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Low-frequency vibration: (a) displacement during four different exposures (t e 0.15T 0 ), (b) MTF's for the four exposures.
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A new method of calculating the optical transfer function (OTF) for image blur caused by arbitrary motion is introduced. Previous methods, except for a few specific types of motion, were numerical rather than analytical. This new method makes it possible to obtain analytical expressions for the OTF deriving from any kind of motion by means of the s...
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... low-frequency vibrations, in which the exposure time (t e ) is smaller than the vibration period (T 0 ), the OTF exhibits a strong random behavior (Fig. 6). Image degradation as a result of low-frequency vibration has been analyzed in detail previously. 3,4 For high-frequency vibration it is convenient to ap- proximate the exposure with an integral number of vibra- tion periods (t e NT 0 , N being an integer). Actually, as long as t e T 0 , the blur extent is the same for both t e NT 0 ...
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... The required optical system includes visible, near-infrared and mid-infrared wavebands, in which the focal lengths in each waveband and the angle of vision should be the same; the performance indexes of each waveband of the system are presented in Table 1. First of all, use of the initial structure generated by the software building system and the set central wavelength, reference wavelength, the value range of focal length f' i , the value range of d interval, the glass catalog, the number of lenses and swarm, the random step index, the total focal length, the target function of difference of focal length, etc. in the software reflect the designing indexes; the specific parameters are shown within Eq. (12). Since the visible light approximates the near-infrared band, we merge these two ranges into one. ...
... Optical modulation transfer function (MTF) and spot diagram are often used to evaluate the imaging quality of optical system. It is objective and reliable to use them to evaluate the imaging quality of optical system [12,13]. Figure 4(a) is the MTF graph of the visible light waveband, from which we observe that the point on-axis is higher than 0.6 and the point off-axis is higher than 0.5, when the visible light wavebands are at 80 lp/mm of the Nyquist frequency. ...
A design method for a common aperture multi-band optical system based on particle swarm optimization (PSO) is proposed. Using the principle of PSO, the optimal parameters of the initial structure of optical system, which meet the requirements of the target function, can be calculated through using multiple iterations. In order to verify the design method, a common aperture multi-band system is created. The optical system can provide images in visible (0.49–0.66 µm), near infrared (0.8–0.9 µm) and medium-wave infrared (3.8–4.8 µm) bands. The focal length of the optical system is 70 mm and the field of view is ±2.5°. The experimental results show that the angular resolution is 1.3 mrad for visible light and near infrared and 4.6 mrad for medium-wave infrared. The optical system can produce images clearly in both the visible and infrared bands, which shows that a design method based on particle swarm optimization is feasible.
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... Many literatures at home and abroad have introduced the method of ground image motion compensation to solve the image motion caused by the change of the relative speed to height ratio [10][11][12]. In this paper, the method of on-board real-time control is used to directly control the image detector, and starts to "compensate" from the camera imaging device, so that the image is more real and accurate. ...
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... Hence, when compared to the previously mentioned mechanically scanned interferometers, it is significantly more tolerant to vibrations, and no special sophistication is required in its mechanical construction. Yet, as in other airborne and spaceborne cameras, system vibrations could cause blur effects and a degradation in image quality [29][30][31] . Compared to our CS-MUSI system, the presented camera also enjoys the advantage of passively acquiring the HS image, which is a key property in spaceborne and unmanned airborne tasks. ...
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Dynamic optical imaging (e.g. time delay integration imaging) is troubled by the motion blur fundamentally arising from mismatching between photo-induced charge transfer and optical image movements. Motion aberrations from the forward dynamic imaging link impede the acquiring of high-quality images. Here, we propose a high-resolution dynamic inversion imaging method based on optical flow neural learning networks. Optical flow is reconstructed via a multilayer neural learning network. The optical flow is able to construct the motion spread function that enables computational reconstruction of captured images with a single digital filter. This works construct the complete dynamic imaging link, involving the backward and forward imaging link, and demonstrates the capability of the back-ward imaging by reducing motion aberrations.
... The authors, instead, have tried to focus on a procedure dedicated to vision-based measurement systems, since they are interested in image restoration from a metrological point of view. The main idea of the work is to fit the OTF estimator with a frequency-domain model of motion blur, aiming to preserve all metrologic information nested in the image (similarly to what is documented in [33]). Another goal is to estimate a motion blur which is variable inside a given image. ...
Digital Image Correlation (DIC) is a widely adopted optical technique
to detect motions and deformations dealing with vision-based systems. Considering
DIC dynamic applications, motion blur represents one of the most relevant sources of
measurement uncertainty. This paper proposes an innovative approach to compensate
the effect of motion blur on images coming from deformable bodies, where the amount
of blur (w) varies within the single frame. A subset-based technique is developed to
estimate and then remove motion blur for each image region. The algorithm is validated
both on synthetic images and experimental data, demonstrating its effectiveness into
improving the accuracy of the displacements measured by DIC.
... The main idea of referenced estimation lies on the estimation of the OTF starting from reference and blurred images. Example of uses of referenced deconvolution procedure can be found in [22,23,24]. ...
... The authors tried to focus on an approach dedicated to vision based measurement systems. The main idea of the work is to fit the OTF estimator with a frequency domain model of motion blur, trying to preserve all metrologic information nested in the image (similarly to what documented in [24]). Another goal is to estimate a motion blur which is variable inside a given image. ...
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... Based on existing literature [19,20], when TDI series is certain, it is stated that the MTF calculation method for low frequency vibration can be approximately expressed as: ...
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... Indeed, the line of sight instabilities can imply image blurring characterized by a degradation of the Optical Transfer Function (OTF) of the imaging system. In [7], Stern and Kopeika show that the OTF degradation due to motion blur is the Fourier transform of the probability-density function (PDF) of the line of sight ground location during the integration time. The Fig. 1 shows that the OTF degradation implied by µvibrations depends on the corresponding maximum displacements during the integration time and also on the type of the µ-vibration characterized by its PDF. ...
... These methods are based on calculations in the spatial domain in contrast to previous methods. A method of calcu- lating the OTF for image blur caused by arbitrary motion has been demonstrated in [6]. The main advantage of this method is that it presents possible ways to produce analytical rather than numerical expressions for any kind of motion by means of the statistical moments of the motion function. ...
Alsat-1B, launched into a 670 km sun-synchronous orbit on board the PSLV launch vehicle from the Sriharikota launch site in India on 26 September 2016, is a medium resolution Earth Observation satellite with a mass of 100 kg. Alsat-1B will be used for agricultural and resource monitoring, disaster management, land use mapping and urban planning. It is based on the SSTL-100 platform, and flies a 24 m multispectral imager and a 12 m panchromatic imager delivering images with a swath width of 140 km.
One of the main factors affecting the performance of satellite-borne optical imaging systems is micro-vibration. Micro-vibration is a low level mechanical disturbance inevitably generated from moving parts on a satellite and exceptionally difficult to be controlled by the attitude and orbital control system (AOCS) of a spacecraft. Micro-vibration usually causes problems for optical imaging systems onboard Earth Observation satellites. The major effect of micro-vibration is the excitation of the support structures for the optical elements during imaging operations which can result in severe degradation of image quality by smearing and distortion. Quantitative characterization of image degradation caused by micro-vibration is thus quite useful and important as part of system level analysis which can help preventing micro-vibration influence by proper design and restoring the degraded image.
The aim of this work is to provide quantitative estimates of the effect of micro-vibration on the performance of Alsat-1B imager, which may be experienced operationally, in terms of the modulation transfer function (MTF) and based on ground micro-vibration tests results.
