Range imager performance comparison in homodyne and heterodyne operating modes

Range imaging cameras measure depth simultaneously for every pixel in a given field of view. In most implementations the basic operating principles are the same. A scene is illuminated with an intensity modulated light source and the reflected signal is sampled using a gain-modulated imager. Previously we presented a unique heterodyne range imaging system that employed a bulky and power hungry image intensifier as the high speed gain-modulation mechanism. In this paper we present a new range imager using an internally modulated image sensor that is designed to operate in heterodyne mode, but can also operate in homodyne mode. We discuss homodyne and heterodyne range imaging, and the merits of the various types of hardware used to implement these systems. Following this we describe in detail the hardware and firmware components of our new ranger. We experimentally compare the two operating modes and demonstrate that heterodyne operation is less sensitive to some of the limitations suffered in homodyne mode, resulting in better linearity and ranging precision characteristics. We conclude by showing various qualitative examples that demonstrate the system’s three-dimensional measurement performance

Conceptual design of a 1-MW CW X-band transmitter for planetary radar

A proposed conceptual design to increase the output power of an existing X-band radar transmitter used for planetary radar exploration from 365 kW to 1 MW CW is presented. The basic transmitter system requirements as dictated by the specifications for the radar are covered. The characteristics and expected performance of the high-power klystrons are considered, and the transmitter power amplifier system is described. Also included is the design of all of the associated high-power microwave components, the feed system, and the phase-stable exciter. The expected performance of the beam supply, heat exchanger, and monitor and control devices is also presented. Finally, an assessment of the state-of-the-art technology needed to meet system requirements is given and possible areas of difficulty are summarized

Shape and deformation measurement using heterodyne range imaging technology

Range imaging is emerging as a promising alternative technology for applications that require non-contact visual inspection of object deformation and shape. Previously, we presented a solid-state full-field heterodyne range imaging device capable of capturing three-dimensional images with sub-millimetre range resolution. Using a heterodyne indirect time-of-flight configuration, this system simultaneously measures distance (and intensity), for each pixel in a cameras field of view. In this paper we briefly describe our range imaging system, and its principle of operation. By performing measurements on several metal objects, we demonstrate the potential capabilities of this technology for surface profiling and deformation measurement. In addition to verifying system performance, the reported examples highlight some important system limitations. With these in mind we subsequently discuss the further developments required to enable the use of this device as a robust and practical tool in non-destructive testing and measurement applications

Heterodyne range imaging as an alternative to photogrammetry

Solid-state full-field range imaging technology, capable of determining the distance to objects in a scene simultaneously for every pixel in an image, has recently achieved sub-millimeter distance measurement precision. With this level of precision, it is becoming practical to use this technology for high precision three-dimensional metrology applications. Compared to photogrammetry, range imaging has the advantages of requiring only one viewing angle, a relatively short measurement time, and simplistic fast data processing. In this paper we fist review the range imaging technology, then describe an experiment comparing both photogrammetric and range imaging measurements of a calibration block with attached retro-reflective targets. The results show that the range imaging approach exhibits errors of approximately 0.5 mm in-plane and almost 5 mm out-of-plane; however, these errors appear to be mostly systematic. We then proceed to examine the physical nature and characteristics of the image ranging technology and discuss the possible causes of these systematic errors. Also discussed is the potential for further system characterization and calibration to compensate for the range determination and other errors, which could possibly lead to three-dimensional measurement precision approaching that of photogrammetry

The Waikato range imager

We are developing a high precision simultaneous full-field acquisition range imager. This device measures range with sub millimetre precision in range simultaneously over a full-field view of the scene. Laser diodes are used to illuminate the scene with amplitude modulation with a frequency of 10MHz up to 100 MHz. The received light is interrupted by a high speed shutter operating in a heterodyne configuration thus producing a low-frequency signal which is sampled with a digital camera. By detecting the phase of the signal at each pixel the range to the scene is determined. We show 3D reconstructions of some viewed objects to demonstrate the capabilities of the ranger

A power-saving modulation technique for time-of-flight range imaging sensors

Time-of-flight range imaging cameras measure distance and intensity simultaneously for every pixel in an image. With the continued advancement of the technology, a wide variety of new depth sensing applications are emerging; however a number of these potential applications have stringent electrical power constraints that are difficult to meet with the current state-of-the-art systems. Sensor gain modulation contributes a significant proportion of the total image sensor power consumption, and as higher spatial resolution range image sensors operating at higher modulation frequencies (to achieve better measurement precision) are developed, this proportion is likely to increase. The authors have developed a new sensor modulation technique using resonant circuit concepts that is more power efficient than the standard mode of operation. With a proof of principle system, a 93–96% reduction in modulation drive power was demonstrated across a range of modulation frequencies from 1–11 MHz. Finally, an evaluation of the range imaging performance revealed an improvement in measurement linearity in the resonant configuration due primarily to the more sinusoidal shape of the resonant electrical waveforms, while the average precision values were comparable between the standard and resonant operating modes

Frailty Identification in Prehospital Care: A Scoping Review of the Literature

The proportion of older adults is increasing worldwide. Frailty assessment in prehospital care was suggested to improve triage decisions and paramedics’ judgment. This study aimed to assess the scope and nature of available evidence around frailty identification in prehospital care. A systematic search of the literature was performed using MEDLINE, SCOPUS, CINHAL, and Web of Science to identify relevant articles published from January 2022 downwards. A list of indexed terms and their associated alternatives were pre-determined. Of the 71 identified and reviewed articles after removing duplicates, six articles were included in the review. Due to the heterogeneity of the included articles, the findings were described narratively. The findings of this review showed that the available evidence is limited and heterogenic. Two themes emerged from the findings of the included articles: 1) Paramedics’ Perceptions about Frailty Assessment in Prehospital Care and 2) Frailty Scores for Application in Prehospital Care. Paramedics recognised frailty assessment in pre-hospital care to be feasible and important. They highlighted the need for a simple and clear frailty score that could be used and mentioned to other healthcare professionals when handing over patients. Six frailty scores were reported to be used in prehospital care. The evidence around each frailty score is very limited. Overall, frailty assessment in prehospital care was shown to be important and feasible. Different frailty scores have been assessed for use in prehospital care. Further research investigating frailty identification in prehospital care is needed

Under-triage of older trauma patients in prehospital care: a systematic review

Background: It is argued that many older trauma patients are under-triaged in prehospital care which may adversely affect their outcomes. This systematic review aimed to assess prehospital under-triage rates for older trauma patients, the accuracy of the triage criteria, and the impact of prehospital triage decisions on outcomes. Methods: A computerised literature search using MEDLINE, Scopus, and CINHAL databases was conducted for studies published between 1966 and 2021 using a list of predetermined index terms and their associated alternatives. Studies which met the inclusion criteria were included and critiqued using the Critical Appraisal Skills Programme tool. Due to the heterogeneity of the included studies, narrative synthesis was used in this systematic review. Results: Of the 280 identified studies, 23 met the inclusion criteria. Current trauma triage guidelines have poor sensitivity to identify major trauma and the need for TC care for older adults. Although modified triage tools for this population have improved sensitivity, they showed significantly decreased specificity or were not applied to all older people. The issue of low rates of TC transport for positively triaged older patients is not well understood. Furthermore, the benefits of TC treatment for older patients remain uncertain. Conclusions: This systematic review showed that under-triage is an ongoing issue for older trauma patients in prehospital care and its impact on their outcomes is still uncertain. Further high-quality prospective research is needed to assess the accuracy of prehospital triage criteria, the factors other than the triage criteria that affect transport decisions, and the impact of under-triage on outcomes

The quantitative study of marked individuals in ecology, evolution and conservation biology: a foreword to the EURING 2003 Conference

Few fields in modern ecology have developed as fast as the analysis of marked individuals in the study of wild animal populations (Seber & Schwarz, 2002). This is the topic of EURING Conferences, which from 1986 have been the premier forum for advances in capture–recapture methodology. In this sense, EURING Conferences still maintain the flavour that originally inspired scientific meetings: to disseminate the very last findings, ideas and results on the field. Traditionally, EURING Conferences have been published in the form of Proceedings, which because of their relevant content, become a required reading to anyone interested in the capture–recapture methodology. EURING 2003 was held in Radolfzell (Germany), hosted by the Max Planck Research Centre for Ornithology, and the Proceedings appear as a special issue of Animal Biodiversity and Conservation. The full title of the 2003 meeting was "The quantitative study of marked individuals in ecology, evolution and conservation biology", which stands for one of the main aims of the meeting: to establish the capture-recapture approach as one of the standard methodologies in studies within these fields. One of the shared views is that capture–recapture methodologies have reached a considerable maturity, but the need still exists to spread their use as a "standard" methodology. The nice review paper by Lebreton et al. (1993) in Trends in Ecology and Evolution is still applicable, in that general ecologists and evolutionary biologists still resist their general use. The same applies to conservation biology, where the analysis of marked individuals may also be a key tool in its development. We hope, with the spread of 2003 Proceedings, to help to fill this gap. The Proceedings follow the same general structure as the Conference. We organised the EURING meeting in 10 technical sessions, covering what we considered as fastest growing areas in the field. We appointed for each session, two chairs, which were charged with selecting 4–7 talks on the topic of their session. Each session additionally included a plenary conference intended to summarise or to provide a general but synthetic flavour of the topic. As a novelty in EURING conferences, we asked session chairs to include at least one talk dealing with study species other than birds. This is the result of a heated but fruitful discussion at EURING 2000 in Point Reyes, and fits with the general aim to spread the capture–recapture methodology beyond zoological groups: although EURING as an organization, deals with birds, and conferences have traditionally focused on this group, the capture–recapture approach is becoming a standard way to address biologically relevant questions on populations and individuals (Schwarz, 2002), for any zoological group. This volume, contains several nice examples of taxa other than birds. As far as possible, we selected chairs so that each session was delineated with a good balance between the biological and the statistician emphasis. This balance has in fact characterised EURING conferences, which in addition to the workshop atmosphere always present, has lead to very fruitful exchanges. Session chairs were also asked to act as editors for the papers within their session. All the papers were hence subjected to peer review, as in any other issue of Animal Biodiversity and Conservation, and presentation of the paper in the Conference did not assure publication in the Proceedings. This has lead to an even higher quality of the papers presented at the Conference. Editors were additionally asked to write a short summary on their session. Given that these summaries also present the views of the Editors on the different topics presented, we have preferred each introduction to appear as a short paper in the front of each one of the sessions, so that it can be cited as a regular paper. The Proceedings start with the Honour Speaker Talk by James Nichols (Nichols, 2004). This talk is traditionally the last one in the Conference, but we think that it nicely summarises how and why capture–recapture has developed to its current healthy state. The talk is in fact a tribute to David Anderson, to whom, as Nichols says, all of us are more or less in debt. Hence, we have preferred to move the Honour Talk to the front position of the Proceedings, and we would like this to be our humble tribute to David. At the end of the Proceedings appear a few papers which were presented in poster format, and a paper summarising several of the main topics presented at the traditional short course on capture–recapture, this time organized by the unflagging Evan Cooch. We would like to thank all the people who helped in one way or another to the successful completion of the EURING Conference and the Proceedings. We thank to the Session Chairs, their dedication and enthusiasm in organizing the sessions and also in editing the different papers. All their names appear in the front page of the Proceedings as credits. We thank Wolfgang Fiedler for the local organization of the event: a very difficult and exhausting task that is not always properly recognized. Jean Clobert, although unfortunately unable to attend the Conference, supported us with ideas and friendship meanwhile preparing the scientific program. Evan Cooch maintained the always successful web page (which probably will also become a classic in EURING conferences…), and organized the traditional course on capture–recapture. Charles Francis very efficiently organized the poster session and acted as editor for the papers sent for publication. Finally we thank the Ministerio de Ciencia y Tecnología for financial support to the publication of this special issue of Animal Biodiversity and Conservation (B.O.S. 2002–12283–E) and to the Natural History Museum of Barcelona for their support