Ms. Annu Jacob Profile

Annu Jacob

at Inter-Univ Ctr for Astronomy and Astrophysics

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Author

Publications (8)

Proceedings Article | 12 May 2023 Poster + Paper

Optical design of FOSC and wide field aberration corrector for the prototype segmented mirror telescope

Radhika Dharmadhikari, Annu Jacob, Padmakar Parihar

Proceedings Volume 12638, 1263807 (2023) https://doi.org/10.1117/12.2669796

KEYWORDS: Spectroscopy, Telescopes, Design and modelling, Optical design, Image quality, Segmented mirrors, Equipment, Cameras, Collimators

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Proceedings Article | 29 August 2022 Paper

Study on segmentation and alignment related effects in a 10m class telescope

Annu Jacob, Padmakar Singh Parihar, Melvin James, Radhika Dharmadhikari

Proceedings Volume 12182, 1218224 (2022) https://doi.org/10.1117/12.2629948

KEYWORDS: Telescopes, Mirrors, Point spread functions, Image segmentation, Error analysis, Optical instrument design, Diffraction, Segmented mirrors, Optical design, Zemax

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Proceedings Article | 29 August 2022 Paper

Design and fabrication of a silicon based micro fiber holder for DOTIFS Integral field unit and associated IFU tests

Annu Jacob, A. N. Ramaprakash, Chaitanya Rajarshi, Pravin Khodade, Hillol Das, Sabyasachi Chattopadhyay, Amitesh Omar

Proceedings Volume 12184, 121847D (2022) https://doi.org/10.1117/12.2629966

KEYWORDS: Semiconducting wafers, Spectrographs, Polishing, Microlens, Photomasks, Optical alignment, Manufacturing, Cameras, Calibration, Optical fibers

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Devasthal Optical Telescope Integral Field Spectrograph (DOTIFS) is a new multi-object integral field spectrograph being built by the Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune, India for the 3.6m Devasthal Optical Telescope, (DOT). Spectrographs, which disperse the light to study various aspects of the source, traditionally follow long slit to enter the light into to the instrument. However, varying slit width, atmospheric dispersion, crowded object field etc, causes this approach to lose its efficiency. A 2D field access using optical fibres solves most of these issues and introduces additional modularity. However, the circular shape of the fibre tip causes light loss as the fill factor < 80 %. There are mainly two ways to solve these issues, one is with 2D field splicers which are usually mirrors which break the field and reflect the beams in different directions, the other a more convenient alternative is using micro lens arrays (MLA) coupled with optical fibres, increasing the fill factor < 90 %. Even with this advantage, the miss alignment of the optical fibre with the MLA can cause increase in optical entropy and hence loss of effective transmission. Therefore, making a precise fiber to micro-lenslet array holder is a necessity. In DOTIFS which uses a combination of MLA and fibers to transmit the light, the IFU unit of the spectrograph consist of fiber array held on a mask and glued to a micro lenslet array. The plano-convex MLA (PCMLA) forms a hexagonal honeycomb structure of 12×12 spaxels. The on-sky footprint of an IFU is designed to be 8.7”×7.4” for a spatial sampling of 0.8”/300µm. The PCMLA has a thickness of 2.32 mm to create the pupil at its flat surface where fibers would be butted to sample the pupil. Each microlens curved side will receive a f/21.486 beam from the magnifier optics assembly sitting between IFU assembly and the Cassegrain side port selection mirror of the telescope. The microlens converts the incoming beam from the magnifier to f/4.5 beam and creates an ideal pupil of 76µm diameter at its at back surface. In this paper we present deep reactive ion etching technique based fibre holder manufacturing for holding the fibres of IFU of DOTIFS spectrograph. We present the design details, fiber routing scheme, manufacturing and gluing and polishing concepts for fibre holder and the tests and results on the IFU deployment system.

Proceedings Article | 3 October 2019 Paper

Study on creating an aspheric primary mirror of a large telescope using spherical mirror segments

Annu Jacob, Padmakar Parihar, Melvin James

Proceedings Volume 11207, 112072U (2019) https://doi.org/10.1117/12.2530932

KEYWORDS: Mirrors, Telescopes, Aspheric lenses, Spherical lenses, Optical instrument design, Zemax, Off axis mirrors, Optical spheres, Segmented mirrors, Large telescopes

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Proceedings Article | 6 July 2018 Presentation + Paper

Prototype segmented mirror telescope: a pathfinder of India's Large Optical-NIR telescope project

Padmakar Parihar, Prasanna Deshmukh, Annu Jacob, Varun Kumar, Abhishek Goudar, S. Sriram, S. Nagabhusan, S. Amitkumar, K. V. Govinda, D. S. Sandeep, P. M. M. Kemkar, G. C. Anupama

Proceedings Volume 10700, 107001A (2018) https://doi.org/10.1117/12.2313079

KEYWORDS: Mirrors, Telescopes, Sensors, Actuators, Segmented mirrors, Prototyping, Optical instrument design

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Proceedings Article | 6 July 2018 Presentation + Paper

Aligning and phasing segmented mirror telescope with the pyramid sensor

Annu Jacob, Padmakar Parihar, Sindhu Divakaran , Melvin James

Proceedings Volume 10700, 107001G (2018) https://doi.org/10.1117/12.2313096

KEYWORDS: Sensors, Telescopes, Mirrors, Segmented mirrors, Point spread functions, MATLAB, Wavefronts, Device simulation, Zemax, Signal generators

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Proceedings Article | 15 June 2015 Paper

Modeling the segmented primary for a 10-meter-class telescope

Vineeth Valsan, S. Sriram, Annu Jacob, J. Lancelot, G. Anupama

Proceedings Volume 9654, 96540C (2015) https://doi.org/10.1117/12.2181743

KEYWORDS: Mirrors, Image segmentation, Telescopes, Point spread functions, Wavefronts, Space telescopes, Zemax, Aspheric lenses, Diffraction, Segmented mirrors

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Proceedings Article | 15 June 2015 Paper

A co-phasing technique for segmented mirror telescopes

Annu Jacob, Padmakar Parihar

Proceedings Volume 9654, 96540G (2015) https://doi.org/10.1117/12.2181778

KEYWORDS: Mirrors, Telescopes, MATLAB, Image segmentation, Zemax, Diffraction, Segmented mirrors, Point spread functions, Coherence (optics), Device simulation

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Showing 5 of 8 publications

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