Search Results (4)

The design of compact hyperspectral cameras with high ground resolution and large field of view (FOV) is a challenging problem in the field of remote sensing. In this paper, the time-delayed integration (TDI) of the digital domain is applied to solve the issue of insufficient light energy brought by high spatial resolution, and a hyperspectral camera with linear variable filters suitable for digital domain TDI technology is further designed. The camera has a wavelength range of 450–950 nm, with an average spectral resolution of 10.2 nm. The paper also analyzed the effects of digital domain TDI on the signal–noise ratio (SNR) and the spectral resolution. During its working in orbits, we have obtained high-SNR images with a swath width of 150 km, and a ground sample distance (GSD) of 10 m @ 500 km. The design of the hyperspectral camera has an improved spatial resolution while reducing the cost. Full article

Although visualization of heart sounds, known as phonocardiography, provides valuable information on cardiovascular hemodynamics, its use has not been widely encouraged due to the scarcity of information on its interpretation. In the present study, using the intraoperative phonocardiogram recorded by an esophageal stethoscope, we quantitatively evaluated the time and frequency domains of modulation of the heart sounds components and their association with left ventricular contractility and systemic vascular resistance under the effects of various cardiovascular drugs. We analyzed 29 pairs of intraoperative digitalized phonocardiographic signals and their corresponding hemodynamic data before and after cardiovascular drug administration (ephedrine, esmolol, phenylephrine, and/or nicardipine) in 17 patients who underwent liver transplantation. The S1 and S2 components of the heart sounds (the first and second heart sounds, respectively) were identified and their modulation in time and frequency domains was analyzed. As an index of cardiovascular function, systolic tissue Doppler wave velocity (TDI S’), maximal dP/dt from the arterial waveform, and systemic vascular resistance were simultaneously evaluated. Ephedrine/esmolol and phenylephrine/nicardipine primarily affected the S1 and S2 components of the heart sounds, respectively. This result implies that the intraoperative phonocardiogram may have the potential to be useful in detecting the changes in contractility and afterload that commonly occur in patients receiving anesthesia. In an era of constant need for noninvasive hemodynamic assessment, phonocardiography has the potential for use as a novel and informative tool for monitoring of hemodynamic function. Full article

The digital time delay integration (digital TDI) technology of the complementary metal-oxide-semiconductor (CMOS) image sensor has been widely adopted and developed in the optical remote sensing field. However, the details of targets that have low illumination or low contrast in scenarios of high contrast are often drowned out because of the superposition of multi-stage images in digital domain multiplies the read noise and the dark noise, thus limiting the imaging dynamic range. Through an in-depth analysis of the information transfer model of digital TDI, this paper attempts to explore effective ways to overcome this issue. Based on the evaluation and analysis of multi-stage images, the entropy-maximized adaptive histogram equalization (EMAHE) algorithm is proposed to improve the ability of images to express the details of dark or low-contrast targets. Furthermore, in this paper, an image fusion method is utilized based on gradient pyramid decomposition and entropy weighting of different TDI stage images, which can improve the detection ability of the digital TDI CMOS for complex scenes with high contrast, and obtain images that are suitable for recognition by the human eye. The experimental results show that the proposed methods can effectively improve the high-dynamic-range imaging (HDRI) capability of the digital TDI CMOS. The obtained images have greater entropy and average gradients. Full article

In this paper, an accumulation technique suitable for digital domain CMOS time delay integration (TDI) image sensors is proposed to reduce power consumption without degrading the rate of imaging. In terms of the slight variations of quantization codes among different pixel exposures towards the same object, the pixel array is divided into two groups: one is for coarse quantization of high bits only, and the other one is for fine quantization of low bits. Then, the complete quantization codes are composed of both results from the coarse-and-fine quantization. The equivalent operation comparably reduces the total required bit numbers of the quantization. In the 0.18 µm CMOS process, two versions of 16-stage digital domain CMOS TDI image sensor chains based on a 10-bit successive approximate register (SAR) analog-to-digital converter (ADC), with and without the proposed technique, are designed. The simulation results show that the average power consumption of slices of the two versions are $6.47\times {10}^{-8}$ J/line and $7.4\times {10}^{-8}$ J/line, respectively. Meanwhile, the linearity of the two versions are 99.74% and 99.99%, respectively. Full article