Query: micro lens array beam homogenization

Candidate papers:

abstract: For many innovative applications a significant improvement in the homogeneity of the laser beam is a critical requirement when using semiconductor lasers. There are several different methods for the homogenization of laser radiation. Homogenization using micro cylinder lens arrays is a considerably elegant and compact solution. In this case the incident laser beam is separated into partial beams by one or more micro lens arrays. These partial beams are then overlaid in the homogenization plane by the downstream optics. Depending on the arrangement and geometry of the micro lenses, this enables homogeneously illuminated lines, rectangles or squares to be generated. The major advantage of this solution lies in the increased freedom of adjustment to account for the initial beam profile, as well as the extremely compact design. In addition to a comparison of different homogenization principles the paper describes new approaches of homogenization via micro lens arrays and compares the impact on the array performance by different manufacturing approaches.
author_names: Volker Sinhoff

Stefan Hambuecker

Klaus R F Kleine

Olaf Ruebenach

Christian Wessling
title: Micro lens arrays for laser beam homogenization and transformation
venue: Photonics West Lasers and Applications in Science and Engineering
year: 2013

abstract: Micro Lens Arrays (MLA) containing thousands of lenses with an aspheric shape and a precise position on large substrates are used in sensor devices directly or as master moulds for the low cost replication of micro lenses in an array. They have to fulfill the high requirements in wafer scale manufacturing of small optics. This high volume manufacturing method for low cost but effective micro optics relies on the sandwich like assembly of the sensors and optical components like lenses as well as mechanical components like apertures and spacers on wafer level. After joining all components the dicing results in a batch of wafer level cameras for the use in cellular phones or webcams. Micro Lens Arrays are also a centrepiece of today's sensor products, either to raise the fill factor and collect more light on each pixel or to deflect the incoming beam to measure the aberrations of the wavefront, the working principle of the Hartmann Shack sensor. Within illumination optics, MLA are commonly used for beam homogenization in projection systems. In all fields of application ranging from automotive, medical, consumer and industrial optics to high end sensors for space instrumentation, high quality lens arrays for direct use or replication must be provided.
title: Micro Lens Array Milling on Large Wafers More Design Freedom for Micro Optics Aspheric Lenslets with Imaging Quality
year: 2009

abstract: Micro Lens Arrays (MLA) containing thousands of lenses with an aspheric shape and a precise position on large substrates are used in sensor devices directly or as master moulds for the low cost replication of micro lenses in an array. They have to fulfill the high requirements in wafer scale manufacturing of small optics. This high volume manufacturing method for low cost but effective micro optics relies on the sandwich like assembly of the sensors and optical components like lenses as well as mechanical components like apertures and spacers on wafer level. After joining all components the dicing results in a batch of wafer level cameras for the use in cellular phones or webcams. Micro Lens Arrays are also a centrepiece of today's sensor products, either to raise the fill factor and collect more light on each pixel or to deflect the incoming beam to measure the aberrations of the wavefront, the working principle of the Hartmann Shack sensor. Within illumination optics, MLA are commonly used for beam homogenization in projection systems. In all fields of application ranging from automotive, medical, consumer and industrial optics to high end sensors for space instrumentation, high quality lens arrays for direct use or replication must be provided.
author_names: Sebastian Scheiding

Andreas Gebhardt

Ramona Eberhardt

Andreas Tunnermann
title: Micro Lens Array Milling on Large Wafers
year: 2009

abstract: Abstract A laser micro bonding process using laser beam shaping is successfully demonstrated for flexible printed circuit boards. A CW Ytterbium fiber laser with a wavelength of 1070 nm and a laser power density of 1 7 W/mm 2 is employed as a local heat source for bonding flexible printed circuit boards to rigid printed circuit boards. To improve the bonding quality, a micro lens array is used to modify the Gaussian laser beam for the bonding process. An electromagnetic modeling and heat transfer simulation is conducted to verify the effect of the micro lens array on the laser bonding process. The optimal bonding parameters are found experimentally. As the measured temperature ramp rate of the boards exceeds 1100 K/s, bonding occurs within 100 200 ms at a laser power density of 5 W/mm 2 The bonding quality of the FPCB is verified with a shear strength test. Process characteristics are also discussed.
author_names: Joohan Kim

Hae woon Choi
title: Flexible printed circuit boards laser bonding using a laser beam homogenization process
year: 2012

abstract: Formed microlens array by different microlens according to a probability distribution, forms a light beam having a predetermined intensity distribution in a predetermined far field scatter pattern within. This difference in the micro lens comprises a random deviation in the sag profile corresponding to the surface shape of the microlens boundary profile corresponding to a boundary of the microlenses, and a spatial distribution corresponding to the relative position of the microlens in the array. Sag distribution deviation may be used to equalize the intensity distribution of the light beam. Border distribution deviation of irregular spatial distribution can be used to provide a predetermined intensity distribution of the light beam in a predetermined scattering pattern.
author_names: tatsuso aru emu serusu
title: Random microlens array for beam shaping and homogenization
year: 2003

abstract: The paper details a square core fiber beam delivery design utilizing a unique micro lens array launch method. The paper includes the resulting performance of a prototype created to verify the design and its stability with an emphasis on homogenization as the fiber is articulated.
author_names: Todd E Lizotte

Fred M Dickey
title: MLA fiber injection for a square core fiber optic beam delivery system: design versus prototype results
venue: International Optical Design Conference
year: 2010

abstract: With the application of source mask optimization (SMO) technology in the 28nm and below nodes photolithography machine, the freeform pupil illumination technology has been widely utilized to achieve resolution enhancement for various complex patterns. The freeform illumination module (FIM) equipped with micro mirror array (MMA) are proposed, which could realize arbitrary pupil by adjusting the angle position distribution of MMA. Therefore, it is necessary to research the freeform pupil illumination technology in immersion photolithography machine. An excellent performance optical system for FIM mainly including homogenization unit, micro lens array (MLA) MMA and Fourier transform lens is proposed in this paper. The homogenization unit is used to increase the uniformity of the beam incident onto MMA. The beam incident onto MLA is divided and focused on MMA. The focused sub beams are reflected by micro mirrors and then incident into Fourier transform lens. And the freeform pupil is generated at its back focal plane. In order to verify the feasibility of the designed optical system, three freeform pupils optimized by SMO are input into the designed FIM and the corresponding simulated pupils are exported. Furthermore, the photolithography performance simulations of the optimized and simulated pupils are implemented in optical model. The results indicate that their critical dimension (CD) differences are less than 0.5nm RMS for thousands of patterns in 40nm 80nm, such as line end, line space, contact hole, end to line, SRAM et. al. which shows that the excellent performance of the designed FIM.
author_names: Zongshun Zeng

Zhiyuan Niu

Fang Zhang

Xiaozhe Ma

Siyu Zhu

Weijie Shi

Aijun Zeng

Huijie Huang
title: An excellent performance optical system for freeform pupil illumination module in immersion photolithography machine
venue: Other Conferences
year: 2018

abstract: For systems based on array source, owing to discrete single sources in the array, variation in power intensity can usually be detected as the receiving end moves. Although uniform illumination in lighting system has been widely investigated, its implemented light sources are commonly LEDs with Lambertian distribution. We further study an optical design applied for optical wireless communication system with VCSEL in this article. The optical system mainly consists of collimating lens and micro lens array to homogenize power intensity of the communication system based on VCSEL array source which has a Gaussian distribution. Our proposed scheme was verified with commercial optical design software Zemax. The simulation result shows that illumination uniformity can reach up to 91% after passing through this optical system, which can fulfill the requirements of high power uniformity in practical applications. The homogenization of power intensity solves the issue of signal power variation at the moving receiver end in optical wireless communication system, which guarantees stable communication link and robust system performance.
author_names: Xin Mu

Zixian Wei

Sailong Wu

Zhenmin Chen

Ying Dong

Hongyan Fu
title: Homogenization of power intensity based on micro lens array in optical wireless communication systems
venue: Other Conferences
year: 2019

abstract: Abstract This paper demonstrates the formation of high fill factor plano convex cylindrical and dome type micro lens arrays on fused silica glass surface using CO2 laser assisted reshaping technique. Cylindrical micro lens array is fabricated by polishing the femtosecond laser engraved linear micro gratings by a CO2 laser beam. Initially, a femtosecond laser beam has been irradiated on the surface of the fused silica glass samples to fabricate periodic micro gratings on the glass surface. Afterwards, these micro gratings encoded glass samples are polished several times by a CO2 laser beam. As a result, plano convex cylindrical micro lens arrays with the lens period varying from 20 mm to 50 mm are developed on the glass surface. Similarly, dome type micro lens array is achieved by femtosecond laser assisted fabrication of periodic micro pillars followed by several times CO2 laser polishing. We report the formation of a large variety of dome shape micro lens array with lens size varying from 20 mm x 20 mm to 50 mm x 50 mm. The fabricated micro lenses show great consistency in size and shape throughout the sample area. We also investigate the intensity distribution of light passed through the micro lens engraved glass samples. Using the dome type micro lens array engraved glass samples, a Gaussian laser beam has been converted to a flat top laser beam for selective patterning of a thin indium tin oxide coating from fused silica glass surface.
author_names: Ik-Bu Sohn

Hun-Kook Choi

Young Chul Noh

Jongyeol Kim

Md Shamim Ahsan
title: Laser assisted fabrication of micro lens array and characterization of their beam shaping property
venue: Applied Surface Science
year: 2019

author_names: Pei Xian Zi Pei Xian-zi

Liang Yong Hao Liang Yong-hao

Wang Fei Wang Fei

Zhu Xiao Li Zhu Xiaoli

Xie Chang Qing Xie Changqing
title: Beam Homogenization of a Fresnel Lens Array with a Randomly Distributed Phase for Laser Beams
year: 2019