A Study on the Non-Uniformity-Correction Method for Cooled Infrared Detector by Scene Temperature, Background Temperature Variation, and Integration Time Change

This paper reports an InAs/InAsSb strained-layer superlattice (SLS) mid-wavelength infrared detector and a focal plane array particularly suited for high-temperature operation. Utilizing the nBn architecture, the detector structure was grown by molecular beam epitaxy and consists of a 5.5 µm thick n-type SLS as the infrared-absorbing element. Through detailed characterization, it was found that the detector exhibits a cut-off wavelength of 5.5 um, a peak external quantum efficiency (without anti-reflection coating) of 56%, and a dark current of 3.4 × 10−4 A/cm2, which is a factor of 9 times Rule 07, at 160 K temperature. It was also found that the quantum efficiency increases with temperature and reaches ~56% at 140 K, which is probably due to the diffusion length being shorter than the absorber thickness at temperatures below 140 K. A 320 × 256 focal plane array was also fabricated and tested, revealing noise equivalent temperature difference of ~10 mK at 80 K with f/2.3 optics and 3 ms integration time. The overall performance indicates that these SLS detectors have the potential to reach the performance comparable to InSb detectors at temperatures higher than 80 K, enabling high-temperature operation.

Download Full-text

Research on Dynamic Modelling and Simulation of Erection System of Mobile Equipment in Absolute Coordinates

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.66-68.2034 ◽

2011 ◽

Vol 66-68 ◽

pp. 2034-2040

Author(s):

Qin He Gao ◽

Xiang Yang Li

Keyword(s):

Rigid Body ◽

Dynamic Models ◽

Dynamic Modelling ◽

Hydraulic Cylinder ◽

Correction Method ◽

Integration Time ◽

Multi Stage ◽

Rigid Body Model ◽

Absolute Coordinates ◽

The Impact

This paper employed the theories of multibody system dynamics to analyze the multi-rigid-body model of erection system and build the general dynamic models in absolute coordinates. The impact theory of contact mechanics and nonlinear spring-damper force function were used to model the impact problems between rods of multi-stage hydraulic cylinder of erection system and educe the dynamic models of multi-rigid-body erection system with impact. An automatic violation correction method according to the step of integration time was given to solve the violation which is an incident problem in numerical integration of dynamic models in absolute coordinates. Simulation results show that these dynamic models are effective.

Download Full-text

Dark Signal Temperature Dependence Correction Method for Miniature Spectrometer Modules

Journal of Sensors ◽

10.1155/2011/608157 ◽

2011 ◽

Vol 2011 ◽

pp. 1-9 ◽

Cited By ~ 25

Author(s):

Joel Kuusk

Keyword(s):

Temperature Dependence ◽

Correction Method ◽

Spectral Measurement ◽

Field Conditions ◽

Integration Time ◽

Laboratory Measurements ◽

Spectral Measurements ◽

Reasonable Range ◽

Dark Signal

A dark signal temperature dependence correction method for miniature spectrometer modules is described in this paper. It is based on laboratory measurements of dark signal temperature dependence at few different integration times. A set of parameters are calculated which make it possible to estimate dark signal at any temperature and integration time within reasonable range. In field conditions, it is not always possible to take frequent dark signal readings during spectral measurements. If temperature is recorded during the measurement, this method can be used for estimating dark signal for every single spectral measurement. The method is validated on two different miniature spectrometers.

Download Full-text

Design of readout integrated circuit structure for single and dual band infrared detector with variable integration time

10.1117/12.900963 ◽

2011 ◽

Cited By ~ 1

Author(s):

Tai-Ping Sun ◽

Yi-Chuan Lu ◽

Hsiu-Li Shieh ◽

Shiuan-Shuo Shiu ◽

Yi-Ting Liu ◽

...

Keyword(s):

Integrated Circuit ◽

Infrared Detector ◽

Dual Band ◽

Integration Time ◽

Readout Integrated Circuit ◽

Circuit Structure ◽

Variable Integration

Download Full-text

Distance Error Correction in Time-of-Flight Cameras Using Asynchronous Integration Time

Sensors ◽

10.3390/s20041156 ◽

2020 ◽

Vol 20 (4) ◽

pp. 1156

Author(s):

Eu-Tteum Baek ◽

Hyung-Jeong Yang ◽

Soo-Hyung Kim ◽

Gueesang Lee ◽

Hieyong Jeong

Keyword(s):

Error Correction ◽

Time Of Flight ◽

Correction Method ◽

Integration Time ◽

Depth Information ◽

Optical Noise ◽

Depth Sensor ◽

Distance Map ◽

Distance Error ◽

Depth Sensors

A distance map captured using a time-of-flight (ToF) depth sensor has fundamental problems, such as ambiguous depth information in shiny or dark surfaces, optical noise, and mismatched boundaries. Severe depth errors exist in shiny and dark surfaces owing to excess reflection and excess absorption of light, respectively. Dealing with this problem has been a challenge due to the inherent hardware limitations of ToF, which measures the distance using the number of reflected photons. This study proposes a distance error correction method using three ToF sensors, set to different integration times to address the ambiguity in depth information. First, the three ToF depth sensors are installed horizontally at different integration times to capture distance maps at different integration times. Given the amplitude maps and error regions are estimated based on the amount of light, the estimated error regions are refined by exploiting the accurate depth information from the neighboring depth sensors that use different integration times. Moreover, we propose a new optical noise reduction filter that considers the distribution of the depth information biased toward one side. Experimental results verified that the proposed method overcomes the drawbacks of ToF cameras and provides enhanced distance maps.

Download Full-text

Improving Optical Measurements: Non-Linearity Compensation of Compact Charge-Coupled Device (CCD) Spectrometers

Sensors ◽

10.3390/s19122833 ◽

2019 ◽

Vol 19 (12) ◽

pp. 2833

Author(s):

Münevver Nehir ◽

Carsten Frank ◽

Steffen Aßmann ◽

Eric P. Achterberg

Keyword(s):

Correction Method ◽

Optical Measurements ◽

Analytical Laboratory ◽

Correction Function ◽

Integration Time ◽

Charge Coupled Device ◽

Temperature Variations ◽

Dark Currents ◽

Compact Charge

Charge-coupled device (CCD) spectrometers are widely used as detectors in analytical laboratory instruments and as sensors for in situ optical measurements. However, as the applications become more complex, the physical and electronic limits of the CCD spectrometers may restrict their applicability. The errors due to dark currents, temperature variations, and blooming can be readily corrected. However, a correction for uncertainty of integration time and wavelength calibration is typically lacking in most devices, and detector non-linearity may distort the signal by up to 5% for some measurements. Here, we propose a simple correction method to compensate for non-linearity errors in optical measurements where compact CCD spectrometers are used. The results indicate that the error due to the non-linearity of a spectrometer can be reduced from several hundred counts to about 40 counts if the proposed correction function is applied.

Download Full-text

Improving the precipitation accumulation analysis using lightning measurements and different integration periods

Hydrology and Earth System Sciences ◽

10.5194/hess-21-267-2017 ◽

2017 ◽

Vol 21 (1) ◽

pp. 267-279 ◽

Cited By ~ 1

Author(s):

Erik Gregow ◽

Antti Pessi ◽

Antti Mäkelä ◽

Elena Saltikoff

Keyword(s):

Positive Impact ◽

Time Integration ◽

Radar Data ◽

Correction Method ◽

Research Field ◽

Local Analysis ◽

Integration Time ◽

Special Focus ◽

Finnish Meteorological Institute ◽

The Impact

Abstract. The focus of this article is to improve the precipitation accumulation analysis, with special focus on the intense precipitation events. Two main objectives are addressed: (i) the assimilation of lightning observations together with radar and gauge measurements, and (ii) the analysis of the impact of different integration periods in the radar–gauge correction method. The article is a continuation of previous work by Gregow et al. (2013) in the same research field. A new lightning data assimilation method has been implemented and validated within the Finnish Meteorological Institute – Local Analysis and Prediction System. Lightning data do improve the analysis when no radars are available, and even with radar data, lightning data have a positive impact on the results. The radar–gauge assimilation method is highly dependent on statistical relationships between radar and gauges, when performing the correction to the precipitation accumulation field. Here, we investigate the usage of different time integration intervals: 1, 6, 12, 24 h and 7 days. This will change the amount of data used and affect the statistical calculation of the radar–gauge relations. Verification shows that the real-time analysis using the 1 h integration time length gives the best results.

Download Full-text

Measurement and Correction Model for Temperature Dependence of an Acousto-Optic Tunable Filter (AOTF) Infrared Spectrometer for Lunar Surface Detection

Applied Spectroscopy ◽

10.1177/0003702819881786 ◽

2019 ◽

Vol 74 (1) ◽

pp. 81-87

Author(s):

Zhiping He ◽

Jinning Li ◽

Chunlai Li ◽

Rui Xu

Keyword(s):

Lunar Surface ◽

Infrared Detector ◽

Correction Method ◽

Tunable Filter ◽

Correction Model ◽

Temperature Characteristics ◽

Response Characteristics ◽

Surface Detection ◽

Infrared Spectrometer ◽

Shortwave Infrared

The photoelectric response characteristics of an infrared spectrometer based on an acousto-optic tunable filter (AOTF) are greatly affected by the temperature change of the radio frequency power amplifier and shortwave infrared detector. If calibration is not conducted, that will affect the quantitative level of the data. This paper puts forward a measurement and correction method for the temperature characteristics of an AOTF infrared spectrometer which is used in lunar surface detection and sets up a temperature characteristics correction model. This model was applied to an AOTF infrared spectrometer mounted on China’s unmanned lunar rover. Laboratory tests show that the temperature causes an instrument variation of ∼20% when the temperature is between −20 ℃ and + 55 ℃, but this model reduces this variation to < 6%. Evaluating data from the lunar surface also verifies the effectiveness of this method.

Download Full-text

Improving the precipitation accumulation analysis using radar-, gauge- and lightning measurements

10.5194/hess-2016-113 ◽

2016 ◽

Author(s):

Erik Gregow ◽

Antti Pessi ◽

Antti Mäkelä ◽

Elena Saltikoff

Keyword(s):

Time Integration ◽

Correction Method ◽

Research Field ◽

Local Analysis ◽

Integration Time ◽

Special Focus ◽

Finnish Meteorological Institute ◽

Real Time Analysis ◽

Statistical Relationships ◽

The Impact

Abstract. The aim of this article is to introduce and compare new methods on how to perform precipitation accumulation analysis, with special focus on the high intensity cases. This includes assimilation of lightning observations, in combination with radar and gauge measurements, and the impact of different integration time intervals on the radar-gauge correction method. The article is a continuation of previous work in the same research field, by Gregow et al. (2011). A new Lightning Data Assimilation (LDA) method has been implemented and validated within the Finnish Meteorological Institute- (FMI) Local Analysis and Prediction System (LAPS). The performed precipitation accumulation analyses show the usefulness of lightning assimilation, together with radar information. The radar-gauge assimilation method is highly dependent on statistical relationships between radar and gauges, when performing the correction to precipitation accumulation field. Here we investigate the usage of different time integration intervals; 1, 6, 12, 24 hours and 7 days. This will change the amount of data used and affect the statistical calculation of the radar-gauge relations. Verification shows that the real-time analysis using the 1 hour integration time length gives the best result.

Download Full-text