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Geometric Superresolution for Removal of Undersampling Effect

Thesis Info

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Author

Sohail, Muhammad

Program

PhD

Institute

Pakistan Institute of Engineering and Applied Sciences

City

Islamabad

Province

Pakistan

Country

Pakistan

Thesis Completing Year

2014

Thesis Completion Status

Completed

Subject

Physics

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/2209/1/2763S.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676726338245

Similar


This dissertation presents work on the Geometric Superresolution. There are two main parameters that can affect Geometric Superresolution, the finite size of pixels and the pitch of the pixels in digital imaging device like CCD (charged coupled device). In superresolution systems, the ultimate limit to resolution generally comes from the Geometric and not from the optical part of an imaging system. This thesis mainly deals with the undersampling of an optical image in which the separation between the neighbouring pixels in a CCD is assumed to be greater than the separation required by Nyquist Sampling. The problem of undersampling an optical image has been dealt with the use of an Optical Mask placed at the Fourier transform plane in a coherent 4f imaging system. The one dimensional version of the Optical Mask consists of a 1-dimensional amplitude grating. The Optical Mask is used to sample the Fourier transform of the input object. Due to the sampled Fourier transform, the image plane contains replicas of the input object. A CCD is used to undersample these replicas. The recorded undersampled image is Fourier transformed and contains replicas of original object spectrum but overlapped due to the undersampled image recorded by CCD. The overlapped spectrum is multiplied with a soft copy of an Optical Mask which removes the overlapping by removing the neighbouring spectral copies. An interpolation is done on the recovered single object spectral copy to fill the holes in the spectrum. The resultant spectrum is then Fourier transformed to obtain an image free of artefacts and free of undersampling effects. Different analogues of Optical Masks and CCD pixels have been presented and discussed in this thesis. Optical Masks may consist of negligibly small line widths or lines with finite widths. Similarly, an ideal CCD may consist of point pixels in which the pixel size is negligible in comparison with the spacing between them or in real situations may have finite size. The effects of these parameters on Geometric Superresolution have been discussed in the thesis. Simulation results in one and two dimensional have been presented to support the idea. A part of the thesis also discusses a technique dealing with subpixeling. An optical image using a Spatial light modulator is projected on a CCD and shifted in subpixel steps. The retrieved data corresponding to each subpixel step is combined to obtain high resolution image. This has been supported with experimental verification.
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مولانا ظفر ؔعلی خان

مرزا سلطان احمد
افسوس ہے کہ اعظم گڑھ کی ممتاز مقبول شخصیت مرزا سلطان احمد صاحب رٹائر ممبر بورڈ آف ریونیو نے طویل علالت کے بعد گزشتہ ۱۷؍ فروری کو انتقال کیا وہ پرانے علیگ اور اپنے زمانہ کے لائق ترین عہدہ داروں میں تھے، اپنی قابلیت سے ڈپٹی کلکٹری سے کلکٹری اور بورڈ کی ممبری تک ترقی کی اور جہاں رہے اپنی دیانتداری اور شرافت سے مقبول و نیک نام رہے، بڑے عہدہ داروں میں ایسے شریف اور خلیق انسان کم دیکھنے میں آئے ہیں، ان کا خمیر ہی اخلاق و شرافت سے گوندھا گیا تھا، ادنی و اعلیٰ ہر شخص کے ساتھ ان کا اخلاق یکساں تھا، ہر ملنے والے کے ساتھ کوئی نہ کوئی ایسی خصوصیت ضرور برتتے تھے جس سے اس کو یہ محسوس ہوتا کہ وہ اس کے ساتھ خاص تعلق رکھتے ہیں۔
بڑے وضعدار، فیاض اور مہمان نواز تھے جس سے جس قسم کے تعلقات تھے، اس کو عمر بھر نباہا، ملازمت کے زمانہ میں ان کا دستر خوان بڑا وسیع اور گھر مستقل مہمان خانہ تھا، ان کے اعزہ و احباب میں سے کوئی نہ کوئی ان کے یہاں مستقل مقیم رہتا تھا اور جس کو ضرورت ہوتی اس کی نقدی سے بھی مدد کرتے تھے، ہر حاجت مند کی مدد کے لیے ہر وقت تیار رہتے تھے اور اس کے لیے ایسے کام کر گزرتے تھے جس کی ہمت ہر شخص نہیں کرسکتا، وہ بڑے تنخواہ دار تھے لیکن جو کچھ کمایا سب صرف کردیا، اعظم گڑھ میں دو ہی ایسے شخص تھے جنھوں نے بہت پیدا کیا، مگر اپنے بعد کچھ نہیں چھوڑا، ایک مرزا صاحب، دوسرے اقبال سہیل مرحوم ملازمت سے ریٹائر ہونے کے بعد حکومت نے ان کے سامنے پبلک سروس کمیشن کی ممبری پیش کی، مگر انھوں نے وطن چھوڑنا پسند نہ کیا اور اعظم...

عصر حاضر اور اجماع

Ijmaa is the fourth source of Islamic law. It is the product of collective Ijthihad of Islamic jurists. This is one of the principal source of Islamic law and is based on the Qur'an and Sunna. It is in a way a kind of Ijthihad and can be termed as a collective Ijthihad. In modern day it can be exercised through parliament or a committee on Ijthihad. Its scope can be further widened for the Umma through an international council or congress of Islamic scholars.

Three Wave Interactions in Non- Degenerate and Degenerate Magneto-Plasmas

In this thesis we study the parametric decay instability problem (three wave interactions) in classical andquantummagneto‐plasmas.Twocombinationsofthethreewaveinteractionshavebeen investigated.First,theparametricdecayinstabilityofupperhybridwaveintolow‐frequency electromagnetic shear Alfven wave and Ordinary mode radiation has been solved in an electron‐ion plasma immersed in uniform external magnetic field. Incorporating quantum effect due to electron spin, the fluid model has been used to investigate the linear and nonlinear response of the plasma species. It is shown that the spin of electrons has considerable effect on the three‐wave coupling interactions even in classical regime. Secondly,theelectronspin‐1/2effectsontheparametricdecayinstabilityofobliqueLangmuir waveintolow‐frequencyelectromagneticshearAlfvenwaveandleft‐handedcircularlypolarized wave(LHCP)hasbeeninvestigatedinanelectron‐ionquantumplasmaimmersedinuniform external magnetic field. Incorporating the quantum effects due to electron spin, Fermi pressure and Bohmpotentialterm,thequantummagneto‐hydrodynamic(QMHD)modelhasbeenusedto investigatethelinearandnonlinearresponseoftheplasmaspeciesforthree‐wavecoupling interactionina quantummagneto‐plasmas.Nonlineardispersionrelationsandgrowthrateshave been derived analytically. It has been shown that the spin of electrons has considerable effect on the growth rate of parametric instability problem even when the external magnetic field B0 is below the quantum critical magnetic field strength BQ = 4.4138 ×1013 G. Finally,theparametricdecayinstabilityofobliqueLangmuirwaveintolow‐frequency electromagnetic shear Alfven wave and LHCP have also been investigated in high density (quantum) and low density (classical) magneto‐plasma environments. QMHD model has been used to find the linear and non‐linear response of the high density quantum magneto‐plasma, and to compare the (h → 0, Pe → Pte ) results with the low density classical plasma we have used classical limit in the results of QMHD model. Nonlinear dispersion relations and growth rates of the problem have been derived analytically. The growth rate both for quantum and classical magneto‐plasma environments has been plotted. The normalized growth rate as a function of number density in the high density degeneratemagneto‐plasmasincreasesexponentiallywhileinthelowdensityclassicalmagneto‐ plasmas it increases logarithmically.