Mechanically controlled robotic gripper with bistability for fast and adaptive grasping.

This paper presents a novel bistable gripper inspired by the closure motion found in the jaw of a hummingbird. With a bistable characteristic, the robotic gripper can grasp objects rapidly without applying continuous external force. The bistable gripper comprises a linkage-driven mechanism and two bionic jaws consisting of thin elastic polyvinyl chloride sheets with two clamped ends connected by a hinge. The shape of the thin sheets was modeled and optimized using geometric analysis, and the morphing processes of the bionic jaw were analyzed using finite element simulations and experiments. Furthermore, we explored the motion characteristics of the clamps during the snap-through and snap-back processes and divided the motion into two phases: delay and snap. Force and response time tests show that the proposed bistable gripper can achieve fast bending within milliseconds under a low pull force during the snap phase. Grasping experiments demonstrated that the proposed robotic gripper is adaptable for grasping objects of various shapes and weights. After grasping, the bistable gripper can release the target by pulling the actuating rod and automatically return to the open state. This study reveals the unique bending mechanism of thin sheets that can be exploited for fast, versatile, and adaptive grasping. The bistable gripper exhibits the potential to reduce energy consumption and simplify control when performing tasks in unstructured environments such as space and underwater.

Image enhancement for multilayer information retrieval by using full-field optical coherence tomography.

When a full-field optical coherence tomography (OCT) system is used to extract tomographic images from a multilayer information carrier, the resulting images may suffer from interlayer modulations and parasitic patterns derived from interference fringes. We describe and analyze these negative influences that degrade the quality of extracted tomographic images and propose practical algorithms and methods to minimize them. The emphasis of the discussion will be the removal of the parasitic fringes produced by the imperfection of a CCD camera. The simulative and experimental results of image enhancement for multilayer tomography extraction using full-field OCT are provided.

Bifocal optical system for distant object tracking.

A new bifocal optical system used for distant object tracking is proposed. This system combines a birefringent element with a conventional glass lens so that the spot image size and its variation with the axial distance can be controlled according to the requirement of a distant object tracker. The lens design for the tracking application is discussed and an example is given. The new lens system provides a more uniform spot image size and an extended focal depth compared to a conventional lens with one focus.

Cemented doublet lens with an extended focal depth.

A method of designing a lens with an extended focal depth is studied. The lens is a cemented doublet composed of a birefringent lens and a conventional lens. The crystal optical axis of the birefringent lens is perpendicular to the axis of the optical system. By properly selecting the parameters of the birefringent lens and the conventional lens, we can flexibly configure an imaging system that simultaneously has a large focal depth and high resolution. We also provide a theoretical analysis which shows that the focal depth of the lens is approximately 1.5 times that of a conventional lens.

Optical system having a large focal depth for distant object tracking.

We analyze an optical system after inserting a simple quartic phase plate in its pupil plane to extend the focal depth. The system is used specifically to track distant objects like stars. We design an optimum quartic phase plate for a real lens system which has an effective focal length of 29 mm, an F-number of 1.6, a field of view of 20 degrees, and a working wavelength range of 0.5~0.75 ?m. By introducing the quartic phase plate, we enhance the focal depth of the system more than threefold as compared to a system having no phase plate.