The General Image Quality Equation and the Structure of the Modulation Transfer Function

2006 ◽  
Author(s):  
Robert B. Hindsley ◽  
Lee J. Rickard
Keyword(s):  
Image Quality ◽  
Transfer Function ◽  
Modulation Transfer Function ◽  
Modulation Transfer

scholarly journals PENINGKATAN KUALITAS FOKUS CITRA IMAGER MULTISPEKTRAL SATELIT LAPAN-A3 (IMAGE-FOCUSING QUALITY IMPROVEMENT ON LAPAN-A3 SATELLITE MULTISPECTRAL IMAGER)

2018 ◽  
Vol 14 (1) ◽  
pp. 37
Author(s):  
Andi Mukhtar Tahir ◽  
Patria Rachman Hakim ◽  
A. Hadi Syafruddin
Keyword(s):  
Image Quality ◽  
Transfer Function ◽  
Modulation Transfer Function ◽  
Near Infrared ◽  
Beam Splitter ◽  
Modulation Transfer ◽  
Color Channel ◽  
Multispectral Imager ◽  
Image Focus

LAPAN-A3 satellite brings a multispectral imager as main payload which has four color channel, i.e.: red, green, blue and near-infrared. The imager optics system uses beam-splitter mechanism, which divides the incoming light passing lens system into each color channel detector. Since each channel detector has different position and orientation with respect to lens center, then images produced by each channel detector will have different image focus quality. Such factor could reduce the quality of image produced. This research aims to improve the composite image quality of LAPAN-A3 satellite multispectral imager by ensuring that every channel detector will have uniform focus setting. The method used in this research consists of taking series of observation of object with zebra-cross pattern, then processed them by using Imatest software. The determination of the quality of each image focus are based on Modulation Transfer Function (MTF) calculation in particular spatial frequency. After several observations and calculation, image focus level of each channel detector can be successfully uniformed by controlling the distance of each detector to the center of lens. Furthermore, the experiment also able to reduce distortion caused by channel co-registration in horizontal axes. As a result, image quality of LAPAN-A3 satellite multispectral imager can be improved significantly. These results can be used as reference on the actual LAPAN-A3 sattelite ground station operation, and to support the development of experimental multispectral imager that is prepared for the next LAPAN-A4 sattelite. ABSTRAKSatelit LAPAN-A3 membawa imager multispektral sebagai muatan utama, yang memiliki empat kanal warna yaitu merah, hijau, biru, dan near-infrared. Sistem optik imager dirancang dengan menggunakan beam-splitter yang akan membagi cahaya yang melewati sistem lensa menuju detektor masing-masing kanal warna. Karena setiap detektor memiliki posisi dan juga orientasi yang berbeda terhadap pusat lensa, maka akan terjadi ketidakseragaman derajat kefokusan untuk setiap citra yang dihasilkan oleh masing-masing kanal warna, yang dapat mengurangi kualitas citra komposit yang dihasilkan. Penelitian ini bertujuan untuk meningkatkan kualitas citra komposit imager multispektral satelit LAPAN-A3 dengan cara memastikan agar setiap kanal warna akan menghasilkan citra dengan derajat kefokusan yang seragam. Metode yang digunakan yaitu dengan mengambil sejumlah data pengamatan terhadap obyek dengan pola geometri zebra-cross, dan kemudian diolah dengan menggunakan perangkat lunak Imatest. Penentuan kualitas fokus citra dilakukan dengan mengukur Modulation Transfer Function (MTF) pada frekuensi spasial tertentu. Berdasarkan sejumlah pengamatan dan perhitungan yang dilakukan, derajat kefokusan citra yang dihasilkan masing-masing detektor dapat diseragamkan dengan mengatur jarak detektor tersebut terhadap pusat lensa. Selain itu, percobaan yang dilakukan juga dapat mengurangi distorsi ko-registrasi kanal yang terjadi pada sumbu horisontal. Kedua hasil tersebut secara signifikan dapat meningkatkan kualitas citra imager multispektral satelit LAPAN-A3, terutama dalam aspek geometri. Hasil penelitian ini diharapkan dapat digunakan sebagai panduan dalam proses operasional satelit LAPAN-A3 selanjutnya dan juga dapat mendukung pengembangan imager multispektral eksperimen yang sedang dikembangkan untuk satelit LAPAN-A4.

scholarly journals PENINGKATAN KUALITAS FOKUS CITRA IMAGER MULTISPEKTRAL SATELIT LAPAN-A3

2016 ◽  
Vol 14 (1) ◽  
pp. 37 ◽  
Author(s):  
Andi Mukhtar Tahir ◽  
Patria Rachman Hakim ◽  
A. Hadi Syafruddin
Keyword(s):  
Image Quality ◽  
Transfer Function ◽  
Modulation Transfer Function ◽  
Near Infrared ◽  
Beam Splitter ◽  
Modulation Transfer ◽  
Color Channel ◽  
Multispectral Imager ◽  
Image Focus

LAPAN-A3 satellite brings a multispectral imager as main payload which has four color channel, i.e.: red, green, blue and near-infrared. The imager optics system uses beam-splitter mechanism, which divides the incoming light passing lens system into each color channel detector. Since each channel detector has different position and orientation with respect to lens center, then images produced by each channel detector will have different image focus quality. Such factor could reduce the quality of image produced. This research aims to improve the composite image quality of LAPAN-A3 satellite multispectral imager by ensuring that every channel detector will have uniform focus setting. The method used in this research consists of taking series of observation of object with zebra-cross pattern, then processed them by using Imatest software. The determination of the quality of each image focus are based on Modulation Transfer Function (MTF) calculation in particular spatial frequency. After several observations and calculation, image focus level of each channel detector can be successfully uniformed by controlling the distance of each detector to the center of lens. Furthermore, the experiment also able to reduce distortion caused by channel co-registration in horizontal axes. As a result, image quality of LAPAN-A3 satellite multispectral imager can be improved significantly. These results can be used as reference on the actual LAPAN-A3 sattelite ground station operation, and to support the development of experimental multispectral imager that is prepared for the next LAPAN-A4 sattelite. Abstrak Satelit LAPAN-A3 membawa imager multispektral sebagai muatan utama, yang memiliki empat kanal warna yaitu merah, hijau, biru, dan near-infrared. Sistem optik imager dirancang dengan menggunakan beam-splitter yang akan membagi cahaya yang melewati sistem lensa menuju detektor masing-masing kanal warna. Karena setiap detektor memiliki posisi dan juga orientasi yang berbeda terhadap pusat lensa, maka akan terjadi ketidakseragaman derajat kefokusan untuk setiap citra yang dihasilkan oleh masing-masing kanal warna, yang dapat mengurangi kualitas citra komposit yang dihasilkan. Penelitian ini bertujuan untuk meningkatkan kualitas citra komposit imager multispektral satelit LAPAN-A3 dengan cara memastikan agar setiap kanal warna akan menghasilkan citra dengan derajat kefokusan yang seragam. Metode yang digunakan yaitu dengan mengambil sejumlah data pengamatan terhadap obyek dengan pola geometri zebra-cross, dan kemudian diolah dengan menggunakan perangkat lunak Imatest. Penentuan kualitas fokus citra dilakukan dengan mengukur Modulation Transfer Function (MTF) pada frekuensi spasial tertentu. Berdasarkan sejumlah pengamatan dan perhitungan yang dilakukan, derajat kefokusan citra yang dihasilkan masing-masing detektor dapat diseragamkan dengan mengatur jarak detektor tersebut terhadap pusat lensa. Selain itu, percobaan yang dilakukan juga dapat mengurangi distorsi ko-registrasi kanal yang terjadi pada sumbu horisontal. Kedua hasil tersebut secara signifikan dapat meningkatkan kualitas citra imager multispektral satelit LAPAN-A3, terutama dalam aspek geometri. Hasil penelitian ini diharapkan dapat digunakan sebagai panduan dalam proses operasional satelit LAPAN-A3 selanjutnya dan juga dapat mendukung pengembangan imager multispektral eksperimen yang sedang dikembangkan untuk satelit LAPAN-A4.

scholarly journals PENGUKURAN KUALITAS CITRA DIGITAL COMPUTED RADIOGRAPHY MENGGUNAKAN PROGRAM PENGOLAH CITRA

2016 ◽  
Vol 12 (2) ◽  
pp. 161-168 ◽  
Author(s):  
D. R. Ningtias ◽  
S. Suryono ◽  
S. Susilo
Keyword(s):  
Quality Control ◽  
Image Quality ◽  
Transfer Function ◽  
Spatial Resolution ◽  
Digital Image ◽  
Modulation Transfer Function ◽  
Computed Radiography ◽  
Modulation Transfer ◽  
Cr System

Penelitian yang telah dilakukan adalah pembuatan dan penghitungan kualitas citra digital menggunakan program Modulation Transfer Function (MTF) pada sistem Computed Radiography (CR) untuk kegiatan Quality Control (QC). MTF dapat digunakan untuk menganalisis resolusi spasial citra digital secara akurat. Pada penelitian ini menggunakan phantom yang terbuat dari tembaga berukuran 15x15 cm dengan ketebalan 1 mm. Phantom dieksposi dengan variasi tegangan 50 kV, 60 kV, 70 kV dan 81 kV dan masing-masing dilakukan variasi arus. Data yang diperoleh berupa file citra digital radiografi format DICOM yang kemudian dilakukan analisis kualitas citranya menggunakan PC diluar sistem CR dengan metode MTF. Metode ini sangat efisien dalam melakukan QC resolusi spasial secara kuantitatif sehingga dapat digunakan untuk menilai kualitas pesawat CR. Hasil pengukuran menunjukkan bahwa semakin tinggi tegangan yang digunakan, maka kualitas citra semakin baik dengan arus optimal pada rentang 4-8 mAs dengan rata-rata nilai resolusi spasial 7,26 lp/mm.The research was analyzing of digital image quality by using Modulation Transfer Function (MTF) on Computed Radiography (CR) system for Quality Control (QC). MTF can be used for analyzing digital image spatial resolution accurately. The research used phantom that made of 15x15 cm2 copper and 1 mm thickness. The phantom was expounded with voltage variations by 50 kV, 60 kV, 70 kV dan 81 kV and each of them have been taken by variations of the current. The the image quality of data obtained in the form of radiography digital image files with DICOM format were then analyzed using PC out of CR system with methode of MTF. This methode is really efficient for QC spatial resolution quantitatively and so it can be used for assesing the quality of CR. The measurement results showed that the higher the voltage, the better image quality with optimal current was on the range between 4-8 mAs with the average value of MTF 7,26 lp/mm.

Observer Performance Using a Video Display

1977 ◽  
Vol 21 (5) ◽  
pp. 406-410
Author(s):  
William S. Beamon
Keyword(s):  
Image Quality ◽  
Transfer Function ◽  
White Noise ◽  
Modulation Transfer Function ◽  
Observer Performance ◽  
Target Acquisition ◽  
Modulation Transfer ◽  
Area Metric ◽  
Acquisition Task

An experiment was conducted to assess observer performance in a simulated air-to-ground target acquisition task. Terrain films depicting targets imbedded in rural scenery were presented by a closed-circuit video system which employed two methods of varying the image quality of the display. The effects produced by these methods, spot wobble and random or ‘white’ noise added to the video signal, were independently manipulated, photometrically measured, and included in the Modulation Transfer Function Area metric of image quality. Correlation with observer target acquisition data suggest that the predictive validity of the Modulation Transfer Function Area (MTFA) concept may be improved by the addition of a third function incorporating some portion of the power spectrum of the imaged scene. The facilitory effects produced by spot wobble and the deleterious effects of white noise on observer performance were also demonstrated.

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