polarisationsrotierende Schichten 4,
• - wobei in einer ersten Alternative für eine optische Detektion in Transmission das Messgerät in der Reihenfolge Lichtquelle LS, erstes Modul M1, Objekt O, zweites Modul M2 sowie optischer Detektor D aufgebaut ist, und
• - wobei in einer zweiten Alternative für eine optische Detektion in Reflektion das Messgerät in der Reihenfolge Lichtquelle LS, Strahlteiler ST, erstes Modul M1 sowie Objekt O, aufgebaut ist, wobei hier der optische Detektor D zum Empfang von durch den Strahlteiler ST ausgekoppelten optischen Signalen geeignet neben den vorgenannten Komponenten angeordnet ist,
• - so dass der optische Detektor D polarisationsmaskierte optische Informationen detektieren kann, wobei für die Linse oder jede Mikrolinse des dem jeweils dem optischen Detektor D zugewandten Linsenrasters L1 des entsprechenden Moduls M1 oder M2 eine Polarisationsinformation vorliegt.

In this respect, the invention also includes a measuring device for the optical detection of properties of the surface and/or the volume of an object O, including

• - at least one module M1, M2, .. consisting in this order of a first lens or a first lens array L1 with microlenses, a switchable or non-switchable optical element 1 according to the invention as described above, and a second lens or a second lens array L2,
• - a light source LS,
• - an optical detector D,
• - optionally a beam splitter ST,
• - optional imaging optics L3 and L4,
• - optional polarization-rotating layers 4,
• - In a first alternative for optical detection in transmission, the measuring device is constructed in the order of light source LS, first module M1, object O, second module M2 and optical detector D, and
• - In a second alternative for optical detection in reflection, the measuring device is constructed in the order of light source LS, beam splitter ST, first module M1 and object O, with the optical detector D being suitable here for receiving optical signals coupled out by the beam splitter ST is arranged next to the aforementioned components,
• - So that the optical detector D can detect polarization-masked optical information, polarization information being present for the lens or each microlens of the respective optical detector D facing lens array L1 of the corresponding module M1 or M2.

For this shows 8th the basic sketch of a measuring device that works in transmitted light, using an optical element 1, and 9 the basic sketch of a measuring device that works in reflection, also using an optical element 1.

The transmission structure (transmitted light) is described below. To understand the structure, the optical elements that are necessary for the operating principle are first discussed. The light source LS can emit collimated light or light from Koehler illumination, other illumination modes are also covered by the invention. The desired polar polarization state is generated with the aid of the 4f system M1, in the center of which is the optical element 1 that generates the polar polarization. In the technical implementations, it is advantageous to also work with imaging optics (L3 and L4) in order to achieve higher resolutions, for example. Element 4, which can rotate polarization, is optional and can be used to optimize contrast.

Such a measuring device allows a wide range of applications for measuring surfaces, curvatures or anisotropic refractive indices, for example. In particular, the direction- and/or polarization-dependent weakening and/or polarization change of the light is used in order to make optical differences visible. Optionally, the measurement can also be carried out confocally with the measuring device according to the invention, for example in order to determine the scattering properties of particles.

The basic idea of the measurement is that the light is brought into the polar polarization state with the optical element 1. This light interacts with the sample, for example due to surface curvatures, surface roughness or anisotropic refractive indices, and the initial polarization is disturbed. After the second passage through the optical element 1, the light is attenuated in accordance with the polarization change. This weakening is detected by a surface sensor (e.g. CCD sensor, CMOS sensor, photo plate or similar) and can be converted into physical properties with a suitable model. The advantage lies in the speed of the method, since numerous propagation angles of the light are recorded simultaneously with one measurement and conclusions on directional dependencies are therefore possible.

This method can be used advantageously when measuring liquid crystal layers, for example. For this purpose, the measurement is carried out in transmission. The light is linearly polarized in relation to the surface normal for different angles of incidence α > 30°. As a result of the passage through a liquid crystal, the linear polarizations of the different angles of incidence are converted differently into elliptically polarized light due to the different orientation between the polarization of the light and due to the anisotropic refractive index, which with the help of the second optical element 1 is made visible. From this, the orientation of the main axes of the liquid crystal, rotations of the main axes, phase delays and tilt angles of liquid crystal layers can be determined.

In 10 is the schematic diagram of a measuring device that works in transmitted light, in a second embodiment using an optical element 1, is shown. The functionality is analogous to that in 8th was described.

The optical element described above, the switchable light filter and the measuring device solve the tasks set: First, an optical element was described in which the light that penetrates it depends on its direction of incidence and its polarization properties and explicitly - but not depending on its position - is transmitted or partially or totally absorbed. Furthermore, a switchable light filter using the optical element, which influences the transmission of light as a function of the angle (optionally perpendicular), was described, it being possible here to switch between at least two operating states. In particular, angular restrictions in the transmission can be switched in certain directions.

The optical element or systems based on it can be implemented inexpensively and can be universally used in particular with different types of screens in order to enable switching between a visual protection—at least in the horizontal direction—and a free viewing mode, with the resolution of such a screen not being reduced in principle . Furthermore, the optical element according to the invention can also be used for measuring applications, as described for the measuring device according to the invention.

The invention described above can be advantageously used in combination with an image display device wherever confidential data is displayed and/or entered, such as when entering a PIN or for data display at ATMs or payment terminals or for entering passwords or when reading emails on mobile devices Devices. As described above, the invention can also be used in passenger cars in order to selectively withhold disturbing image content from the driver or passenger.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• US 6765550 B2 [0004]
• US5993940A [0005]
• WO 2012/033583 A1 [0006]
• US 2012/0235891 A1 [0007]
• US2012/0235891 [0007]
• JP2007155783A [0008]
• US 2013/0308185 A1 [0009]
• WO 2015/121398 A1 [0010]

Claims (10)

Optical element (1), comprising, - at least one, preferably more than five layers (S1, S2, ...), - wherein each layer (S1, S2, ...) comprises material with a plurality of light-absorbing electric absorption dipoles which, in at least a first state, are oriented parallel to or fluctuate around a selectable preferential direction, said preferential direction having an angle between 0 ° and 45° to the surface normal of layer S1, - so that light which is incident on the optical element is transmitted or partially or completely absorbed depending on its direction of incidence relative to the layers (S1, S2, ...) and its polarization properties. Optical element (1) after claim 1 , characterized in that each of the layers (S1, S2, ...) is constructed non-periodically in its structure. Optical element (1) according to one of the preceding claims, characterized in that it is produced by lamination of a plurality of polymer film polarisers and/or by photoalignment of molecules or particles. Optical element (1) after claim 1 or 2 , characterized in that the light-absorbing electrical absorption dipoles in each layer (S1, S2, ...) can be varied in their orientation and/or their absolute value and/or in their density in order to adapt the respective layer (S1, S2, . ..) in at least two different states. Optical element (1) according to one of Claims 1 until 4 , characterized in that the switchable light filter (5) is divided into a plurality of separately switchable segments, so that local switching between the respective possible operating states is made possible. Optical element (1) according to one of Claims 1 until 5 , A polarization filter (P) being located in front of or behind the optical element (1) in the viewing direction. Screen which can be operated in at least a first operating state for a horizontally free viewing mode and in at least a second operating state for a horizontally restricted viewing mode, comprising - an optical element (1) according to one of Claims 1 until 6 , and - an image reproduction unit which is arranged upstream or downstream of the optical element (1) as seen from an observer. screen after claim 7 , characterized in that the image display unit is an LCD panel, one polarizing filter of which corresponds to the polarizing filter (P), if present. Using a screen after claim 7 or 8th in a mobile device, a motor vehicle, aircraft or watercraft, in a payment terminal or in an access system. Use of an optical element (1) according to one of Claims 1 until 6 with a static image or a dynamic image generator to make advertising content visible only in a limited field of vision.

Images