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Browsing by Author "Prasad, B. R"

Browsing by Author "Prasad, B. R"

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  • Optical limiting in bacteriorhodopsin using a four-state model for two-beam illumination 
    Jagadish, C. S; Prashant, S. T; Prasad, B. R; Venkataramaniah, K; Sivasankara Sai, S (Department of Applied Optics and photonics, University of Calcutta, 2009)
    In this paper we have discussed a four state model in bacteriorhodopsin (bR) for two beam illumination. The paper presents simulation studies showing the change in the population levels of the various states in the bR ...
  • Optical metrology on primary mirror of visible emission line coronagraph on board Aditya-L1 mission 
    Venkata Suresh, Narra; Singh, Darshika; Venkatasubramanian, N; Budhiraju, Vishweshwar Rao; Hegde, Bhavana; Bhat, Nishchith; Utkarsha, D; Somasundaram, P. K; Ramaswamy, Venkateswaran; Kamath, P. U; Sriram, Kuppuswamy Venkatesan; Prasad, B. R (SPIE-Society of Photo-Optical Instrumentation Engineers, 2022-10)
    The visible emission line coronagraph (VELC) on board the Aditya-L1 mission is an internally occulted reflective coronagraph. It is capable of simultaneous observations of the solar corona in imaging, spectroscopic, and ...
  • Optimization of existing centroiding algorithms for Shack Hartmann sensor 
    Vyas, A; Roopashree, M. B; Prasad, B. R (2009)
    Three centroiding techniques to estimate the position of the spots in a Shack Hartmann sensor: Normalized Centre of Gravity (CoG), Iteratively Weighted Centre of Gravity (IWCoG) and Intensity Weighted (IWC) centroiding are ...
  • Optimizing the modal index of Zernike polynomials for regulated phase screen simulation 
    Vyas, A; Roopashree, M. B; Prasad, B. R (SPIE--The International Society for Optical Engineering, 2010-07)
    Simulations of optical wavefronts propagating through the atmosphere are widely used in the design and testing of adaptive optics systems. Phase screens are defined by their spatial and temporal statistics. In many ...
  • Performance analysis of fourier and vector matrix multiply methods for phase reconstruction from slope measurements 
    Roopashree, M. B; Vyas, A; Prasad, B. R (Central Scientific Instruments Organisation (CSIR), 2009-11)
    The accuracy of wavefront reconstruction from discrete slope measurements depends on the sampling geometry, coherence length of the incoming wavefronts, wavefront sensor specifications and the accuracy of the reconstruction ...
  • Performance of centroiding algorithms at low light level conditions in adaptive optics 
    Vyas, A; Roopashree, M. B; Prasad, B. R (The Institute of Electrical and Electronics Engineers, Inc, 2009)
    The performance metrics of different centroiding algorithms at low light level conditions were optimized in the case of a Shack Hartmann Sensor (SHS) for efficient performance of the adaptive optics system. For short ...
  • Phase characteristics of reflecting and transmitting type twisted nematic spatial light modulators 
    Roopashree, M. B; Vyas, A; Banyal, R. K; Prasad, B. R (Central Scientific Instruments Organisation (CSIR), 2009-11)
    The phase characteristics of reflecting and transmitting type twisted nematic liquid crystal based Spatial Light Modulators (SLMs) were measured using interferometry. Device parameters like contrast, brightness, input ...
  • Pixel size and pitch measurements of liquid crystal 
    Banyal, R. K; Prasad, B. R (Indian Academy of Sciences, 2005-08)
    We present a simple technique for the determination of pixel size and pitch of liquid crystal (LC) based spatial light modulator (SLM). The proposed method is based on optical diffraction from pixelated LC panel that has ...
  • Prediction of wavefronts in adaptive optics to reduce servo lag errors using data mining 
    Vyas, A; Roopashree, M. B; Prasad, B. R (Central Scientific Instruments Organisation (CSIR), 2009-11)
    Servo lag errors in adaptive optics lead to inaccurate compensation of wavefront distortions. An attempt has been made to predict future wavefronts using data mining on wavefronts of the immediate past to reduce these ...
  • Professor M.G.K. Menon Laboratory for Space Sciences 
    Prasad, B. R (Indian Institute of Astrophysics, 2012-06-21)
  • Progressive prediction of turbulence using wave-front sensor data in adaptive optics using data mining 
    Vyas, A; Roopashree, M. B; Prasad, B. R (Macmillan Publishers India Ltd., 2009)
    Nullifying the servo bandwidth errors improves the strehl ratio by a substantial quantity in adaptive optics systems. An effective method for predicting atmospheric turbulence to reduce servo bandwidth errors in real time ...
  • Proposed visible emission line space solar coronagraph 
    Singh, J; Prasad, B. R; Venkatakrishnan, P; Sankarasubramanian, K; Banerjee, D; Bayanna, R; Mathew, S; Murthy, J; Subramaniam, P; Ramesh, R; Kathiravan, S; Nagabhushana, S; Mahesh, P. K; Manoharan, P. K; Uddin, W; Sriram, S; Amit Kumar; Srivastava, N; Koteswara Rao; Nagendra, C. L; Chakraborty, P; Sriram, K. V; Venkateswaran, R; Krishnamurthy, T; Sreekumar, P; Sarma, K. S; Murthy, R; Navalgund, K. H; Samudraiah, D. R. M; Narayan Babu, P; Patra, A (Indian Academy of Sciences, 2011-01-25)
    The outer atmosphere of the sun – called the corona – has been observed during total solar eclipse for short periods (typically < 6 min), from as early as the eighteenth century. In the recent past, space-based instruments ...
  • Prospect for UV observations from the moon. III. assembly and ground calibration of lunar ultraviolet cosmic imager (LUCI) 
    Mathew, J; Nair, B. G; Safonova, M; Sriram, S; Prakash, A; Mayuresh, Sarpotdar; Ambily, S; Nirmal, K; Sreejith, A. G; Murthy, J; Kamath, P. U; Kathiravan, S; Prasad, B. R; Brosch, Noah; Kappelmann, Norbert; Gadde, Nirmal Suraj; Narayan, Rahul (Springer, 2019-03)
    The Lunar Ultraviolet Cosmic Imager (LUCI) is a near-ultraviolet (NUV) telescope with all-spherical mirrors, designed and built to fly as a scientific payload on a lunar mission with Team Indus—the original Indian entry to ...
  • Real-time wind speed measurement using wavefront sensor data 
    Roopashree, M. B; Vyas, A; Prasad, B. R (SPIE-The International Society for Optical Engineering, 2010-02)
    Real-time measurement of effective wind speed helps in continuous monitoring of the temporal bandwidth in adaptive optics systems. In this paper, we propose a simple and efficient method for estimating wind speed from ...
  • Scatter due to Ultraviolet (UV) photopolymerization of molecular contamination on optical surfaces 
    Venkata Suresh, Narra; Prasad, B. R; Somasundaram, P. K; Kathiravan, S; Venkatasubramanian, N; Padavu, U. K; Mani, V. T; Basavaraja, S; Naik, Rajesh (Springer Nature B.V., 2020-12)
    Molecular contamination on optical surfaces is a serious issue for space payloads. For ultraviolet (UV) payloads, molecular contamination results in loss of throughput. Whereas, for visible (VIS) payloads loss of throughput ...
  • Scatter due to Ultraviolet (UV) photopolymerization of molecular contamination on optical surfaces 
    Venkata Suresh, Narra; Prasad, B. R; Somasundaram, P. K; Sriraman, K; Venkatasubramanian, N; Padavu, U. K; Mani, V. T; Basavaraja, S; Naik, R (Springer, 2020-12)
    Molecular contamination on optical surfaces is a serious issue for space payloads. For ultraviolet (UV) payloads, molecular contamination results in loss of throughput. Whereas, for visible (VIS) payloads loss of throughput ...
  • Scatter studies for visible emission line coronagraph on board ADITYA-L1 mission 
    Venkata Suresh, Narra; Prasad, B. R; Raj Kumar, Nalla; Singh, J (SPIE-The International Society for Optical Engineering, 2017-01)
    Visible emission line coronagraph (VELC) on board ADITYA-L1 mission is an internally occulted mirror coronagraph designed for solar coronal observations over a field of view (FOV) of 1.05 Ro to 3 Ro. To achieve the proposed ...
  • Solar coronal magnetic fields and sensitivity requirements for spectropolarimetry channel of VELC onboard Aditya-L1 
    Sasikumar Raja, K; Venkata Suresh, Narra; Singh, J; Prasad, B. R (Elsevier, 2022-01-01)
    Understanding solar coronal magnetic fields is crucial to address the long-standing mysteries of the solar corona and solar wind. Although routine photospheric magnetic fields (MFs) are available for decades, coronal MFs ...
  • Spatial light modulator for wave-front correction 
    Vyas, A; Roopashree, M. B; Banyal, R. K; Prasad, B. R (Department of Applied Optics and photonics, University of Calcutta, 2009)
    We present a liquid crystal method of correcting the phase of an aberrated wave-front using a spatial light modulator. A simple and efficient lab model has been demonstrated for wave-front correction. The crux of a wave-front ...
  • Spectropolarimeter on board the Aditya-L1: polarization modulation and demodulation 
    Nagaraju, K; Prasad, B. R; Hegde, Bhavana S; Venkata Suresh, Narra; Utkarsha, D; Kumar, Amit; Singh, J; Kumar, Varun (Optical Society of America, 2021-09-10)
    One of the major science goals of the Visible Emission Line Coronagraph (VELC) payload aboard the Aditya-L1 mission is to map the coronal magnetic field topology and quantitative estimation of longitudinal magnetic field ...

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