Dynamic Modulation Transfer Function Research Articles

Improved On-Orbit MTF Measurement Method Based on Point Source Arrays

The modulation transfer function (MTF) is a key characteristic used to assess the performance of optical remote sensing satellite sensors. MTF detection can directly measure a sensor’s two-dimensional (2D) point spread function (PSF); therefore, it has been applied to various high-resolution remote sensing satellites (e.g., Pleiades) using point sources. However, current point source methods mainly use 2D Gaussian functions to fit the discrete digital number (DN) of the point source on the image to extract the center of the point source and fit the PSF after encrypting multiple point sources; thus, noise robustness is poor and measurement accuracy varies widely. In this study, we developed a noise-resistant on-orbit MTF detection method based on the object space constraint among point source arrays. Utilizing object space constraint relationships among points in a point source array, a homography transformation model was established, enabling accurate extraction of sub-pixel coordinates for each point source response. Subsequently, aligning the luminosity distribution of all point sources concerning a reference point source, the encrypted PSF was obtained and then fitted to obtain the MTF. To validate the method, Gaofen-2 (GF-2) satellite images were used to conduct an in-orbit imaging experiment on the point source array of the Chinese Zhongwei remote sensing satellite calibration site. Compared with the Gaussian model methods, the proposed method yielded more accurate peak positions for each point source. Standard deviations of peak position constant ratios in along- and cross-track directions improved by 2.8 and 4.8 times, respectively. The root-mean-square error (RMSE) of the collinearity test results increased by 92%, and the noise resistance of the MTF curve improved by two times. Dynamic MTF values at the Nyquist frequency for the GF-2 panchromatic band in along- and cross-track directions were 0.0476 and 0.0705, respectively, and MTF values in different directions were well distinguished.

Hyper-Temporal Data Based Modulation Transfer Functions Compensation for Geostationary Remote Sensing Satellites

Over the past years, the acquisition of hyper-temporal data (HTD) from geostationary orbit remote sensing satellites (GEORSS) has provided numerous new research opportunities. Many factors influence the in-orbit dynamic modulation transfer function (MTF) of GEORSS, making it difficult to satisfy the requirements for space-borne cameras. The MTF compensation (MTFC) technique can effectively optimize the design of dynamic MTFs for GEORSS. The traditional MTFC methods mainly consider the sensor, atmosphere and relative motion of the satellite platform when improving GEORSS image quality. They will introduce new high frequency noise, resulting in image information loss. In this paper, a mixed sparse higher-order non-convex total variation (MS-HONCTV) model-aided MTFC method is proposed. By introducing the group sparse regularization (GSR) term into the MS-HONCTV model, it increases the robustness to noise and hence reduces the degeneration of the MTF produced by satellite’ low pointing stability. The MS-HONCTV model is then applied to solve the problem of image degradation. The quality of remote sensing data is improved by the proposed MTFC and this is achieved without modifying the aperture diameter, focal length, or detector size of the satellite’s optical system. Experimental results show that the proposed MS-HONCTV effectively improves the images’ MTF, SNR, gray mean gradient (GMG) and standard deviation (SD), as evidenced by subjective qualitative analysis and objective quantitative assessments of simulated data, laboratory data, and GF-4 satellite data. Compared with other methods, the SNR of the proposed method is increased by 30%, GMG by 14.21% and SD by 6.3% on average.

Test method of the dynamic modulation transfer function in an indoor analog environment

Test method of the dynamic modulation transfer function in an indoor analog environment

Dynamic modulation transfer function measuring device for photoelectric imaging system

In the optical imaging system, the dynamic modulation transfer function (DMTF) is affected by the wave aberration of optical system, the signal resolution and transfer characteristics of detector modules, and the image blur caused by the carrier motion, which has become one of the important parameters of the photoelectric imaging system. Based on the testing principle of dynamic and static modulation transfer function of photoelectric imaging system, a DMTF measuring device was developed, in which the focal length of optical collimation system was 10 000 mm, and the speed control range of moving target was 30 mm/s~5 000 mm/s, which met the DMTF test of photoelectric imaging system with long focal length. A series of experiments were carried out, and the results show that the repeatability of DMTF measurement is better than 0.01, and the uncertainty of measurement can reach to U= 0.05 (k=2).

52‐4: Simulation of Dynamic MTF Measurement Method for Pixelated Displays

A method for measuring the dynamic modulation transfer function (MTF) of a display is introduced. A single moving vertical line is displayed, and a high‐speed imaging light measuring device (LMD) captures a small region of the screen. The effect of smooth‐pursuit eye‐tracking of the moving line is simulated by aggregating a series of supersampled luminance profiles.

Theoretical Model of Dynamic MTF of Low-Light-Level ICCD

During the integration time of the low-light intensified charge-coupled device(ICCD),the spatial vibration causes a decrease in the imaging quality of the low-light ICCD camera.In the case of imaging using low-light ICCD cameras in a vibrating environment,the dynamic modulation transfer function(MTF)is used to evaluate the effect of spatial vibration on imaging quality.Combined with the unique structure of the low-light ICCD camera,the dynamic MTF theoretical model of the low-light ICCD camera is proposed,which can be used to analyze the influence of different factors such as amplitude of vibration,period of vibration and integration time on the imaging quality in low-frequency and high-frequency sinusoidal vibrations.

Analysis of Dynamic Modulation Transfer Function for Complex Image Motion

In remote-sensing imaging, the modulation transfer function (MTF) for image motion relevant to the mixing of multiple forms of motions is hard to calculate because of the complicated image motion expression. In this paper, a new method for calculating the MTF for complex image motion is proposed. The presented method makes it possible to obtain an analytical MTF expression derived from the mixing of linear motion and sinusoidal motion at an arbitrary frequency. On this basis, we used the summation of infinitely many terms involving the Bessel function to simplify the MTF expression. The truncation error obtained by the use of finite order sum approximations instead of infinite sums is investigated in detail. In order to verify the MTF calculation method, we proposed a simulation method to calculate the variation of MTF in an actual optical system caused by image motion. The mean value of the relative error between the calculation method and the simulation method is less than 5%. The experimental results are consistent with the MTF curve calculated by our method.

High Sensitive Night-time Light Imaging Camera Design and In-orbit Test of Luojia1-01 Satellite.

Luojia1-01 satellite is the first scientific experimental satellite applied for night-time light remote sensing data acquisition, and the payload is an optical camera with high sensitivity, high radiation measurement accuracy and stable elements of interior orientation. At the same time, a special shaped hood is designed, which significantly improved the ability of the camera to suppress stray light. Camera electronics adopts the integrated design of focal plane and imaging processing, which greatly reduces the volume and weight of the system. In this paper, the design of the optical camera is summarized, and the results of in-orbit imaging performance tests are analyzed. The results show that the dynamic modulation transfer function (MTF) of the camera is better than 0.17, and the SNR is better than 35 dB under the condition of 10 lx illuminance and 0.3 reflectivity and all indicators meet the design requirements. The data obtained have been widely applied in many fields such as the process of urbanization, light pollution analysis, marine fisheries detection and military.

Dynamic modulation transfer function analysis and short exposure technique for planar flow cytometric microimaging system

A planar flow cytometric microimaging system is introduced for cell recognition and classification in urinary sediment analysis. In order to make clear imaging of the motor cells, the dynamic modulation transfer function(DMTF) is analyzed. At the Nyquist frequency, the DMTF of the imaging system must be more than 0.9 to achieve the imaging quality of static system. Based on this, the exposure time requirement of the system is derived. The system adopts LED optical pulse acceleration circuit and rising edge exposure. In this way, 1μs exposure time can be reached. The dynamic transmission is also up to 0.93, and the image clarity is improved significantly.

航空相机像旋动态调制传递函数分析与研究

航空相机像旋动态调制传递函数分析与研究

Dynamic Modulation Transfer Function Analysis of Images Blurred by Sinusoidal Vibration

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.

Dynamic modulation transfer function of a retina-like sensor

In this paper, we propose a method to deduce the dynamic modulation transfer function (DMTF) of a space-variant sampling retina-like sensor and demonstrate its utilization in the forward motion imaging process. With the analysis of sampling and the motion imaging property of the sensor, DMTF has been derived. Next, the performance of DMTF between a retina-like sensor and a rectilinear sensor is compared, and the results show that the degradation of DMTF in forward motion is less than that of a rectilinear sensor. Then, the output images are obtained through simulation based on DMTF, and they are compared with that obtained from a CMOS camera with the same forward motion conditions. The Pearson correlation coefficients between the two kinds of images are all larger than 0.85. Thus, the effectiveness of DMTF is shown.

正弦振动对航空相机成像影响的分析与验证

The imaging resolution of aerial camera is limited by vibration during exposure. Dynamic modulation transfer function is used to study the impact of the sinusoidal vibration on imaging. Modulation transfer function (MTF) of high-frequency and low-frequency vibrations are analyzed through the calculation method based on spatial domain. When exposure time is not equal to an integer multiples of the vibration cycle, the impact of high-frequency vibrations on image quality is also random, but the randomness is less apparent than low-frequency vibration. The fast steering mirror is used to simulate vibrations, complementary metal oxide semiconductor (CMOS) sensor is used to capture images, wavelet transform is used to extract high frequency information. Exposure time is set to 20 ms, when the vibration frequency is 50 Hz, the fluctuation range of high-frequency information is only 0.0582104, which can be ignored compared with the total number of high-frequency information. When the vibration frequency is 15 Hz, the fluctuation range is 0.6233104 and randomness is obvious. But when the vibration frequency is 65 Hz, the fluctuation range is 0.1245104 and randomness is not obvious. By the correspondence between high-frequency information and MTF, the correctness of theoretical analysis is proved. On the basis of theoretical analysis and experiments, the general conclusion of sinusoidal vibration's effect on imaging is summed. This conclusion can not only be used to analyze the design of the imaging system structure, but also can be applied to image deblurring.

Edge regularized restoration for laser bubble detection

Laser bubble detection based on optical photography is widely used in industrial areas such as air tightness measurements. However, the precision of detection is severely affected by the degradation of detecting images. In order to enhance the visual quality of bubble detection, an image semiblind restoration method with edge regularization is applied along with the estimation of the dynamic modulation transfer function. We use objective-image quality metrics to limit the deconvolution iterations of the semiblind deconvolution algorithm. We compare the performance of the binary morphology filter. Improvement by the proposed method can be seen from the experimental results. It can be concluded that the proposed approach can effectively enhance quality and edge details of the laser bubble detecting images, so that greater precision can be achieved.

Space Camera Dynamic Image Quality Measurement and Evaluation

By using analysis of the infinity image of the space camera, we intend to obtain the curve of the dynamic modulation transfer function. We extract the pixel gray values at the image edge which distribute as a knife-edge function, and make differential calculation and Fourier transformation of it, and then we can obtain the dynamic MTF curve of the optical system. The value of the curve at the Nyquist frequency is the most important parameter that reflects the image quality. We add push-scanning imaging and environmental effects to the static MTF of space camera and compare the MTF value with the dynamic MTF at Nyquist frequency. The comparison result can help us verify the accuracy of the calculating results and the feasibility of our method.

Study of the Dynamic Modulation Transfer Function of Modified Super-Wide-Angle Sagnac Imaging Interferometer

Modulation transfer function (MTF) is an important parameter for one image system. In order to obtain the more imaging quality performance of the modified super-wide-angle Sagnac imaging interferometer (MSASII) put forward by our group, and also have a qualitative analysis of its advantages and disadvantages in the process of application. Its dynamic MTF is focused on in this paper. The dynamic MTF expression of the MSASII is calculated. According to earlier research parameters of the MSASII, the dynamic MTF curve is described and corresponding corrective measures in theoretical is given. The result is demonstrated that the imaging quality of MSASII could satisfy the need of detecting upper atmospheric wind field.

Evaluation of moving‐line contrast degradation without motion

Abstract— A method for evaluation of the contrast of moving step‐grating patterns under smooth‐pursuit eye‐tracking conditions without imaging data acquisition and image analysis is introduced. Periodic optical responses of the display to a set of simple driving signals have been recorded at a fixed location, and the luminance vs. time data has been evaluated to obtain two types of contrast for characterization of the dynamical performance of the display under test: the frame‐convoluted contrast and the frame‐integrated contrast. The relation of this characterization with respect to modulation transfer functions from impulse responses and to the dynamic modulation transfer function from sine‐gratings is explained and discussed. The approach described here provides a detailed and comprehensive characterization of the dynamical properties of electronic displays including both extreme cases of step‐response and impulse‐response with quantities that are related to visual perception. With this type of evaluation, the visual resolution of displays can be described by the same characteristics in the static and the dynamic case. The method is attractive due to limited instrumental efforts and the transparent method of evaluation.

Evaluation of moving‐line contrast degradation without motion

A method for evaluation of the contrast of moving step‐grating patterns under smooth‐pursuit eye‐tracking conditions without imaging data acquisition and image analysis is introduced. Periodic optical responses of the display to a set of simple driving signals have been recorded at a fixed location, and the luminance vs. time data has been evaluated to obtain two types of contrast for characterization of the dynamical performance of the display under test: the frame‐convoluted contrast and the frame‐integrated contrast. The relation of this characterization with respect to modulation transfer functions from impulse responses and to the dynamic modulation transfer function from sine‐gratings is explained and discussed. The approach described here provides a detailed and comprehensive characterization of the dynamical properties of electronic displays, including both extreme cases of step‐response and impulse‐response with quantities that are related to visual perception. With this type of evaluation, the visual resolution of displays can be described by the same characteristics in the static and the dynamic case. The method is attractive due to limited instrumental efforts and the transparent method of evaluation.

高分辨率航空相机动态调制传递函数数值分析

高分辨率航空相机动态调制传递函数数值分析

Dynamic modulation transfer function: a method to characterize the temporal performance of liquid-crystal displays

A method to measure the dynamic modulation transfer function (DMTF) of a liquid-crystal display (LCD) is proposed to characterize its performance when rendering motion images. The method includes a measurement system to capture the temporal luminance variation of a LCD while using a well-designed input data sequence and a simulation model based on smooth pursuit eye tracking and temporal light integration at the human retina. It predicts the perceived performance of a moving sine wave pattern on a LCD and subsequently calculates the DMTF. With this approach, several technologies to reduce motion blur were evaluated and discussed.