基于自由曲面的LED准直透镜设计

本文基于准直光束照明的自由曲面透镜设计方法,设计了一种以单颗LED为光源的准直透镜,其可应用于投影仪的照明系统。根据几何光学原理构造自由曲面,该方法无需求解复杂的偏微分方程,计算简单。准直透镜由内自由曲面折射面、球面、抛物面全反射曲面以及平面组成,利用Matlab编程求出自由曲面轮廓曲线的离散数据点,导入Solidworks中进行曲线拟合,建立透镜的实体模型。为探讨LED光源尺寸对准直透镜光斑影像的影响,在Tracepro中对透镜进行非序列光线追迹,模拟结果表明:当光源半径不大于1 mm时,其光学效率达到86.26%以上,视场半角达到3.3度以内。     

基于几何曲面结构的金属狭缝阵列透镜研究

金属狭缝阵列透镜是一种通过激发和操控表面等离子体激元,突破衍射极限,实现光束调控的纳米光子器件。如何快速、高效地设计具有一定功能的金属狭缝阵列,并且在不影响器件功能的前提下,增大狭缝尺寸,使器件便于加工,是该类器件走向实际应用的关键问题。本文提出一种可以实现光束调控的新的金属狭缝阵列透镜的设计方法,将金属狭缝阵列作成几何曲面结构,可快速、高效地设计透镜,实现光束的调控作用。该方法设计的透镜,金属狭缝尺寸在80 nm,便于设计之后的加工制备,将加速纳米光子器件的实用化。     

新型太阳能收集器可成为一种强光源

芝加哥大学E.费米研究所的R.Winston教授和博士后学生P.Gleckmar成功地设计了一种新型高效太阳能收集器。这种收集器用了一种与一般光学成像透镜完全不同的非成像光学透镜,后者的主要功能在于使太阳能的收集率达到最高。再辅以特别设计的光学腔及高折射率的油,它可以输出强度超过入射光强6万倍的宽     

微热模塑法制备聚苯乙烯球面微透镜阵列

用软刻蚀中的微热模塑技术制备聚苯乙烯(PS)微立方体阵列, 再利用材料在液态或熔融状态时其表面自由能会不断地减小直至最低从而达到最稳定的状态这一特性, 通过加热熔融方法成功地将PS微立方体结构变成了PS微半球体结构, 光学成像测试验证了PS微半球体阵列具有良好的光学成像功能, 可以作为微透镜阵列使用. 用微热模塑技术制备高聚物的微透镜阵列, 其过程简单, 成本低, 适用于很多材料, 所制备的微透镜阵列结构精确度高, 并因所用到的模具为弹性印章, 有望在非平面上制备微透镜阵列, 为微透镜阵列的制备提供了一种新的途径.     

亚微米级红色荧光粉NaEu(MoO4)2的水热合成及光谱特性

20世纪90年代,GaN基发光二极管(LED)技术上的突破为白光LED的出现奠定了基础[1～3].白光LED作为一种新型固态照明光源已备受瞩目,它具有光效高,寿命长,无污染等优点[4,5].实现白光LED有多种方案.最理想的是将近紫外LED芯片与可被近紫外有效激发而发射红、绿、蓝三基色荧光体有机结合组成白光LED[6].     

采用丝网印刷技术制备发光陶瓷并实现仿自然光照明

近年来白光LED照明技术广泛应用,但仍然存在散热差和蓝光过高的问题。以透明Al_2O_3陶瓷为基片,与多种LED发光材料、介质及基础釉料复合制作发光陶瓷。改变荧光粉的组成及发光层的厚度,可以调节发射光谱和发光效率。在此发光陶瓷的基础上,组装LED芯片,得到散热性好和仿自然光LED照明器件。此LED照明器件色温5127 K,色坐标为(0.3427, 0.3654),显色指数R_a达到98,发光效率85 Lm·W~(-1)。     

长春应化所红光荧光粉制备实现新突破

由中科院长春应化所科研人员研制的“一种发光二极管用红光荧光粉及制备方法”，实现了红光荧光粉制备的新突破，为使LED更广泛地用于照明、显示和背光源等领域进一步奠定了基础，近日获得国家发明专利授权。     

无透镜数字全息显微成像技术与应用

针对微结构和微光学元件等微小物体的表面定量检测,本文介绍了一种利用无透镜数字全息的快速、无损的显微成像方法。首先介绍了基于球面波的无透镜数字全息显微成像技术的基本原理,采用CCD作为光电转换器件,基于迈克尔逊干涉光路,设计了无透镜数字全息显微成像系统,利用反射镜构成折反式光路,系统结构简单、紧凑,提升了系统便携性。然后利用USAF1951分辨率板对构建的成像系统进行了标定实验,得出其横向分辨率为6.69μm,放大倍率为3.375,系统工作距离为12.0mm。此外,还对晶圆表面结构进行实际测量。实验验证了该系统的可行性和有效性,有望进一步应用于MEMS、微光学元件、光学元件等表面形貌的定量测量中。     

便携式低压钠灯电子镇流器设计

针对现有低压钠灯光源功耗高、输出稳定性差的问题，提出一种便携式低压钠灯电子镇流器设计方法。通过分析低压钠灯伏安特性曲线，对比现有典型低压钠灯镇流器的特点，根据低压钠灯工作原理设计相应的镇流电路。在电磁滤波的基础上，加入功率因数校正及恒功率控制电路以保证电路输出功率的稳定，加入LC谐振电路以保证电路输出频率的稳定，通过反馈控制实现电路的可靠工作。采用GP20NA-1型低压钠灯作为输出对象对低压钠灯电子镇流器输出电压、电流及低压钠灯辐射光谱进行验证，结果表明，低压钠灯电子镇流器输出功率稳定，常态下输出功率不大于20 W，钠灯辐射光谱稳定于589.3 nm，在光学计量、实验室照明等方面具有较高的应用价值。     

Sr3SiO5:Eu2+荧光粉的微波合成及性能研究

0 引 言 白光LED是一种具有广阔前景的节能照明灯具,被誉为人类的第四代照明用灯具.白光LED实现主要有两种方案,其中在蓝光LED芯片上涂覆黄色荧光粉,蓝光芯片发出的蓝光与荧光粉发出的黄光复合而获得白光,受到人们的重点关注[1-5].     

Sensitivity enhancement of fluorescence detection in CE by coupling and conducting excitation light with tapered optical fiber

This paper reports the enhancement of sensitivity of detection for in‐column fiber optic‐induced fluorescence detection system in CE by tapered optical fiber (TOF). Two types of optical fiber, TOF and conventional cylindrical optical fiber (COF), were employed to construct the CE (TOF‐CE and COF‐CE) and were compared for sensitivity to riboflavin (RF). The fluorescence intensities from a RF sample with excitation light sources and fibers at various coupling angles were investigated. The fluorescence signal from TOF‐CE was ca. ten times that of COF‐CE. In addition, the detection performance of four excitation light source‐fiber configurations including Laser‐TOF, Laser‐COF, LED‐TOF, and LED‐COF were compared. The LODs for RF were 0.21, 0.82, 0.80, and 7.5 nM, respectively, for the four excitation light source–fiber configurations. The results demonstrate that the sensitivity obtained by LED‐TOF is close to that of Laser‐COF. Both Laser‐TOF and LED‐TOF can greatly improve the sensitivity of detection in CE. TOF has the major attribute of collecting and focusing the excitation light intensity. Thus, the sensitivity obtained by LED‐TOF without focusing lens is just same as that of LED‐COF with a focusing lens. This demonstrates that the CE system can be further simplified by eliminating the focusing lens for excitation light. LED‐TOF‐CE and LED‐COF‐CE system were applied to the separation and determination of RF in real sample (green tea), respectively. The tapered fiber optic‐induced fluorescence detection system in CE is an ideal tool for trace analysis.     

Lensless CCD-based fluorometer using a micromachined optical Söller collimator

In this paper, we describe a simple charge-coupled device (CCD) based lensless fluorometer with sensitivity in the range of current ELISA plate readers. In our lensfree fluorometer, a multi-wavelength LED light source was used for fluorophore excitation. To collimate the light, we developed a simple optical S?ller collimator based on a "stack of pinholes" (a stack of black PMMA with array of pinholes machined with laser) enabling the light to be collimated from the LED through the filters and the assay's microfluidics directly onto the CCD without a lens. The elimination of the lens that is used in almost all other current CCD based detection systems has four major advantages: (1) It simplifies the device design and fabrication while reducing cost. (2) It reduces the distance between the sample and the measuring device (without a lens the distance needed to focus the image on the CCD is reduced and the fluorometer can be more compact). (3) It couples the CCD and the detected surface by using an optical S?ller Collimator which allows the use of filters for fluorescence detection. (4) It also uncouples the CCD and the microfluidics to enable the use of interchangeable fluidics while protecting the delicate CCD. The lensless CCD-based fluorometer is capable of detecting 16 samples simultaneously, and was used for in vitro detection of botulinum neurotoxin serotype A (BoNT-A) activity with a FRET assay that measures cleavage of a fluorophore-tagged peptide substrate specific for BoNT-A (SNAP-25) by the toxin light chain (LcA). The limit of detection (LOD) of our lensless fluorometer is 1.25 nM, which is similar to the LOD of a modern ELISA plate reader. Combined with microfluidics, this simple low cost point-of-care (POC) medical diagnostic system may be useful for the performance of many other complex medical diagnostic assays without a laboratory and thus potentially enhancing the accessibility and the quality of health care delivery in underserved populations.     

大数值孔径光学镜约束多级衍射机理

针对基于激光照明的离轴全息显微成像系统存在散斑和寄生条纹噪声,以及基于部分相干光照明的离轴数字全息显微技术存在相干条纹对比度差的问题,本文提出了一种基于单色LED照明的衍射相位显微成像系统。该系统利用大数值孔径物镜及光栅对物光进行多级衍射,并采用4f系统和空间滤波器分离出0级和+1级信息,分别作为参考光和物光,最终两束光在CCD阵面上干涉产生离轴全息图,从而形成共光路全息成像结构。通过理论分析和计算,对实验用到的光学元器件进行选型,确保衍射光频谱信息能够分开且满足抽样条件。最后与传统激光离轴数字全息显微成像检测结果进行对比,实验结果表明,本文提出的系统能够获得较高的成像准确度和信噪比。     

Effects of white light‐emitting diode (LED) light exposure with different Correlated Color Temperatures (CCTs) on human lens epithelial cells in culture

Cataract is the major cause for legal blindness in the world. Oxidative stress on the lens epithelial cells (hLECs) is the most important factor in cataract formation. Cumulative light‐exposure from widely used light‐emitting diodes (LEDs) may pose a potential oxidative threat to the lens epithelium, due to the high‐energy blue light component in the white‐light emission from diodes. In the interest of perfecting biosafety standards for LED domestic lighting, this study analyzed the photobiological effect of white LED light with different correlated color temperatures (CCTs) on cultured hLECs. The hLECs were cultured and cumulatively exposed to multichromatic white LED light with CCTs of 2954, 5624, and 7378 K. Cell viability of hLECs was measured by Cell Counting Kit‐8 (CCK‐8) assay. DNA damage was determined by alkaline comet assay. Intracellular reactive oxygen species (ROS) generation, cell cycle, and apoptosis were quantified by flow cytometry. Compared with 2954 and 5624 K LED light, LED light having a CCT of 7378 K caused overproduction of intracellular ROS and severe DNA damage, which triggered G₂/M arrest and apoptosis. These results indicate that white LEDs with a high CCT could cause significant photobiological damage to hLECs.     

Exposure geometry and spectral environment determine photobiological effects on the human eye

Photobiological effects upon the human retina, cornea and lens are highly dependent on the optical exposure geometry as well as spectral characteristics of the exposure. The organ of sight is exquisitely sensitive to light because it performs well in very low nighttime illumination levels and yet it also must adapt to extremely bright environments where light exposures are greater by many orders of magnitude. The eye has evolved to protect itself reasonably well against excessive exposure in bright environments. The retina is minimally exposed in extremely bright environments and the cornea and lens are surprisingly well protected in harsh environments. Although these protective mechanisms are good, they are not perfect and adverse changes from both acute and chronic exposures to sunlight still exist. The geometrical protective factors must be understood and appreciated whenever assessing potential adverse effects of environmental UV radiation and light on ocular structures. These natural ocular protective factors also work with the ever-changing spectrum of sunlight and the different spectral distribution of light and UV radiation across the eye's field of view. Spectral characteristics of the ocular media are also important. One can visualize a series of intraocular color filters that progressively filter shorter wavelengths and thereby aid in color vision, reduce the impact of chromatic aberrations and significantly reduce the optical radiation hazards to the lens and retina.     

Integrated chemical sensor array platform based on a light emitting diode, xerogel-derived sensor elements, and high-speed pin printing

We report a new, solid-state, integrated optical array sensor platform. By using pin printing technology in concert with sol-gel-processing methods, we form discrete xerogel-based microsensor elements that are on the order of 100 μm in diameter and 1 μm thick directly on the face of a light emitting diode (LED). The LED serves as the light source to excite chemically responsive luminophores sequestered within the doped xerogel microsensors and the analyte-dependent emission from within the doped xerogel is detected with a charge coupled device (CCD). We overcome the problem of background illumination from the LED reaching the CCD and the associated biasing that results by coating the LED first with a thin layer of blue paint. The thin paint layer serves as an optical filter, knocking out the LEDs red-edge spectral tail. The problem of the spatially-dependent fluence across the LED face is solved entirely by performing ratiometric measurements. We illustrate the performance of the new sensor scheme by forming an array of 100 discrete O₂-responsive sensing elements on the face of a single LED. The combination of pin printing with an integrated sensor and light source platform results in a rapid method of forming (∼1 s per sensor element) reusable sensor arrays. The entire sensor array can be calibrated using just one sensor element. Array-to-array reproducibly is <8%. Arrays can be formed using single or multiple pins with indistinguishable analytical performance.     

Light-emitting diodes are better illumination sources for biological microscopy than conventional sources.

Light-emitting diodes (LEDs) can be easily and inexpensively integrated into modern light microscopes. There are numerous advantages of LEDs as illumination sources; most notably, they provide brightness and spectral control. We demonstrate that for transmitted light imaging, an LED can replace the traditional tungsten filament bulb while offering longer life; no color temperature change with intensity change; reduced emission in the infrared region, which is important for live cell imaging; and reduced cost of ownership. We show a direct substitution of the typical tungsten bulb with a commercially available LED and demonstrated the color stability by imaging a histology section over a wide range of light intensities. For fluorescent imaging, where the typical illumination sources are mercury or xenon lamps, we demonstrate that LEDs offer advantages of providing a longer lifespan, having a more constant intensity output over time, more homogeneous illumination, and significantly lower photon dose. Our LED equipped system was used to image and deconvolve dual fluorescently labeled cells, as well as image cells undergoing mitosis expressing green fluorescent protein-histone 2B complex. The timing of the stages of mitosis is well established as an indicator of cell viability.     

A facile LED backlight in situ imaging technique to investigate sub-micron level processing

Many laboratory experimental techniques used for investigating fine fluid structure, such as fiber spinning, microfluidic flow, and electrospinning, require high quality images with good contrast. Common processes of observation and image recording rely heavily on highly technical light and camera setups which can be difficult to operate in some processing conditions and expensive as well. Here, we report a facile technique using LED backlight imaging to investigate ultrathin fluid profile in two different processes, melt electrospinning and tubeless siphoning. The setup comprises of a simple LED light source facing toward the camera, directly shining into the camera lens. The object under investigation was placed between the camera and the light source. The high-quality captured images and video recordings enable the precise analysis of the cone diameter and jet solidification in case of melt electrospinning, and extensional behavior profiles for tubeless siphoning. The LED backlight setup with high resolution camera is a useful tool to investigate sub-micron scale dimensions in fiber spinning, microfluidic flow, solution electrospinning, contact angle measurement for surface properties analysis, etc.