Real-time distortion correction of fish-eye lens based on Bayer image signal

The imaging system based on a fish-eye lens generally has to correct the distortion of fish-eye images. The distortion correction based on the Bayer image signal is valuable, such as reducing the computation burden of image signal processing chips and providing a new imaging system structure of fish-eye lens. In this paper, a distortion correction method of fish-eye lens based on the Bayer image signal is proposed. Firstly, a distortion correction method that focuses on vertical straight lines and processing delay is proposed. Secondly, according to the correlation among color channels of the Bayer image, a novel Hermite interpolation method appropriate for Bayer image signal is proposed. Finally, a prototype system of fish-eye-lens-based imaging is established and the real-time field-programmable gate array (FPGA) implementation of the proposed method is demonstrated. The experiment demonstrates that the proposed distortion correction is not only characteristic of real-time processing and the smaller computation amount, but also applicable to embedded hardware.     

用于监控系统的鱼眼镜头光学设计

为了满足监控系统中单镜头可实现全景监控的需求,运用仿生学原理,在原有鱼眼镜头的基础上结合监控系统的需求,运用ZEMAX软件设计了一款视场为180°,相对孔径为1/1.6的鱼眼镜头.该镜头由9片透镜组成,总长度为68.5mm,采用1/3英寸CCD作为图像接收器件.在120lp/mm时,其MTF曲线在轴上大于0.4,在80...     

Design of object surveillance system based on enhanced fish-eye lens

A new method is proposed for the object surveillance system based on the enhanced fish-eye lens and the high speed digital signal processor （DSP）. The improved fish-eye lens images an ellipse picture on the charge-coupled device （CCD） surface, which increases both the utilization rate of the 4：3 rectangular CCD and the imaging resolution, and remains the view angle of 183° The algorithm of auto-adapted renewal background subtraction （ARBS） is also explored to extract the object from the monitoring image. The experimental result shows that the ARBS algorithm has high anti-jamming ability and high resolution, leading to excellent object detecting ability from the enhanced elliptical fish-eye image under varies environments. This system has potential applications in different security monitoring fields due to its wide monitoring space, simple structure, working stability, and reliability.     

基于热声相控阵列的声聚焦效应

研究基于热声相控阵列的宽频带声聚焦效应.设计新型热声相位控制单元,通过改变单元的空气温度控制声波波速,实现声波透射与反射相位延迟覆盖2π区间.设计四种不同类型的热声相控阵列聚焦透镜,采用8种或2种热声相位控制单元分别实现了透射与反射声聚焦效应.与其他类型的声聚焦透镜相比,热声相控阵列聚焦透镜具有宽频带、高聚焦性能、设计方案简单等优点.     

Thermoacoustic-reflected focusing lens based on acoustic Bessel-like beam with phase manipulation

We report the realization of broadband reflected acoustic focusing lenses based on thermoacoustic phased arrays of Bessel-like beams, in which the units of phase manipulation are composed of three rigid insulated boundaries and a thermal insulation film in air with different temperatures. Based on these units, we realize a reflected focusing lens which can focus reflected acoustic energy on a line, and its fractional bandwidth can reach about 0.29. In addition, we discuss the influences of the base angle of Bessel-like beam, the number of basic unit, and the variation of unit temperature on focusing performances in details. Furthermore, the reflected focusing lens for the cylindrical acoustic wave based on the Bessel-like beam is also demonstrated. The proposed focusing lens has the advantages of a broad working bandwidth, large focus size,and high robustness, which may provide possibilities for the design and application of acoustic lenses.     

基于近零折射率材料的声非对称聚焦透镜

研究基于近零折射率声子晶体的声非对称聚焦透镜。声非对称聚焦透镜的两侧分别为竖直平面与圆弧面结构,由于近零折射率材料的声波方向选择性,当声波从竖直平面一侧入射时,可以通过透镜,实现高性能声聚焦效应;而当声波从圆弧面一侧任意方向入射时,声波无法通过透镜,从而实现同时具有聚焦与非对称传输特性的声学透镜。在此基础上,改变透镜圆弧面的曲率半径,可以调控非对称透镜的正向聚焦焦点位置,且声非对称传输性能保持不变.此外,透镜内部的刚性散射体对声非对称聚焦性能的影响较小。研究结果表明所设计的声非对称聚焦透镜具有多功能、单一结构及高鲁棒性等优点,为设计新型近零折射率声学器件提供相应的理论方案与实验参考.      

Horizontal parallax distortion in toed-in camera with wide-angle lens for mobile device

An effect of the toed-in camera configuration is keystone distortion, which causes vertical and horizontal parallax in the stereoscopic image. The horizontal parallax is the source of the depth plane curvature. However, if the stereoscopic image captured by the toed-in camera system with fish-eye lens is displayed on mobile device, it is uncomfortable to view because the horizontal parallax contains horizontal parallax distortion occurred by the wide field of view of the lenses. Therefore, in this paper, we propose a novel correction method of the horizontal parallax distortion, which is one of the keystone distortions, in a toed-in camera with fish-eye lenses for mobile device. We have experimented to attest the proposed method. In experiment, we used two charge coupled device cameras, whose field of view is 48.48°. In addition, the captured stereoscopic image was corrected for the barrel distortion and the horizontal parallax distortion. Therefore, the proposed method provides correcting of the horizontal parallax distortion from a toed-in camera system in order that the users can enjoy three-dimensional effects without the visual fatigue. Additionally, the proposed method is able to apply to toed-in camera consisting of any kinds of cameras.     

红外热成像鱼眼镜头设计中若干特殊问题的处理

提出鱼眼镜头光阑球差的级数表达式及其基于有限差分的近似计算方法,解决了通常的光阑倒追方法面临的难题;讨论孔径光阑与入瞳的特殊"共轭"关系,分析了光阑彗差和像差渐晕;运用Aitkin插值技术填补"溢出"光线在像面上的落点,以保证像质函数定义的一致性,维持自动优化持续进展,从而克服频繁的光线"溢出"造成的严重困难;提出充分利用像差渐晕改善像面照度均匀性的方法;论述标定轴外光束边界的逐次渐近过程和运用入瞳距离变量实现孔径光阑位置全域优化的技术.     

Broadband acoustic focusing by symmetric Airy beams with phased arrays comprised of different numbers of cavity structures

We realize broadband acoustic focusing effect by employing two symmetric Airy beams generated from phased arrays,in which the units of the phased arrays consist of different numbers of cavity structures, each of which is composed of a square cavity and two inclined channels in air. The exotic phenomenon arises from the energy overlapping of the two symmetric Airy beams. Besides, we demonstrate the focusing performance with high self-healing property, and discuss the effects of structure parameters on focusing performance, and present the characteristics of the cavity structure with straight channels. Compared with other acoustic lenses, the proposed acoustic lens has advantages of broad bandwidth(about 1.4 kHz), high self-healing property of focusing performance, and free adjustment of focal length. Our finding should have great potential applications in ultrasound imaging and medical diagnosis.     

Automatic surveillance system using fish-eye lens camera

This letter presents an automatic surveillance system using fish-eye lens camera. Our system achieves wide-area automatic surveillance without a dead angle using only one camera. We propose a new human detection method to select the most adaptive classifier based on the locations of the human candidates. Human regions are detected from the fish-eye image effectively and are corrected for perspective versions. An experiment is performed on indoor video sequences with different illumination and crowded conditions, with results demonstrating the efficiency of our algorithm.     

一款宽光谱鱼眼镜头的设计

讨论了一款用于监控侦查的鱼眼镜头设计.首先根据使用要求,选择了可以由图像直接提取出目标方位信息的等距离投影方式;又由系统对目标分辨率的要求,选择了焦距相对较长的全帧成像形式.通过合理布局系统结构及材料选择,使各种像差得到较好的校正,并通过加大光阑慧差改善系统照度均匀性.最终设计出工作波段486～900nm,视场180°,F/2.8的宽光谱鱼眼镜头,设计结果系统全视场在乃奎斯特频率63lp/mm处的调制传递函数大于0.3,边缘视场照度大于中心视场照度的50%,f-θ畸变小于3%,各项指标满足系统要求.     

Non-iterative spot center location algorithm based on Gaussian for fish-eye imaging laser warning system

The directional accuracy of threaten laser is highly dependent on the laser spot center location accuracy for the laser warning system. On the basis of analyzing the spot features on wide field of view (FOV) fish-eye imaging laser warning system, a refinement of existing methodology based on fitting a 2D Gaussian distribution for estimating the center of the spot is developed. The proposed procedure is using a linear least squares based algorithm to determine the best-fitting parameters of the Gaussian. However, in contrast to the standard Gaussian Fitting procedure, this new scheme gives rise to equations that are rigorously linear in the transformed unknown parameters which can be solved easily by linear least squares estimators. To validate the accuracy of the proposed algorithms, experimental approaches with a type of laser warning detector and simulated threaten laser in laboratory are used to quantify its performance. The experimental results show that this method outperforms significantly the commonly used location technique. It is less susceptible to the non-100% fill ratio of CMOS and large unsymmetrical optical aberration of fish-eye lens. The positioning precision in paraxial region and 80° incident angle region are 1/60 pixels, 1/30 pixels respectively. The biggest error is less than 1/20 pixels. The proposed method is suitable for wide FOV laser warning system for high accuracy and low computational complexity.     

通用型数字鱼眼镜头检测系统的设计

设计了一种通用型数字鱼眼镜头检测系统,由照明系统、检测标板、等效平行平板系统和球幕组成。照明系统内部设有平面反光镜、柱体蝇眼透镜阵列、准直物镜,起到了缩小系统体积,提高光能利用率和照明均匀性,以及实现照明光斑大小尺寸可调的作用。其球幕内壁刻有角度分划尺,用于测量被测镜头的视场角。测试系统的照明视场范围为φ8.1 mm~φ36.3 mm,照度均匀度达到91%,光通量大于5 000 lm,且大小可调。检测系统可实现对芯片尺寸为0.55″~1.55″的1DLP、3DLP、3LCD、3LCOS的各种类型的数字投影或放映鱼眼镜头的像方视场角、分辨率、彩色还原性能、色差等性能和放映效果进行测试,降低了检测成本,通用性强。     

一款宽光谱鱼眼镜头的设计

讨论了一款用于监控侦查的鱼眼镜头设计.首先根据使用要求,选择了可以由图像直接提取出目标方位信息的等距离投影方式;又由系统对目标分辨率的要求,选择了焦距相对较长的全帧成像形式.通过合理布局系统结构及材料选择,使各种像差得到较好的校正,并通过加大光阑慧差改善系统照度均匀性.最终设计出工作波段486~900 nm,视场180°,F/2.8的宽光谱鱼眼镜头,设计结果系统全视场在乃奎斯特频率63 lp/mm处的调制传递函数大于0.3,边缘视场照度大于中心视场照度的50%,f-θ畸变小于3%,各项指标满足系统要求.     

Maxwell fish-eye and Eaton lenses emulated by microdroplets

Despite strong experimental and theoretical evidence supporting superresolution imaging based on microlenses, the imaging mechanisms involved are not well understood. Based on the transformation optics approach, we demonstrate that a microlens may act as a two-dimensional fish-eye or an inverted Eaton lens. An asymmetric inverted Eaton lens may exhibit considerable image magnification, which has been confirmed experimentally.     

Near-field multiple super-resolution imaging from Mikaelian lens to generalized Maxwell's fish-eye lens

Super-resolution imaging is vital for optical applications, such as high capacity information transmission, real-time bio-molecular imaging, and nanolithography. In recent years, technologies and methods of super-resolution imaging have attracted much attention. Different kinds of novel lenses, from the superlens to the super-oscillatory lens, have been designed and fabricated to break through the diffraction limit. However, the effect of the super-resolution imaging in these lenses is not satisfactory due to intrinsic loss, aberration, large sidebands, and so on. Moreover, these lenses also cannot realize multiple super-resolution imaging. In this research, we introduce the solid immersion mechanism to Mikaelian lens (ML) for multiple super-resolution imaging. The effect is robust and valid for broadband frequencies. Based on conformal transformation optics as a bridge linking the solid immersion ML and generalized Maxwell's fish-eye lens (GMFEL), we also discovered the effect of multiple super-resolution imaging in the solid immersion GMFEL.     

利用维纳滤波改善声透镜光声成像系统的分辨率

为了克服衍射效应对光声成像系统分辨率的限制,需要采用逆卷积方法进行图像反演.从理论上分析了声透镜成像原理,模拟仿真了声透镜的点扩展函数对声透镜成像系统分辨率的影响和维纳滤波解卷积方法复原光声成像的过程,并利用自搭建的声透镜光声成像系统进行了深入的实验研究,得到了物平面上相距4 mm和3 mm的两个黑胶带点的直接成像光声...     

基于鱼眼镜头的目标监控与测量系统分析

为了实现超大范围的目标监控与测量,设计和分析了一种基于鱼眼镜头的超广角监测系统。以鱼眼镜头和CCD作为图像采集系统,以DSP作为控制和处理中心,采用自适应动态更新背景差方法进行目标识别,利用图像处理方法进行目标方位角测量,对前方半球空间中可能出现的目标进行监测。实验结果表明,基于鱼眼镜头的监控系统具有超大的监控视角,在各种环境下都具有较高的监控能力;基于动态更新背景的背景差目标识别方法具有较强的抗干扰性,能准确地识别出各种可能出现的目标,并能对其进行方位角测量。相对于传统的监控系统来说,具有监控范围大,结构简单,工作稳定可靠,在各种安全监控领域有着广泛的应用。     

鱼眼镜头的光瞳

本文介绍了在设计鱼眼镜头时,在不同的视场角情况下,入瞳和光阑的位置,以及对f′_1、D、l_p和h_p的要求。     

基于蜷曲空间结构的近零折射率声聚焦透镜

研究基于蜷曲空间结构的近零折射率声聚焦透镜.根据近零折射率材料的声波方向选择机理,采用蜷曲空间结构为基本单元进行排列,设计具有特定入射与出射界面的几何结构,对透射声波的出射方向进行调控,实现了平面声波与柱面声波的聚焦效应,并深入讨论了透镜内部刚性散射体对声聚焦性能的影响.在此基础上,改变近零折射率透镜的出射界面,可以精确调控声波阵面的形状与方向.该类型透镜具有单一的单元结构、高聚焦性能及高鲁棒性等优点.研究结果为设计新型近零折射率声聚焦透镜提供了理论指导与实验参考,同时也为研究声波阵面的调控提供了新思路.