Dark Noise Level Research Articles

A 64 × 128 3D-Stacked SPAD Image Sensor for Low-Light Imaging.

Low-light imaging capabilities are in urgent demand in many fields, such as security surveillance, night-time autonomous driving, wilderness rescue, and environmental monitoring. The excellent performance of SPAD devices gives them significant potential for applications in low-light imaging. This article presents a 64 (rows) × 128 (columns) SPAD image sensor designed for low-light imaging. The chip utilizes a three-dimensional stacking architecture and microlens technology, combined with compact gated pixel circuits designed with thick-gate MOS transistors, which further enhance the SPAD's photosensitivity. The configurable digital control circuit allows for the adjustment of exposure time, enabling the sensor to adapt to different lighting conditions. The chip exhibits very low dark noise levels, with an average DCR of 41.5 cps at 2.4 V excess bias voltage. Additionally, it employs a denoising algorithm specifically developed for the SPAD image sensor, achieving two-dimensional grayscale imaging under 6 × 10-4 lux illumination conditions, demonstrating excellent low-light imaging capabilities. The chip designed in this paper fully leverages the performance advantages of SPAD image sensors and holds promise for applications in various fields requiring low-light imaging capabilities.

Noise spectrum analysis of superconducting kinetic inductance detectors

As a newly developed pair-breaking superconducting detector, microwave kinetic inductance detectors are simple to integrate in the frequency domain and have already been used in astronomical detection and array imaging at the (sub)millimeter and optical wavelengths. For these applications, the dark noise level of kinetic inductance detector is one of the key performance indicators. Herein a noise power spectrum analysis method is introduced in detail, which can accurately and effectively analyze the noise spectrum of kinetic inductance detector in a wide frequency range. This method can well balance the noise spectrum resolution and variance performance, by taking the noise data at the resonance frequency with two sampling rates and setting the appropriate frequency resolutions for different frequency bands. This method is used to characterize and compare the noise of aluminum (Al) kinetic inductance detectors made from two different micromachining processes. We deposite a 25-nm-thick aluminum film on high-resistivity silicon substrate for one device, while place one silicon nitride (SiN<sub><i>x</i></sub>) film on the top and one on the bottom of the aluminum film for another device. It is found that the frequency noise of the device with two silicon nitride films is about 25% to 50% of the bare aluminum device. Using this double silicon nitride film fabrication technique, we further fabricate a few groups of lumped-element aluminum kinetic inductance detectors with various inductor and interdigitated capacitor designs. We investigate the noise properties of these devices at different microwave driven power and bath temperatures, and the experimental results show typical two-level system noise behaviors. Our work provides a standard method to characterize the noise power spectrum of kinetic inductor detector, and also paves the way to developing low-noise aluminum kinetic inductance detectors for terahertz imaging, photon-counting and energy-resolving applications.

Inflight calibration of the optical navigation camera for the extended mission phase of Hayabusa2

After delivering its sample capsule to Earth, the Hayabusa2 spacecraft started its extended mission to perform a flyby of asteroid 2001 CC21 in 2026 and rendezvous with asteroid 1998 KY26 in 2031. During the extended mission, the optical navigation camera (ONC) of Hayabusa2 will play an important role in navigation and science observations, but it has suffered from optical deterioration after the spacecraft’s surface contact with and sampling of asteroid Ryugu. Furthermore, the sensitivity of the telescopic camera (ONC-T) has continued to decrease for more than a year, posing a serious problem for the extended mission. These are problems that could potentially be encountered by other sample-return missions involving surface contact. In this study, we evaluated the long-term variation of ONC performance over the 6.5 years following the launch in 2014 to predict how it will perform during observations of the two target asteroids in its extended mission (6 and 11 years from the Earth return, respectively). Our results showed several important long-term trends in ONC performance, such as transmission, dark noise level, and hot pixels. During the long cruising period of the extended mission, we plan to observe both zodiacal light and exoplanet transits as additional science targets. The accuracy of these observations is sensitive to background noise level and stray-light contamination, so we conducted new test observations to search for the lowest stray light, which has been found to depend on spacecraft attitude. The results of these analyses and new test observations suggest that the Hayabusa2 ONC will be able to conduct cruising, flyby, and rendezvous observations of asteroids with sufficient accuracy.Graphical

How to Calibrate Your CCD in the Dark? a Precise CCD Calibration Method

Single particle tracking and super-resolution microscopy experiments require good knowledge of CCD pixels’ gains in terms of photoelectrons per ADU (Analog to Digital Unit, output of the CCD camera) registered by the read-out electronics of the CCD camera. This is because the observed CCD output in a given time period produced by light with constant intensity follows, ignoring other noise sources, statistics of photoelectrons produced by incident photons. It is common practice to calibrate the gain of a CCD camera using a constant intensity light source to get the gain in photoelectron per ADU. This procedure requires a stable light source and it is not always possible to achieve a truly uniform and stable illumination. We propose an easier calibration method that uses dark noise as the calibration source for a CCD camera; the method requires that the dark noise level is stable during the calibration data taking. The proposed method works as demonstrated under assumptions that statistics of photoelectrons and thermal electrons follow Poisson distribution and CCD pixel gains in electrons per ADU are the same for the both sources of electrons. We will show that these assumptions are valid and will demonstrate that it is possible to calibrate individual gain of each pixel at ∼1% level or better using real and simulated data. As a byproduct, the proposed calibration method provides properties of individual pixel, not only its gain but also other properties such as linearity in low photon intensity and dark noise level. This information gives assessment of quality of the CCD camera. All the necessary software is developed using freely available software package Octave similar to Matlab. This method might improve the localization of fluorescent molecules in super-resolution and particle tracking measurements.

Illuminating the capabilities of Landsat 8 for mapping night lights

Abstract Remote sensing of night-lights has been enhanced in recent years with the availability of the new VIIRS Day and Night band, the commercial EROS-B satellite and astronaut photographs from the International Space Station. However, dedicated space-borne multispectral sensors offering radiance calibrated night lights imagery are yet to be launched. Here we examined the capabilities of Landsat 8 to acquire night time light images of the Earth. Examining seven night-time Landsat 8 scenes, we found that brightly lit areas in both urban (Berlin, Las Vegas, Nagoya and Tel-Aviv) and gas flares (Basra, Kuwait) areas were detected in all eight bands of Landsat 8. The threshold for detection of lit areas was approximately 0.4 W/m 2 /μm/sr in bands 1–5 and 8 of Landsat 8. This threshold level was higher than Landsat dark noise levels, and slightly lower than post launch Landsat 8 OLI band dependent noise equivalent radiance difference levels. Drawing on this, we call on the USGS to plan an annual night-time acquisition of urban and gas flares areas globally, and to enable the performance of the future Landsat 10 to be established in a way that it will be sensitive enough to image the Earth at night, thus performing as Nightsat during the night.

Effects of solar activity on noise in CALIOP profiles above the South Atlantic Anomaly

Abstract. We show that nighttime dark noise measurements from the spaceborne lidar CALIOP contain valuable information about the evolution of upwelling high-energy radiation levels. Above the South Atlantic Anomaly (SAA), CALIOP dark noise levels fluctuate by ±6% between 2006 and 2013, and follow the known anticorrelation of local particle flux with the 11-year cycle of solar activity (with a 1-year lag). By analyzing the geographic distribution of noisy profiles, we are able to reproduce known findings about the SAA region. Over the considered period, it shifts westward by 0.3° year−1, and changes in size by 6° meridionally and 2° zonally, becoming larger with weaker solar activity. All results are in strong agreement with previous works. We predict SAA noise levels will increase anew after 2014, and will affect future spaceborne lidar missions most near 2020.

Room-temperature mid-infrared single-photon spectral imaging

The spectral imaging and detection of mid-infrared wavelengths is emerging as an enabling technology of great technical and scientific interest, primarily because important chemical compounds display unique and strong mid-infrared spectral fingerprints that reveal valuable chemical information. Modern quantum cascade lasers have evolved as ideal coherent mid-infrared excitation sources, but simple, low-noise, room-temperature detectors and imaging systems lag behind. We address this need by presenting a novel, field-deployable, upconversion system for sensitive, two-dimensional, mid-infrared spectral imaging. A room-temperature dark noise of 0.2 photons/spatial element/second is measured, which is a billion times below the dark noise level of cryogenically cooled InSb cameras. Single-photon imaging and a resolution of up to 200 × 100 spatial elements are obtained with a record-high continuous-wave quantum efficiency of ∼20% for polarized incoherent light at 3 µm. The proposed method is relevant for existing and new mid-infrared applications such as gas analysis and medical diagnostics. Researchers experimentally demonstrate an upconversion system for field-deployable mid-infrared spectral imaging. The system provides a room-temperature dark noise of 0.2 photons per spatial element per second — a billion times below the dark noise level of cryogenically cooled cameras — and a quantum efficiency of 20%.

Thermal Decay of Rhodopsin: Role of Hydrogen Bonds in Thermal Isomerization of 11-cis Retinal in the Binding Site and Hydrolysis of Protonated Schiff Base

Although thermal stability of the G protein-coupled receptor rhodopsin is directly related to its extremely low dark noise level and has recently generated considerable interest, the chemistry behind the thermal decay process of rhodopsin has remained unclear. Using UV-vis spectroscopy and HPLC analysis, we have demonstrated that the thermal decay of rhodopsin involves both hydrolysis of the protonated Schiff base and thermal isomerization of 11-cis to all-trans retinal. Examining the unfolding of rhodopsin by circular dichroism spectroscopy and measuring the rate of thermal isomerization of 11-cis retinal in solution, we conclude that the observed thermal isomerization of 11-cis to all-trans retinal happens when 11-cis retinal is in the binding pocket of rhodopsin. Furthermore, we demonstrate that solvent deuterium isotope effects are involved in the thermal decay process by decreasing the rates of thermal isomerization and hydrolysis, suggesting that the rate-determining step of these processes involves breaking hydrogen bonds. These results provide insight into understanding the critical role of an extensive hydrogen-bonding network on stabilizing the inactive state of rhodopsin and contribute to our current understanding of the low dark noise level of rhodopsin, which enables this specialized protein to function as an extremely sensitive biological light detector. Because similar hydrogen-bonding networks have also been suggested by structural analysis of two other GPCRs, beta1 and beta2 adrenergic receptors, our results could reveal a general role of hydrogen bonds in facilitating GPCR function.

The Effects of Sensor Spectral Sensitivity, Pixel Pitch, Photon Shot Noise, and Dark Noise on Perceived Image Quality

Image sensor noise was estimated in an approximately perceptually uniform space with a color image sensor model. Particularly, the noise level with respect to an image sensor's pixel pitch and the dark noise was investigated. It was shown that the noise level could be about half when spectral sensitivity was optimized considering noise with reduced color reproduction accuracy. It was also shown that for a 2.0µm pixel pitch sensor, the exposure index should be less than 100-150 in order to keep the noise level σ94 less than 5 even if it had no dark noise, whereas the exposure index could reach about 2000-4000 for a 8.0µm pixel pitch sensor depending on the sensor sensitivity and the dark noise level.

Ultrahigh-definition color video camera system with <inline-formula><math display="inline" overflow="scroll"><mrow><mn>8</mn><mi mathvariant="normal">K</mi><mo>×</mo><mn>4</mn><mi mathvariant="normal">K</mi></mrow></math></inline-formula> pixels

We developed an experimental ultrahigh-definition color video camera 7680H4320V pixels using four 8-million-pixel charge-coupled devices (CCDs) to increase the camera’s resolution. This involves attaching four CCDs to a special color separation prism. Two CCDs are used for the green image; the other two are used for the red and blue images. Our prototype camera attains a limiting resolution of more than 2700 television lines, both horizontally and vertically. Camera sensitivity is F/2.8 at 2000 lux, with a luminance signal dark-noise level of approximately 50 dB in high definition television format. To analyze camera performance, we estimated the spatial position error between the two green CCDs and the chromatic aberration. Based on these estimations, the cause of resolution deterioration and ways to improve resolution are discussed.

イメージセンシング技術とその応用 走査線４０００本級４板式超高精細動画カメラ

An experimental ultrahigh-definition color video camera system with 7, 680 (H) x 4, 320 (V) pixels has been developed using four 8-million-pixel CCDs. Each 8-million-pixel CCD with a progressive scanning rate of 60 frames per second has 4, 046 (H) x 2, 048 (V) effective imaging pixels, each of which is 8.4 micron2. We applied the four-imager pickup method to increase the camera's resolution. This involves attaching the CCDs to a special color-separation prism. Two CCDs are used for the green image, and the other two are used for the red and blue images. The spatial image sampling pattern of these CCDs relative to the optical image is equivalent to one with 32 million pixels in the Bayer pattern color filter. The prototype camera attains a limiting resolution of more than 2, 700 TV lines both horizontally and vertically, which is higher than that of an 8-million-pixel CCD. The sensitivity of the camera is 2, 000 lux, F 2.8 at approx. 50 dB of dark-noise level on the HDTV format. This camera system also has a new contour compensation circuit. It suppresses the false color caused by the non-linearity and the pixel-count difference between green and red (or blue). The technique has contributed to the reduction of the camera's signal process circuitry.

1025 サイドスライド式消音器による予混合バーナ燃焼系の振動騒音抑制

The boiler with a pre-mixed combustion method, which realizes a decrease of NOx and a miniaturization of a boiler, has a strong tendency to be extremely loud by the combustion driven noise. A method reduces this kind of noise is required. This noise is created by the oscillating phenomenon of the flame, and the frequency of it depends on the geometric structure of the combustion system with the specific spectrum. In this paper, we propose one of the reducing methods applying a side slide type muffler, which drives as a resonator muffler. It has been confirmed that the noise was reduced under to the dark noise level by making the noise excitation phenomenon caused by the flame reduced, from the experimental result.

Rhodopsin: insights from recent structural studies.

The recent report of the crystal structure of rhodopsin provides insights concerning structure-activity relationships in visual pigments and related G protein-coupled receptors (GPCRs). The seven transmembrane helices of rhodopsin are interrupted or kinked at multiple sites. An extensive network of interhelical interactions stabilizes the ground state of the receptor. The ligand-binding pocket of rhodopsin is remarkably compact, and several chromophore-protein interactions were not predicted from mutagenesis or spectroscopic studies. The helix movement model of receptor activation, which likely applies to all GPCRs of the rhodopsin family, is supported by several structural elements that suggest how light-induced conformational changes in the ligand-binding pocket are transmitted to the cytoplasmic surface. The cytoplasmic domain of the receptor includes a helical domain extending from the seventh transmembrane segment parallel to the bilayer surface. The cytoplasmic surface appears to be approximately large enough to bind to the transducin heterotrimer in a one-to-one complex. The structural basis for several unique biophysical properties of rhodopsin, including its extremely low dark noise level and high quantum efficiency, can now be addressed using a combination of structural biology and various spectroscopic methods. Future high-resolution structural studies of rhodopsin and other GPCRs will form the basis to elucidate the detailed molecular mechanism of GPCR-mediated signal transduction.

Rhodopsin: structural basis of molecular physiology.

The crystal structure of rod cell visual pigment rhodopsin was recently solved at 2.8-A resolution. A critical evaluation of a decade of structure-function studies is now possible. It is also possible to begin to explain the structural basis for several unique physiological properties of the vertebrate visual system, including extremely low dark noise levels as well as high gain and color detection. The ligand-binding pocket of rhodopsin is remarkably compact, and several apparent chromophore-protein interactions were not predicted from extensive mutagenesis or spectroscopic studies. The transmembrane helices are interrupted or kinked at multiple sites. An extensive network of interhelical interactions stabilizes the ground state of the receptor. The helix movement model of receptor activation, which might apply to all G protein-coupled receptors (GPCRs) of the rhodopsin family, is supported by several structural elements that suggest how light-induced conformational changes in the ligand-binding pocket are transmitted to the cytoplasmic surface. The cytoplasmic domain of the receptor is remarkable for a carboxy-terminal helical domain extending from the seventh transmembrane segment parallel to the bilayer surface. Thus the cytoplasmic surface appears to be approximately the right size to bind to the transducin heterotrimer in a one-to-one complex. Future high-resolution structural studies of rhodopsin and other GPCRs will form a basis to elucidate the detailed molecular mechanism of GPCR-mediated signal transduction.