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

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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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Measurement of the Modulation Transfer Function of Infrared Imaging System by Modified Slant Edge Method

  • Li, Hang;Yan, Changxiang;Shao, Jianbing
    • Journal of the Optical Society of Korea
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    • v.20 no.3
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    • pp.381-388
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    • 2016
  • The performance of a staring infrared imaging system can be characterized based on estimating the modulation transfer function (MTF). The slant edge method is a widely used MTF estimation method, which can effectively solve the aliasing problem caused by the discrete undersampling of the infrared focal plane array. However, the traditional slant edge method has some limitations such as the low precision of the edge angle extraction and using the approximate function to fit the edge spread function (ESF), which affects the accuracy of the MTF estimation. In this paper, we propose a modified slant edge method, including an edge angle extraction method that can improve the precision of the edge angle extraction and an ESF fitting algorithm which is based on the transfer function model of the imaging system, to enhance the accuracy of the MTF estimation. This modified slant edge method presents higher estimation accuracy and better immunity to noise and edge angle than other traditional methods, which is demonstrated by the simulation and application experiments operated in our study.

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.

Evaluation of color CRT monitor by MTFA (MTFA에 의한 칼라 CRT의 화질 평가)

  • 김태희
    • Korean Journal of Optics and Photonics
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    • v.9 no.3
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    • pp.205-211
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    • 1998
  • The MTF(modulation transfer function) measuring system with a linear CCD(charge coupled-device) was constructed to cvaluate a color CRT(catode ray tube). The measured MTF values were corrected by considering the spectral response and the pixel sizes of CCD. The effects of a spot size, video bandwidth, pitch of shadow mask holes, display luminance, and ambient illumination on image quality were studied. The uniformity of resolution and the contrast Ioss by ambient light of the color CRT monitor were measured, and the results were analyzed by MTFA(modulation threshold area).

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Image quality assessment of color LCD monitors by polychromatic modulation transfer function (다색광전달함수를 사용한 컬러 LCD 모니터의 광학적 상평가법)

  • Song, Jong-Sup;Jo, Jae-Heung;Hong, Sung-Mok;Lee, Yun-Woo;Yang, Ho-Soon;Cho, Hyun-Mo;Lee, In-Won
    • Korean Journal of Optics and Photonics
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    • v.16 no.1
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    • pp.63-70
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    • 2005
  • We propose a method for evaluating the image quality of color liquid crystal display(LCD) monitors by using the polychromatic modulation transfer function(PMTF), which is calculated from the modulation transfer function(MTF) weighted by the overall color response of the system including the test LCD monitor. We confirm that experimental results using the PMTF agree well with simulated results of the PMTF of a color LCD monitor by using three bar targets with different amplitudes and three elementary colors such as red(R), green(G), and blue(B). As a results, we should choose the PMTF instead of the white color MTF or monochromatic MTF in order to evaluate correctly the image quality of color LCD monitors.

Modulation Transfer Function Measurement of a Linear Charge Coupled Device Imager by Using a Knife-Edge Scanner (칼날주사방법에 의한 일차원 CCD의 MTF 측정)

  • 조현모;이윤우;이인원;이상태;이종웅
    • 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.

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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%.

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.

Vibration effects on remote sensing satellite images

  • Haghshenas, Javad
    • Advances in aircraft and spacecraft science
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    • v.4 no.5
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    • pp.543-553
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    • 2017
  • Vibration is a source of performance degradation in all optical imaging systems. Performance of high resolution remote sensing payloads is often limited due to satellite platform vibrations. Effects of Linear and high frequency sinusoidal vibrations on the system MTF are known exactly in closed form but the low frequency vibration effects is a random process and must be considered statistically. Usually the vibration MTF budget is defined based on the mission requirements and the overall MTF limitations. For analyzing low frequency effects, designer must know all the systems specifications and parameters. With a good understanding of harmful vibration frequencies and amplitudes in the system preliminary design phase, their effects could be removed totally or partially. This procedure is cost effective and let the designer to eliminate just harmful vibrations and avoids over-designing. In this paper we have analyzed the effects of low-frequency platform vibrations on the payload's modulation transfer function. We have used a statistical analysis to find the probability of imaging with a MTF equal or greater than a pre-defined budget for different missions. The worst and average cases have been discussed and finally we have proposed "look-up figures". Using these look-up figures, designer can choose the electro-optical parameters in such a way that vibration effects be less than its pre-defined budget. Furthermore, using the results, we can propose a damping profile based on which vibration frequencies and amplitudes must be eliminated to stabilize the payload system.

Design and Performance Verification of a LWIR Zoom Camera for Drones

  • Kwang-Woo Park;Jonghwa Choi;Jian Kang
    • Current Optics and Photonics
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    • v.7 no.4
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    • pp.354-361
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    • 2023
  • We present the optical design and experimental verification of resolving performance of a 3× long wavelength infrared (LWIR) zoom camera for drones. The effective focal length of the system varies from 24.5 mm at the wide angle position to 75.1 mm at the telephoto position. The design specifications of the system were derived from ground resolved distance (GRD) to recognize 3 m × 6 m target at a distance of 1 km, at the telephoto position. To satisfy the system requirement, the aperture (f-number) of the system is taken as F/1.6 and the final modulation transfer function (MTF) should be higher than 0.1 (10%). The measured MTF in the laboratory was 0.127 (12.7%), exceeds the system requirement. Outdoor targets were used to verify the comprehensive performance of the system. The system resolved 4-bar targets corresponding to the spatial resolution at the distance of 1 km, 1.4 km and 2 km.