Association between air temperature and unintentional drowning risk in the United Kingdom 2012-2019: A nationwide case-crossover study.

OBJECTIVE: Drowning is a leading cause of death. The World Health Organization (WHO) and United Nations (UN) emphasise the need for population-level data-driven approaches to examine risk factors to improve water safety policies. Weather conditions, have the potential to influence drowning risk behaviours as people are more likely to spend time around water and/or undertake risky activities in aquatic spaces as a behavioural thermoregulatory response (e.g., seeking coolth). METHODS: A case-crossover approach assessed associations between changes in daily maximum air temperature (data from the nearest weather station to each drowning event) and unintentional drowning risk using anonymous data from the validated UK Water Incident Database 2012-2019 (1945 unintentional deaths, 82% male). Control days were selected using a unidirectional time-stratified approach, whereby seven and 14 days before the hazard day were used as the controls. RESULTS: Mean maximum air temperature on case and control days was 15.36 °C and 14.80 °C, respectively. A 1 °C increase in air temperature was associated with a 7.2% increase in unintentional drowning risk. This relationship existed for males only. Drowning risk was elevated on days where air temperature reached 15-19.9 °C (Odds Ratio; OR: 1.75), 20-24.9 °C (OR: 1.87), and ≥ 25 °C (OR: 4.67), compared with days <10 °C. The greatest elevations in risk appeared to be amongst males and when alcohol intoxication was suspected. Precipitation showed no significant association with unintentional drowning risk. CONCLUSIONS: Identifying such relationships highlights the value of considering weather conditions when evaluating environmental risk factors for drowning, and may inform water safety policy and allocating resources to prevention and rescue.

Proximity of alcohol outlets and presentation to hospital by young people after self-harm: A retrospective geospatial study using the integrated data infrastructure.

OBJECTIVES: There is a well-established association between alcohol use, misuse, intoxication and self-harm, the latter of which is associated with suicide. This study aimed to better understand the association between proximity to alcohol outlets and the likelihood of young people presenting to hospital following self-harm. METHODS: This was a nationwide retrospective geospatial study using data from the New Zealand Integrated Data Infrastructure using population-level data for 10-29-year-olds for the 2018 and 2017 calendar years. Presentations to hospital following self-harm were identified using the national minimum data set. Proximity to alcohol outlets was defined in road network distance (in kilometres) and ascertained using Integrated Data Infrastructure geospatial data. Alternative measures of proximity were employed in sensitivity analyses. Complete-case two-level random intercept logistic regression models were used to estimate the relationship between alcohol outlet proximity and hospital presentation for self-harm. Adjusted models included sex, age, ethnicity, area-level deprivation, urbanicity and distance to nearest medical facility. Analyses were also stratified by urbanicity. RESULTS: Of the 1,285,368 individuals (mean [standard deviation] age 20.0 [5.9] years), 7944 (0.6%) were admitted to hospital for self-harm. Overall, the odds of presenting to hospital for self-harm significantly decreased as the distance from the nearest alcohol outlet increased, including in adjusted models (adjusted odds ratio 0.980; 95% confidence interval = [0.969-0.992]); the association was robust to changes in the measure of alcohol proximity. The effect direction was consistent across all categorisations of urbanicity, but only statistically significant in large urban areas and rural areas. CONCLUSIONS: The findings of this study show a clear association between young people's access to alcohol outlets and presentation to hospital for self-harm and may provide a mandate for government policies and universal interventions to reduce young people's access to alcohol outlets. Further research regarding causative mechanisms is needed.

Economic evaluation of population-based, expanded reproductive carrier screening for genetic diseases in Australia.

PURPOSE: This study aimed to evaluate the cost effectiveness of population-based, expanded reproductive carrier screening (RCS) for a 300 recessive gene panel from health service and societal perspectives. METHODS: A microsimulation model (PreConMod) was developed using 2016 Australian Census data as the base population. Epidemiologic, health, and indirect cost data were based on literature review. The study assessed the incremental cost effectiveness ratio of expanded RCS compared with (1) no population screening and (2) 3-condition screening for cystic fibrosis, spinal muscular atrophy, and fragile X syndrome in a single birth cohort. Averted affected births and health service savings with expanded RCS were projected to year 2061. Both one-way and probability sensitivity analyses were conducted to assess the uncertainty of the parameter inputs. RESULTS: Expanded RCS was cost saving compared with no population screening and cost effective compared with the 3-condition screening (incremental cost effectiveness ratio of Australian dollar [AUD] 6287 per quality-adjusted life year gained) at an uptake rate of 50% for RCS, 59% for in vitro fertilization and preimplantation genetic testing, 90% for prenatal diagnosis testing, and 50% for elective termination of affected pregnancies and a cost of AUD595 per couple screened. Our model predicts that expanded RCS would avert one-third of affected births in a single birth cohort and reduce lifetime health service spending by AUD632.0 million. Expanded RCS was estimated to be cost saving from the societal perspective. CONCLUSION: Expanded RCS is cost effective from health service and societal perspectives. Expanded RCS is projected to avert significantly more affected births and result in health service saving beyond those expected from 3-condition screening or no population screening.

Disparities in utilisation of combined oral contraceptives in Aotearoa New Zealand: A cross-sectional whole-of-population study.

AIMS: The combined oral contraceptive (COC) is the most commonly used hormonal contraceptive in Aotearoa New Zealand (Aotearoa/NZ). Currently there is limited data available on who uses COC in Aotearoa/NZ. The aims were to (i) define the population of reproductive-aged females in Aotearoa/NZ in 2018 and identify the rate of COC use among this group and (ii) describe the sociodemographic and geographic characteristics of the population of COC users compared to the general population of reproductive-aged females in 2018. METHODS: This whole-of-population cross-sectional study used the Integrated Data Infrastructure, a large research database managed by Statistics New Zealand. Females aged 16-50 years with complete sociodemographic and geographic information in 2018 from Aotearoa/NZ's estimated resident population were included. COC dispensing records to this cohort were identified from the national Pharmaceutical Collection. This paper reports descriptive counts of COC use and employs generalised linear regression with a binomial distribution and a log link to estimate adjusted risk ratios (aRR) of COC use for key sociodemographic and geographic subgroups. RESULTS: Of 1 113 750 individuals in the study, 159 789 (14.3%) were dispensed as COC in 2018. European/other individuals were most likely to use COC (aRR: 2.72, 2.67-2.78), and Pacific Peoples were least likely (aRR: 0.56, 0.55-0.58) to use COC. Individuals residing in the most deprived quintile had less COC use than individuals in the least deprived quintile (aRR: 0.73, 0.72-0.74). CONCLUSION: Our study is able to highlight significant disparities in use by ethnicity, area-level deprivation, and geographic factors.

InAsSb Photodiode Fibre Optic Thermometry for High-Speed, near-Ambient Temperature Measurements.

Infrared radiation thermometers (IRTs) overcome many of the limitations of thermocouples, particularly responsiveness and calibration drift. The main challenge with radiation thermometry is the fast and reliable measurement of temperatures close to room temperature. A new IRT which is sensitive to wavelengths between 3 µm and 11 µm was developed and tested in a laboratory setting. It is based on an uncooled indium arsenide antimony (InAsSb) photodiode, a transimpedance amplifier, and a silver halogenide fibre optic cable transmissive in the mid- to long-wave infrared region. The prototype IRT was capable of measuring temperatures between 35 °C and 100 °C at an integration time of 5 ms and a temperature range between 40 °C and 100 °C at an integration time of 1 ms, with a root mean square (RMS) noise level of less than 0.5 °C. The thermometer was calibrated against Planck's law using a five-point calibration, leading to a measurement uncertainty within ±1.5 °C over the aforementioned temperature range. The thermometer was tested against a thermocouple during drilling operations of polyether ether ketone (PEEK) plastic to measure the temperature of the drill bit during the material removal process. Future versions of the thermometer are intended to be used as a thermocouple replacement in high-speed, near-ambient temperature measurement applications, such as electric motor condition monitoring; battery protection; and machining of polymers and composite materials, such as carbon-fibre-reinforced plastic (CFRP).

High-Speed Infrared Radiation Thermometer for the Investigation of Early Stage Explosive Development and Fireball Expansion.

The understanding of blast loads is critical for the development of infrastructure that protects against explosions. However, the lack of high-quality experimental work on the characterisation of such loads prevents a better understanding of many scenarios. Blast loads are typically characterised by use of some form of pressure gauge, from which the temperature can be inferred from a pressure measurement. However, such an approach to temperature measurement is limited; it assumes ideal gas laws apply throughout, which may not be the case for high temperature and pressure scenarios. In contrast, infrared radiation thermometers (IRTs) perform a measurement of temperature based upon the emitted radiance from the target object. The IRTs can measure fast changes in transient temperature, making them seemingly ideal for the measurement of a fireball's temperature. In this work, we present the use of a high-speed IRT for the measurement of early-stage explosive development and fireball expansion within a confined blast, with the temperature of the explosive fireball measured from its emitted radiance. The temperature measured by the IRT was corroborated against the temperature inferred from a pressure gauge measurement; both instruments measured the same temperature from the quasi-static pressure (QSP) point onwards. Before the QSP point, it is deduced that the IRT measures the average temperature of the fireball over a wide field-of-view (FOV), as opposed to that inferred from the singular shocks detected by the pressure gauge. Therefore, use of an IRT, in tandem with a pressure gauge, provides a potential invaluable measurement technique for the characterisation the early stages of a fireball as it develops and expands.

High-Resolution Hyperspectral Imaging Using Low-Cost Components: Application within Environmental Monitoring Scenarios.

High-resolution hyperspectral imaging is becoming indispensable, enabling the precise detection of spectral variations across complex, spatially intricate targets. However, despite these significant benefits, currently available high-resolution set-ups are typically prohibitively expensive, significantly limiting their user base and accessibility. These limitations can have wider implications, limiting data collection opportunities, and therefore our knowledge, across a wide range of environments. In this article we introduce a low-cost alternative to the currently available instrumentation. This instrument provides hyperspectral datasets capable of resolving spectral variations in mm-scale targets, that cannot typically be resolved with many existing low-cost hyperspectral imaging alternatives. Instrument metrology is provided, and its efficacy is demonstrated within a mineralogy-based environmental monitoring application highlighting it as a valuable addition to the field of low-cost hyperspectral imaging.

A systematic review of the validity, reliability, and feasibility of measurement tools used to assess the physical activity and sedentary behaviour of pre-school aged children.

Physical activity (PA) and sedentary behaviour (SB) of pre-school aged children are associated with important health and developmental outcomes. Accurate measurement of these behaviours in young children is critical for research and practice in this area. The aim of this review was to examine the validity, reliability, and feasibility of measurement tools used to assess PA and SB of pre-school aged children.Searches of electronic databases, and manual searching, were conducted to identify articles that examined the measurement properties (validity, reliability or feasibility) of measurement tools used to examine PA and/or SB of pre-school aged children (3-7 years old). Following screening, data were extracted and risk of bias assessment completed on all included articles.A total of 69 articles, describing 75 individual studies were included. Studies assessed measurement tools for PA (n = 27), SB (n = 5), and both PA and SB (n = 43). Outcome measures of PA and SB differed between studies (e.g. moderate to vigorous activity, step count, posture allocation). Most studies examined the measurement properties of one measurement tool only (n = 65). Measurement tools examined included: calorimetry, direct observation, combined heart rate and accelerometry, heart rate monitors, accelerometers, pedometers, and proxy report (parent, carer or teacher reported) measures (questionnaires or diaries). Studies most frequently assessed the validity (criterion and convergent) (n = 65), face and content validity (n = 2), test-retest reliability (n = 10) and intra-instrument reliability (n = 1) of the measurement tools. Feasibility data was abstracted from 41 studies.Multiple measurement tools used to measure PA and SB in pre-school aged children showed some degree of validity, reliability and feasibility, but often for different purposes. Accelerometers, including the Actigraph (in particular GT3X versions), Actical, ActivPAL and Fitbit (Flex and Zip), and proxy reported measurement tools used in combination may be useful for a range of outcome measures, to measure intensity alongside contextual information.

The good, the bad, and the environment: developing an area-based measure of access to health-promoting and health-constraining environments in New Zealand.

BACKGROUND: Accounting for the co-occurrence of multiple environmental influences is a more accurate reflection of population exposure than considering isolated influences, aiding in understanding the complex interactions between environments, behaviour and health. This study examines how environmental 'goods' such as green spaces and environmental 'bads' such as alcohol outlets co-occur to develop a nationwide area-level healthy location index (HLI) for New Zealand. METHODS: Nationwide data were collected, processed, and geocoded on a comprehensive range of environmental exposures. Health-constraining 'bads' were represented by: (i) fast-food outlets, (ii) takeaway outlets, (iii) dairy outlets and convenience stores, (iv) alcohol outlets, (v) and gaming venues. Health-promoting 'goods' were represented by: (i) green spaces, (ii) blue spaces, (iii) physical activity facilities, (iv) fruit and vegetable outlets, and (v) supermarkets. The HLI was developed based on ranked access to environmental domains. The HLI was then used to investigate socio-spatial patterning by area-level deprivation and rural/urban classification. RESULTS: Results showed environmental 'goods' and 'bads' co-occurred together and were patterned by area-level deprivation. The novel HLI shows that the most deprived areas of New Zealand often have the most environmental 'bads' and less access to environmental 'goods'. CONCLUSIONS: The index, that is now publicly available, is able to capture both inter-regional and local variations in accessibility to health-promoting and health-constraining environments and their combination. Results in this study further reinforce the need to embrace the multidimensional nature of neighbourhood and place not only when designing health-promoting places, but also when studying the effect of existing built environments on population health.

The water incident database (WAID) 2012 to 2019: a systematic evaluation of the documenting of UK drownings.

BACKGROUND: Death by drowning is a leading cause of accidental death in the United Kingdom (UK) and worldwide. The World Health Organization (WHO) states that effective documentation of drowning is required to describe drowning frequency and to underpin effective drowning prevention intervention, thus improving the quality of data describing drowning frequency represents a key initiative. The water incident database (WAID) has been used to document UK fatal and non-fatal water-based incidents since 2009. WAID has not undergone a systematic evaluation of its data or data collection procedures to establish if the database meets the WHO requirements. The present study investigated the characteristics of UK fatal drowning incidents and audited current WAID data capture procedures. METHODS: Data for the fatal drowning cases recorded between 2012 and 2019 were reviewed. Descriptive data were generated 1) to describe fatal drownings in the UK's WAID in this period; 2) a sub-set of drownings were audited i) for completeness of data entry and, based on source documents, ii) for quality of data entry; 3) these processes were used to make recommendations for onward revisions to WAID. RESULTS: A total of 5051 fatalities were recorded between 2012 and 2019. Drowning was most frequent amongst males aged 35 to 60 years (n = 1346), whilst suspected accidents and suicides accounted for 44 and 35% of fatalities. Suicide by drowning was at a peak in the most recent year of data analysed (i.e., 2019; 279 cases) highlighting an urgent need for targeted intervention. Audit part 2i) indicated that 16% of all fields were incomplete, thus indicating potential redundancy, duplication, or the need for onward review. Audit part 2ii) indicated high levels of agreement (80 ± 12%) between audited cases and the 'true' WAID entries. CONCLUSIONS: This study confirms WAID as a rigorous, transparent and effective means of documenting UK drownings thereby meeting WHO requirements for data quality; yet future improvements are recommended. Such findings allow researchers and policy makers to use WAID to further investigate UK drowning with a view to improving public safety measures and drowning prevention interventions. Observations alongside several expert recommendations have informed a revised version of WAID.

Spatial-temporal patterns of childhood immunization in New Zealand (2006-2017): an improving pattern but not for all?

BACKGROUND: Declining childhood immunization represents a serious public health problem globally and in New Zealand. To guide efforts to increase immunization coverage, this study monitors nationwide change in immunization coverage since the introduction of the National Immunisation Register (NIR) in 2005 and spatiotemporal patterns of immunization coverage from 2006 to 2017. METHODS: The study population consisted of 4 482 499 individual immunization records that were obtained from the NIR (2005-2017). Data on yearly and average immunization coverage in census area units (CAUs) in New Zealand were calculated by milestone age (6/8/12/18/24/60/144 months). Data for 2005 were excluded due to missing records in the introductory period of the NIR. We analyzed spatial and spatiotemporal patterns using Gi* and SaTScan methods. RESULTS: Immunization coverage improved since the introduction of the NIR in 2005, reaching a peak in 2014 and 2015 with a slight decrease in 2016 and 2017. Well and insufficiently immunized areas were identified with spatial autocorrelation analyses highlighting several hot- and cold-spots. Comparison of CAUs with neighbouring CAUs allowed for the identification of places where immunization coverage was significantly higher or lower than expected, over both time and space. CONCLUSION: We provide the first spatiotemporal analysis of childhood immunization in New Zealand that utilizes a large sample of over 4.4 million individual immunization records. Our spatial analyses enable policymakers to understand the development of childhood immunization coverage and make more effective prevention strategies in New Zealand.

Degradation and remobilization of endogenous retroviruses by recombination during the earliest stages of a germ-line invasion.

Endogenous retroviruses (ERVs) are proviral sequences that result from colonization of the host germ line by exogenous retroviruses. The majority of ERVs represent defective retroviral copies. However, for most ERVs, endogenization occurred millions of years ago, obscuring the stages by which ERVs become defective and the changes in both virus and host important to the process. The koala retrovirus, KoRV, only recently began invading the germ line of the koala (Phascolarctos cinereus), permitting analysis of retroviral endogenization on a prospective basis. Here, we report that recombination with host genomic elements disrupts retroviruses during the earliest stages of germ-line invasion. One type of recombinant, designated recKoRV1, was formed by recombination of KoRV with an older degraded retroelement. Many genomic copies of recKoRV1 were detected across koalas. The prevalence of recKoRV1 was higher in northern than in southern Australian koalas, as is the case for KoRV, with differences in recKoRV1 prevalence, but not KoRV prevalence, between inland and coastal New South Wales. At least 15 additional different recombination events between KoRV and the older endogenous retroelement generated distinct recKoRVs with different geographic distributions. All of the identified recombinant viruses appear to have arisen independently and have highly disrupted ORFs, which suggests that recombination with existing degraded endogenous retroelements may be a means by which replication-competent ERVs that enter the germ line are degraded.

Targeted exome sequencing designed for blood group, platelet, and neutrophil antigen investigations: Proof-of-principle study for a customized single-test system.

BACKGROUND: Immunohematology reference laboratories provide red blood cell (RBC), platelet (PLT), and neutrophil typing to resolve complex cases, using serology and commercial DNA tests that define clinically important antigens. Broad-range exome sequencing panels that include blood group targets provide accurate blood group antigen predictions beyond those defined by serology and commercial typing systems and identify rare and novel variants. The aim of this study was to design and assess a panel for targeted exome sequencing of RBC, PLT, and neutrophil antigen-associated genes to provide a comprehensive profile in a single test, excluding unrelated gene targets. STUDY DESIGN AND METHODS: An overlapping probe panel was designed for the coding regions of 64 genes and loci involved in gene expression. Sequencing was performed on 34 RBC and 17 PLT/neutrophil reference samples. Variant call outputs were analyzed using software to predict star allele diplotypes. Results were compared with serology and previous sequence genotyping data. RESULTS: Average coverage exceeded 250×, with more than 94% of targets at Q30 quality or greater. Increased coverage revealed a variant in the Scianna system that was previously undetected. The software correctly predicted allele diplotypes for 99.5% of RBC blood groups tested and 100% of PLT and HNA antigens excepting HNA-2. Optimal throughput was 12 to 14 samples per run. CONCLUSION: This single-test system demonstrates high coverage and quality, allowing for the detection of previously overlooked variants and increased sample throughput. This system has the potential to integrate genomic testing across laboratories within hematologic reference settings.

The physical demands of professional soccer goalkeepers throughout a week-long competitive microcycle and transiently throughout match-play.

The physical demands of English Premier League soccer goalkeepers were quantified during training and match-play in a two-part study. Goalkeeper-specific micromechanical electrical systems (MEMS) devices, profiled training and match-day activities throughout one competitive week (n=8; part A). Changes in MEMS-derived outputs were also profiled throughout match-play (100 matches; n=8, 18±14 observations per goalkeeper; part B). In part A, goalkeeping-training elicited the most dives (51±11) versus all activities (all p≤0.030) except shooting-training (p=0.069). Small-sided games elicited the fewest (5±3) dives (all p≤0.012). High-speed distance covered in match (103±72 m) was similar to goalkeeping-training (p=0.484), while exceeding shooting-training, small-sided games, pre-match shooting, and pre-match warm-up (all p=0.012). Most changes of direction (34±12) and explosive efforts (70±18) occurred during goalkeeping-training, with values exceeding match (both p=0.012). In part B, between-half reductions in total distance, but increased high-speed changes of direction and explosive efforts, occurred (both p≤0.05). Excluding the number of high jumps, all variables differed from 0-15-min during at least one match epoch, with more dives (1.3±1.4 vs 1.0±1.1) and explosive efforts (2.5±2.4 vs 2.0±1.8) performed between 75-90-min versus 0-15-min (all p<0.05). These data highlight the differing physical demands of various activities performed by professional soccer goalkeepers throughout a competitive week.

Low-Cost Hyperspectral Imaging System: Design and Testing for Laboratory-Based Environmental Applications.

The recent surge in the development of low-cost, miniaturised technologies provides a significant opportunity to develop miniaturised hyperspectral imagers at a fraction of the cost of currently available commercial set-ups. This article introduces a low-cost laboratory-based hyperspectral imager developed using commercially available components. The imager is capable of quantitative and qualitative hyperspectral measurements, and it was tested in a variety of laboratory-based environmental applications where it demonstrated its ability to collect data that correlates well with existing datasets. In its current format, the imager is an accurate laboratory measurement tool, with significant potential for ongoing future developments. It represents an initial development in accessible hyperspectral technologies, providing a robust basis for future improvements.

Commentary on a recent article on the effects of the 'Daily Mile' on physical activity, fitness and body composition: addressing key limitations.

A recent pilot study by Chesham et al. in BMC Medicine established some initial effects of the Daily Mile™ using a quasi-experimental repeated measures design, with valid and reliable outcome assessments for moderate-to-vigorous physical activity, fitness and body composition. Their contribution is important and welcome, yet, alone, it is insufficient to justify the recent UK-wide adoption of the Daily Mile within the Childhood Obesity Plan. The study concluded that the Daily Mile had positive effects on moderate-to-vigorous physical activity, fitness and body composition, suggesting that intervention effectiveness was confirmed. However, only some of the significant limitations of the work were addressed. Herein, we identify and discuss six key limitations, which, combined, suggest a more tentative conclusion. In summary, evidence supporting the effectiveness of the Daily Mile is in its infancy and requires refinement to fully justify its widespread adoption. Further, we need to be cautious considering that the full range of its impacts, both positive and negative, remain to be fully established.

A Delphi study to build consensus on the definition and use of big data in obesity research.

BACKGROUND: 'Big data' has great potential to help address the global health challenge of obesity. However, lack of clarity with regard to the definition of big data and frameworks for effectively using big data in the context of obesity research may be hindering progress. The aim of this study was to establish agreed approaches for the use of big data in obesity-related research. METHODS: A Delphi method of consensus development was used, comprising three survey rounds. In Round 1, participants were asked to rate agreement/disagreement with 77 statements across seven domains relating to definitions of, and approaches to, using big data in the context of obesity research. Participants were also asked to contribute further ideas in relation to these topics, which were incorporated as new statements (n = 8) in Round 2. In Rounds 2 and 3 participants re-appraised their ratings in view of the group consensus. RESULTS: Ninety-six experts active in obesity-related research were invited to participate. Of these, 36/96 completed Round 1 (37.5% response rate), 29/36 completed Round 2 (80.6% response rate) and 26/29 completed Round 3 (89.7% response rate). Consensus (defined as > 70% agreement) was achieved for 90.6% (n = 77) of statements, with 100% consensus achieved for the Definition of Big Data, Data Governance, and Quality and Inference domains. CONCLUSIONS: Experts agreed that big data was more nuanced than the oft-cited definition of 'volume, variety and velocity', and includes quantitative, qualitative, observational or intervention data from a range of sources that have been collected for research or other purposes. Experts repeatedly called for third party action, for example to develop frameworks for reporting and ethics, to clarify data governance requirements, to support training and skill development and to facilitate sharing of big data. Further advocacy will be required to encourage organisations to adopt these roles.

Quantitative traceable temperature measurement using novel thermal imaging camera.

Conventional thermal imaging cameras, based on focal-plane array (FPA) sensors, exhibit inherent problems: such as stray radiation, cross-talk and the calibration uncertainty of ensuring each pixel behaves as if it were an identical temperature sensor. Radiation thermometers can largely overcome these issues, comprising of only a single detector element that can be optimised and calibrated. Although the latter approach can provide excellent accuracy for single-point temperature measurement, it does not provide a temperature image of the target object. In this work, we present a micromechanical systems (MEMS) mirror and silicon (Si) avalanche photodiode (APD) based single-pixel camera, capable of producing quantitative thermal images at an operating wavelength of 1 µm. This work utilises a custom designed f-theta wide-angle lens and MEMS mirror, to scan +/- 30° in both x- and y-dimensions, without signal loss due to vignetting at any point in the field of view (FOV). Our single-pixel camera is shown to perform well, with 3 °C size-of-source effect (SSE) related temperature error and can measure below 700 °C whilst achieving ± 0.5 °C noise related measurement uncertainty. Our measurements were calibrated and traceable to the International Temperature Scale of 1990 (ITS-90). The combination of low SSE and absence of vignetting enables quantitative temperature measurements over a spatial field with measurement uncertainty at levels lower than would be possible with FPA based thermal imaging cameras.

Quantitative thermal imaging using single-pixel Si APD and MEMS mirror.

Accurate quantitative temperature measurements are difficult to achieve using focal-plane array sensors. This is due to reflections inside the instrument and the difficulty of calibrating a matrix of pixels as identical radiation thermometers. Size-of-source effect (SSE), which is the dependence of an infrared temperature measurement on the area surrounding the target area, is a major contributor to this problem and cannot be reduced using glare stops. Measurements are affected by power received from outside the field-of-view (FOV), leading to increased measurement uncertainty. In this work, we present a micromechanical systems (MEMS) mirror based scanning thermal imaging camera with reduced measurement uncertainty compared to focal-plane array based systems. We demonstrate our flexible imaging approach using a Si avalanche photodiode (APD), which utilises high internal gain to enable the measurement of lower target temperatures with an effective wavelength of 1 µm and compare results with a Si photodiode. We compare measurements from our APD thermal imaging instrument against a commercial bolometer based focal-plane array camera. Our scanning approach results in a reduction in SSE related temperature error by 66 °C for the measurement of a spatially uniform 800 °C target when the target aperture diameter is increased from 10 to 20 mm. We also find that our APD instrument is capable of measuring target temperatures below 700 °C, over these near infrared wavelengths, with D* related measurement uncertainty of ± 0.5 °C.

Design and realization of a wide field of view infrared scanning system with an integrated micro-electromechanical system mirror.

We present a wide field of view (FOV) infrared scanning system, designed for single-pixel near-infrared thermal imaging. The scanning system consisted of a two-axis micro-electromechanical system (MEMS) mirror that was incorporated within the lens. The optical system consisted of two groups of lenses and a silicon avalanche photodiode. The system was designed for both the production of thermal images and also to utilize the techniques of radiation thermometry to measure the absolute temperature of targets from 500°C to 1100°C. Our system has the potential for real-time image acquisition, with improved data acquisition electronics. The FOV of our scanning system was ±30° when fully utilizing the MEMS mirror's scanning angle of ±5°. The pixel FOV (calculated from the distance to target size ratio) was 100:1. The image quality was analyzed, including the modulation transfer function, spot diagrams, ray fan plots, lateral chromatic aberrations, distortion, relative illumination, and size-of-source effect. The instrument was fabricated in our laboratory, and one of the thermal images, which was taken with the new lens, is presented as an example of the instrument optical performance.