A New Range Finding Method Using a Varifocal Mirror

A new range finding method is proposed in this paper which makes use of a varifocal mirror. The three-dimensional object space is first discretized into a sequence of spherical shells with a specially designed nonlinear vibrating varifocal mirror. These discrete spherical shell images are then recorded by a video camera. A deblurring algorithm is introduced in this paper which is used to remove the blurred components in the images. Different depth ranges can be obtained by controlling the vibration amplitude and the direct current component of the driving wave for the varifocal mirror. The depth accuracy is adjusted by varying the vibration period of the varifocal mirror. This range finding technique can be made real time by increasing the frame frequency of the camera

MEMS Varifocal Mirror for High-Power Laser Focusing

Today, lasers are used in many surgical procedures due to their ability of performing precise incisions, and ablations. With the development of fiber-coupled lasers, even minimally invasive procedures started making use of laser tools. However, existing fiber tools do not provide the same performance as traditional laser systems, often causing significantly more tissue carbonization. This can be attributed to the lack of optics in fiber tools, which requires the tip of the fiber to be placed in direct contact with the tissue, increasing the collateral damage of the laser. To avoid this issue, a compact focusing system should be integrated in the fiber tool. However, traditional optical systems based on moving lenses are too large and bulky for that. To solve this problem, this thesis proposes a focusing system based on MEMS deformable mirrors. Using microfabrication methods, we develop a novel MEMS varifocal mirror, designed for focusing high-power laser in a fiber laser system. The design of this mirror is based on state-of-the-art MEMS deformable mirrors, which have been proposed for microscopy applications, with significant adaptations for high-power lasers, including different actuation mechanisms and control strategies. We explore the use of hydraulic actuation to achieve large focal length range, while providing compatibility with high-power laser. The deflection of the mirror is controlled using a feed-forward model, in which parameters are obtained through characterization of the fabrication process. This allows controlling the mirror without a beam splitter or external sensors, which contributes to the miniaturization of the focusing system

Losing Focus: Can It Be Useful in Robotic Laser Surgery?

This paper proposes a method to regulate the tissue temperature during laser surgery by robotically controlling the laser focus. Laser-tissue interactions are generally considered hard to control due to the inherent inhomogeneity of biological tissue, which can create significant variability in its thermal response to laser irradiation. In this study, we use methods from nonlinear control theory to synthesize a temperature controller capable of working on virtually any tissue type without any prior knowledge of its physical properties. The performance of the controller is evaluated in ex-vivo experiments.Comment: Provisionally Accepted at the Hamlyn Symposium on Medical Robotics 202

Statics and dynamics of electrothermal micromirrors

Adaptive and smart systems are growing in popularity as we shift toward personalization as a culture. With progressive demands on energy efficiency, it is increasingly important to focus on the utilization of energy in a novel way. This thesis investigates a microelectromechanical system (MEMS) mirror with the express intent to provide flexibility in solid state lighting (SSL). By coupling the micromirror to an optical source, the reflected light may be reshaped and directed so as to optimize the overall illumination profile. In addition, the light may be redirected in order to provide improved signal strength in visible light communications (VLC) with negligible impact on energy demands. With flexibility and full analog control in mind, the design of a fully integrated tip-tilt-piston micromirror with an additional variable focus degree of freedom is outlined. Electrothermal actuators are used to both steer the light and tune the focal length. A detailed discussion of the underlying physics behind composite beams and thermal actuators is addressed. This leads directly into an overview of the two main mirror components, namely the segmented mirror and the deflection actuators. An in-depth characterization of the dynamics of the mirror is discussed including the linearity of the thermal response. Frequency domain analysis of such a system provides insight into tunable mechanical properties such as the resonant frequency and quality factor. The degenerate resonant modes can be separated significantly. It is shown that the frequency response may be tuned by straining specific actuators and that it follows a predictable pattern. As a result, the system can be scanned at increasingly large angles. In other words, coupled mechanical modes allow variable damping and amplification. A means to determine the level of coupling is examined and the mode shape variations are tracked as a function of the tuning parameters. Finally, the applications of such a device are explored and tested. Such applications include reliable signal-to-noise ratio (SNR) enhancements in VLC of 30 dB and color tunable steerable lights using laser diodes. A brief discussion of the implications of dynamic illumination and tunable systems is juxtaposed with an explanation behind the integration of an electrothermal micromirror and an all digital driver

Format and basic geometry of a perspective display of air traffic for the cockpit

The design and implementation of a perspective display of air traffic for the cockpit is discussed. Parameters of the perspective are variable and interactive so that the appearance of the projected image can be widely varied. This approach makes allowances for exploration of perspective parameters and their interactions. The display was initially used to study the cases of horizontal maneuver biases found in experiments involving a plan view air traffic display format. Experiments to determine the effect of perspective geometry on spatial judgements have evolved from the display program. Several scaling techniques and other adjustments to the perspective are used to tailor the geometry for effective presentation of 3-D traffic situations

Characterization of a fast piezoelectric varifocal MEMS mirror

We present the characterization of a novel design for a varifocal MEMS mirror with piezoelectric actuation and defocus movement up to 100 kHz. The device was simulated using a finite-element method, fabricated using a multi-user silicon-oninsulator process, and its mechanical response to piezoelectric actuation evaluated through laser vibrometry and a dynamic white-light interferometer

Three--dimensional medical imaging: Algorithms and computer systems

This paper presents an introduction to the field of three-dimensional medical imaging It presents medical imaging terms and concepts, summarizes the basic operations performed in three-dimensional medical imaging, and describes sample algorithms for accomplishing these operations. The paper contains a synopsis of the architectures and algorithms used in eight machines to render three-dimensional medical images, with particular emphasis paid to their distinctive contributions. It compares the performance of the machines along several dimensions, including image resolution, elapsed time to form an image, imaging algorithms used in the machine, and the degree of parallelism used in the architecture. The paper concludes with general trends for future developments in this field and references on three-dimensional medical imaging

Beam shaping with tip-tilt varifocal mirror for indoor optical wireless communication

MEMS mirrors are currently used in many applications to steer beams of light. An area of continued research is developing mirrors with varifocal capability that allows the beam to be shaped and focused. In this work, we study the varifocal capability of a 380 mu m diameter, thermally actuated MEMS mirror with a +/- 40 degrees tip-tilt angle and a radius of curvature between -0.48 mm to 20.5 mm. Light is coupled to the mirror via a single mode optical fiber, similar to an indoor optical wireless communication architecture. The performance of the mirror is characterized with respect to (1) the profile of the reflected beam as the mirror deforms and (2) the mirror's impact when integrated into an optical communication system. We found that the mirror can focus light to a beam with a 0.18 degrees half-angle divergence. Additionally, the ability to change the shape of fiberized light from a wide to narrow beam provides an unmatched level of dynamic control and significantly improves the bit error rate in an optical communication system. (C) 2017 Optical Society of America