Optical transfer function

About: Optical transfer function is a research topic. Over the lifetime, 6079 publications have been published within this topic receiving 90526 citations. The topic is also known as: modulation transfer function & OTF.

The effect of random phase variation of turbulence on image resolution

Abstract: The turbulence produced by the shearing process between the cooling gas and atmosphere of a hypersonically moving vehicle, which contributes to the image degradation, is addressed. Based on the random phase variation of the optical wavefront, the modulation transfer function (MTF) can be specified to characterize the effect of turbulence on the image resolution. The use of computer simulation to generate the random phase variation and variance and the corresponding MTF is reported. Different types of phase variation are investigated. The MTF for each case is used to find the effect on image degradation and resolution. The effect of the nonuniform turbulence intensity across the optical window is also investigated and compared with results for the uniform case.

A CMOS-based high resolution fluoroscope (HRF) detector prototype with 49.5 μm pixels for use in endovascular image guided interventions (EIGI).

Abstract: X-ray detectors to meet the high-resolution requirements for endovascular image-guided interventions (EIGIs) are being developed and evaluated. A new 49.5-micron pixel prototype detector is being investigated and compared to the current suite of high-resolution fluoroscopic (HRF) detectors. This detector featuring a 300-micron thick CsI(Tl) scintillator, and low electronic noise CMOS readout is designated the HRF- CMOS50. To compare the abilities of this detector with other existing high resolution detectors, a standard performance metric analysis was applied, including the determination of the modulation transfer function (MTF), noise power spectra (NPS), noise equivalent quanta (NEQ), and detective quantum efficiency (DQE) for a range of energies and exposure levels. The advantage of the smaller pixel size and reduced blurring due to the thin phosphor was exemplified when the MTF of the HRF-CMOS50 was compared to the other high resolution detectors, which utilize larger pixels, other optical designs or thicker scintillators. However, the thinner scintillator has the disadvantage of a lower quantum detective efficiency (QDE) for higher diagnostic x-ray energies. The performance of the detector as part of an imaging chain was examined by employing the generalized metrics GMTF, GNEQ, and GDQE, taking standard focal spot size and clinical imaging parameters into consideration. As expected, the disparaging effects of focal spot unsharpness, exacerbated by increasing magnification, degraded the higher-frequency performance of the HRF-CMOS50, while increasing scatter fraction diminished low-frequency performance. Nevertheless, the HRF-CMOS50 brings improved resolution capabilities for EIGIs, but would require increased sensitivity and dynamic range for future clinical application.

Intensifying the spatial resolution of 3D thermal models from aerial imagery using deep learning-based image super-resolution

Abstract: Abstract Nowadays, 3D thermal models can play an important role in buildings' energy management while acquiring multisource data to generate a high-resolution 3D thermal model. Consequently, in this article, a method for intensifying 3D thermal model using deep learning-based image super-resolution is presented. In the proposed method, first, the enhanced deep residual super-resolution (EDSR) deep network is re-trained based on thermal aerial images. Second, the resolution of low-resolution thermal images is enhanced using the newly trained network. Finally, the state-of-the-art structures from motion (SfM), semi global matching (SGM) and space intersection are utilized to generate intensified 3D thermal model from the resolution enhanced thermal images. Spatial evaluations indicate a 5% increase in edge-based image fusion metric (EFM) for the intensified 3D model. Besides, the evaluations show that the modulation transfer function (MTF) curves of the intensified 3D thermal model are closer to a reference model against the original 3D thermal model. Highlights A 3D thermal model intensification solution using EDSR is proposed which is independent of hardware techniques and multisource data. Considering the importance of edge sharpness in the intensified 3D thermal model, the quality of edges is assessed using MTF curves and the EFM metric. In comparison to the original 3D thermal model, the MTF curves of the intensified 3D thermal model are closer to the MTF curve of the high-resolution 3D model. The EFM metric shows higher values for MTF curves of the intensified 3D thermal model against MTF curves of the original 3D thermal model.

Optical design of a wide-angle pinhole lens for VR and AR inspection

Abstract: Virtual reality (VR) and augmented reality (AR) have widespread applications in education, military, medical treatment, and entertainment. The key parameters of near-eye displays, such as field of view (FOV), eye box size, resolution, and virtual image distance will critically influence the performance of the final display products. Meanwhile, VR and AR displays are designed to achieve a very wide FOV to improve the immersive visual experience recently. Especially in VR applications, the FOV has been more than 90° to blur the boundary between the virtual and real world. Thus, a wide-angle forward-stop anthropomorphic vision lens for VR and AR inspection should be studied. However, it is very challenging to achieve wide FOV and high resolution simultaneously in a compact pinhole lens. In this study, a pinhole lens using an advanced photo system-classic (APS-C) size sensor with a FOV of 110° and an entrance pupil diameter (EPD) of 4 mm is designed. The optimization process is introduced, and the optical performance is analyzed. In our design, optical aberration is well corrected to improve the image quality. The cut-off spatial frequency of the modulation transfer function (MTF) across the whole field is 200 cycles/mm. The MTF is greater than 0.43 at the Nyquist frequency (NF), the field curvature is controlled within 0.04 mm, and the distortion of the system is less than 10% across the 0.82 field. The overall length (OAL) of the system is less than 230 mm. The result shows that our pinhole lens is a high-resolution wide-angle optical system and meets the requirements for VR and AR inspection.