IMAGE (spacecraft) | EPFL Graph Search

IMAGE (Imager for Magnetopause-to-Aurora Global Exploration, Explorer 78 or MIDEX-1) is a NASA Medium Explorer mission that studied the global response of the Earth's magnetosphere to changes in the solar wind. It was believed lost but as of August 2018 might be recoverable. It was launched 25 March 2000, at 20:34:43.929 UTC, by a Delta II launch vehicle from Vandenberg Air Force Base on a two-year mission. Almost six years later, it unexpectedly ceased operations in December 2005 during its extended mission and was declared lost. The spacecraft was part of NASA's Sun-Earth Connections Program, and its data has been used in over 400 research articles published in peer-reviewed journals. It had special cameras that provided various breakthroughs in understanding the dynamics of plasma around the Earth. The principal investigator was Jim Burch of the Southwest Research Institute. In January 2018, an amateur satellite tracker found it to be transmitting some signals back to Earth. NASA m

Gaussian channel transmission of images and audio files using cryptcoding

Vladimir Ilievski

Random codes based on quasigroups (RCBQ) are cryptcodes, i.e. they are error-correcting codes, which provide information security. Cut-Decoding and 4-Sets-Cut-Decoding algorithms for these codes are defined elsewhere. Also, the performance of these codes for the transmission of text messages is investigated elsewhere. In this study, the authors investigate the RCBQ's performance with Cut-Decoding and 4-Sets-Cut-Decoding algorithms for transmission of images and audio files through a Gaussian channel. They compare experimental results for both coding/decoding algorithms and for different values of signal-to-noise ratio. In all experiments, the differences between the transmitted and decoded image or audio file are considered. Experimentally obtained values for bit-error rate and packet error rate and the decoding speed of both algorithms are compared. Also, two filters for enhancing the quality of the images decoded using RCBQ are proposed.

2019

Method of displaying an image on a see-through display

Adrien Birbaumer, Martinus Bosch, Sabine Süsstrunk

The present invention concerns a method of displaying an image on a see-through display. The method comprises: obtaining (101) a first electromagnetic radiation matrix of an object, the first matrix comprising first matrix elements representing radiation intensity values of corresponding locations of the object; dividing (103) the first matrix into a second matrix representing a first subset of the radiation intensity values of the matrix elements, and a third, different matrix representing a second, different subset of the radiation intensity values of the matrix elements; generating (105) a first histogram for the second matrix; equalising (107) the first histogram to obtain an equalised second histogram; generating (109) a first grayscale image representing the first subset of the radiation intensity values from the second matrix and the equalised second histogram; colouring (111) the first grayscale image with a first colourmap to obtain a first colour image; generating (113) a second grayscale image representing the second subset of the radiation intensity values image by mapping substantially linearly the second subset of the radiation intensity values to a given number of encoded radiation intensity values; colouring (115) the second grayscale image with a second colourmap, which is different from the first colourmap, to obtain a second colour image; combining (117) the first colour image and the second colour image to obtain a combined colour image; and displaying (123) the combined colour image on the see-through display.

2019

Tone mapping for high dynamic range images

Laurence Meylan

Tone mapping is an essential step for the reproduction of "nice looking" images. It provides the mapping between the luminances of the original scene to the output device's display values. When the dynamic range of the captured scene is smaller or larger than that of the display device, tone mapping expands or compresses the luminance ratios. We address the problem of tone mapping high dynamic range (HDR) images to standard displays (CRT, LCD) and to HDR displays. With standard displays, the dynamic range of the captured HDR scene must be compressed significantly, which can induce a loss of contrast resulting in a loss of detail visibility. Local tone mapping operators can be used in addition to the global compression to increase the local contrast and thus improve detail visibility, but this tends to create artifacts. We developed a local tone mapping method that solves the problems generally encountered by local tone mapping algorithms. Namely, it does not create halo artifacts, nor graying-out of low contrast areas, and provides good color rendition. We then investigated specifically the rendition of color and confirmed that local tone mapping algorithms must be applied to the luminance channel only. We showed that the correlation between luminance and chrominance plays a role in the appearance of the final image but a perfect decorrelation is not necessary. Recently developed HDR monitors enable the display of HDR images with hardly any compression of their dynamic range. The arrival of these displays on the market create the need for new tone mapping algorithms. In particular, legacy images that were mapped to SDR displays must be re-rendered to HDR displays, taking best advantage of the increase in dynamic range. This operation can be seen as the reverse of the tone mapping to SDR. We propose a piecewise linear tone scale function that enhances the brightness of specular highlights so that the sensation of naturalness is improved. Our tone scale algorithm is based on the segmentation of the image into its diffuse and specular components as well as on the range of display luminance that is allocated to the specular component and the diffuse component, respectively. We performed a psychovisual experiment to validate the benefit of our tone scale. The results showed that, with HDR displays, allocating more luminance range to the specular component than what was allocated in the image rendered to SDR displays provides more natural looking images.

EPFL2006

Tone mapping for high dynamic range images

Laurence Meylan

EPFL2006