Miniature Camera Module Research Articles

Solar position detection method by bionic polarized light compass.

To address the needs of polarized light navigation for accurate position information of feature points in the sky, an accurate solar position detection method based on an all-sky polarization pattern imaging system is proposed. Unlike the traditional spot-based solar position detection method, this method uses the polarization information inherent in the atmosphere to accurately measure solar position. This approach is characterized by simple detection, high accuracy, and wide application range. The optical acquisition system is composed of three miniature large-field camera modules and polarizers, which enables a more compact structure, smaller size, and lesser height. Based on this principle, the solar position solution algorithm was simulated and then verified in various weather environments using the optical acquisition system built as part of this study. Solar position was detected at different moments on the same day in clear weather, and the accuracy of the measured solar altitude and azimuth angles was 0.024° and 0.03°, respectively. The accuracy of the measured solar altitude and azimuth angles was 0.08° and 0.05°, respectively, when the sun was shielded by high-rise buildings and 0.3° and 0.1° when the sun was shielded by branches and tree leaves. Aerosol concentrations exceeding a certain amount destroyed the Rayleigh distribution pattern of polarized light, thus affecting solar position detection accuracy. It is concluded that this novel detection method can not only meet the needs of polarized light navigation for solar position, but also provide a new exploration idea for enthusiasts who are eager to explore the mysteries of the universe.

Miniature camera module with a hollow linear ultrasonic motor-based focus feature

The construction of a miniature camera module that can explore inside limited spaces is of great interest for the design of millimeter-scale devices, such as endoscopes. This article presents a miniature camera module with a focus feature using a hollow linear ultrasonic motor. The hollow stator, which is simplified by the expansion and thickness-shear piezoelectric effects, is suitable for the miniaturization of the camera module because it can contain a lens group. The linear slider, which is thin and cylindrical with a slit, is inserted into the stator’s hole and generates a preload that exploits optimal motor performance measures. The resultant camera module is 4.6 mm × 4.6 mm square, which is the smallest one of camera modules reported to date. The motion of the miniature camera module is demonstrated by the wire-driven mechanism and a visual feedback control system. The orientation of the camera module head is controlled by a wire-driven mechanism until the target object is set in the range of view. The lens group placed inside the slider is controlled by the hollow linear ultrasonic motor in a visual feedback-loop system.

Design and Implementation of Robust Resonant Controller for Piezoelectrically Driven Micro-Lens Actuator

MEMS based piezoelectrically driven micro-lens actuator experiences resonance frequency shift with changing actuation voltage and exhibits low level of damping. In this paper, we present the design and experimental implementation of a resonant controller, robust against the variation in dynamics, to enhance the damping at the first resonance frequency. The controller is designed using an identified model of the micro-lens actuator from experimental frequency response data at a fixed actuating voltage. The closed-loop stability is guaranteed using the mixed negative-imaginary and small-gain approach. The experimental results demonstrate a damping of 21dB of the first resonance mode. The designed controller achieved the similar level of damping for the shift in resonance frequency due to the change in the actuation voltage. The settling time, due to a step change, of the piezoelectric micro-lens actuator is reduced to 7ms from 120ms. Such quick settling time is necessary for the fast auto-focusing functionality of the piezoelectrically driven micro-lens actuator in a miniaturized camera module. [2022-0137]

A Head-Mounted Multi-Camera System for Electrophysiology and Behavior in Freely-Moving Mice.

Advances in the ability to monitor freely-moving mice may prove valuable for the study of behavior and its neural correlates. Here we present a head-mounted multi-camera system comprised of inexpensive miniature analog camera modules, and illustrate its use for investigating natural behaviors such as prey capture, courtship, sleep, jumping, and exploration. With a four-camera headset, monitoring the eyes, ears, whiskers, rhinarium, and binocular visual field can all be achieved simultaneously with high-density electrophysiology. With appropriate focus and positioning, all eye movements can be captured, including cyclotorsion. For studies of vision and eye movements, cyclotorsion provides the final degree of freedom required to reconstruct the visual scene in retinotopic coordinates or to investigate the vestibulo-ocular reflex in mice. Altogether, this system allows for comprehensive measurement of freely-moving mouse behavior, enabling a more holistic, and multimodal approach to investigate ethological behaviors and other processes of active perception.

Practical Approach for Controlling Optical Image Stabilization System

This paper proposes a practical methodology for designing an optical image stabilization system controller that consists of a gyro signal filter and feedback controller for a smart phone camera module called miniature camera module. Since the advent of smartphone, miniature camera modules have become much more compact and sophisticated than the modules in the digital single-lens reflex camera. Therefore, a greater consideration on designing controller for the miniature camera module is necessary to obtain higher performance. This paper proposes 1) the OIS system’s block diagram connecting the physical part and the controller part and 2) the methodology for designing feedback controller according to the performance index from the block diagram. A linear feedback controller and gyro signal filter are designed using the proposed methodology and its performance is verified via experimentation.

Multifunctional liquid lens for variable focus and zoom

This paper presents a novel multifunctional liquid lens (MLL) for miniature camera modules integrated with smart devices such as smartphones and pads. MLL firstly offers concurrent variable-focus and variable-magnification functions in a single liquid lens system using two different actuation schemes: electrowetting-on-dielectric (EWOD) actuation for controlling the curvature of liquid interface and electromagnetic actuation for controlling the height of the liquid column. Imaging focus test is carried out using the prototype of MLL. When a target electrical voltage is applied to an electrode covered by a hydrophobic dielectric layer on the inside wall of a glass cylindrical lens chamber, the curvature of liquid interface is changed according to the principle of EWOD and the focal length of the lens is changed. As a result, an initially blurred check pattern image is clearly focused. Imaging magnification test is separately conducted. When an electrical voltage is applied to an electromagnetic system located beneath the prototype of MLL, a ring-shaped magnet presses an elastic membrane down. As a consequence, liquid residing in the actuation chamber is pumped into the lens chamber through open walls of a supporting frame, and the height of the liquid column in the lens chamber rises. The height change of the liquid column as a function of the applied voltage is measured by using a CCD camera. The height of the liquid column is linearly increased from 0 mm to 1.2 mm with the rise of applied voltage from 0 V to 50 V with 5 V increment. The average height variation per volt is about 24 μm. For the proof of concept, the sequential imaging focus and magnification test of MLL is demonstrated using simultaneous EWOD and electromagnetic actuation. Finally, the response time of MLL is measured by using a high-speed camera. The proposed MLL offers a simple design structure to be easily miniaturized but covers a wide range of imaging focus and magnification operations for high optical performance.

Design and Simulation of a New Miniature Camera Module Using Voice Coil Motor for Optical Image Stabilization

This paper proposes a new design for miniature camera module, which is mainly used to realize optical image stabilization for mobile device with dual-camera. It can compensate the 3 degrees vibration disturbance introduced by the user’s hand-shake. Finite element analysis (FEA) and design of experiments (DOE) are introduced to find the optimum design. Controller design and simulations based on actual hand-shake data collected from the gyro sensors are presented. Simulation results show that the designed camera module can compensate hand-shake up to 50Hz in 3 degrees.

Development of Miniature Camera Module Integrated With Solid Tunable Lens Driven by MEMS-Thermal Actuator

The design, fabrication, assembly, and characterization of a miniature adjustable-focus camera module driven by MEMS-thermal actuators are presented. The camera module consists of one solid tunable lens for optical power variation, two identical MEMS-thermal actuators integrated with displacement amplifiers for lens element driving, a CMOS image sensor for recording, and necessary CNC fabricated components for supporting and housing. Fully 3D-multiphysics simulations with valid material properties are performed to explore the design and, hence, optimize the performance of the system. In this paper, the fabricated MEMS-devices are clearly demonstrated, and followed by the detailed characterization of the camera module. Static characterizations of the system, including the temperature distribution on actuators, electric resistance change with temperature increase, displacement-voltage curve of actuator, and the focal length tuning capability, are tested. Dynamic response speed and imaging performance of the camera module are also covered. Results show that the designed MEMS actuator is able to provide a maximum output displacement of 135 μm when a 10 V driving voltage is applied. Driven by the thermal actuator, the solid tunable lens presents a repeatable focal length tuning from 9.2 to 7.9 mm with precise focus control. The adjustable-focus capability of the miniature camera module is experimentally demonstrated by clearly focusing targets placed at different object distances.

A Shape-Adjusted Tridimensional Reconstruction of Cultural Heritage Artifacts Using a Miniature Quadrotor

The innovative automated 3D modeling procedure presented here was used to reconstruct a Cultural Heritage (CH) object by means of an unmanned aerial vehicle. Using a motion capture system, a small low-cost quadrotor equipped with a miniature low-resolution Raspberry Pi camera module was accurately controlled in the closed loop mode and made to follow a trajectory around the artifact. A two-stage process ensured the accuracy of the 3D reconstruction process. The images taken during the first circular trajectory were used to draw the artifact’s shape. The second trajectory was smartly and autonomously adjusted to match the artifact’s shape, then it provides new pictures taken close to the artifact and, thus, greatly improves the final 3D reconstruction in terms of the completeness, accuracy and quickness, in particular where the artifact’s shape is complex. The results obtained here using close-range photogrammetric methods show that the process of automated 3D model reconstruction based on a robotized quadrotor using a motion capture system is a realistic approach, which could provide a suitable new digital conservation tool in the cultural heritage field.

A wide-angle camera module for disposable endoscopy

A wide-angle miniaturized camera module for disposable endoscope is demonstrated in this paper. A lens module with 150° angle of view (AOV) is designed and manufactured. All plastic injection-molded lenses and a commercial CMOS image sensor are employed to reduce the manufacturing cost. The image sensor and LED illumination unit are assembled with a lens module. The camera module does not include a camera processor to further reduce its size and cost. The size of the camera module is 5.5 × 5.5 × 22.3 mm3. The diagonal field of view (FOV) of the camera module is measured to be 110°. A prototype of a disposable endoscope is implemented to perform a pre-clinical animal testing. The esophagus of an adult beagle dog is observed. These results demonstrate the feasibility of a cost-effective and high-performance camera module for disposable endoscopy.

Electrowetting-Based Variable-Focus Lens for Miniature Systems

The meniscus between two immiscible liquids of different refractive indices can be used as a lens. A change in curvature of this meniscus by electrostatic control of the solid/liquid interfacial tension leads to a change in focal distance. It is demonstrated that two liquids in a tube form a self-centred variable-focus lens. The optical properties of this lens were investigated experimentally. We designed and constructed a miniature camera module based on this variable lens suitable for mobile applications. Furthermore, the liquid lens was applied in a Blu-ray Disc optical recording system to enable dual layer disc reading/writing.

Variable-focus liquid lens for miniature cameras

The meniscus between two immiscible liquids can be used as an optical lens. A change in curvature of this meniscus by electrowetting leads to a change in focal distance. It is demonstrated that two liquids in a tube form a self-centered lens with a high optical quality. The motion of the lens during a focusing action was studied by observation through the transparent tube wall. Finally, a miniature achromatic camera module was designed and constructed based on this adjustable lens, showing that it is excellently suited for use in portable applications.