An accurate characterization of optical elements is one of the pivotal skills to be learnt in the context of undergraduate optics lab work or that of continuing education. We will show an experimental apparatus design...
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ISBN:
(纸本)9781510600287
An accurate characterization of optical elements is one of the pivotal skills to be learnt in the context of undergraduate optics lab work or that of continuing education. We will show an experimental apparatus designed to measure the modulation transfer function (MTF) of a camera lens. The educational scope of this apparatus ranges from the study of the aberrations of the lens and its suitability for use with a given sensor, to the design of the test bench itself. A first, purely visual observation allows the trainees to single-out the aberrations exhibited by an objective. The presence of the spherical and chromatic aberrations on the axis of the objective is thus identified, and a first estimate of the cut-off frequency of this objective can be given. There, the importance of the geometrical extent of the source and the impact of the optical elements of the test bench on the measurement can also be assessed. The second part of the experiment makes use of a CMOS camera to measure the Linear Spread function (LSF) of the camera lens and the MTF is then retrieved by Fourier transform. The experimental setup consists of a fine slit as a source, a collimator, the studied objective exhibiting conspicuous aberrations and a microscope objective to re-image the LSF either for direct observation with an eye-piece or for analysis with the camera. The latter is performed with a home-developed Matlab software.
The modulation transfer function (MTF) is the main parameter that is used to evaluate image quality in electro-optical systems. Detector sampling MTF in most electro-optical systems determines the cutoff frequency of ...
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The modulation transfer function (MTF) is the main parameter that is used to evaluate image quality in electro-optical systems. Detector sampling MTF in most electro-optical systems determines the cutoff frequency of the system. The MTF of the detector depends on its pixel shape. In this work, we calculated the MTF of a detector with an equilateral triangular pixel shape. Some new results were found in deriving the MTF for the equilateral triangular pixel shape.
In this theoretical study the modulation transfer function (MTF) of an ideal one-dimensional image sensor array is calculated using computer simulations and simple mathematical concepts. These calculations take into a...
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In this theoretical study the modulation transfer function (MTF) of an ideal one-dimensional image sensor array is calculated using computer simulations and simple mathematical concepts. These calculations take into account the finite size of the pixels, the discrete and periodic arrangement of the pixels, and the effect of the phase shift between the pixel array and the signal incident on the imager. It is found that the actual MTF of the sensor is more feature rich than implied by the Sinc function. In particular, when imaging periodic patterns on the sensor, for example to measure the resolution, phase shift between the incident pattern and the sensor and the spatial frequency can dramatically affect the results. An exact formula for the phase averaged MTF is derived. (C) 2015 Optical Society of America
A method to tune the parameters of the controller of an inertially stabilized platform is presented. This platform carries an electro-optical system. The image quality is obviously influenced by the movements of the p...
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A method to tune the parameters of the controller of an inertially stabilized platform is presented. This platform carries an electro-optical system. The image quality is obviously influenced by the movements of the platform: the Line of Sight (LoS) of the imager has to remain fixed in an inertial frame. The more the LoS controller manages to counter the movement of the platform, the better the image quality will be. The motion modulation transfer function (motion MTF) measures the amount of blur brought into the image by the motion of the platform. It represents the contrast over spatial frequencies. Up to now, it has mostly been used as a validation tool for controllers already tuned from derived low level and conservative considerations. The proposed methodology aims to tune LoS controllers using directly the motion MTF as a criterion in the design procedure.
The retina-like sensor is a kind of anthropomorphic visual sensor. It plays an important role in both biological and machine vision due to its advantages of high resolution in the fovea, a wide field-of-view, and mini...
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The retina-like sensor is a kind of anthropomorphic visual sensor. It plays an important role in both biological and machine vision due to its advantages of high resolution in the fovea, a wide field-of-view, and minimum pixel count. The space-variant property of the sensor makes it difficult to directly measure its modulation transfer function (MTF). The MTF of a retina-like sensor is measured with the bar-target pattern method. According to the pixel arrangement, the sensor is divided into rings and the MTF of each ring is measured using spoke targets with different periods. Comparison between the measured MTF and the theoretical MTF of the sensor showed that they coincide. The differences between them are also analyzed and discussed. The measured MTF helps to analyze the performance of an imaging system containing a retina-like sensor. (C) 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)
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 t...
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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. (C) 2014 Optical Society of America
In this work, we develop a method for simulating the modulation transfer function (MTF) of infrared detector arrays, which is based on numerical evaluation of the detector physics. The finite-difference time-domain an...
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In this work, we develop a method for simulating the modulation transfer function (MTF) of infrared detector arrays, which is based on numerical evaluation of the detector physics. The finite-difference time-domain and finite element methods are used to solve the electromagnetic and electrical equations for the device, respectively. We show how the total MTF can be deconvolved to examine the effects of specific physical processes. We introduce the MTF area difference and use it to quantify the effectiveness of several crosstalk mitigation techniques in improving the system MTF. We then apply our simulation methods to two-thirds generation mercury cadmium telluride (HgCdTe) detector architectures. The methodology is general, can be implemented with commercially available software, has experimentally realizable analogs, and is extendable to other material systems and device designs.
One-dimensional modulation transfer function (1-D MTF) has been generally calculated to evaluate the image quality of optical imaging systems, such as the horizontal MTF and vertical MTF. These MTFs can be measured by...
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One-dimensional modulation transfer function (1-D MTF) has been generally calculated to evaluate the image quality of optical imaging systems, such as the horizontal MTF and vertical MTF. These MTFs can be measured by the use of some mature ways. However, the information of 1-D MTF for performance evaluation may not enough for the systems handling two-dimensional (2-D) targets of high resolution, thus discussing 2-D MTF will be necessary. We investigate the measurement method for the 1-D and 2-D MTF of optical imaging systems based on the random target method, and the characteristics of 2-D MTF and 1-D MTF in terms of MTF values and cutoff frequency are also noted. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.
A method for determining the modulation transfer function (MTF) in direct X-ray fluorescence mapping (XFM) system is reported. With a standard container filled with homogeneous gold nanoparticle (GNP) solution (1% by ...
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A method for determining the modulation transfer function (MTF) in direct X-ray fluorescence mapping (XFM) system is reported. With a standard container filled with homogeneous gold nanoparticle (GNP) solution (1% by weight), sharp edges are made and utilized to acquire the data for edge spread function (ESF). Through necessary data processing such as signal extraction, attenuation correction and curve fitting and proper calculations of differentiating and Fourier transform, MTF can be determined. Influencing factors of MTF determination in XFM system are thoroughly discussed in theory and validated by experiments. The results show that different mapping steps do not noticeably affect the measured MTF, while MTF is greatly degraded as the collimator-to-object distance increases. The theoretical analyses and experimental validations of the MTF determination are useful and helpful for imaging performance evaluation, system design and optimal operations. The presented methodology could be applied in other XRF based systems with modified imaging trajectories. (C) 2014 Optical Society of America
Wavefront coding as an optical-digital hybrid imaging technique can be used to extend the depth of field. The key to wavefront coding lies in the design of suitable phase masks to achieve the invariant imaging propert...
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Wavefront coding as an optical-digital hybrid imaging technique can be used to extend the depth of field. The key to wavefront coding lies in the design of suitable phase masks to achieve the invariant imaging properties over a wide range of defocus. In this Letter, we propose another phase mask with a tangent function to enrich the odd symmetrical kind of phase masks. The performance of the tangent phase mask is evaluated by comparison with a cubic mask, improved-1 logarithmic mask, improved-2 logarithmic mask, and sinusoidal mask. The results demonstrate that the tangent phase mask has superior performance in extending the depth of field. (C) 2014 Optical Society of America
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