A lead-free tunable lens

Abstract

The present invention relates to the field of optical devices, specifically to tunable optical lens assemblies. These assemblies utilize piezoelectric actuators, including those made from lead-free materials, to dynamically adjust the shape and optical properties of the lens. The invention addresses the need for environmentally friendly and regulatory-compliant alternatives to traditional lead-based piezoelectric materials while maintaining or enhancing the performance characteristics required for applications in consumer electronics, medical devices, industrial machine vision systems, augmented reality devices, and other precision optical systems. Additionally, the invention encompasses the integration of advanced driver integrated circuits (ICs) for efficient control and actuation of the lens system.

Description

[0001] A LEAD-FREE TUNABLE LENS

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to the field of optical devices, specifically to tunable optical lens assemblies.

[0004] In particular, the present invention relates to an optical lens assembly comprising a transparent, deformable, non-fluid lens body sandwiched between a bendable transparent membrane and a transparent back substrate forming a lens and an actuator system for applying forces to change an overall shape of the lens.

[0005] BACKGROUND OF THE INVENTION

[0006] In recent years, there has been a significant push towards environmental sustainability and regulatory compliance in various industries, including optics and electronics.

[0007] The use of lead-containing materials such as traditional PZT (lead zirconate titanate) in actuators for tunable lenses has been popular due to their superior piezoelectric properties, which provide high performance in terms of actuation speed, precision, and reliability.

[0008] While PZT has been a popular choice for actuators in tunable lenses due to its performance advantages, the push towards environmental sustainability and regulatory compliance is driving research and development towards lead-free alternatives. Lead-free piezoelectric materials are being developed to offer similar or improved performance while eliminating the environmental and health concerns associated with lead-containing materials like traditional PZT.

[0009] Due to the environmental regulations and restrictions on lead usage as well as a growing motivation to be more sustainable and more respectful of the nature there is a growing demand for lead-free piezoelectric materials that can replace PZT without compromising on performance. Research and development efforts are focused on finding materials that offer similar or even improved piezoelectric and ferroelectric properties while being environmentally benign.

[0010] Lead-free alternatives such as barium titanate (BaTiOs) and potassium sodium niobate (KNaNi) are being explored for their potential to meet these requirements. These materials aim to provide a balance between high electromechanical coupling coefficients, thermal stability, and mechanical robustness, which are essential for the reliable operation of tunable lenses in various applications. However, manufacturers are increasingly looking for other lead-free alternatives to PZT to ensure compliance and sustainability.

[0011] The adoption of lead-free piezoelectric materials brings several advantages beyond regulatory compliance. Firstly, it addresses the environmental and health risks posed by lead, making the manufacturing and disposal processes safer. Secondly, advancements in material science have enabled the development of lead-free materials with tailored properties that can be optimized for specific applications, potentially offering improved performance characteristics compared to traditional PZT.

[0012] In the technical field of optical lens assemblies, integrating lead-free piezoelectric materials into the actuator systems presents both challenges and opportunities. Actuators play a critical role in the tunability of lenses, allowing for precise control over the focal length and other optical properties. The performance of these actuators directly impacts the quality and functionality of optical devices used in various fields, including consumer electronics, medical imaging, industrial machine vision, and augmented reality. Therefore, the transition to lead-free materials necessitates careful consideration of their electromechanical properties and compatibility with existing lens assembly designs.

[0013] Indeed, to effectively utilize lead-free piezoelectric materials in actuators, there is the need of an associated driver circuitry which must be capable of delivering the required electrical signals with precision and efficiency.

[0014] Hence an improved Lead-free optical assembly comprising advanced driver ICs facilitating the integration of lead-free piezoelectric actuators by providing the necessary control and performance characteristics required for dynamic lens adjustments would be advantageous.

[0015] OBJECT OF THE INVENTION

[0016] It is an object of the present invention to provide an optical lens assembly that incorporates environmentally friendly, lead-free piezoelectric materials for its actuator system, thereby ensuring compliance with environmental regulations and reducing health risks associated with lead-based materials.

[0017] A further object of the present invention is to ensure that the lead-free piezoelectric materials used in the actuator system offer performance characteristics comparable to or better than those of traditional PZT, including high electromechanical coupling, precision, and reliability.

[0018] In particular, it may be seen as an object of the present invention to provide a sustainable, high-performance optical lens assembly which complies with adhering environmental and health safety standards as well as offering performance characteristics suitable for a wide range of applications, including consumer electronics, medical devices, industrial machine vision systems and augmented reality devices and other areas requiring precise optical adjustments.

[0019] It is a further object of the present invention to provide an alternative to the prior art.

[0020] SUMMARY OF THE INVENTION

[0021] The above described objects and several other objects are intended to be obtained in a first aspect of the invention by providing an optical lens assembly comprising : a first bendable transparent membrane having a first and a second opposite surface and a transparent back substrate; a transparent, deformable, non-fluid lens body sandwiched between the first bendable transparent membrane and the transparent back substrate forming a lens having an optical axis; an actuator system for applying forces to the lens cover to change an overall shape of the lens located onto said bendable transparent membrane; wherein the actuator system comprises piezoelectric materials.

[0022] The optical lens assembly of the invention may also be referred to as a Lead-free tunable lens assembly, being optical components that can change their focal length or focus by altering their shape or refractive index without the use of lead- containing materials.

[0023] Integrating these new materials with advanced driver integrated circuits (ICs) like the PD50 series can enable the development of high-performance, environmentally friendly optical systems suitable for a wide range of applications.

[0024] In some embodiments, the optical lens assembly further comprises a frame connected to the first bendable transparent membrane and to the actuator system. In some further embodiments, the transparent back substrate is a second bendable transparent membrane.

[0025] In some embodiments, the actuator system comprises ferroelectric materials, thereby exhibiting a spontaneous electric polarization that can be reversed by applying an external electric field.

[0026] In some other embodiments, the piezoelectric materials are ferroelectric materials

[0027] Ferroelectrics with a huge coercive field materials are a subset of piezoelectric materials in that they also possess a spontaneous polarization, i.e. which remains without applied field in the unit cell, which can be reoriented by application of an electric field.

[0028] Ferroelectric with a huge coercive field materials are a subclass of dielectric materials that possess spontaneous polarization (at least two equilibrium states) which can be switched by an external electric field

[0029] The actuator system may comprise one or more layers of said ferroelectric material.

[0030] Ferroelectric materials with a huge coercive field exhibit spontaneous electric polarization that can be controlled and reversed by applying an external electric field, allowing for highly accurate and responsive actuation.

[0031] The presence of one or more layers of ferroelectric materials may provide better mechanical strength and durability under repeated actuation cycles. This makes the lens assembly with higher tunable range and more reliable over time, reducing the likelihood of performance degradation.

[0032] For example, the actuator system may comprise at least two layers of said ferroelectric materials.

[0033] Incorporating at least two layers of such ferroelectric materials can amplify the force generated by the actuator system. This is particularly beneficial for applications requiring significant mechanical movement or higher force output to achieve the desired optical adjustments.

[0034] Furthermore, multiple layers of ferroelectric materials can offer better control over the actuation process. The layered structure allows for more refined manipulation of the electric fields applied, resulting in smoother and more stable adjustments of the lens shape.

[0035] In some embodiments, the actuator system is located at least onto the first surface of the first bendable transparent membrane or non-transparent beam

[0036] The actuator system may be located on both the first and the second opposite surface of the first bendable transparent membrane.

[0037] Placing actuators on both surfaces of the first bendable transparent membrane / beam allows for more balanced application of ferees. This may result in smoother and more symmetric deformation of the lens, improving optical performance and reducing distortions.

[0038] Having actuators on both sides of the membrane may also provide greater control over the lens shape. This dual-surface actuation may enable more complex and dynamic adjustments, enhancing the versatility of the lens assembly for different applications.

[0039] The combined effect of actuators on both surfaces can lead to improved actuation efficiency and effectiveness. This setup can achieve larger and more precise deformations with less power consumption, optimizing the performance of the optical lens assembly.

[0040] For example, the actuator system may comprise at least two layers of the ferroelectric materials on each of the first and the second opposite surface of the first bendable transparent membrane.

[0041] The actuator on the first surface of the first bendable transparent membrane may comprise at least two layers of the ferroelectric materials and the actuator on the second opposite surface of the first bendable transparent membrane may comprise at least two layers of the ferroelectric materials.

[0042] Using at least two layers of ferroelectric materials on each surface may significantly increase the actuation force generated. This is beneficial for applications requiring substantial mechanical movement or precise control over larger deformations of the lens.

[0043] Multiple layers on both surfaces allow also for fine-tuned control of the electric fields applied to the actuators. This leads to more accurate and nuanced adjustments of the lens shape, enhancing the optical performance and adaptability of the lens assembly.

[0044] By employing multiple layers on both sides, the actuator system may also ensure greater stability and symmetry in lens deformation. This balanced approach minimizes optical aberrations and maintains high-quality imaging.

[0045] The placement and layering of the actuator system on the bendable transparent membrane may provide several advantages in terms of control, performance, stability, and reliability. These benefits enhance the overall functionality and versatility of the optical lens assembly, making it suitable for a wide range of advanced applications.

[0046] In some embodiments, the actuator system comprises AIScN.

[0047] AIScN may produce mechanical displacements or forces in response to an applied electric field, enhancing the actuation performance of the optical lens assembly. AIScN also exhibits excellent thermal stability, maintaining its piezoelectric properties over a wide temperature range. This ensures reliable performance in various environmental conditions, making it suitable for applications in harsh or fluctuating environments.

[0048] Furthermore, AIScN has low dielectric loss, which means it can operate efficiently with minimal energy dissipation. This is particularly important for battery-powered or energy-sensitive applications, as it helps extend the operational lifespan of the device. In summary, the use of AIScN in the actuator system of an optical lens assembly provides significant advantages in terms of piezoelectric performance, environmental safety, thermal stability, mechanical durability, and manufacturing compatibility.

[0049] The optical lens assembly may further comprise a driver integrated circuit (IC) configured for driving capacitive loads to the actuator system.

[0050] A driver IC specifically designed for capacitive loads ensures precise control over the actuator system. This precision is crucial for fine-tuning the shape of the lens, leading to better optical performance and image quality.

[0051] The driver maybe configured to provide selectable polarity.

[0052] Selectable polarity allows the driver to reverse the direction of the electric field applied to the actuators. This enables bidirectional control of the lens deformation, offering more versatile and dynamic adjustments to the lens shape.

[0053] By providing selectable polarity, the driver can maximize the actuation range of the lens system. This leads to greater flexibility in achieving the desired focal adjustments and optical effects.

[0054] In general, the selectable polarity enhances the adaptability of the lens assembly to different operating conditions. It allows for more flexible control strategies, which can be tailored to specific application requirements or environmental changes.

[0055] The optical lens assembly utilizes an actuator system, potentially comprising ferroelectric materials, to deform the lens body and change its overall shape. This actuation system could benefit from a driver IC, which is specifically designed to drive capacitive loads such as the actuators in the lens assembly.

[0056] In some embodiments, the driver IC has a differential output with selectable polarity and includes a digital-to-analog converter (DAC) for controlling an output voltage. Integrating a DAC within the driver IC simplifies the overall system design. It eliminates the need for separate DAC components, reducing the complexity and cost of the optical lens assembly.

[0057] The driver IC with differential output and selectable polarity, along with an integrated DAC, offers significant advantages in terms of signal integrity, control precision, power efficiency, and system simplicity.

[0058] In some further embodiments, the driver IC features a power-on reset circuit to guarantee 0V output voltage at start-up, a power-down mode to reduce current consumption, and integrated electromagnetic interference (EMI) reduction.

[0059] The driver IC is configured to perform a polarity change by first setting the output voltage to zero before the polarity change takes place and then transitioning to the final voltage value.

[0060] The driver IC communicates via an interface operating at up to 400kHz, and the output voltage is controlled through a 10-bit DAC integrated into the driver IC.

[0061] The driver IC may include a fully integrated charge pump that allows for a maximum output voltage of 50V and utilize the 10-bit DAC controlled via an interface for precise voltage regulation.

[0062] The inclusion of a power-on reset circuit guarantees that the optical lens assembly remains in a safe state during power-up, preventing unintended activations that could harm the device. Furthermore, the power-down mode enhances the energy efficiency of the system by minimizing power usage when the device is not actively adjusting the lens, thus prolonging battery life in portable applications.

[0063] Integrated EMI reduction not only ensures compliance with stringent regulatory standards but also maintains the integrity of the optical performance by minimizing potential interference. These features collectively enhance the reliability, efficiency, and regulatory compliance of the optical lens assembly, making it a robust and efficient solution for advanced optical applications. The power-on reset circuit ensures that the output voltage is OV at start-up. This prevents unintended activation of the actuators during power-up, protecting the optical lens assembly from potential damage and ensuring a safe start-up procedure.

[0064] The power-down mode significantly reduces current consumption when the driver IC is not in active use. This feature is particularly beneficial for battery-powered devices, as it helps to extend battery life and improve overall energy efficiency. Integrated EMI reduction helps minimize electromagnetic emissions from the driver IC. This is crucial for maintaining the performance and reliability of the optical lens assembly, as EMI can interfere with other electronic components and degrade the quality of the optical output. The first and other aspects or embodiments of the present invention may each be combined with any of the other aspects and embodiments. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

[0065] BRIEF DESCRIPTION OF THE FIGURES

[0066] The optical lens assembly according to the invention will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

[0067] Figures 1-4 are schematic drawing of an optical lens assembly according to different embodiments of the invention.

[0068] DETAILED DESCRIPTION OF EMBODIMENTS

[0069] Figure 1 is a schematic drawing of an optical lens assembly 1 showing an actuator system multilayer stack located on the top surface of the bendable transparent membrane 6, according to some embodiments of the invention.

[0070] The actuator system of the optical lens assembly 1 comprises a multiple layers comprising ferroelectric layers 4 sandwiched between electrode layers 2 and 3. Electrode layers 2 and 3 may be alternatively connected to ground and to a positive or a negative voltage, thus proving opposite polarities reversing the spontaneous electric polarization of the ferroelectric layers 4.

[0071] The bendable transparent membrane 6 of the optical assembly 1 is located onto a wall 5, such as a Si based wall.

[0072] Figure 2 is an exploded view of the actuator system multilayer of figure 1 located onto the bendable transparent membrane 6.

[0073] Figure 3 is a schematic drawing of an optical lens assembly 7 showing an actuator system multilayer stack 8 located on the bottom surface of the bendable or deformable transparent membrane, according to some other embodiments of the invention.

[0074] The multilayer stack 8 presents layers as shown in figure 2, although inverted in position, due to their location at the bottom surface of the deformable transparent membrane.

[0075] Figure 4 is a schematic drawing of an optical lens assembly 9 showing an actuator system comprising multilayer stacks 10 and 11 located on the bottom and top surface of the deformable transparent membrane, respectively, according to some further embodiments of the invention.

[0076] The multilayer stacks 10 and 11 are a combination of the multilayer stacks of figure 1 and the one of figure 2. Passivation layers (not shown) may be applied on either the top and / or bottom surface of the deformable membrane to protect against humidity that may influence the performance of the ferroelectric and electrode materials used.

[0077] Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

Claims

CLAIMS1. An optical lens assembly comprising:- a first bendable transparent membrane having a first and a second opposite surface and a transparent back substrate;- a transparent, deformable, non-fluid lens body sandwiched between said bendable transparent membrane and said transparent back substrate forming a lens having an optical axis;- an actuator system for applying forces to the first bendable transparent membrane to change an overall shape of the lens, wherein said actuator system is located onto said bendable transparent membrane; wherein said actuator system comprises piezoelectric materials; wherein said actuator system comprises ferroelectric materials, thereby exhibiting a spontaneous electric polarization that can be reversed by applying an external electric field, and wherein said actuator system comprises at least two layers of said ferroelectric materials.

2. An optical lens assembly according to claim 1, further comprising a frame connected to said first bendable transparent membrane and to said actuator system.

3. An optical lens assembly according to any of the preceding claims 1-2, wherein said transparent back substrate is a second bendable transparent membrane.

4. An optical lens assembly according to claim 1, wherein said piezoelectric materials are said ferroelectric materials5. An optical lens assembly according to any of the preceding claims 1-4, wherein said actuator system comprises one or more layers of said ferroelectric material.

6. An optical lens assembly according to any of the preceding claims 1-5, wherein wherein said actuator system is located at least onto said first surface of said first bendable transparent membrane.

7. An optical lens assembly according to any of the preceding claims 1-6, wherein said actuator system is located on both said first and said second opposite surface of said first bendable transparent membrane.

8. An optical lens assembly according to claim 7, wherein said actuator system comprises at least two layers of said ferroelectric materials on each of said first and said second opposite surface of said first bendable transparent membrane.

9. An optical lens assembly according to any of the preceding claims 1-8, wherein said actuator comprises AIScN.

10. An optical lens assembly according to any of the preceding claims 1-9, further comprising a driver integrated circuit (IC) configured for driving capacitive loads to said actuator system.

11. An optical lens assembly according to claim 10, wherein said driver is configured to provide selectable polarity.

12. An optical lens assembly according to any of the preceding claims 9-11, wherein said driver IC has a differential output with selectable polarity and includes a digital-to-analog converter (DAC) for controlling an output voltage.

13. An optical lens assembly according to any of the preceding claims 9-12, wherein said driver IC features a power-on reset circuit to guarantee 0V output voltage at start-up, a power-down mode to reduce current consumption, and integrated electromagnetic interference (EMI) reduction.

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