Yuxin Peng

Differential time domain method improves performance of pulsed laser ranging and three-dimensional imaging.

A ranging method based on the differential time domain method (DTDM) is proposed in order to improve ranging accuracy and the range of active measurement based on peak discriminator (PD). We develop mathematical models and deduce that zero-crossing sensitivity is an important factor, which affects the ranging error of DTDM. Additionally, zero-crossing sensitivity is determined by delayed time. We carried out relative experiments and obtained the smallest ranging error when delayed time is receiving pulse width. We also compare ranging, three-dimensional (3D) point clouds and depth images based on two methods under same testing conditions. The results show that DTDM is beneficial in improving performance of pulse laser ranging and 3D imaging.

Modeling and simulations on retina-like sensors based on curved surface.

A space-variant lens array on a curved surface (SVLACS) with a large field of view is proposed to decrease the size and improve the performance of a space-variant lens array on a plane (SVLAP). The whole mathematical models are developed and tested, and comparative simulations between SVLACS and SVLAP are carried out. Under the identical simulated situations, the radius of SVLACS decreases to 58% of SVLAP. Meanwhile, the performance of optical information loss rate is improved from 0.22 to 0.08. The results are beneficial for designing a retina-like image sensor based on SVLACS.

A linear actuator for precision positioning of dual objects

In this paper, a linear actuator for precision positioning of dual objects is proposed based on a double friction drive principle using a single piezoelectric element (PZT). The linear actuator consists of an electromagnet and a permanent magnet, which are connected by the PZT. The electromagnet serves as an object 1, and another object (object 2) is attached on the permanent magnet by the magnetic force. For positioning the dual objects independently, two different friction drive modes can be alternated by an on–off control of the electromagnet. When the electromagnet releases from the guide way, it can be driven by impact friction force generated by the PZT. Otherwise, when the electromagnet clamps on the guide way and remains stationary, the object 2 can be driven based on the principle of smooth impact friction drive. A prototype was designed and constructed and experiments were carried out to test the basic performance of the actuator. It has been verified that with a compact size of 31 mm (L) × 12 mm (W) × 8 mm (H), the two objects can achieve long strokes on the order of several millimeters and high resolutions of several tens of nanometers. Since the proposed actuator allows independent movement of two objects by a single PZT, the actuator has the potential to be constructed compactly.

Method based on bioinspired sample improves autofocusing performances

Abstract. In order to solve the issue between fast autofocusing speed and high volume data processing, we propose a bioinspired sampling method based on a retina-like structure. We develop retina-like models and analyze the division of sampling structure. The optimal retina-like sample is obtained by analyzing two key parameters (sectors and radius of blind area) of the retina-like structure through experiments. Under the typical autofocus functions, including Vollath–4, Laplacian, Tenengrad, spatial frequency, and sum-modified-Laplacian (SML), we carry out comparative experiments of computation time based on the retina-like sample and a traditional uniform sample. The results show that the retina-like sample is suitable for those autofocus functions. Based on the autofocus function of SML, the average time of uniform sample decreases from 3.5 to 2.1 s for the retina-like sample.

Improving the performance of time-domain pulsed echo laser profile using tunable lens

We theoretically and experimentally examined the effects of the different positions between receiving lens (RL) and detector, namely, defocus, off-axis, and tilt, on the time-domain pulsed echo laser profile (TDPELP). Results show that distortions including saturation and broadening of TDPELP are obtained, regardless of the position between RL and detector. Thus, we adjust the focal length of RL to successfully obtain an optimal TDPELP using tunable lens under extreme situations, such as too strong or too weak intensity of the TDPELP.

Three-dimensional pulsed laser imaging based on retina-like structure

We propose a three-dimensional imaging system based on retina-like structure. The system has advantages of space-variant resolution, rotation and scaling invariance. Those properties are more suitable where requires high speed and large volume data processing.

Design of a linear-rotary micro-stage

This paper presents a linear-rotary micro-stage that can generate motions along and about the Z-axis using piezoelectric elements (PZTs). The small stroke of a PZT is extended by repeating the PZT motions based on a mechanism of impact friction drive. The friction drive mechanism has a simple driving unit, which only consists of a PZT element and a friction element. The moving element of the stage, which is a steel cylinder, is supported and actuated by a driving unit, which consists of two PZTs and a friction component made by permanent magnet. The magnetic force is employed for holding the moving element and stabilizing the driving condition. The dimension of the stage is 7.0 mm × 8.8 mm × 7.5 mm. The moving ranges of the stage are about 5.0 mm in the Z-direction and 360 degrees in the θz-direction, respectively. The maximum moving speeds are approximately 30 mm/s and 84 rpm in the two directions, respectively.