TWI705268B - Liquid crystal beam control device with improved zone transition and method of manufacture thereof - Google Patents

Abstract

A liquid crystal optical device is described configured to provide variable beam steering or refractive Fresnel lens control over light passing through an aperture of the device. The device includes at least one layer of liquid crystal material contained by substrates having alignment layers. An arrangement of electrodes is configured to provide a spatially varying electric field distribution within a number of zones within the liquid crystal layer. The liquid crystal optical device is structured to provide a spatial variation in optical phase delay with a transition at a boundary between zones which is an approximation of a sawtooth waveform across the boundaries of multiple zones. The arrangement of electrodes, device layered geometry and methods of driving the electrodes increase the effective aperture of the overall optical device.

Description

Liquid crystal beam control device with improved zone transition and manufacturing method thereof Related application

This application claims priority for US provisional patent application No. 62/216,951 filed on September 10, 2015, and PCT patent application No. PCT/CA2015/051222 filed on November 24, 2015, all of which The content is incorporated herein by reference.

The disclosure of this application relates to liquid crystal optical devices, such as lenses and beam steering devices, which have adjacent segments or regions, and their manufacturing methods.

It is a known technology to use a beam steering device and a Fresnel lens of nematic liquid crystal cells, which are dynamically controlled by a controlled electric field, and have separate cell areas. These devices have spatial changes in refractive index due to spatial changes in the orientation of liquid crystal molecules. This produces a spatial variation of the optical phase delay, which can produce beam steering devices and Fresnel lenses. Liquid crystal beam control devices are well known in the art.

Such devices usually use patterned electrodes on liquid crystal cells to create a spatial variation of refractive index for controlling the beam. To keep the voltage low, electrodes can be placed on the inside or both sides of the unit substrate. In order to improve optical performance, the size or aspect ratio of the beam adjustment unit defined by the patterned electrode may be small. To provide a device with a large light through hole, multiple beam steering elements are arranged together, much like a Fresnel lens or beam steering device. In the liquid crystal beam steering device, the boundary between adjacent beam steering elements can occupy a large part of the light through hole, for example, up to 50%, because from one side of the boundary to the other side, the change in the orientation of the liquid crystal almost reaches 90 degrees.

Unlike a physical (fixed) Fresnel lens or beam steering device, it can have different parts (referred to herein as "micro-elements". It should be understood that this part or micro-elements are not necessarily limited to very small sizes). With the sudden change of refractive index on the boundary between ), in the case of controlling the orientation of liquid crystal molecules with an electric field, it is difficult to realize a sharp change in the orientation of liquid crystal molecules caused by the electric field. This will result in a relatively large portion of the optical through hole of the optical device that cannot be used for the desired optical operation of the device. This part can be referred to as the "fly back" zone or non-linear zone (NLZ).

There are also various problems, including the range of angle control, the quality of the beam intensity distribution, the cost of manufacturing, the operating voltage and so on. When the boundary between adjacent micro-elements cannot be properly controlled, the useful part of the optical device is reduced due to improper control of the boundary area of the liquid crystal.

The applicant has discovered a lot of relevant light beam steering liquid crystal The characteristics of the optical performance of the device.

The applicant proposes a liquid crystal optical device to realize a spatial variation of optical phase retardation with a sudden transition at the boundary between microelements, which cannot be realized using the electric control field electrode system of a conventional liquid crystal optical device. This phase delay distribution can be an approximate saw-tooth waveform at the boundary of a plurality of micro-elements. The phase delay distribution on the optical through hole does not have to be a saw-tooth waveform. However, the ideal result is that the phase delay is spatially compressed or suddenly changed in the boundary area, similar to a saw-tooth waveform. The applicant also proposed a liquid crystal optical device to improve the electric field control of the liquid crystal at the boundary between the microelements. This reduces incorrect steering (redirection) or focusing of light, and it also increases the effective light through hole of the optical device.

A combination of low-frequency and high-frequency electric fields can be used on dual-frequency liquid crystals to achieve an improved phase retardation transition at the boundary between microelements.

Floating electrodes can be used for shaping the electric field within the micro-elements to achieve an improved phase delay transition at the boundary between the micro-elements.

A pair of liquid crystal layers can be used, each liquid crystal layer having microelements separated by an optically inert area, which corresponds to the optically inert area and another layer of microelements, so that the electric field acts on the liquid crystal of the microelements, but not on the inert area , To achieve an improved phase delay transition at the boundary between the lens and/or steering element.

The conductive walls arranged between the liquid crystal microelements can be used to achieve an improved phase retardation transition at the boundary between the lens elements, Therefore, the electric field acting on the liquid crystal of one micro element will not act on the liquid crystal of the adjacent micro element.

The improved phase delay transition at the boundary between the lens and/or the steering element can be achieved by applying electrical signals with phase difference to the electrodes of the liquid crystal micro-element, so that the electric field acting on the liquid crystal of a micro-element is reduced. A part of the direction is guided to the direction of the liquid crystal layer. As a result, the electric field generated by the electrodes of the adjacent micro-elements has a small influence on the phase retardation distribution. The voltage difference between the electrodes of the micro-elements can also be used to achieve the required interaction between the electric field and the liquid crystal control.

The applicant has found that the bias between the strip electrode on one side of the liquid crystal cell and the wider intermediate electrode on the opposite side of the liquid crystal cell can achieve an electric field distribution suitable for beam steering, that is, a sawtooth distribution. The result of this electrode geometry is the formation of a strong electric field on the liquid crystal cells near the strip electrodes, and a gradually weakening electric field on the liquid crystal cells extending on the middle electrode. The bias makes the electric field lines of the electric field extending from the strip electrode substantially perpendicularly pass through the cell surrounding the opposite side of the middle electrode. The lines of the electric field pass through the liquid crystal quite perpendicularly, and the electrode structure is not provided with a weakly conductive layer, or there is no large distance between the opposite electrodes.

This electrode arrangement provides a beam-turned liquid crystal distribution, in which no effective electrode is provided on the opposite side of the strip electrode of the liquid crystal, but a wider middle electrode is provided. To achieve beam steering on the entire light through hole, two layers of liquid crystals can be arranged as one layer with spaced beam steering liquid crystal elements aligned with the other layer with free or non-beam steering liquid crystal elements.

The direction of turning can be changed by using an additional intermediate electrode (so that the orientation distribution of the beam turned to the liquid crystal is formed in other directions), or an additional strip electrode can be arranged on the opposite side of the intermediate electrode.

The applicant has also discovered that this bias electrode structure can provide a good effective light through hole for a beam steering device with a single-layer structure, which uses time multiplexed control electrodes. Therefore, when the electrodes of the odd-numbered elements are energized, the electrodes of the even-numbered elements can be disconnected, that is, electrically floating; and when the electrodes of the even-numbered elements are energized, the electrodes of the odd-numbered elements can be disconnected, that is, electrically floating.

Applicants have also discovered that when the electric field is different near one substrate and another substrate of the liquid crystal cell, the optical performance of the device may depend on the direction of light propagation through the device, for example, from top to bottom versus bottom to top. The difference caused by the different light propagation directions through the device is very significant for certain geometric shapes or designs of the device.

The applicant has also discovered that patterned electrode arrays in different directions (for example, orthogonal) can be separated by a thin insulating layer on a common substrate, and a single layer of liquid crystal (polarization direction controlled by the layer) is used to provide bidirectional beam control. This device can provide beam control independently in all directions.

3‧‧‧Electric field

4‧‧‧Liquid crystal molecules

10‧‧‧Beam steering LCD device

12a, 12b, 12c, 12d, 12e‧‧‧Area, section

13‧‧‧Floating electrode

14a‧‧‧Electrode, narrow electrode, electrode segment

14b, 14c‧‧‧Boundary electrode, control electrode

14d‧‧‧electrode, control electrode

14e, 14f‧‧‧electrodes, drive electrodes, control electrodes

15‧‧‧Plane electrode

16‧‧‧layer, conductive layer, high resistance layer

17‧‧‧Conductive wall

18‧‧‧Light through hole

19‧‧‧Transparent Wall

20‧‧‧Drive circuit

22, 24, 26‧‧‧Drive

100‧‧‧device

110‧‧‧LCD device

111‧‧‧Substrate

114、114A‧‧‧Strip electrode, electrode

114B‧‧‧electrode

115‧‧‧Transparent plane electrode, electrode

118‧‧‧Orientation layer

120‧‧‧Liquid crystal layer

120a, 120b‧‧‧LCD

122‧‧‧filling

The present invention will describe the embodiments in detail with reference to the attached drawings to better understand the implementation of the present invention, in which: Figure 1 is a prior art liquid crystal beam steering device with two areas or beam steering micro-elements A schematic cross-sectional view of a part, wherein the control of the electric field is realized by a large number of electrodes to improve For a spatially variable electric field; Figure 2 is a schematic cross-sectional view of a part of a prior art liquid crystal beam steering device with two areas or beam steering micro-elements, wherein the electric field is controlled by each area Two electrodes and a layer of high-resistance material help spread the electric field in each area; Figure 3 is a schematic cross-sectional view of a dual-frequency liquid crystal (DFLC) beam steering device with two areas or beam steering elements, where, The control of the electric field is realized by two electrodes in each area and a layer of high-resistance material to control the extension of the electric field in each area, wherein high-frequency electrical signals are input to the electrodes to make the local parts of the liquid crystal The orientation is perpendicular to the non-local local orientation of the liquid crystal under a lower frequency electric field; Figure 4 is a graph that simulates the phase retardation caused by the orientation of the liquid crystal as a function of the distance between the electrodes in the embodiments in Figures 2 and 3 , Showing the non-linear region (NLZ) in two cases; Figure 5 is a schematic cross-sectional view similar to Figure 3, where each region has two electrode strips with frequency f1; Figure 6 is The schematic diagram of the device in Figure 5 is a plan view with five areas connected to the drive circuit; Figure 7A is a schematic cross-sectional view across adjacent areas or beam steering elements in the LC beam steering device, where according to the proposed The solution is that the electric field is controlled by two control electrodes in each area and a conductive wall set in the transition area; Figure 7B is the LC beam steering device shown in Figure 7A across adjacent areas Or a schematic cross-sectional view of the beam steering element, which According to the proposed solution, the control of the electric field is enhanced by using a layer of weakly conductive material to extend the electric field in each area; Fig. 7C shows another LC as shown in Fig. 7B A schematic cross-sectional view of a beam steering device, according to the proposed solution, with an electrically floating electrode.

Figure 8A is a schematic cross-sectional view across adjacent areas or beam steering elements in the LC beam steering device. According to the proposed solution, the electric field is controlled by a control electrode in each area, where A wide optically transparent wall is used to extend to every other element area; Figure 8B is a schematic cross-sectional view across adjacent areas or beam steering elements in the LC beam steering device shown in Figure 8A, where according to the proposed Solution, the control of the electric field is enhanced by using a layer of weakly conductive material to extend the electric field in each area; Figure 8C is a schematic diagram showing another LC beam steering device as shown in Figure 8B Sexual cross-sectional view, according to the proposed solution, with an electrically floating electrode.

Figure 9A is a schematic cross-sectional view of a double LC beam steering device that spans adjacent areas or beam steering elements. According to the proposed solution, the electric field is controlled by one control electrode in each area. Among them, staggered, wide optically transparent walls are used to extend to each other element area; Figure 9B is a schematic cross-sectional view across adjacent areas or beam steering elements in the LC beam steering device shown in Figure 9A, which According to the proposed solution, the control of the electric field is enhanced by using a layer of weakly conductive material to extend the electric field in each area; Fig. 9C shows another LC as shown in Fig. 9B A schematic cross-sectional view of the beam steering device, according to the proposed solution, which has an electrically floating electrode; Figure 10A is a schematic cross-sectional view across a single area or beam steering element in the LC beam steering device, where according to The proposed solution is that the device has two working electrodes driven by drive signal components of the same frequency, phase and amplitude in the non-steered state; Figure 10B is the LC beam steering device as shown in Figure 10A across a single area or A schematic cross-sectional view of the beam steering element, in which, according to the proposed solution, the two working electrodes are driven by drive signal components with the same frequency and phase but with opposite amplitudes; Figure 10C is the LC as shown in Figure 10A A schematic cross-sectional view of a beam steering device that spans a single area or beam steering element, in which, according to the proposed solution, two working electrodes are driven by drive signal components with the same frequency and phase but with different opposite amplitudes; Figure 11 is a schematic cross-sectional view of a beam steering optical device. According to the proposed solution, it has a patterned electrode with 4 beam shaping units in a liquid crystal cell, where the strip-shaped electrode is on a substrate and the plane The electrodes are on the opposite substrate of the unit; Figure 12 is a schematic cross-sectional view of the beam steering optical device. According to the proposed solution, it has 4 beam shaping units in the liquid crystal cell, of which the strip electrode is on one of the unit On the substrate, to shape A plane and fringe electric field between the electrodes; Figure 13A is an enlarged view of a variant of a cell as shown in Figure 12, in which, according to the proposed solution, the aspect ratio of the strip electrode gap and the cell thickness gap Figure 13B is a modified enlarged view of one element of the cell as in Figure 12, in which, according to the proposed solution, the aspect ratio of the strip electrode gap and the cell thickness gap is small; Figure 13C Figure is an enlarged view of one element of the unit of Figure 12 according to an embodiment of the proposed solution; Figure 14 is a schematic plan view of the element of Figure 13C, according to the proposed solution, in which the liquid crystal orientation is parallel to the strip 15A is a schematic cross-sectional view of a liquid crystal beam steering device with two liquid crystal cells, according to the proposed solution, in which the strip electrode is powered on a substrate, and the biased middle electrode is grounded, the upper part The odd-numbered element of the cell has a middle electrode, while the even-numbered cell does not have a middle electrode; the even-numbered element of the lower cell has a middle electrode, while the odd-numbered cell does not have a middle electrode; Figure 15B shows a modification as in Figure 15A, according to the proposed solution The scheme, where the bias is such that the middle electrode extends outwards, and the strip electrodes are biased inward; Figure 16 is based on the proposed solution, such as the electric field lines in Figure 15A and the reorientation of the liquid crystal derived from the simulation Figure 17 is a simulation of the optical phase delay as a function of the position across the device in Figure 15A according to the proposed solution Figure 18A is a schematic cross-sectional view of a single liquid crystal cell beam steering device. According to the proposed solution, it can be operated in a time multiplexed manner to provide each element in the device The optical phase delay distribution (i.e. odd and even) of the beam steering is shown as the working state of odd-numbered elements; Fig. 18B is the same diagram as Fig. 18A, which shows the working state of even-numbered elements according to the proposed solution Figure 19 is an embodiment according to the proposed solution, showing the simulation results of the structure of Figures 18A and 18B; Figure 20 is a schematic plan view of the strip electrode array according to an embodiment of the proposed solution , Which has a variable gap or pitch between the strip electrodes; Figure 21 shows a schematic cross-sectional view of the optical axis orientation: at the top, a cross-section of a conventional refractive Fresnel lens; in the middle, optical The cross-section of the geometry of the device, which corresponds optically to a conventional refractive Fresnel lens, includes four stacked LC layers to reduce the sensitivity or aberration of incident light passing through the entire device, where the incident light is not parallel to The optical axis of the entire device; and at the bottom, a schematic diagram showing a plan view of the liquid crystal lens, according to the proposed solution, which has a circular geometric shape in the middle, which includes a central circular micro-elements and four Concentric ribbon-shaped micro-elements; and Figure 22 is based on the proposed solution, as shown in Figure 21 A schematic plan view of the device shown in the figure, wherein similar features in each figure use similar reference numerals. The order of the described layers is meaningful, and the definitions of "top" and "bottom" in this specification are only for reference in the directions in the drawings of this application, and do not mean any absolute spatial directions.

Cross-plane field control

Figure 1 shows a beam steering liquid crystal device 10, which has two regions or sections 12a and 12b. Liquid crystal materials are arranged between the substrates to form light through holes, and are closed in their edges (not shown). The electric field is provided by the narrow electrodes 14a (for example, arranged in strips, as shown in FIG. 6), each of which has the required voltage supply, and is arranged opposite to the planar electrode 15. In this embodiment, the electrodes are provided on the substrate in the cell. This can reduce the required voltage while enabling electrodes to be arranged on the outside of the cell, for example on the opposite side of a relatively thin substrate.

It is known in the art that the electrodes of the transmissive liquid crystal device may be transparent, such as a coating made of indium tin oxide (ITO) material. The approximate voltage shown (at the top of the figure) increases from zero or a minimum on one side of the area 12a, and starts to increase again on the other side at the area boundary of the area 12b. The driving frequency can be the same for all the electrodes 14a, and the liquid crystal molecules 4 are automatically positioned parallel to the electric field 3. Although the driving signal of the liquid crystal cell is usually an AC signal, in some cases, it should be understood that a low-voltage DC signal can also be used.

The orientation layer on the cell wall (not shown) maintains the ground state nematic The liquid crystal molecules are aligned in one direction, as shown in the figure. Such alignment layers (such as rubbed polyimide) are well known in the art.

。因此，需要減小寬度w。 The width of the region 12 is'w', and the beam turning angle θ of the region increases with the change value δ n of the refractive index of the liquid crystal material at the relatively extreme of the region 12 and the thickness of the cell L, but it increases with the width'w' Increases and decreases, namely

. Therefore, the width w needs to be reduced.

Electric field lines extend from areas of voltage difference, and the intensity of the electric field decreases with the distance from these areas. The electric field lines (corresponding to the above-mentioned change section) are schematically shown as dashed lines in Figure 1, and different line widths correspond to different electric field strengths. When the voltages applied to the electrode segments 14a are equal, and the plane electrodes 15 are at a common voltage or ground voltage, the electric field in the cell is basically uniform (no voltage change), and the electric field lines are basically It is perpendicular to the cell wall substrate (not shown). The electric field strength is proportional to the voltage divided by the distance between the electrodes 14a and 15, or the size of the cell gap.

When the voltage is changed by using the small electrode segment 14a, the electric field intensity will change spatially across the light through hole (for example, as shown schematically in the figure). The electric field changes in space, but the parallel lines are perpendicular to the pair of substrates throughout the light through hole, which is ideal for the control of liquid crystals.

If some electrode segments 14a are not connected to a potential, the electric field lines opposite these electrode segments 14a will be bent, and the strength will decrease as the distance from other connected electrode segments 14a increases. Such curved electric field lines are also called fringe electric fields.

The zero voltage or minimum voltage electrode section 14a of the area 12b has a fringe electric field generated by the adjacent maximum voltage electrode section 14a of the area 12a, which is formed by generating some electric field lines between the two electrodes 14a at the area boundary (also having In the cell, the electric field generated by the maximum voltage electrode segment 14a of the area 12a opposite to the zero voltage or minimum voltage electrode segment 14a of the area 12b). This schematically shows the arc-shaped dashed line between the electrode segments between the regions 12a and 12b in the central part of Figure 1. Therefore, the zero or minimum electric field desired in the region 12b is not achieved. In addition, the electric field lines in the cells on the opposite sides of the zero or minimum voltage electrode segment 14a of the region 12b are not parallel, which results in undesirable orientation of the liquid crystal molecules between the regions 12a and 12b.

When the electric field changes from the region controlled by Vmax to zero or the region controlled by Vmin, a non-linear orientation zone (NLZ) is created in the transition region between regions 12a and 12b. It is impossible to use this electrode alone to achieve a sudden change in the electric field. The non-linear orientation zone can also be referred to as a reset zone or "flyback zone."

As a result, when many areas 12 are provided on the light through hole across the device, the effective working portion (linear change) of the device is reduced to the (w-NLZ)/w portion. The NLZ deflects the light beam to an undesired direction (redirects the light to the desired direction with respect to the linear change portion), so this is not ideal.

In Figure 2, the series of electrode segments 14a is simplified by using a weakly conductive (or high resistance) layer 16 and a pair of boundary electrodes 14b and 14c. The weakly conductive layer helps to gradually expand each area 12a on the optical via It is not necessary to control a series of electrodes 14a separately, as shown schematically by the dashed line in Figure 2. The spread of the voltage can be controlled by the frequency of the voltage applied to the electrode 14c to control the distribution of the voltage. However, the frequency will also cause the liquid crystal molecules to be aligned parallel to the electric field (when the dielectric anisotropy of the LC is positive). The electrode 14b can be grounded or connected to a lower voltage level as required. In the setup in Figure 2, the number of electrodes in each area is reduced from many in Figure 1 to only two. It is possible to include one or a small number of additional electrodes to help form the voltage distribution in the light via, especially near the edges.

The electric field generated using such a ring electrode arrangement with a weakly conductive layer has electric field lines substantially parallel to each other and perpendicular to the substrate on the light through hole of the device, and is therefore suitable for controlling liquid crystal. The expression "ring electrode" means that the electrode structure uses the missing electrode to create spatial variation in the resulting electric field, whether the ring-shaped hole is a gap between two independent electrodes, a gap extending beyond the electrode, or A single electrode hole.

It should be understood that the NLZ (Fig. 2) here is basically the same as in Fig. 1, which is still a problem, in which the complexity of the control electrode has been reduced, that is, fewer electrodes 14 in each region 12 need to be driven.

In Figure 3, the electrode 14d is provided and connected to a high-frequency voltage (f2 shown in the figure) to act on the liquid crystal to generate an orientation perpendicular to the electric field. As known in the art, the liquid crystal is a dual frequency liquid crystal (DFLC). While the electrode 14c is connected to a lower frequency (shown as f1), the electrode arrangement makes the orientation of the liquid crystal molecules parallel to the electric field, and the electrode 14c orients the liquid crystal in the cell To be almost perpendicular to the alignment layer, the higher frequency applied to the electrode 14d helps to force the liquid crystal molecules in the cell to be perpendicular to the electric field, thereby forming a direction parallel to the alignment layer. Because the frequency of the voltage applied to the electrode 14d is high, the weakly conductive layer does not help spread the high-frequency electric field relative to the lower frequency applied to the electrode 14c. The opposite can also be considered, if the ground state orientation of the LC is different, for example, perpendicular to the orientation layer.

As the electric field lines shown in Figure 3, f1 is a solid line and f2 is a broken line. The two fields overlap, and their influence is still felt from the liquid crystal material. The electrode 14c generates a relatively large extended electric field, trying to align the liquid crystal molecules into an electric field parallel to f1, while the electrode 14d generates a relatively local electric field, trying to align the liquid crystal molecules into an electric field perpendicular to f2. The electric fields on the electrodes 14c and 14d overlap as shown in the figure, but the liquid crystal molecules between the electrodes 14c, 14d and the electrode 15 are as shown, and are oriented in a spatial compression transition from a substantially parallel orientation to a substantially vertical orientation.

Depending on the nature of the layer 16 and the geometry of the LC cell, an example of a suitable frequency for f1 may be in the range of 1 to 15 kHz. Depending on the properties of the DFLC material and the operating temperature, an example of a suitable frequency for f2 is generally higher than 30 kHz, for example 50 kHz.

The effective effect is to have overlapping electric fields of different frequencies, and its effect on the liquid crystal molecules is to rapidly change (in time and space) the orientation of the liquid crystal at the boundary, thereby reducing the NLZ area as shown in the figure. In the simulation in Figure 4, the parameters used are: the liquid crystal layer using MLC-2048 liquid crystal (a DFLC material of Merck) is 60μm thick, repeating beam steering unit with a period of 150μm, electrodes with a width of 10μm, and a gap of 10μm The electrodes 14d and 14c have a 10V voltage f1 with a frequency of 5-10 kHz, and a 5.5V voltage f2 with a frequency of 100 kHz. The vertical axis is the phase retardation (micron order) of light passing through the liquid crystal cell.

The function of the high-frequency field is to orient the liquid crystal to the direction perpendicular to the electric field. The combined effect of the control electrode 14d and the electrode 14c is that in the case of Fig. 3, the lower frequency electric field makes the net orientation of the liquid crystal more peaked than in the other cases of Figs. 1 and 2, wherein the control electrode 14d is simulated as It is connected to 0V. However, the greatly improved shape of the phase delay distribution in the NLZ region is also greatly reduced. It can also be seen that the minimum phase delay in Figure 3 has also been reduced, thus providing a change in the phase delay in Figure 3, which is almost the same as the corresponding first and second driving voltage f1. The simulation results in the embodiment of the figure are the same. In the case of Fig. 3, the shape of the phase delay distribution is more linearly inclined (closer to an ideal saw-tooth waveform) and has a less sinusoidal shape.

It should be understood that the reduction of the NLZ area achieved in the embodiment of Figure 3 can be achieved by using the multiple segmented electrode system of Figure 1, where the first electrode 14a of the area 12b will be driven by a high-frequency voltage, so that The liquid crystal is oriented perpendicular to the electric field.

In the embodiment of Figure 5, the electrodes of the (non-circular) ring-shaped (linear paired) regions 12a and 12b include electrodes 14b and 14c connected to the minimum and maximum drive voltages of frequency f1. Then, the electrode 14d located between the boundary regions 12a and 12b and between the electrodes 14c and 14b is connected to the driving voltage of the frequency f2. This provides better control over the spatial distribution of the resulting (total) dielectric torque and therefore better control of the liquid crystal orientation. As will be understood, if a beam steering device is used to variably turn the light in two directions, and the steering is in the opposite direction (as described above), it is ideal to drive 14b with the maximum voltage and the minimum voltage Drive 14c. It should be understood that although separate electrodes 14c and 14d are provided to be connected to low and high frequencies, the desired phase delay spatial distribution can still be achieved by driving a single electrode with two frequencies.

The liquid crystal device 10 is schematically shown in Figures 1 to 5, and includes a single layer of liquid crystal oriented in one direction. As known in the art, such a device acts on a single linear polarization direction of light, and unpolarized light passing through the device 10 is processed by the device as two linear polarization states. The spatial modulation of the refractive index in the liquid crystal material is relative to one polarization direction of light, and the other polarization direction does not have the spatial modulation of the refractive index. In order for the device 10 to act on unpolarized light, a second cell is usually provided with LC molecules orthogonal to the orientation of the LC molecules of the first cell shown in Figures 1 to 5, and act on other polarization directions. Add electrodes 14 and 15 for the additional cells in a similar manner to the first cell.

For example, in the International Patent Application Publication No. WO2009/146530 published on December 10, 2009, four units are arranged together, and an alignment layer with two units acts in the opposite direction of the same polarization direction. When light that is not parallel to the optical axis of the device 10 passes through the element, such an arrangement reduces the sensitivity or aberration of the device 10.

Figure 6 shows a schematic plan view of the beam steering device, showing that the areas 12a, 12b, 12c, 12d, and 12e together create the light through hole 18. The arrangement of electrodes 14b, 14c and 14d configured according to Figure 5 is shown A suitable drive circuit 20 connected to the electrodes is schematically shown.

According to the typical size of the liquid crystal cell, that is, the cell gap between the substrates of about 120 microns, and the Δn of about 0.2, it will be necessary to set an area width in the device, such as about 100 microns as shown in Figure 6, to Provides a beam control range of approximately ±13 degrees. If the light through hole 18 of the device is 3 mm wide, 30 areas 12 will be provided instead of the five shown schematically in Figure 6.

The driving circuit of such a device can be completed by a dedicated circuit, FPGA device, DSP device, and can include a programming processor for control. As shown in the schematic diagram, the driving circuit 20 has an operating frequency f1 of the driver 22 to control the left electrode 14b, an operating frequency f1 of the driver 24 to control the right electrode 14c, and an operating frequency f2 of the driver 26 to control the electrode 14c. What is not shown in FIG. 6 is that the driving circuit 20 is also connected to the corresponding planar electrode 15. Such drivers 22, 24, 26 may be simply turned on or off, or they may be variable and adjustable to control a variable and controllable light parameter, that is, the beam steering angle. The drivers 22, 24 may also be frequency-regulated and/or voltage-regulated. The driver 26 may have a fixed voltage and frequency, although parameter control of its driving signal is also possible. The controller 28 is provided as a part of the driving circuit 20 in the embodiment of FIG. 6 to provide the setting of the drivers 22, 24, 26 in response to the external control signal input terminal. Such a controller 28 may be provided from the drivers 22, 24, 26, respectively, for example in software. The controller 28 typically stores calibration data to allow the control signal to be converted into a specific drive signal value. The phase delay control between the control signals can be as 10A, 10B and The reference implementation described in Figure 10C.

Although Figure 6 shows a beam steering device for light propagating from right to left (or vice versa, on the same plane), it should be understood that by stacking additional units with orthogonally arranged electrodes, the beam steering device can be The light is guided in two directions, namely left-right and up-down.

According to another embodiment of the proposed solution, Figure 7A shows the adjacent area 12 or the beam steering element 12 of the LC beam steering device 10, wherein the electric field is controlled by two control electrodes in each area 12 14c and 14b use conductive walls 17 provided in the transition area to reduce the fringe field of each area 12 penetrating to the next area to form NLZ. The conductive wall 17 can be shorted to the plane electrode 15. In order to turn in a given direction, the electrode 14c may be driven when the electrodes 14b and 15 and the conductive wall 17 are connected to the same voltage (or ground). It has been found that this can reduce NLZ and increase the potential linearity (prismatic) in each zone 12 and improve beam steering (or increase the operating efficiency of the Fresnel lens in a circular geometry).

For clarity, connecting the electrode 14b and the conductive wall 17 to the same voltage can be selectively implemented in the external driving circuit 20. An isolation layer (not shown) may be used between the electrode 14c/14b and the conductive wall 17. For example, by connecting the electrodes 14c, 15 and the conductive wall 17 to the same voltage (or ground) while the electrode 14b is driven, the incident light can be turned in the opposite direction.

Figure 7B shows another embodiment of the proposed solution, which uses the weakly conductive in the geometry of the optical element shown in Figure 7A 性 or high resistance layer (WCL) 16. An improved sawtooth distribution can be achieved by controlling the frequency of the drive signal component supplied to the electrodes 14b and 14c. Using the floating electrode 13, according to yet another embodiment of the proposed solution, shown in Figure 7C, the electric field distribution can be increased to obtain more linear prismatic modulation distribution. The use of floating electrodes can be used in combination with other embodiments, for example, in combination with the embodiments shown in FIGS. 2 to 6.

According to another embodiment of the proposed solution, Figure 8A shows the adjacent area 12 or the beam steering element 12 of the LC beam steering device 10, which has two stacked LC layers (these layers do not need to be in close proximity or in the Staggered across the width of the entire area), where the electric field is controlled by a control electrode (replaceable 14e/14f) in each area 12, where wide optically transparent walls 19 are used, which are spaced between each LC layer The undriven element region 12 extends, and the LC layers form a staggered pattern.

The transparent wall 19 can allow the electric field to penetrate, and under the action of the driven electrode 14e or 14f, provide a smooth electric field transition between the driven and undriven optical device elements 12. In order to turn in a given direction, the electrode 14f may be driven when the electrodes 14e and 15 are both connected to the same voltage (or ground). In order for the top and bottom units to have the same effect, the geometry and arrangement direction of the electric field can be the same as in Figure 8A.

It has been found that the arrangement of Figure 8A in each region 12 (because there is no LC in this region) under the action of the driven electrode 14f, substantially eliminates the undesired reorientation caused by the fringe field of the liquid crystal, thereby improving the phase retardation operating. By connecting the electrodes 14f and 15 to the same voltage (or ground), while the electrode 14e is driven, the incident light can be turned in the opposite direction to. Each LC layer operates with half of the driven optical device elements 12, while the incident light on each undriven optical device element 12 of one LC layer is diverted by the driven optical device elements 12 of the corresponding other LC layer .

Figure 8B shows another embodiment of the geometry of the optical device using WCL16 as shown in Figure 8A. An improved sawtooth distribution can be achieved by controlling the frequency of the driving signal components applied to the electrodes 14e and 14f. According to a further implementation of the proposed solution, a floating electrode 13 is used in each driven element area 12, as shown in Figure 8C, to improve the electric field distribution to obtain more in each area 12 The linear prismatic modulation distribution.

According to another embodiment of the proposed solution, Fig. 9A shows the beam steering element 12 of the adjacent area 12 or the double LC layer beam steering device 10 using staggered wide optically transparent walls 19, where the wall 19 extends to each In another undriven region 12 of an LC layer, the electric field is controlled by a control electrode (alternating 14e/14f) of each region 12. In the embodiment of Figures 8A, 8B, and 8C, there is a possibility that the front LC layer will redirect the light, and then the rear LC layer will redirect the light, thereby representing a different way of affecting NLZ. It has been found that this can reduce the light output in each area 12. In order to reduce the loss due to this re-steer and improve the phase delay operation, the central substrate 11b in the layered geometry of the optical element is omitted. In wafer-level manufacturing, an electrode layer 15 (and associated orientation layer) is deposited on each transparent wall 19. The flip chip manufacturing technique can be used to fit the interlaced electrode strips to the electrode layer 15 as shown. The LC material can be applied to the element area 12 of the driven optical device, for example For example, by vacuum, injection or capillary action.

According to another embodiment of the proposed solution, Fig. 9B shows the use of WCL 16 in the geometric shape of the optical device shown in Fig. 9A. An improved sawtooth distribution can be achieved by controlling the frequency of the drive signal components supplied to the electrodes 14e and 14f. Floating electrodes 13 are used in each driven element area 12, according to a further embodiment of the proposed solution, shown in Figure 9C, to improve the electric field distribution to obtain more in each area 12 The linear prismatic modulation distribution.

According to another embodiment of the proposed solution, Figure 10A shows a single area or beam steering element 12 of the liquid crystal beam steering device 10, which has two driven electrodes 14e and 14f, each electrode correspondingly composed of one The drive signal components drive the drive, each of which has amplitude, frequency and phase. The generated potential distribution of the cross-area element 12 is a curved surface with a dashed line as shown in the figure, in which a 5V drive signal of the electrode 15 (the same phase and the same frequency) is used to control the electrodes 14e and 14f. The element area 12 in this state does not provide beam control. For reference, according to the solution of the present embodiment, the unconnected electrode 14c is shown to confirm that the potential distribution can be adjusted, and it can be used for the geometry of other optical devices without departing from the proposed solution.

Figure 10B shows the two driven electrodes 14e and 14f in Figure 10A, on which corresponding drive signal components of the same frequency and amplitude are used, but with opposite phases. The beam steering can be realized by the 5V driving electrode 14e and the -5V driving electrode 14f, wherein the electric potential distribution of the electric field causes the orientation of the LC molecules to have an inflection point in the area element 12. 10C The figure shows two driven electrodes 14e and 14f in Figure 10A, on which corresponding drive signal components of different frequencies, amplitudes and phases are used. When the frequency is the same but has a phase difference, such as 180 degrees, then there is a large electric field component between the electrodes and the resulting extension along the liquid crystal layer. When the frequency of the drive signal is different, the voltage between the electrodes 14e and 14f is an alternating voltage with a jumping frequency, which generates an extended electric field along the liquid crystal layer. The beam steering is adjusted by the 5V driving electrode 14f and the -2V driving electrode 14e, wherein the electric potential distribution of the electric field affects the orientation of the LC molecules, so that the central inflection point moves from the middle to one side of the area element 12.

In-plane electric field control

The beam control device is an optical device that controls the beam to achieve: either the beam diverges, or converges, or the direction of the beam is adjusted, that is, an optical device that controls the beam.

In the case of liquid crystal devices, an electric field is generally used to control the orientation of the liquid crystal material. The change in orientation affects the refractive index, and so-called gradient index (GRIN) lenses can be created. To achieve beam control, a focusing lens may not be needed.

When the light through hole of the device is large, it is difficult to achieve large-angle beam control with a liquid crystal GRIN device because the refractive index change in the light through hole is relatively small. By using multiple beam control elements on the light through hole, a small optical element with a smaller aspect ratio can provide greater beam steering capability.

The electric field on the light through hole of the liquid crystal optical device can be Line spatial modulation to spatially modulate the liquid crystal orientation. For the lens, it is desirable to have a smoothly changing orientation control on the light through hole without using multiple lens elements to form the lens. In the case of a beam steering device, it may be desirable to use multiple elements, as described above, and the electric field distribution on the small light through hole area of each element and its interaction with the liquid crystal, which is the same as the large light flux The device of the hole is different.

In some beam control devices, electrodes provided on opposite sides of the liquid crystal layer are used to control the electric field, and in other cases, electrodes provided on a substrate (11a/11b) containing the liquid crystal layer are used to form an electric field.

The nematic liquid crystal that uses the rubbed alignment layer to achieve alignment can only affect one polarization direction of unpolarized incident light. To modulate unpolarized light, two orthogonal liquid crystal alignment layers are usually used. The first layer splits the light into two orthogonal polarizations, only one polarization direction is modulated according to the liquid crystal spatial modulation method, and the other polarization direction is basically unmodulated. The second layer is arranged to perform the required complementary modulation of the polarization direction not modulated by the first layer and allows the polarization direction modulated by the first layer to pass through with little modulation.

For the purpose of beam steering, it is possible to use a first liquid crystal layer to controllably steer the light of one polarization direction in one direction, while a second liquid crystal layer is used to controllably steer the light of other polarization directions in the orthogonal direction. Turn in the direction.

This can be better understood with reference to Figure 11, which schematically shows a device with a single liquid crystal layer 120 with interconnected, Parallel strip electrodes 114 on one substrate are separated by an electrode gap g, and transparent planar electrodes 115 are provided on the other opposite substrate 111 to achieve a controlled electric field across the liquid crystal layer of thickness L (the The thickness is sometimes called the cell gap). The strip electrodes 114 may also be transparent, even though they are usually only 10 to 20 microns wide and do not hinder the propagation of the light beam. The scratched polymer alignment layer 118 is used on the inner surfaces of the two substrates 111 to provide an initial ground state alignment of the liquid crystal 120. The strip electrodes 114 are preferably provided on the substrate side of the unit where light is incident, although they may also be provided on the opposite substrate 111.

The device 100 shows schematically and not to scale 4 electrode gaps in cross section, each with a controllable cylindrical lens element for beam control. The configuration of the electrode 114 may be linear (ie, finger-shaped), concentric ring, spiral, or any other geometric configuration. The number of electrode gaps on the light through holes can vary according to applications.

As in Figure 11, when a voltage is applied between the electrodes 114 and 115 (see the electric field lines shown in the cell on the right), the electric field in the space under the electrodes 114 and 115 is stronger than the gap between the electrodes. A high-resistance material layer can be added near the electrode 114 to help distribute the electric field at the gap, but the gap has a relatively small aspect ratio compared to the thickness of the liquid crystal layer, so such a high-resistance material layer may not bring much benefit.

The nematic liquid crystal material layer 120 controls a single polarization direction of light. As is known in the art, such layers can be stacked together so that the device can adjust the two linear polarization directions of light. In the embodiment of Figure 11, the liquid crystal material 120 is shown to have an orientation almost parallel to the substrate, so that So its ground state has a low pretilt angle from left to right. To modulate the orthogonal polarization direction, it is possible to provide another layer of nematic liquid crystal with a parallel orientation extending into or out of the page with the substrate. In this structure, a transparent (preferably optically matched) filler 122 of the required size is provided to separate the electric field of the liquid crystal or adjacent cells. The first controllable voltage source V1 is connected to the straddle strip electrode 114A and the opposed planar electrode 115, and the second controllable voltage source V2 is connected to the electrode 114B and the opposed planar electrode 115. The voltages V1 and V2 determine the orientation of the liquid crystal and therefore the direction of the tilt of the light beam. The filler may be any suitable material, preferably a transparent material, and also preferably has a refractive index similar to that of a liquid crystal material. In contrast, the separation of the electric fields of adjacent cells is achieved only by the filler 122 being conductive and controllable. The liquid crystal phase retardation distribution between the two fillers 122 can have desired beam control quality.

In addition, for the purpose of beam control, the strip electrode pattern shown in Figure 11 can be used to cause beam steering in only one direction. For beam steering in both directions, additional layers can be used, which have orthogonal control electrodes 114.

Similar to Figure 11, Figure 12 shows a single liquid crystal layer 120 on a substrate 111 with independent electrodes 114A and 114B separated by gaps to provide a control electric field between the electrodes. The liquid crystal below is spatially variable. When a cross voltage is applied to the electrodes 114A and 114B in Figure 12 (see the electric field lines on the right of the two cells in the figure), the geometric shape formed by the electric field is basically parallel to the direction of the midpoint of the gap between the electrodes. At the same time, in the space between the electrodes without filler 122 At the edge of the gap, it becomes a substantially vertical direction. The control electric field has a very different geometry compared to Figure 11, but the orientation of the liquid crystal is similar (but not the same) according to the conditions of the applied voltage. In this embodiment, the transparent material 122 does not respond to an electric field, and is arranged to form the refractive index distribution of the beam steering of the liquid crystal 120 unit. The transparent material 122 is arranged in a staggered manner on the two layers. This will provide the ability to tilt the light "left or right" in a single polarization direction in the plane of the illustration.

Compared with the embodiment in Fig. 11, the embodiment in Fig. 12 has the disadvantage that the steering can only be controlled in one direction. For steering in other directions, a separate unit should be used for this purpose, or alternatively, if a dual-frequency liquid crystal is used, a high frequency above the overall frequency can be used to cause the liquid crystal orientation to be orthogonal to the electric field, thereby providing another The steering of direction provides the required distribution.

In Figure 12, the relationship between the aspect ratio (R) of the distance (g) between the electrodes 114A and 114B and the thickness (L) of the liquid crystal layer is R=g/L, which may be, for example, 0.7 And 4 (preferably about 2.5, corresponding to a microlens device), wherein there is no need to provide any weakly conductive coating on the insulating substrate 111 where the electrodes 114A and 114B are located. For example, g may be about 100 microns, while L may be about 50 microns, and the aspect ratio is about 2. The aspect ratio plays an important role in determining the required electric field spatial variation mentioned above. The electrodes 114A and 114B are arranged on the inner cell side of the substrate 111 as shown in the figure, however, they may also be located on one outer side of the substrate 111. This latter setting may require a higher driving signal voltage, however, the electric field geometry may be more suitable for modulating the electric field in the liquid crystal material. field.

FIGS. 13A to 13C schematically illustrate in more detail the electric field generated by a pair of parallel strip electrodes 114A and 114B similar to that of FIG. 12. Figure 13A shows that the aspect ratio is about 5. The electric field lines in the cell are mostly parallel to the substrate, except for the edge area near the electrode. This arrangement is known for use in displays, where the liquid crystal needs to be switched between two states, namely a grounded state (for example twisted nematic or vertical), and a power supply state where the liquid crystal is arranged parallel to the substrate. In this case, the goal is to achieve uniform reorientation of the liquid crystal within the cell (between the electrodes 114A and 114B).

Figure 13B shows the geometry of the cell, where the aspect ratio R is less than about 1. This aspect ratio can provide an intensity distribution that has the function of a marginal extreme observation angle and is not suitable for beam steering.

Figure 13C shows the geometry of the cell, where the aspect ratio R is greater than about 1 and less than about 4. This geometry provides good beam steering performance.

In the embodiment of Figures 12 and 13C, the electric field has a "vertical" component (called "out-of-plane"), that is, perpendicular to the substrate where the electrodes 114A and 114B are located, and a "horizontal" component, that is Extend between the electrodes.

When the liquid crystal is in the ground state oriented by the alignment layer 118, which extends in the direction between the electrodes 114A and 114B (perpendicular to the electrode strips), the intensity distribution of the deflected beam can be due to the electric field and the desired space for the liquid crystal orientation in the cell The angles between the distributions are changed asymmetry. As shown in Figure 13C, the left side orientation of the liquid crystal 120a is aligned with the electric field, The right orientation of any liquid crystal (at 120b) of the object 122 is perpendicular to the electric field.

As can be understood from Figures 13A, 13B, and 13C, the aspect ratio affects the spatial distribution of the liquid crystal orientation in the cell. As shown in Figure 13C, a proper aspect ratio can realize a proper beam adjustment optical device. Figures 13A and 13C provide that the beam adjustment is uneven or ineffective.

The strip electrodes 114A and 114B may be narrow enough to reduce the size of the boundary area between adjacent cells. The light through hole of the device with cells shown in Figure 13C can have many such cells, whether they are configured as strips, loops, spirals or other geometric patterns, the small gap between each cell is limited to about 30 microns To about 90 microns, and typically about 50 microns, there are about 20 units per linear millimeter unit of optical through hole.

The configurations in Figures 11 and 12 do not provide light modulation under zero-power conditions, and then provide beam control when driven by power.

In Figure 14, another structure is schematically shown in a plan view in which the orientation of the alignment layer is almost the same as the orientation of the strip electrodes 114A and 114B. Here, the electric field component in the horizontal direction or the X direction will act on the molecules, turning them into the lateral direction, resisting the orientation effect of the orientation layer. However, the vertical or Z-direction component of the electric field acts on the liquid crystal molecules with good symmetry across the gap. This configuration provides a good phase delay distribution for beam steering.

In Figure 15A, a different electric field setting is shown for beam adjustment and beam steering. In this arrangement, two LC 120 units from left to right are used to steer (manipulate) light beams with fast axis polarization, or vice versa. All LC molecules are oriented on the same plane of the page, although the orientation of the liquid crystal relative to the direction of the strip electrodes 114A and 114B can be selected, for example, parallel to the direction of the electrodes, as described in other embodiments above.

For the steering operation, the electrode 114C is grounded (ie, connected to the ground or the driving signal source has the opposite polarity). A voltage is applied to the electrode 114A, and the electrode 114B is floating or disconnected. Therefore, for turning in one direction, the electrodes 114A and 114C may be connected to, for example, an AC voltage source; while the electrode 114B is disconnected. In this case, due to the action of the upper unit, about half of the light propagating in the vertical direction will be turned to the right, and due to the action of the lower unit, the other light is turned to the same direction. Leaving the electrode 114A floating and the electrode 114B connected to a voltage will divert the light beam to the left (corresponding to liquid crystals with positive dielectric and optical anisotropy). The two intermediate substrates 111 between the two liquid crystal layers 120 may be provided as a single substrate 111.

The electric field between the electrode 114A or 114B and the ground electrode 114C is basically "vertical", that is, perpendicular to the lateral extension of the liquid crystal layer, even though the electrodes 114A and 114B are slightly separated on one side of the electrode 114C. This is shown in Figure 16.

It can be understood that the electric field will be between a driven electrode (such as 114B) and the nearest grounded intermediate electrode 114C, the ground electrode 114C on the opposite side of the intermediate substrate 111, and the farther ground electrode on the same side of the intermediate substrate 111. Extend between 114C. The electric field is strong enough to extend to the nearest intermediate electrode 114C to control the orientation of the liquid crystal 120; and to extend farther The electric field of the electrode 114C is sufficiently weak that the orientation of the liquid crystal 120 can be ignored. Therefore, such electric field lines are suitable for the liquid crystal 120 in the direction (provided by the alignment layer) having a grounded state near the substrate plane 111, as shown in the figure. The electric field lines are strongest in the area under the driven electrodes 114A and/or 114B, and are much weaker in the direction away from the nearest electrode 114C, and similarly, the intensity gradually decreases toward the middle of the electrode 114C. This provides an electric field gradient suitable for spatially variable orientation of the liquid crystal material 120 to provide beam steering or beam adjustment elements.

The strip electrode arrangement provided with a biased middle electrode 114C on the opposite side realizes the phase delay distribution, as shown in FIG. 17. The simulated state in FIG. 17 is a liquid crystal with a thickness of 50 microns, a strip electrode 114 with a width of 20 microns, and the gap between the strip electrodes 114A and 114B is 100 microns. The offset in Figure 16 does not need to be very large. Measured from the center of the beam control element, the outer edge of the strip electrode 114A or 114B extends about 20 microns from the corresponding outer edge of the offset middle electrode 114C. This is the width of the strip electrode 114A or 114B. The inner edge of the electrode 114A or 114B may actually overlap the middle electrode 114C, or not overlap (in Figure 18A, the parameter "D" can be positive, zero, or slightly negative, as long as there is a strip electrode 114B that extends beyond the middle Electrode 114C). The amount of bias in this way can be changed as needed, and its effect is to reduce the outer fringe electric field of the element 112.

As shown in FIG. 15B, the bias may also be a result of the middle electrode 114C extending farther than the strip electrodes 114A and 114B. The result is the same, that is, the fringe electric field is reduced, and the desired The beam turning phase delay distribution.

The asymmetry between turning right and turning left can be explained by the orientation of a liquid crystal plane extending vertically between the strip electrodes 114A and 114B, and the response of the element to the electric field will be somewhat asymmetric.

What is worth noting in the simulation results in Figure 17 is the steep rise in phase delay from minimum to maximum, as indicated by reference sign B. Due to the offset, this causes a reduction in fringe field as described above. As shown in the figure, the rising or returning area only represents about 20% of the light through hole area. It should also be noted that this is achieved by using electrodes on the inner surface of the substrate, thereby reducing the voltage and using a single control signal. The device also avoids the need for any weakly conductive layers.

About 20% of the return area of the light via will scatter or direct the beam in the opposite direction. In some application devices, this effect is acceptable, while in other cases, it is unacceptable. When it is unacceptable, the part of the beam control element in which the return area is found can be shielded. Although this reduces the transmission efficiency of the device, it can remove scattered or misoriented light. As shown in Figure 17, if the combined return area for the left and right steering is shielded, there will be an available steering area of 60 microns in the electrode gap of 100 microns to form the steering element. As mentioned above, if the liquid crystal orientation is as shown in Figure 14, it can be expected that the size of the combined return area will be smaller due to the large symmetry between the left and right steering modes.

Figure 18A shows an embodiment similar to Figure 15A, in which the intermediate electrodes 114C and 114D are biased for both odd and even elements. This device alternately applies the driving signal as shown in Figure 18A, but After that, drive as shown in Figure 18B. Each configuration is used to form an electric field to form an odd or even number of beam steering elements of the device. Through the time-multiplexed electrode drive configuration, the liquid crystal layer 120 can be provided with the light beam steering phase delay distribution of all components.

Using a drive circuit that includes an electronic switch, a drive signal is first applied to the electrodes 114A and 114C (while 114B and 114D are disconnected) for turning in one direction, but a drive signal is applied to the electrodes 114B and 114C ( 114A and 114D are disconnected), so that the other direction can be turned. In Fig. 19, the phase delay of the first "driven finger group" is shown. The beam turning ramp is about 80 microns, and the return zone is about 20 microns. Secondly, a driving signal is applied to the electrodes 114B and 114D (while 114A and 114C are disconnected) for turning in one direction, but a driving signal is applied to the electrodes 114A and 114D (while 114B and 114C are disconnected) Up to make the steering in the other direction. In Figure 19, the phase delay of the second "driven finger group" is shown (the driving voltage is 10V, the liquid crystal material is 50 microns thick LC80, and the electrode period is 120 microns, and the electrodes 114A and 114B are 20 Micron width). In these two settings, the characteristics of the beam turning slope and the return zone are basically the same, and the display produces small ripples of modulation caused by each setting on the unmodulated element between the currently driven or modulated elements . The drive circuit is selected back and forth between the first and second configurations to achieve the maintenance of the beam steering phase delay distribution on all elements of the device.

In the embodiment of Figure 18A, it is preferable to use the middle electrode 114C, which is embedded in the opposite strip electrode as shown in the figure, because Each strip electrode can be used for left and right beam steering control. However, the structure of Figure 15B below can be implemented in the case of Figure 18A, but the offset requires separate embedded strip electrodes for left and right beam steering to match the electrode 114C with a very small separation gap. And 114D. Therefore, the electrodes 114A and 114B will be regarded as electrodes 114A-right, 114A-left, 114B-right and 114B-left.

The device in Figure 15A or 18A controls a linear polarization direction of light in a plane, and can be regarded as a "1/4 unit". Two such elements with orthogonal electrode lines but with LC molecules in the same plane are used to control the same polarization direction in the two planes to form a "half cell". In addition, two "half cells" (8 LC cells in total) can be provided to operate on unpolarized light in two planes. A beam steering device that operates in two planes can control the beam in two orthogonal directions.

The beam controller is provided to generate control signals. For example, a light source (such as an LED core) can use a beam controller to control the intensity and/or color. In addition, a beam controller can be used to control the dynamic liquid crystal control element, that is, the electrodes 114A and 114B (or any of the electrode arrangements described above) can be controlled by a beam control circuit. The beam controller may include a dedicated circuit, or it may include a configurable circuit (such as an FPGA), or it may be implemented using a program code running on a suitable platform, such as a CPU or DSP system.

The beam controller can be configured to receive control commands from the data network to adjust the beam direction. Some light sources (e.g. infrared light sources) can Used to provide data communication, and in this case, the beam controller can be used to adjust the data-containing light source, and the dynamic LC control element can be used to control the data-containing beam. In addition to light projection or light source, this can also be used for scanners, receivers and readers.

In the embodiment of FIG. 20, an electrode array having strip electrodes 114A and 114B is shown. The electrode pitch is 50 micrometers in the middle of the 6 mm light through hole of the device and 100 micrometers on the outside. In the example shown, the gap increases/decreases by 5 microns from one gap to the next. Small gaps have higher beam adjustment or beam steering capabilities or optical power, and larger gaps have lower optical power.

Such a change in the gap between the strip electrodes may be linear or non-linear. The effect of the change or fine-tuning is to eliminate or reduce any color separation and hot spot formation in the transmitted light. This is because different parts of the optical element redirect the same wavelength (ie color) of light to different directions.

For example, the light beam may have symmetry with respect to the optical axis. In this case, the electrodes may be concentric rings 114A and 114B (substantially form a Fresnel lens). The pitch of the rings can be smaller near the central optical axis and relatively larger near the outermost ring to make the beam spread more uniformly. The pitch can also take into account the intensity distribution of the beam, and more components can be provided at positions with greater intensity. This type of electrode (concentric ring) can be used in conjunction with the star-digital electrode structure on the opposite substrate of the unit.

It can be understood that as described herein, the strip electrode pattern can be applied to various liquid crystal cell designs. In the case of concentric rings, in a The beam adjustment or beam steering is performed relative to the optical axis in the radial direction, and therefore a typical design may have two layers of liquid crystal, one for each polarization direction. Spatial fine adjustment can also be applied to circular or star-shaped electrodes.

The liquid crystal device 10/110 as in the above-mentioned embodiment includes an LC layer having an alignment layer arranged in one direction. As mentioned briefly above, such a device 10/110 acts on a single linear polarization direction of light, and unpolarized light passes through the device and is processed by the optical device into two linear polarization states. The spatial modulation of the refractive index of the LC material acts on the fast-axis polarized light, while other slow-axis polarized lights are not subject to the spatial modulation of the refractive index. In order to control unpolarized light, the second optical device 10/110 usually has an orientation layer that is orthogonal to the orientation of the first optical device and acts on other polarization directions. This is schematically shown in Fig. 21, where additional electrodes 114 and 115 of the LC cell are arranged in a similar manner to the first liquid crystal cell. This solution was published in International Patent Application Publication No. WO2009/146530 published on December 10, 2009. As shown in Figure 21, four LC cells are arranged together, and the alignment layers of the two LC cells act on the same light polarization. Direction, which has an orientation layer oriented in the opposite direction. Such an arrangement of 4 LC cells reduces the sensitivity or image aberration of the device 10/110 to incident light that is not parallel to the optical axis of the entire device.

Although Figures 5 to 20 show the beam control device, the configuration used to make the liquid crystal change the orientation in the boundary of the cross-over area to have a reduced nonlinear region can also be used in the design of various Fresnel lenses, for example, As shown in Figure 22. In this case, the geometry of the electrode will be different, and will not only form a rectangular area, but usually an arcuate or circular area, which is well known in the design of Fresnel lenses. The lens shown in Figure 22, often The lens corresponding to the regular refraction is shown by the dashed line in the cross section on the page, and it is aligned with a four-layer liquid crystal gradient index lens having a similar function. The central area is formed by the central ring-shaped electrode 14c combined with the weakly conductive material 16 (not shown in Figure 21) to achieve an axisymmetric voltage distribution in the central area, and the vicinity of the axis tends to zero. In this figure, the frequency band is maintained as a conventional Fresnel lens of the same size, but it should be understood that using such a liquid crystal device, as opposed to using a thicker optical refractive material to make the Fresnel lens, each The size of the micro components will be much smaller than usual and the number will be much larger. For better illustration, the illustration of electrodes 14c and 14d has a larger separation than actual size. The electrical connection between the electrodes 14c and 14d and the driving signal source are also not shown for ease of drawing. The four-layer liquid crystal material (Figure 21) has the orientation shown in the figure to provide good optical performance to natural light (two polarization directions) and reduce the sensitivity to light that is not parallel to the optical axis. If the light beam is nearly parallel to the optical axis, such a lens 10 can have only two layers, which can work fully and effectively against natural light. Additional layers can also be used to increase the thickness of the lens material, thereby increasing the optical power.

As mentioned above, the device schematically shown in Figure 6 uses a different electric field control structure than that described in Figures 7 to 22, or can use a different Fresnel lens design for various applications, including Redirection of light emitted by LED light sources for illumination. Liquid crystal materials can also be used to steer or focus infrared light, such as 850 nanometer wavelength light, and the devices described above can be used to scan in the infrared spectrum.

It should also be understood that the optical device of the above embodiment can be operated at a terahertz frequency, that is, the wavelength range is Human body radiation frequency of 8000 to 14000 nanometers. Therefore, according to the control of the Fresnel refractive lens and/or the beam steering control of the infrared light projection beam, the detectors sensitive to the wavelength range can find useful applications, for example, the optical system of the infrared motion detector.

Although the present invention has been shown and described with reference to its preferred embodiments, those skilled in the art will understand that various changes in form and details can be made in the present invention without departing from the invention defined by the scope of the appended application Spirit and scope.

111‧‧‧Substrate

114A‧‧‧Strip electrode, electrode

114B‧‧‧electrode

118‧‧‧Orientation layer

120‧‧‧Liquid crystal layer

122‧‧‧filling

Claims (29)

A liquid crystal optical device configured as a plurality of refraction or refractive Fresnel lens-type element control for beam steering of light passing through a light through hole, the device comprising: a liquid crystal material layer, contained by a substrate, the substrate having an alignment layer And an electrode arrangement, which is configured to form a spatially varying voltage distribution in the area of the many microelements in the liquid crystal layer; the liquid crystal optical device is configured to provide a spatial variation of optical phase retardation, which has an inter-microelements An abrupt change at the boundary, which is similar to the saw-tooth waveform of the boundary of a plurality of micro-elements, to increase the effective light through hole of the optical device; wherein, the electrode arrangement includes: a patterned electrode structure, which is included in the substrate The first strip electrode and the second strip electrode on one of the substrates, and an intermediate electrode on the other of the substrates, the intermediate electrode is located in the middle of the area close to the micro element and has a first edge and The second edge, the first edge and the second edge are offset from a first position relative to the first strip electrode and a second position relative to the second strip electrode, so that the The electric field between the first and second strip electrodes and the intermediate electrode generates a strong electric field, which has a bias close to between the first and second strip electrodes and the intermediate electrode The reduced fringe field, and across the middle electrode from the first edge of the middle electrode or relative to the first strip electrode The gradually decreasing electric field from the first position to the second edge of the intermediate electrode does not require a weakly conductive material for generating the voltage distribution of the electrode on the light via hole in each region. The liquid crystal optical device described in item 1 of the scope of patent application further includes a driving circuit configured to provide a driving signal to the electrode arrangement. The liquid crystal optical device according to claim 2, wherein the liquid crystal layer includes a dual-frequency liquid crystal material, and the electrode arrangement includes first and second areas near the boundary between adjacent areas of the area. Electrode, the driving signal for the first electrode is a low-frequency signal to make the orientation of the dual-frequency liquid crystal material parallel to the electric field, and the driving signal for the second electrode is a high-frequency signal to make the dual The orientation of the frequency liquid crystal material is perpendicular to the electric field. The device according to item 1 or 2 of the scope of patent application, wherein the electrode arrangement further includes a floating electrode, which helps to adjust the electric field in the micro element. The device as described in item 1 or 2 of the scope of the patent application includes a pair of liquid crystal layers, each liquid crystal layer having microelements separated by an optically inert area which is not affected by a variable electric field, wherein The combination of the pair of liquid crystal layers described provides the desired optical control, and the optically inert region allows abrupt changes in the phase retardation between the liquid crystal and the optically inactive region. The device according to item 5 of the scope of patent application, wherein the micro-element on one liquid crystal layer corresponds to the optically inactive area of the other liquid crystal layer. The device described in item 1 or 2 of the scope of patent application includes conductive walls between the liquid crystal micro-elements, so that the electric field acting on the liquid crystal of the micro-elements will not act on the adjacent micro-elements. On the LCD. The device according to claim 2, wherein the drive circuit is configured to provide a voltage difference to the electrical signal supplied to the electrode of the liquid crystal micro element at a substrate, so that the micro element acting on the micro element A part of the electric field on the liquid crystal is directed toward the direction of the liquid crystal layer. The device according to item 8 of the scope of patent application, wherein the driving signal is an AC signal, and the voltage difference of the electrical signal is the phase difference of the signal. The device according to claim 1, wherein the electrode arrangement includes ring electrodes. The device according to item 10 of the scope of patent application, wherein the electrode arrangement further includes a weakly conductive material for distributing voltage on the electrodes on the optical vias in each region. The device according to the first item of the scope of patent application, wherein the strip electrodes are arranged near both sides of each of the intermediate electrodes to selectively drive all of the selected sides of the intermediate electrode The strip electrodes are used to selectively steer the beam to different directions. The device according to item 12 of the scope of patent application, wherein the intermediate electrode is inserted between the strip electrodes. The device according to item 12 of the scope of patent application, wherein the strip electrode is inserted between the intermediate electrodes. The device according to the first item of the scope of patent application, wherein the device includes two liquid crystal cells, the first of the two cells provides an odd number of beam steering elements separated by elements that are not driven, so The second of the two units provides even-numbered beam turning elements separated by non-driven elements, and the odd-numbered beam turning units have the same orientation as the non-driven elements that separate the even-numbered beam turning elements. The device according to claim 15, wherein the intermediate electrode is arranged in each of the beam steering elements arranged adjacently, and the intermediate electrode can be driven in an alternating manner to maintain the The beam is turned to the spatial distribution. The device as claimed in claim 1, wherein the electrode arrangement has a linear pattern. The device according to the first item of the patent application, wherein the electrode arrangement has a spiral or circular pattern. The device according to the first item of the scope of patent application, wherein the micro-element area has a variable width on the light through hole of the device. The device as described in item 1 of the scope of patent application further includes a driving signal controller for generating at least one driving signal for the electrode arrangement. The device according to item 15 of the scope of patent application further includes a driving signal controller for generating at least one driving signal for the electrode arrangement, wherein the driving signal controller is configured to selectively combine some of the The electrode is connected to the driving signal, and the other electrodes are disconnected to float. The device according to claim 21, wherein the drive signal controller is configured to drive the device in a beam broadening mode. The device according to item 21 of the scope of patent application, wherein the drive signal controller is configured to alternately connect drive signals to the electrodes of different groups, which correspond to the plurality of beam steering elements of different groups, and The other electrodes are disconnected to float. The device according to claim 1, wherein the beam turning device is configured to turn light on two orthogonal planes. The device described in item 1 of the scope of patent application, wherein the device is a Fresnel lens, and the electrode arrangement includes strip electrodes that define the boundary between the Fresnel microelements. The device described in item 1 of the scope of the patent application includes two liquid crystal layers close to each other, and orthogonal liquid crystal orientations are arranged between the two layers. The device described in item 1 of the scope of patent application includes four liquid crystal layers close to each other, and orthogonal liquid crystal orientations in opposite directions are arranged between the four layers. A liquid crystal optical device configured as a plurality of refraction or refractive Fresnel lens-type element control for beam steering of light passing through a light through hole, the device comprising: a liquid crystal material layer, contained by a substrate, the substrate having an alignment layer An electrode arrangement, which is configured to form a spatially varying voltage distribution in the area of the many micro-elements in the liquid crystal layer; and a pair of liquid crystal layers, each liquid crystal layer having an optically inert area divided Spaced apart microelements, the inert region is not affected by a variable electric field, wherein the combination of the pair of liquid crystal layers provides the desired optical control, and the optically inactive region allows the phase between the liquid crystal and the optically inactive region A sudden change in retardation, where the micro-elements on one liquid crystal layer correspond to the optically inert area of the other liquid crystal layer, and the liquid crystal optical device is configured to provide a spatial variation of the optical phase retardation, which has a boundary between the micro-elements Abrupt change, which approximates the saw-tooth waveform of the boundary of a plurality of micro-elements to increase the effective light through hole of the optical device; wherein the electrode arrangement includes: a patterned electrode structure, which is included on one of the substrates The strip electrode of the substrate, and the middle electrode on the other one of the substrates, the middle electrode is located close to the middle of the micro element and offset from the position relative to the strip electrode, so that the strip The electric field between the strip electrode and the intermediate electrode generates a strong electric field, which has a reduced fringe field near the bias between the strip electrode and the intermediate electrode, and a gradually decreasing fringe field across the intermediate electrode The electric field does not require weakly conductive materials used to generate the voltage distribution of the electrodes on the optical vias in each area. A liquid crystal optical device configured as a plurality of refraction or refractive Fresnel lens-type element control for beam steering of light passing through a light through hole, the device comprising: a liquid crystal material layer, contained by a substrate, the substrate having an alignment layer ;as well as Electrode arrangement, which is configured to form a spatially varying voltage distribution in the area of many micro-elements in the liquid crystal layer; two of the liquid crystal cells, the first of the two cells is provided by an element that is not driven Separate odd-numbered beam steering elements, the second of the two units provides an even-numbered beam steering element separated by an element that is not driven, the odd-numbered beam steering unit and the non-beamed The orientation of the driven elements is the same, and the liquid crystal optical device is arranged to provide a spatial variation of optical phase retardation, which has a sudden change at the boundary between micro elements, which approximates the sawtooth waveform of the boundary of multiple micro elements to increase The effective light through hole of the optical device; wherein the electrode arrangement includes: a patterned electrode structure including a strip electrode on one of the substrates and an intermediate electrode on the other of the substrates, The intermediate electric level is located close to the middle of the steering element and is offset from the position relative to the strip electrode, so that the electric field between the strip electrode and the intermediate electrode generates a strong electric field, which has close The reduced fringe field of the bias between the strip electrode and the middle electrode, and the gradually reduced electric field across the middle electrode, without the need to generate the voltage of the electrode on the optical via in each area Distributed weakly conductive materials.

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