Igoe, Damien P. and Parisi, Alfio V. 
ORCID: https://orcid.org/0000-0001-8430-8907 and Amar, Abdurazaq and Rummenie, Katherine J.
(2018)
Median filters as a tool to determine dark noise thresholds in high resolution smartphone image sensors for scientific imaging.
Review of Scientific Instruments, 89 (1):015003.
pp. 1-8.
ISSN 0034-6748
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Text (Published Version)
Median filters as a tool to determine dark noise thresholds in high resolution smartphone image sensors for scientific imaging.pdf Download (1MB) | Preview |
Abstract
An evaluation of the use of median filters in the reduction of dark noise in smartphone high resolution image sensors is presented. The Sony Xperia Z1 employed has a maximum image sensor resolution of 20.7 megapixels, with each pixel having a side length of just over 1 µm. Due to the large number of photosites, this provides an image sensor with very high sensitivity, but also makes them prone to noise effects such as hot-pixels. Similar to earlier research with older models of smartphone, no appreciable temperature effects were observed in the overall average pixel values for images taken in ambient temperatures between 5°C and 25°C. In this research, hot-pixels are defined as pixels with intensities above a specific threshold. The threshold is determined using the distribution of pixel values of a set of images with uniform statistical properties associated with the application of median-filters of increasing size. An image with uniform statistics was employed as a training set from 124 dark images and the threshold was determined to be 9 digital numbers. The threshold remained constant for multiple resolutions and did not appreciably change even after a year of extensive field use and exposure to solar ultraviolet radiation. Although the temperature effects uniformity masked an increase in hot-pixel occurrences, the total number of occurrences represented less than 0.1% of the total image. Hot-pixels were removed by applying a median filter, with an optimum filter size of 7 x 7, similar trends were observed for four additional smartphone image sensors used for validation. Hot-pixels were also reduced by decreasing image resolution. The method outlined in this research provides a methodology to characterise the dark noise behaviour of high resolution image sensors for use in scientific investigations, especially as pixel sizes decrease.
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| Item Type: | Article (Commonwealth Reporting Category C) |
|---|---|
| Refereed: | Yes |
| Item Status: | Live Archive |
| Faculty/School / Institute/Centre: | Historic - Faculty of Health, Engineering and Sciences - School of Agricultural, Computational and Environmental Sciences (1 Jul 2013 - 5 Sep 2019) |
| Faculty/School / Institute/Centre: | Historic - Faculty of Health, Engineering and Sciences - School of Agricultural, Computational and Environmental Sciences (1 Jul 2013 - 5 Sep 2019) |
| Date Deposited: | 06 Mar 2022 23:43 |
| Last Modified: | 19 Jul 2022 00:53 |
| Uncontrolled Keywords: | Smartphone; hot pixels; median; filter; dark noise; UV |
| Fields of Research (2008): | 02 Physical Sciences > 0299 Other Physical Sciences > 029999 Physical Sciences not elsewhere classified |
| Fields of Research (2020): | 51 PHYSICAL SCIENCES > 5199 Other physical sciences > 519999 Other physical sciences not elsewhere classified |
| Socio-Economic Objectives (2008): | E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences |
| Socio-Economic Objectives (2020): | 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280120 Expanding knowledge in the physical sciences |
| URI: | http://eprints.usq.edu.au/id/eprint/46789 |
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