Multispectral imaging of the ocular fundus using light emitting diode illumination

Abstract

We present an imaging system based on light emitting diode (LED) illumination that produces multispectral optical images of the human ocular fundus. It uses a conventional fundus camera equipped with a high power LED light source and a highly sensitive electron-multiplying charge coupled device camera. It is able to take pictures at a series of wavelengths in rapid succession at short exposure times, thereby eliminating the image shift introduced by natural eye movements (saccades). In contrast with snapshot systems the images retain full spatial resolution. The system is not suitable for applications where the full spectral resolution is required as it uses discrete wavebands for illumination. This is not a problem in retinal imaging where the use of selected wavelengths is common. The modular nature of the light source allows new wavelengths to be introduced easily and at low cost. The use of wavelength-specific LEDs as a source is preferable to white light illumination and subsequent filtering of the remitted light as it minimizes the total light exposure of the subject. The system is controlled via a graphical user interface that enables flexible control of intensity, duration, and sequencing of sources in synchrony with the camera. Our initial experiments indicate that the system can acquire multispectral image sequences of the human retina at exposure times of 0.05 s in the range of 500-620 nm with mean signal to noise ratio of 17 dB (min 11, std 4.5), making it suitable for quantitative analysis with application to the diagnosis and screening of eye diseases such as diabetic retinopathy and age-related macular degeneration.

Multispectral retinal image analysis: a novel non-invasive tool for retinal imaging

“…Modifications to the equipment have been designed and completed 26,27 so that faster image acquisition is possible and these artefacts minimised and this adapted equipment is currently being tested; the investigators are currently using the improved image acquisition system to validate MRIA for MP quantification against the current clinical gold standard, heterochromatic flicker photometry, and also to prove MRIA has an acceptable test-retest variability.…”

“…The investigators are currently investigating the use of a new imaging system, 26,27 and formulating new techniques for analysing the data that take into account unknown factors that may affect the image formation process.…”

Portable multispectral imaging system based on light-emitting diodes for spectral recovery from 370 to 1630 nm

“…Seeking to take advantage of the properties provided by the LED elements, some proposals of multispectral systems using LED illumination and covering the VIS range of the electromagnetic spectrum have been recently published [3,4,[19][20][21][22]. For example, Bouchard et al [4] proposed a low-cost two-channel system with active LED illumination combined with filters in the visible region for fast acquisition of cortical oxygenation, blood flow, and intracellular calcium dynamics.…”

“…Spectral imaging is a field of research with many scientific and technological applications such as remote sensing [1], color imaging [2], biometrics and medicine [3][4][5][6][7], cultural heritage and art work studies [8][9][10], and the food industry [11,12]. Different multispectral imaging systems have been devised to encompass this wide range of applications, mainly single point spectrometers with 2D scanning systems [13], digital cameras combined with line-scan spectrographs [12], color filter wheels [14], filter mosaics [15], lenslet arrays and narrowband filters [6,16], and tunable filters of liquid crystal or acousto-optic technology [17,18].…”

Multispectral and colour imaging systems for the detection of small vertebrate fossils: A preliminary study

“…This last approach is achieved through colour filter wheels (Vilaseca et al, 2006) and tunable filters of liquid crystal or acousto-optic technology (Hardeberg et al, 2002;Tran, 2005). Multispectral imaging is a recent field of research with many applications such as remote sensing (Weng, 2011), colour imaging (Shrestha et al, 2011), biometrics and medicine (Vilaseca et al, 2008;Paquit et al, 2009;Bouchard et al, 2009;Basiri et al, 2010;Everdell et al, 2010), cultural heritage, and art work studies (Kubik, 2007;Padoan et al, 2008;Marengo et al, 2011;HerreraRamírez et al, 2014). However, its use in palaeontology has been anecdotal, with only one brief reference on its application on fake-fossil detection (Kaye et al, 2010).…”