Lithuanian Journal of Physics article / Lietuvos fizikos žurnalo straipsnis

SPECTRALLY TUNABLE LIGHT SOURCE BASED ON A DIGITAL MICROMIRROR DEVICE FOR RETINAL IMAGE CONTRAST ENHANCEMENT
Piotr Bartczak^a, Daiga Čerāne^b, Pauli Fält^a, Pasi Ylitepsa^c, Elina Hietanen^c, Niko Penttinen^a, Lauri Laaksonen^d, Lasse Lensu^d, Markku Hauta-Kasari^a, and Hannu Uusitalo^c,e
^aSchool of Computing, University of Eastern Finland, Yliopistokatu 2, P. O. Box 111, FI-80101, Joensuu, Finland
E-mail: piotr.bartczak@uef.fi
^bDepartment of Optometry and Vision Science, University of Latvia, 8 Kengaraga Street, Riga, LV-1063, Latvia
^cDepartment of Ophthalmology, University of Tampere, Kalevantie 4, FI-33014 University of Tampere, Tampere, Finland
^dMachine Vision and Pattern Recognition Laboratory, Lappeenranta University of Technology, P.O. Box 20, Skinnarilankatu 34, FI-53851 Lappeenranta, Finland
^eSILK Research and Development Center for Ophthalmic Innovations, School of Medicine, Biokatu 14, FI-33014 University of Tampere, Tampere, Finland

Received 21 May 2015; revised 29 June 2015; accepted 29 September 2015

Different optical methods for retinal imaging provide a significant improvement for image analysis and help with data interpretation. The use of tunable light sources, which have been optimized for contrast enhancement of various retinal features or lesions in retinal images, could simplify the eye fundus examination through enhanced image quality. In this study, we have developed and described a research prototype which consists of a spectrally tunable light source based on a digital micromirror device which is further coupled to a fundus camera. The overall aim of this construction was to generate illuminations optimized for enhanced retinal image feature visibility. The optimized illumination conditions were compared to traditional red-free imaging and the measurements were executed for an artificial eye followed by in vivo measurements of the eyes of three volunteers. In all cases, the retinal image contrast was observed to improve compared to the traditional red-free imaging. Depending on the observed retinal feature, the perceptual improvements in the contrast varied from a few percent to nearly 70 percent.

Keywords:biomedical optical imaging, diabetes, lighting control, tunable light source, micromirrors
PACS: 87.57.-s, 87.85.Ox, 87.57.cj

SPEKTRIŠKAI DERINAMAS ŠVIESOS ŠALTINIS TINKLAINĖS VAIZDO KONTRASTUI DIDINTI, NAUDOJANTIS SKAITMENINĮ MIKROVEIDRODĮ
Piotr Bartczak^a, Daiga Čerāne^b, Pauli Fält^a, Pasi Ylitepsa^c, Elina Hietanen^c, Niko Penttinen^a, Lauri Laaksonen^d, Lasse Lensu^d, Markku Hauta-Kasari^a, Hannu Uusitalo^c,e
^aRytų Suomijos universitetas, Joensuu, Suomija
^bLatvijos universitetas, Ryga, Latvija
^cTamperės universiteto Oftalmologijos katedra, Tamperė, Suomija
^dLapenrantos technologijos universitetas, Lapenranta, Suomija

^eTamperės universiteto Medicinos mokykla, Tamperė, Suomija

References / Nuorodos

[1] N.L. Everdell, I.B. Styles, A. Calcagni, J. Gibson, J. Hebden, and E. Claridge, Multispectral imaging of the ocular fundus using light emitting diode illumination, Rev. Sci. Instrum. 81, 093706-1–9 (2010),
http://dx.doi.org/10.1063/1.3478001
[2] I.B. Styles, A. Calcagni, E. Claridge, F. Orihuela-Espina, and J.M. Gibson, Quantitative analysis of multispectral fundus images, Med. Image Anal. 10, 578–597 (2006),
http://dx.doi.org/10.1016/j.media.2006.05.007
[3] G. Liang, R.T. Smith, and T.S. Tkaczyk, Snapshot hyperspectral retinal camera with the Image Mapping Spectrometer (IMS), Biomed. Opt. Express 3(1), 48–54 (2012),
http://dx.doi.org/10.1364/boe.3.000048
[4] R.P. Francis, K.J. Zuzak, and R. Ufret-Vincenty, Hyperspectral retinal imaging with a spectrally tunable light source, Proc. SPIE 7932, 793206 (2011),
http://dx.doi.org/10.1117/12.873891
[5] A. Calcagni, J.M. Gibson, I.B. Styles, E. Claridge, and F. Orihuela-Espina, Multispectral retinal image analysis: a novel non-invasive tool for retinal imaging, Eye 25(12), 1562–1569 (2011),
http://dx.doi.org/10.1038/eye.2011.202
[6] P. Fält, J. Hiltunen, M. Hauta-Kasari, I. Sorri, V. Kalesnykiene, and H. Uusitalo, Extending diabetic retinopathy imaging from color to spectra, in: Proceedings of the 16th Scandinavian Conference on Image Analysis, eds. A.-B. Salberg, J.Y. Hardeberg, and R. Jenssen (Springer-Verlag Berlin, Heidelberg, 2009) pp. 149–158,
http://dx.doi.org/10.1007/978-3-642-02230-2_16
[7] P. Fält, J. Hiltunen, M. Hauta-Kasari, I. Sorri, V. Kalesnykiene, J. Pietilä, and H. Uusitalo, Spectral imaging of the human retina and computationally determined optimal illuminants for diabetic retinopathy lesion detection, J. Imaging Sci. Technol. 55, 030509-1–10 (2011),
http://dx.doi.org/10.2352/j.imagingsci.technol.2011.55.3.030509
[8] S. Tominaga, T. Horiuchi, H. Kakinuma, and A. Kimachi, Spectral imaging with a programmable light source, in: 17th Color and Imaging Conference Final Program and Proceedings (Society for Imaging Science and Technology, 2009) pp. 133–138,
http://www.ingentaconnect.com/content/ist/cic/2009/00002009/00000001/art00025
[9] F.C. Delori, R.H. Webb, and D.H. Sliney, Maximum permissible exposures for ocular safety (ANSI 2000), with emphasis on ophthalmic devices, J. Opt. Soc. Am. A 24, 1250–1265 (2007),
http://dx.doi.org/10.1364/josaa.24.001250
[10] K. Tran, T.A. Mendel, K.L. Holbrook, and P.A. Yates, Construction of an inexpensive, handheld fundus camera through modification of a consumer “point-and-shoot” camera, Invest. Ophthalmol. Vis. Sci. 53(12), 7600–7607 (2012),
http://dx.doi.org/10.1167/iovs.12-10449
[11] F.W. Leong, M. Brady, and J.O.D. McGee, Correction of uneven illumination (vignetting) in digital microscopy images, J. Clin. Pathol. 56(8), 619–621 (2003),
http://dx.doi.org/10.1136/jcp.56.8.619
[12] A.A. Michelson, Studies in Optics (University of Chicago Press, Chicago, USA, 1927),
http://www.amazon.co.uk/Studies-Optics-Michelson/dp/0486687007