• Imaging Science in Dentistry
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• v.49 no.2
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• pp.131-137
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• 2019

Purpose: This study was designed to investigate the effects of voxel size, the oversampling technique, and the direction and area of measurement on modulation transfer function (MTF) values to identify the optimal method of MTF measurement. Materials and Methods: Images of the wire inserts of the SedentexCT IQ phantom were acquired, and MTF values were calculated under different conditions(voxel size of 0.1, 0.2, and 0.3 mm; 5 oversampling techniques; simulated pixel location errors; and different directions and areas of measurement). The differences in the MTF values across various conditions were evaluated. Results: The MTF 10 values showed smaller standard deviations than the MTF 50 values. Stable and accurate MTF values were obtained in the 0.1-mm voxel images. In the 0.3-mm voxel images, oversampling techniques of 11 lines or more did not show significant differences in MTF values depending on the presence of simulated location errors. MTF 10 values showed significant differences according to the direction and area of the measurement. Conclusion: To measure more accurate and stable MTF values, it is better to measure MTF 10 values in small-voxel images. In large-voxel images, the proper oversampling technique is required. MTF values from the radial and tangential directions may be different, and MTF values vary depending on the measured area.

• Korean Journal of Optics and Photonics
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• v.7 no.1
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• pp.1-8
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• 1996

Charge-coupled device(CCD) array detectors are widely used in real time modulation transfer function(MTF) measurement systems. This paper presents the characteristics of two-dimensional CCDs used in a real time MTF measurement system for copy lenses. The MTF characteristics of a copy lens measured by this equipment show different results according to the direction of shift register, shutter speed and the amplifier gain of CCDs. An object generator is fabricated to reduce the variation of MTF values for the irradiance nonuniformity in on-axis and off-axis image plane and this MTF equipment is calibrated by using a standard lens.

• Korean Journal of Optics and Photonics
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• v.6 no.3
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• pp.173-177
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• 1995

The scanning type modulation transfer function (MTF) measurement system of linear charge coupled device (CCD) imagers is fabricated and the MTF of a linear CCD imager is tested. Measured MTF values are very sensitive to small angle knife-edge skew within 1 degree and show different results in several wavelengths. The MTF of the linear CCD imager is measured in different color temperatures of a tungsten filament lamp and the MTF uniformity of ti,t eel) pixels is tested.tested.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.604-607
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• 2004

The on-orbit MTF for the electro-optical camera (EOC) of the KOMPSAT I was calculated from sampled image of edge target. The image derived MTF values are smaller than ground measurement values but meet original requirements of EOC. The MTF from MTF compensated image was larger than and ground measurement result.

• Journal of Advanced Navigation Technology
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• v.16 no.2
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• pp.401-408
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• 2012

There is a clear need for characterizing optical components with the growing role played by optical devices in measurement, communication, and photonics. A basic and useful measuring parameter to meet this need, especially for imaging systems, is the Modulation Transfer Function, or MTF. Over the past few decades new instrument, including the laser interferometer, the CCD camera, and the computer have revolutionized the measurement and calculation of the MTF. This has made what was tedious and involved into virtually an instantaneous measurement. We proposed a Simpson approxiamtion method to create MTF graph and illustrated real example to verify its method in this paper. This method is very useful while it is very useful because its error is very minor and small although its approximation.

• Journal of radiological science and technology
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• v.28 no.2
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• pp.111-115
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• 2005

The quality of image from the system that creates medical images by using X-ray depends on the various different reasons such as the X-ray generator, the subject and the image transmission medium. In other words, thereare various factors existing that can influence on the quality of image from the moment when the X-ray is generated and until the final image is created. Therefore, the operator who creates images at the clinical site should make continuous evaluation and observation from the final image. There are various methods of evaluating the medical images, but it is assumed that the MTF measurement method can be suitable for measuring actual or effective resolution. So in this study, the MTF measurement method by using X-ray film has been avoided and the MTF features according to the deterioration of the X-ray system have been measured by using the software (the program used Borland C++ builder software and LEAD tools software) that can measure the MTF of the digital medical images. As the result of this measurement, it has been found out through the MTF graph that the resolution and sharpness from the old x-ray generator with a many years of using and many numbers of times of using were deteriorated for the quality of image comparing to those from the new system. Also a simple and easy measurement method for the MTF from the digital medical images can be obtained in this study.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.10
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• pp.98-103
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• 2005

The Flight Model of MAC (Medium-sized Aperture Camera), a 2.5m GSD class earth observation camera has been aligned and assembled. Topics discussed in this paper include the ground MTF performance of the MAC system, and the alignment of the focal plane assembly. MTF was measured by a knife-edge scanning technique, and a 450 mm diameter Cassegrain collimator with diffraction-limited performance was made and used for the MTF measurements. System MTF was used as the figure-of-merit to find the best focus of the focal plane assembly.

• Korean Journal of Optics and Photonics
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• v.26 no.3
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• pp.162-167
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• 2015

In this paper, we developed a MTF (Modulation Transfer Function) measurement system using a knife-edge scanning method for infrared optics. It consists of an objective part to generate the target image, a collimator to make the beam parallel, and a detector to analyze the image. We used a tungsten filament as the light source and MCT (Mercury Cadmium Telluride) to detect the mid-infrared(wavelength $3-5{\mu}m$) image. We measured the MTF of a standard lens (f=5, material ZnSe) to test this instrument and compared the result to the theoretical value calculated using the ZEMAX commercial software. It was found that the difference was within ${\pm}0.035$ at the cut-off frequency (50 1/mm). Also, we calculated the A-type measurement uncertainty to check the reliability of the measurement. The result showed only 0.002 at 20 1/mm in spatial frequency, which means very little variation in the MTF measurement under the same conditions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.264-270
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• 1996

In this paper, a computer automated system has been developed for measuring the focal length of camera lens using the MTF(Modurar Transfer Function) based on the signal processing around a line CCD and autocollimator. An optical Path for the focal length measurement system has been designed around thelight sourec, collimator, camera, mirror and the line CCD. The eyepiece of the collimator is replaced byline CCD, and the mirror is moved along the focal axis by a PC driven step motor. An efficient method has been designed for finding the optimum MTF value for the focal length based on the least squares approach. The developed system is fullycomputer automated: signal transmission to and from the camera, MTF evaluation based on the line CCD, step motor contorl, etc. The developed system has been applied to a practical camera manufacturing process and demonstrated its performance

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.489-493
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• 2004

The Modulation Transfer Function (MTF) is commonly used to characterize the spatial quality of imaging systems. This work is the attempt to measure the MTF for KOMPSAT EOC using the non-parametric method as ground inputs. The spatial performance of the KOMPSAT EOC was analyzed by edge method while in flight using multi-temporal image data collected over test site in Seoul. The results from this work demonstrate the potential applicability of this method to estimate MTF for high spatial resolution satellite KOMPSAT-2 that is being developed to be launched in 2005.