217,621 research outputs found
An automated calibration method for non-see-through head mounted displays
Accurate calibration of a head mounted display (HMD) is essential both for research on the visual system and for realistic interaction with virtual objects. Yet, existing calibration methods are time consuming and depend on human judgements, making them error prone, and are often limited to optical see-through HMDs. Building on our existing approach to HMD calibration Gilson et al. (2008), we show here how it is possible to calibrate a non-see-through HMD. A camera is placed inside a HMD displaying an image of a regular grid, which is captured by the camera. The HMD is then removed and the camera, which remains fixed in position, is used to capture images of a tracked calibration object in multiple positions. The centroids of the markers on the calibration object are recovered and their locations re-expressed in relation to the HMD grid. This allows established camera calibration techniques to be used to recover estimates of the HMD display's intrinsic parameters (width, height, focal length) and extrinsic parameters (optic centre and orientation of the principal ray). We calibrated a HMD in this manner and report the magnitude of the errors between real image features and reprojected features. Our calibration method produces low reprojection errors without the need for error-prone human judgements
A flux calibration method for remote sensing satellites using stars
Star surveys and model analyses show that many stars have absolute stable
fluxes as good as 3% in 0.3-35{\mu}m wavebands and about 1% in the visible
wavebands. The relative flux calibrations between stars are better than 0.2%.
Some stars have extremely stable fluxes and can be used as long term flux
calibration sources. Stellar brightness is several orders of magnitude lower
than most ground objects while the stars do not usually appear in remote
sensing cameras, which makes the stars inappropriate for being calibration
sources. The calibration method using stars discussed in this paper is through
a mini-camera attached to remote sensing satellite. The mini-camera works at
similar wavebands as the remote sensing cameras and it can observe the stars
and the ground objects alternatively. High signal-to-noise ratio is achieved
for the relatively faint stars through longer exposure time. Simultaneous
precise cross-calibration is obtained as the mini-camera and remote sensing
cameras look at the ground objects at the same time. The fluxes from the stars
used as calibration standards are transferred to the remote sensing cameras
through this procedure. Analysis shows that a 2% accurate calibration is
possible.Comment: 12 page
Development of a strategy for calibrating the novel SiPM camera of the SST-1M telescope proposed for the Cherenkov Telescope Array
CTA will comprise a sub-array of up to 70 small size telescopes (SSTs) at the
southern array. The SST-1M project, a 4 m-diameter Davies Cotton telescope with
9 degrees FoV and a 1296 pixels SiPM camera, is designed to meet the
requirements of the next generation ground based gamma-ray observatory CTA in
the energy range above 3 TeV. Silicon photomultipliers (SiPM) cameras of
gamma-ray telescopes can achieve good performance even during high night sky
background conditions. Defining a fully automated calibration strategy of SiPM
cameras is of great importance for large scale production validation and online
calibration. The SST-1M sub-consortium developed a software compatible with CTA
pipeline software (CTApipe). The calibration of the SST-1M camera is based on
the Camera Test Setup (CTS), a set of LED boards mounted in front of the
camera. The CTS LEDs are operated in pulsed or continuous mode to emulate
signal and night sky background respectively. Continuous and pulsed light data
analysis allows us to extract single pixel calibration parameters to be used
during CTA operation.Comment: All CTA contributions at arXiv:1709.0348
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