EP4302012A1

EP4302012A1 - Active module based on liquid crystals for adjustable car headlights and other lamps and a lamp with said module

Info

Publication number: EP4302012A1
Application number: EP21843798.6A
Authority: EP
Inventors: David SEC; Miha Ravnik; Urban MUR
Original assignee: Univerza v Ljubljani
Current assignee: Univerza v Ljubljani
Priority date: 2021-06-11
Filing date: 2021-12-01
Publication date: 2024-01-10
Also published as: WO2022260603A1

Abstract

The invention belongs to the field of optics, more precisely lighting devices. The invention relates to an active module based on liquid crystals (LC), which can change its optical properties in real time, wherein said module comprises: − a light source for emitting light for illumination, − at least one liquid crystal cell that partially or fully covers the light source, − an external field provided in, on, around the liquid crystal cell or at least partly enclosing it, for adjusting the state of the liquid crystal cell or the refractive index in the liquid crystal cell, − a control unit for controlling the external field, wherein said control unit is preferably connected to a light source and optional sensors that detect the surroundings of the active liquid crystal module, based on which the control unit is arranged to adjust the state of the liquid crystal cell based on algorithms of machine learning used to programme the control unit. The module has an undefined number of states, between which switching is triggered as a response to a sensed condition in the environment of the module.

Description

ACTIVE MODULE BASED ON LIQUID CRYSTALS FOR ADJUSTABLE CAR HEADLIGHTS AND OTHER LAMPS AND A LAMP WITH SAID MODULE

Field of the invention

The invention belongs to the field of physics, more precisely to the field of optics, namely to lamps in which the light generated by a light source is diverted by means of a system of lenses and reflectors. In the context of one of the possible ways of use, the invention also belongs to the field of vehicles, more precisely lighting and signalling equipment for vehicles, in particular headlights and fog lamps. The invention relates to a active module based on liquid crystals (LC), which can change its optical properties in real time, thus allowing any adjustable shape and intensity of the light beam, and a lamp provided with said liquid crystal module.

Background of the invention and the technical problem

A motor vehicle lamp typically comprises a light source, at least one reflector that reflects light from the light source, and a system of lenses that appropriately forms a beam. More advanced headlights use an Adaptive Front-Lighting System (AFS) and adjust the intensity and shape of the beam to the driving mode: e.g. (i) at lower speeds, the beam is wider to ensure better view of pedestrians and other traffic participants; and (ii) at higher speeds, typically above 100 km/h, the beam is much longer and narrower, thus better illuminating the road when driving on a motorway. AFS systems can use classic, HID (e.g., xenon lamps), LED lamps or laser light sources. Typically, the adjustment is performed through shifts of the light source and the system of lenses with electric actuators. Recent development is increasingly focused on selective switching on and off of source parts, such as (i) by selectively switching off individual parts of the light source; or (ii) by a device which acts as a projector and uses apertures to transmit only a certain part of the beam. Both ways upgrade the existing matrix LED technology, where the light beam is adjusted by turning individual LED segments on and off. The first way to selectively turn off parts of the source is to implement small pixel LED segments that can be turned on or off individually. The advantage over projector lights is lower energy consumption, as unused parts of the light source can be turned off. On the other hand, projector lights offer more flexibility and the ability to display complex patterns, such as navigation symbols, to the road surface. This can be achieved by local dimming of light using a liquid crystal aperture with a resolution of a few thousand pixels between the light source and the lens.

The invention is based on the problem of how to change a light beam into an arbitrarily spatially and temporally modulated shape in order to achieve the desired optical characteristics during operation and depending on certain external conditions. For this purpose, mechanical components such as moving mechanical mirrors known from patent application WO2014121315A1 or mechanically adjustable lenses described in patent application DE102019103898A1 can be used. Such solutions have a known disadvantage, they namely include many mechanical parts. Alternatively, liquid crystals can be used to direct light.

A technical problem that has not yet been satisfactorily solved is the modulation of a light beam into any shape by means of a liquid crystal module, so that the light is diverted and not dipped.

Prior art

Several ways of directing light based on liquid crystals have been described in the literature. One way of directing light with a liquid crystal module in car headlights is described in patent EP 2 013 536 B1 , which describes a special headlight unit comprising a sequence of several liquid crystal cells. Each cell has two states: a first state, which has the least possible effect on the light beam, and a second state, which refracts light beams according to the signal from the AFS headlight control unit. The two states are switchable by means of two electrodes. In this way, the emitted light beam is affected by adjusting it according to pre-prescribed modes. This achieves the inclination of the light up or down and the width of the emitted beam. Liquid crystal cells can have a surface relief, different shapes of electrodes, they can be anisotropically scattering cells, and several cells can be grouped in parallel lines.

Similarly, patent application WO 2018152644 A1 describes a device for AFS headlights based on a liquid crystal cell. Depending on the angle of rotation of the steering wheel and the perception of oncoming vehicles, the device can affect the width of the emitted light beam via the liquid crystal cell via an electric field, separately for the left and right headlights. Multiple consecutive cells can be combined to more accurately modulate light in two planes. The main disadvantage of this solution is that the beam propagates symmetrically on both sides and does not change its intensity distribution, which is usually not desirable.

Patent application DE 102016120222 A1 discloses a lighting device for a car headlight comprising a mechanical control and an additional light control. The light control can be a DMD (micro-mirrors), a liquid crystal display (LCD or LCoS type) or a laser scanner. By using a combination of mechanical control and light control, the light control operates in a smaller area and can be simpler and smaller and therefore cheaper, while mechanical control is not used for more frequent, fast and dynamic movements while driving and therefore extends its service life. Here, the device comprises both basic mechanical control and additional "fine" light control. In the case of a liquid crystal display, this control works pointwise and only changes the portion of transmitted light in each point.

Patent application EP 3501 896 A1 discloses a liquid crystal cell device that transmits a light beam of dipped lights smoothly and modulates only the light beam of full beam lights by determining the transmissivity of parts of the liquid crystal cell by means of an electric field. By dimming individual pixels of the cell, much of the light flux of the long beam is lost while the short beam remains unchanged and fixed. In this way, much of the light flux is lost and merely roughly transforms the emitted light beam.

All of the solutions described above are limited to a few predefined states, where they cannot affect the entire light beam at once, or require several consecutive cells to achieve this, which further reduces the light intensity and increases the complexity of the device itself. Modulation of the illumination of the source also reduces the overall light intensity, which is not desirable.

Description of the solution to the technical problem

The aim of the invention is construction of an active module based on liquid crystals which enables arbitrary and precise control of the light beam, the module having an indefinite number of states, between which switching will occur in response to the detected state in the vicinity of the lightning device, detected by said module. The active module based on liquid crystals comprises:

- A light source for emitting light for illumination,

- At least one liquid crystal cell at least partially covering the light source, wherein the light emitted from the light source can be converted into any shape with any intensity profile,

- An external field present in, on, around the liquid crystal cell or at least partly enclosing it, for adjusting the state of the liquid crystal cell or the refractive index in the liquid crystal cell,

- A control unit for controlling the external field, said control unit is preferably connected to a light source and optional sensors that detect the surroundings of the active liquid crystal module, based on which the control unit adjusts the state of the liquid crystal cell based on algorithms of machine learning used to programme the control unit.

The control unit comprising a computing processor unit, a memory and input and output modules and is adapted to actively in real-time: i. read and process an electrical signal from the sensors and the user's lighting settings, ii. recalculate settings of the external fields affecting the liquid crystal cells, and iii. send appropriate electrical signals to the system of electrodes and/or conductors and/or coils and/or irradiation lasers of the external field.

The light source can be any suitable light source, but preferably emits white, monochromatic or polychromatic light, which can be incoherent, partially coherent or coherent (laser). The liquid crystal cell at least partially covers the light source, but can cover it completely. It can also be configured in a movable manner to mechanically move based on the light source in known ways. There may be at least one or several light sources, in the latter case the sources may be the same or different.

The liquid crystal cell can be configured in different ways depending on the most appropriate use. The cell is preferably formed as a glass plan parallel cell, but may be flat, curved, of various thicknesses, layers, or from an emulsion of liquid crystals in a host medium. The cell can also be wedge-shaped, made of several layers, it can have a profiled surface or surfaces, or a cell with wells. The surface of the cells can be of any form, smooth or patterned. The surfaces of cells and colloidal particles or dispersed components can impose any surface orientation arrangement of liquid crystal molecules. The arrangement can be perpendicular, planar, degenerate planar, tilted and degenerate tilted. This orientation coincides with the local optical axis of the liquid crystal and affects the flowof light. The cell may contain various types of birefringent liquid crystals that allow controlled guiding, modulation and scattering of light, the liquid crystal being selected from the group of nematic liquid crystals, cholesteric liquid crystals, smectic liquid crystals, chiral nematics, liquid crystal dispersions with polymers or combinations thereof. The liquid crystals can also be in drops or in an emulsion.

Additionally, to improve the optical properties or response to the external field, the liquid crystal may be doped with particles or nanoparticles of various dimensions, shapes and optical material properties, such as dielectric, conductor, ferromagnet. Colloidal particles that can be used to dope liquid crystals can be of various sizes, for example from 1 nm to 10 pm, and shapes, such as spherical, cylindrical, ellipsoidal, toroidal with or without slit, flat, conical and their derivatives.

To achieve various complex patterns in the liquid crystal that would affect the guiding of light, the cell can be equipped with a suitable pump that allows creating a flow of the liquid crystal in the cell, which can alternatively be achieved by an external field that causes the movement of particles, with which the liquid crystal is doped. The properties of the liquid crystal in the cell change due to the external field that is a part of the module according to the invention. Namely, the external field influences the orientation of the liquid crystal in the cell and thus affects the direction of the light emitted by the source. The external field can be electric, magnetic or laser, which is a combination of the electric and magnetic external fields, however, a combination of the said fields may also be used. The external electric field is applied via arbitrarily arranged electrodes outside, on the surface and/or inside the liquid crystal cell. The electrodes may be on one or more cell surfaces and may form various geometric patterns such as lines, a grid, and the like. Possible electrode types include (i) a light- transparent or opaque electrode, or (ii) an electrode system in which the electrodes can be individually controlled. The external magnetic field is applied through current- carrying conductors of various shapes such as straight conductors, wires, coils, either outside, on the surface, or inside the cell. Conductor types include (i) a light- transparent or opaque conductor, or (ii) a conductor system in which the conductors can be individually controlled. The combined electric and magnetic field can also be created by irradiating the cell with laser light from an external laser. The external laser must be oriented into the liquid crystal cell, so that the EM field can change the LC arrangement and thus the local refractive index. Laser light can be linear, circular or otherwise polarized. The focus of the laser is adjustable based on the cell, the same goes for the optical aperture and the intensity cross-section of the laser beam. The control unit is suitably connected to the external field so that the external field can affect the liquid crystal cell with respect to the desired illumination, i.e., distribution of light by locally reducing the intensity of light in one place by diverting it to another place.

The control unit comprises a computing processor unit, a memory and input and output modules. This control unit actively in real time (i) reads and processes the electrical signal from at least one sensor, preferably multiple sensors and lighting settings by the user, (ii) then recalculates the settings of the external fields affecting the liquid crystal cells, and (iii) sends appropriate electrical signals to the system of electrodes and conductors and irradiation lasers. Thus, the control unit creates complex patterns of liquid crystal orientation in the cell via external fields and influences the optical properties of the cell. The control unit can also modify the output intensity profile by changing the brightness of the source. In the case of an electric or magnetic field, it is for instance connected to electrodes via analogue voltage or current outputs.

The module according to the invention does not have pre-set (pre-defined) states between which the external field would switch, but adjusts the brightness, the shape of illumination and the intensity distribution based on the detected exterior (environment, surroundings) of the module, which is enabled by the control unit. For this purpose, suitable sensors are preferably used, which are coupled or connected to the control unit, and are used to detect the surroundings, such as the shape and course of the road, other traffic participants and other special features such as traffic signs, road damage, animals and the like. Sensors may, inter alia, include photo detectors, radar sensors, TOF cameras, photo cameras, thermal imaging cameras, gyroscopes and accelerometers, speedometers, GPS sensors, internet connection sensors, and the like, or any combination thereof. The control unit can also read data from other sensors in the vehicle or external data obtained via the network and other vehicles. The user-defined lighting settings determine the input signal for the control unit that corresponds to the required lighting intensity profiles, such as a profile of dipped light, full-beam or fog lights, or a combination of two or a combination of all three. Based on the electrical signal from the sensors and predefined parameters of the external fields for achieving standard intensity profiles, the control unit calculates the required external field, thus creating the desired output intensity profile depending on the environmental conditions (e.g., slope and course of the road, other traffic participants).

The active liquid crystal module according to the invention is preferably provided with a feedback loop, namely a light distribution sensor connected to the control unit that checks if the illumination is adequate with respect to the desired illumination. If the control unit detects inadequate illumination, the control unit recalculates the necessary changes and rearranges the settings of the external field that affects the liquid crystal cell. The control unit further corrects and modifies the external fields, also through interaction with dopants and the current, by diverting the light from the areas where the actual intensity is greater than desired to the areas where the actual intensity is lower than desired, thus approximating the actual intensity distribution to the desired one. The modifications are achieved by differently switching on and off suitable electrodes, coils, conductors or other components of the external field, thus affecting the local refractive index of the liquid crystal.

The computing processor unit uses machine learning and artificial intelligence algorithms to determine external fields, it can inter alia use algorithms of neural networks and their derivatives and generalizations to perform computationally complex operations to calculate the distribution of external fields needed to achieve the desired liquid crystal orientation profile in the cell. Machine learning and artificial intelligence methods use model-based synthetic and real-time data for learning. In the machine learning process, a set of fields with real models is generated, where a director field is calculated on the basis of the electric field and an optical field is created. The electric field and the optical image are then the input data for the neural network, and the computing processor unit then learns with a plurality of input data thus generated how to adjust the external field to achieve the desired form of illumination. When the illumination is adjusted according to the situation, it can be further optimized with the feedback loop. The algorithms in the control unit can be upgraded during the period of use, if necessary.

Through the above-mentioned sensors, the control unit recognizes a situation and connects it with the learned patterns using machine learning algorithms, so that it can detect and recognize the surroundings and divert the light accordingly or adjust the distribution of light intensity by illuminating or dimming certain areas, e.g., oncoming vehicles, pedestrians and traffic signs. It adjusts the lighting by adjusting the external field accordingly, which is calculated based on the learned situations. The control unit may additionally communicate with the driver and other traffic participants by divert part of the light of greater or lesser intensity or a different colour or projecting any light pattern onto the surface in front of the vehicle. The diverted part of the light can also indicate the movement of traffic participants predicted by the control unit. The control unit can further be connected to and communicate with other networks, such as vehicle positioning networks, and in the same way project on the surface in front of the vehicle e.g., travelling directions. Additionally, the control unit can use the connection to the vehicle positioning networks to predict the route of the vehicle (e.g., the road turns a bend). Even such adaptation is machine-learned as described above.

Optionally, the module is provided with additional optical elements that further passively affect the light distribution without active adjustment via the control unit. Additional optical elements include lenses, mirrors, translucent mirrors and lenses, polarizers, phase plates, optical fibres, and waveguides.

The module, as described above, can be built into new lightning devices, especially vehicle headlights, or existing ones by simply adding it to an existing lightning device or is used as a replacement for parts of lightning devices (e.g., lens). Additional optical elements may be part of an existing headlight in which the module according to the invention is installed.

The active module based on liquid crystals according to the invention and the lightning device provided therewith enable the creation of any shape of the beam without predetermined discrete states, continuous switching between states and real-time change of the beam according to detected external conditions and user settings. This is especially suitable for illuminating different scenarios while driving, e.g., other vehicles and traffic participants in order to either reduce the blinding of others or attract the driver's attention, as well as the display of complex patterns on the road surface, such as navigation symbols.

The active module based on liquid crystals for adjustable car headlights and other lightning devices and lightning devices provided with said module will be described in further detail based on exemplary embodiments and figures, which show:

Figure 1 An active module based on liquid crystals according to a possible embodiment Figure 2 Demonstration of three examples of illumination with an active module based on liquid crystals, namely in the case of a) a combination of full-beam and dipped head-lights, b) a combination of full-beam and additionally shortened beam in the opposite lane where another vehicle is approaching, and c) display of warning signs when a traffic sign and a pedestrian walking along the roadway are detected.

The active module based on liquid crystals according to the embodiment shown in Figure 1 comprises:

- a light source 4 emitting light for illumination,

- an active element based on liquid crystals 1 comprising a liquid crystal cell that overlaps the light source 4, wherein the emitted light from the light source 4 can be converted into any shape with any intensity profile, and an external field, which at least partly encloses the liquid crystal cell for adjusting the state of the liquid crystal cell or the refractive index in the liquid crystal cell,

- a control unit 2 that allows control of the external field and is connected to the light source 4, the active liquid crystal element 1 and/or its external field and optional sensors 6 that detect the surroundings of the active liquid crystal module, based on which the control unit 2 is arranged to adjust the state of the liquid crystal cell in agreement with the algorithms of machine learning 5 used to program the control unit 2. The machine learning algorithms include input data for beamforming, such as daytime lights, fog lights, high beams, and the like.

The external field is preferably an electric field defined by electrodes arranged in, on or around the liquid crystal cell. The electrodes may be on one or more cell surfaces and may form various geometric patterns such as lines, a grid, and the like.

The active element based on liquid crystals 1 arbitrarily diverts the light from the source 4. When the external field is switched off, the basic state of the liquid crystal cell can be such that the light beam has the same shape as in usual dipped lights. Thus, in the event of a system failure, the headlight is still safely used even in road traffic, wherein no energy is consumed during use of dipped lights.

When the environment is suitably changed, the module provides dipped headlights, full-beam lights and fog lights in just one device, by creating patterns that are on the one side equal to the full-beam light, on the other side to usual dipped lights, so that the driving lane is illuminated to a larger distance than the opposite lane, on which another vehicle can drive (Figure 2a). As the module can adjust the illumination mode, a lightning device provided with such module does not need a separate assembly for full-beam lights, dipped lights or fog lights, which simplifies vehicle lighting elements.

In addition, the module allows diversion of light from certain areas e.g., in the case of oncoming vehicles (Figure 2b) or diversion to certain areas, e.g., pedestrians or traffic signs and the projection of arbitrary symbols (2c), thus contributing to an increased passive safety of traffic participants. When the sensors detect an oncoming vehicle in the opposite lane, the control unit calculates the necessary changes in the external field based on the patterns learned during machine learning, so that the light beam in the driving lane is further shortened to prevent blinding the driver of the oncoming vehicle as shown in Figure 2b.

The control unit may also create such an external field that can display various signs in front of a vehicle, such as a triangle symbol for a detected traffic sign and/or a pedestrian symbol when a pedestrian walking along the roadside is detected, as shown in Figure 2c. If a pedestrian is detected at the roadside, the light is partially diverted onto him, so that the driver of the vehicle can see him well. The pedestrian is illuminated with dipped lights, so he is not blinded. A detected traffic sign on the other side of the road is additionally illuminated, so that the driver can better see what the sign is showing and adjust driving accordingly. Such conditions are not pre programmed but are adjusted in real time with the control unit and/or the external field. When the pedestrian and/or sign is out of the field of view, the light beam changes again, so that the illumination is as optimal as possible depending on the driving situation.

Claims

Patent claims

1. An active module based on liquid crystals (LC) for adjustable car headlights and other lightning devices, characterized in that the module comprises:

- a light source for emitting light for illumination,

- at least one liquid crystal cell at least partially covers the light source, wherein the light emitted from the light source can be converted into any shape with any intensity profile,

- an external field provided in, on, around the liquid crystal cell or at least partly enclosing it, for adjusting the state of the liquid crystal cell or the refractive index in the liquid crystal cell,

- a control unit for controlling the external field, wherein said control unit is preferably connected to a light source and optional sensors that detect the surroundings of the active liquid crystal module, based on which the control unit is arranged to adjust the state of the liquid crystal cell based on algorithms of machine learning used to programme the control unit, wherein the module has an undefined number of states, between which switching is triggered as a response to a sensed condition in the environment of the LC module.

2. The module based on LC according to claim 1 , characterized in that the control unit comprises a computing processing unit, a memory, input and output modules and is arranged to actively and in real-time:

(i) read and process an electrical signal from sensors and user's lighting settings,

(ii) recalculate settings of the external fields affecting the liquid crystal cells, and

(iii) send appropriate electrical signals to a system of electrodes and/or conductors and/or coils and/or irradiation lasers of the external field.

3. The active module based on LC according to claim 1 or claim 2, characterized in that the external field is electric, magnetic and/or laser field or a combination thereof, which continuously changes LC arrangement and does not dim the light, but locally divertsthe light.

4. The active module based on LC according to claim 3, characterized in that the external field is defined with electrodes, electrical conductors and wires, laser sources, coils installed inside the LC cell, on the surface of the LC cell or near the LC cell.

5. The active module based on LC according to claim 4, characterized in that used electrodes and electrical conductors have an arbitrary shape and are optically transparent or opaque and are controlled individually or as group.

6. The active module based on LC according to any of the preceding claims, characterized in that is provided with an integrated feedback loop, which comprises sensors for sensing distribution of the light intensity emitted from the LC cell, wherein the sensors are connected to the control unit, so that the feedback loop functions in the following way: a light distribution sensor connected to the control unit checks if the distribution of light intensity, obtained information is sent to the control unit, which is arragend to adjust the external field if necessary, so that the LC cell can change the distribution of light intensity if needed.

7. The active module based on LC according to any of the preceding claims, characterized in that sensors sense the shape and course of the road, other traffic participants and other objects, such as traffic signs, road surface damage, and the sensor may be a photo detector, a radar sensor, a TOF camera, a photo camera, a thermal imaging camera, a gyroscope and accelerometer, a speed meter, a GPS sensor, a sensor for internet connection or any combination thereof.

8. The active module based on LC according to any of the preceding claims, characterized in that the liquid crystal is selected in a group consisting of nematic liquid crystals, chiral nematics, smectic liquid crystals, combinations thereof and liquid crystal dispersions with polymers.

9. The active module based on LC according to the preceding claim, characterized in that the liquid crystal is doped, for example with nanoparticles.

10. The active module based on LC according to any of the preceding claims, characterized in that the active LC module has several different light sources with different wavelengths for projecting an arbitrary light source on the surface in front of the vehicle with a higher intensity or a different colour.

11. The active module based on LC according to any of the preceding claims, characterized in that the active module based on LC further comprises a module for wireless internet connection.

12. A lightning device comprising an active module based on LC according to any of the preceding claims.

13. The lightning device according to the preceding claim, wherein the lamp is a car light or a projector.

14. The lightning device according to the preceding claim, wherein the light is a car light provided with the active module based on LC according to any claim from 1 to 10 as an additional optical element for diverting light.

15. The lightning device according to claim 12 or 13, wherein the basic state of the active module based on LC is such that the light intensity is the same as in usual dipped lights.