• Title/Summary/Keyword: modulation-transfer function (MTF)

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Modulation Transfer Function System for a Mid-infrared Lens by Knife-edge Scanning Technique (칼날 주사방식을 이용한 중적외선 렌즈의 변조전달함수 측정 장치)

  • Song, Se-Yong;Jo, Jae-Heung;Hong, Sung-Mok;Lee, Hoi-Youn;Lee, Yun-Woo
    • Korean Journal of Optics and Photonics
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    • v.22 no.1
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    • pp.16-22
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    • 2011
  • We fabricate a measuring system to measure the modulation transfer function (MTF) of a mid-infrared imaging silicon lens by using the knife-edge scanning technique. In particular, we measure on-axial tangential MTF of the silicon lens with the focal length of 50 mm and F-number F/4 in the wavelength band of mid-infrared between $3\;{\mu}m$ and $5\;{\mu}m$. In order to obtain the infinite object, the off-axial parabolic reflector with the focal length of 2.545 m is utilized. In the comparison with measured MTF data and designed MTF values curve, we find that the tolerance of measured MTF data below the spatial frequency of 7 lp/mm is within 2%.

Dynamic Modulation Transfer Function Analysis of Images Blurred by Sinusoidal Vibration

  • Du, Yanlu;Ding, Yalin;Xu, Yongsen;Sun, Chongshang
    • Journal of the Optical Society of Korea
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    • v.20 no.6
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    • pp.762-769
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    • 2016
  • The dynamic modulation transfer function (MTF) for image degradation caused by sinusoidal vibration is formulated based on a Bessel function of the first kind. The presented method makes it possible to obtain an analytical MTF expression derived for arbitrary frequency sinusoidal vibration. The error obtained by the use of finite order sum approximations instead of infinite sums is investigated in detail. Dynamic MTF exhibits a stronger random behavior for low frequency vibration than high frequency vibration. The calculated MTFs agree well with the measured MTFs with the slant edge method in imaging experiments. With the proposed formula, allowable amplitudes of any frequency vibration are easily calculated. This is practical for the analysis and design of the line-of-sight stabilization system in the remote sensing camera.

Numerical calculation of contrast transfer function for periodic line-space patterns (주기적인 선물체에 대한 Contrast Transfer Function의 수치계산)

  • 김형수;전영세;이종웅;김성호
    • Korean Journal of Optics and Photonics
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    • v.9 no.6
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    • pp.396-402
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    • 1998
  • The measurement of OTF(optical transfer function) is used for evalution of imaging performance of optical system as a standard method. In the mass-production, the contrast measurement of projected patterns is also popular because of its simplicity. In this study, a computer program which evaluates the CTF(contrast transfer function) of optical system for periodic line-space patterns is developed by using the diffraction imaging theory. The MTF(modulation transfer function) and CTF of an aberrated system are evaluated and analyzed for the third order aberrations expressed by the C-coefficients and the Zemike polynomials.

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Factors affecting modulation transfer function measurements in cone-beam computed tomographic images

  • Choi, Jin-Woo
    • 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.

MTF Assessment and Image Restoration Technique for Post-Launch Calibration of DubaiSat-1 (DubaiSat-1의 발사 후 검보정을 위한 MTF 평가 및 영상복원 기법)

  • Hwang, Hyun-Deok;Park, Won-Kyu;Kwak, Sung-Hee
    • Korean Journal of Remote Sensing
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    • v.27 no.5
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    • pp.573-586
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    • 2011
  • The MTF(modulation transfer function) is one of parameters to evaluate the performance of imaging systems. Also, it can be used to restore information that is lost by a harsh space environment (radioactivity, extreme cold/heat condition and electromagnetic field etc.), atmospheric effects and falloff of system performance etc. This paper evaluated the MTF values of images taken by DubaiSat-1 satellite which was launched in 2009 by EIAST(Emirates Institute for Advanced Science and Technology) and Satrec Initiative. Generally, the MTF was assessed using various methods such as a point source method and a knife-edge method. This paper used the slanted-edge method. The slantededge method is the ISO 12233 standard for the MTF measurement of electronic still-picture cameras. The method is adapted to estimate the MTF values of line-scanning telescopes. After assessing the MTF, we performed the MTF compensation by generating a MTF convolution kernel based on the PSF(point spread function) with image denoising to enhance the image quality.

SATELLITE OPERATION DESIGN FOR ASSESSING MTF PERFORMANCE OF EARTH OBSERVATION SATELLITE USING STELLAR SOURCES (별을 이용한 지구 관측 위성의 MTF 성능 분석을 위한 위성 운영 설계)

  • Kim, Hee-Seob;Chung, Dae-Won;Choi, Hae-Jin
    • Journal of Astronomy and Space Sciences
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    • v.24 no.4
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    • pp.379-388
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    • 2007
  • Modulation Transfer Function (MTF) of satellite image is an important performance index in satellite image applications. Therefore MTF performance is assessed using satellite image for the ground target during LEOP phase after launch. But the MTF performance assessment using the ground target can be affected by imaging conditions such as cloud and weather. In this paper system requirements and satellite operation for assessing MTF performance of satellite image using stellar sources are proposed. Satellite capability in collecting stellar sources using the satellite which is designed for earth observation and satellite image usefulness for assessing MTF performances were analyzed. The proposed approach will be useful to assess MTF performance of earth observation satellite in lower earth orbit.

Effects of the Geometrical Misalignment on the MTF Measurement (변조전달함수 측정에 있어 기하학적 조정 불량이 해상도에 미치는 영향)

  • Kim, Jun-Woo
    • Journal of the Korean Society of Radiology
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    • v.15 no.5
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    • pp.705-713
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    • 2021
  • The modulation transfer function (MTF) is calculated to analyze the resolution of the spatial frequency of the image acquired from the x-ray imaging system. In general, the response function of the detector acquires a line spread function (LSF) using a slit-camera, and derives a modulation transfer function through a Fourier transform. Because of the fact that the x-ray must always be incident on the center of the slit-camera, the tilt of the detector and slit-camera caused by the experimenter will affect the detector performance. In addition, if the tilt increases, the performance evaluation of the x-ray image system will be problematic. In this study, we analyzed the experimental and analytical models in the modulation transfer function, ie, the Fourier domain, based on the experimental error and analyzed the effect on the spatial frequency. Furthermore, performance evaluation is being carried out for various x-ray imaging systems, and experimental errors are indispensable, and the extent to which they can be tolerated should be reviewed.

Study of MTF Measure That Adopts a Fitting Curve for the Variable Angle of a Slant Target in Presampled MTF (Presampled MTF 기법에서 Slant Target의 다양한 각도에 대한 함수 Fitting이 적용된 MTF 측정기법에 관한 연구)

  • Choi, Siyoun;Kim, Junghwan;Kong, Hyunbae;Kim, Donghwan;Baek, Kyounghoon;Park, Ingu;Jeon, Hyowon;Lee, Kinam
    • Korean Journal of Optics and Photonics
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    • v.33 no.6
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    • pp.310-316
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    • 2022
  • In this paper, the difference in modulation transfer function (MTF) results according to the change in the angle of a slant target when measuring a presampled MTF was confirmed, and the difference was reduced by fitting the edge spread function graph obtained to reduce the error by the target's rotation. Due to the feature of the presampled MTF method, the spatial frequency changed due to the sensor's projected intensity being changed by the target's rotation, and it was confirmed that the difference in the MTF value occurred depending on the rotation angle of the target. In this paper, the MTF was calculated after fitting only one column of the acquired image. It was confirmed that the rotation error is smaller compared to the case of the presampled MTF method and this fitting method can be applied to a scene that contains various target angles, such as auto-focusing using the MTF.

Evaluation of Angle Optimization on Edge Test Device Setting in Modulation Transfer Function (변조전달함수 방법에서 엣지 장치 설정에 대한 각도 최적화 평가)

  • Min, Jung-Whan;Jeong, Hoi-Woun
    • Journal of radiological science and technology
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    • v.43 no.1
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    • pp.15-21
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    • 2020
  • This study was purpose to evaluation of Modulation Transfer Function in Measurements by using the International electrotechnical commission standard(IEC 62220-1) which were edge device each angle by using edge method. In this study was Aero(Konica, Japan) image receptor which is a indirect Flat panel detector(FPD) was used. The size of matrix 1994 × 2430 (14"× 17" inch) which performed 12 bit processing and pixel pitch is 175 ㎛. The results of shown as MTF measurements at IEC standard. The amount of data seemed reasonable and at an MTF value of 0.1 the spatial frequencies were 2.56 cycles/mm at an angle of 2.4°. MTF value of 0.5 the spatial frequencies were 1.32 cycles/mm at an angle of 2.4°. This study were to evaluate MTF by setting each angle 2.0°~2.8° degrees the most effective optimal edge angle and to suggest the quantitative methods of measuring by using IEC.

Analysis and Evaluation of Slanted-edge-based Modulation Transfer Function and Focus Measurements for Optimal Assembly of Imaging Modules in Gastrointestinal Endoscopy

  • Wonju Lee;Ki Young Shin;Dong-Goo Kang;Minhye Chang;Young Min Bae
    • Current Optics and Photonics
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    • v.7 no.4
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    • pp.398-407
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    • 2023
  • We explored a method to evaluate imaging performance for the optimal assembly of an endoscopic miniature lens and a sensor constituting an imaging module at the distal end of gastrointestinal endoscopy. For the assembly of the imaging module, the image sensor was precisely located at the focal plane when collimated light passed through the endoscopic lens. As another method, the distance between the lens and sensor was adjusted to obtain the highest focus index from images measured the star chart of the International Organization for Standardization (ISO) standard at various positions. We analyzed the slanted-edge modulation transfer function (MTF), corresponding depth of field, and number of line pairs for MTF 50% and 20% at each working distance within the range of 5-100 mm for imaging modules assembled in different ways. Assembly conditions of the imaging module with better MTF performance were defined for each working distance range of 5-30 mm and 30-100 mm, respectively. In addition to the MTF performance, the focus index of each assembled module was also compared. In summary, we examined the performance of imaging modules assembled with different methods within the suggested working distance and tried to establish the optimal assembly protocol.