Suggesting the use of Infrared RGB filters for chromatic Aberration Correction of a Digital Infrared Image

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1 , pp Suggesting the use of Infrared RGB filters for chromatic Aberration Correction of a Digital Infrared Image Jongwoo Joo(First Author) 1, Daewook Kim(Corresponding Author) 2 1 Division of Multimedia, Digital imaging major, Kyungwoon University, kangdongro 730, Gumi, #730739, South Korea 2 Diviaion of Photography and Film, Daegu art University, San Dabu-ri, Gasan-myeon, Chilgok-gun, Gyeongsangbuk-do, South Korea jw4150@gmail.com 1, real7610@daum.net 2 Abstract. How to improve the resolution of a digital infrared image is to remove diffraction and reduce the chromatic aberration. In this study, for adjusting the chromatic aberration we narrowed the range of wavelengths that is sensitive to light. Using three representative sections narrowed, we proposed the infrared RGB filter. The proposal of the infrared RGB filter improves resolution and not by just particular sections of infrared, but all sections shot by consumer digital cameras are possible to be taken. Furthermore, we can adjust the chromatic aberration by using an commercial image conversion program. In this study, we suggest the ways to improve. Keywords: digital, infrared, sharpness, RGB filter, chromatic aberration, quality improvement 1 Introduction Infrared is used for a diagnosis and care in the areas of dermatology, hemorrheology, ophthalmology, and surgical care. Also, it is used for judging the disease of plants in the fields of microscope scans, agriculture, and forestry. In the filed of archaeology and art, infrared is used for determining the fake[1]. Photographs of criminal investigations in the areas of science photos, photographs can record the fact, which is difficult to be perceived and also impossible to be perceived by a photographer. For this reason, infrared is very appropriate for a criminal investigation. Infrared is also utilized for taking pro-photographs and general landscape photographs. In order to enhance the efficiency of infrared, the research is needed by using general digital cameras. The spectral sensitivity range of an image sensor in a commercial digital camera is approximately between 380nm~1200nm and the figure includes some near-infrared areas[2]. This means it is possible to take infrared photographs by not using additional devices. However, the use of the infrared photographs taken with consumer digital cameras is limited because ISSN: ASTL Copyright 2015 SERSC

2 of the resolution degradation. In the study of the medical profession and Conservation, the studies related to the resolution are now fledgling because of a lack of technical knowledge. Therefore, studying the resolution of infrared images by professional photographers is necessary and we proposed ways to reduce the chromatic aberration in this study. 2 Related Researches 2.1 The Existing technologies The research, which aimed to improve the resolution of visible light, calculates the pixel size of image sensor and adjusts values of aperture for which the pixel pitch has to be at least the required distance of the two Airy circles and so removed diffraction[3]. Also, the research suggested the development of a lens for correcting chromatic aberration and how to control an aperture to minimize chromatic aberration[4]. On photographing in visible light, diffraction and chromatic aberration determines the resolution. Infrared is also similar electromagnetic wave with visible light and diffraction and chromatic aberration determines the resolution. Also, Willams Robin & Williams Gigi(2002) mention that the change of refraction is greater than visible light because infrared is longer wavelength than visible light and also has wider wavelength band[5]. 2.2 The Advanced technologies If we use a Narrowband-pass filter, chromatic aberration does not occur and the resolution increased. However, the actual use is limited due to the lack of light. Therefore, Jongwoo Joo(2014) gained the recordable exposure, and set the broadband section which has less chromatic aberration and high resolution. Using a Hi-pass filter and Low-pass filter, he set the spectral region which chromatic aberration similar to visible light occurred and then he got the image of resolution which is similar to visible light. Through this research, he could resolve the exposure time of the disadvantage of a Narrowband-pass filter[6]. By using a general digital camera, an infrared photograph has lower resolution. However, if a photographer controls the wavelength region photographed, the chromatic aberration is lower and the photograph can obtain the similar level of resolution with visible light. Also, because the wavelength range is narrowed, areas that have excellent resolutions are more than one[fig. 1]. Copyright 2015 SERSC 71

3 Fig. 1. The result by using a Hi-pass filter and Low-pass filter (black-visible light) 3. System Configuration(The proposal of an Infrared RGB filter) This study makes improving the resolution by decreasing the chromatic aberration of an infrared image. In that way, we suggest using the commercial image conversion program. By the result of 2.2 The Advanced technologies, we progressed by choosing three sections that had the excellent resolution. In the image taken by visible light, the chromatic aberration can be adjustable by using a commercial image program, but the adjustment of chromatic aberration is impossible by using a commercial image program in the image taken by infrared[7]. The correction of chromatic aberration by using the commercial program 1. The image of three wavelengths that has less chromatic aberration should be created 2. By controlling the size and location of the image, finally 4 a piece of image is produced[fig. 2]. In the infrared image by using a general camera, the chromatic aberration does not decrease even if the size and location is adjusted, because all wavelengths of infrared are taken separately in three pieces. Therefore, wavelength section for infrared has to be established. and then it is called by the infrared RGB filter. 72 Copyright 2015 SERSC

4 Fig. 2. The correction method of chromatic aberration in the commercial program 4 Conclusion As the result of this study, we got infrared images of high-resolution, and whole range of wavelength(approximately 700nm-1200nm) in infrared to which a general camera respond, could be displayed. According to each wavelength range, the speed which image sensor responds to light is different. Then image sensor cannot record the full spectrum of infrared at a time. One time shooting can make get three images, and each image has independent range of wavelengths that chromatic aberration does not happen nearly. This study proposes the infrared RGB filter. In the experiment, we did not use infrared RGB filter at the forefront of sensor and we used three photographs taken by using the filter that corresponded to infrared RGB on the front lens. We are convinced that this study taken by separating the range of wavelengths of infrared, could have huge significance in various fields including Conservation area of science which analyzes the cultural assets, crime picture, and so on. (especially, for all field which needs separating the range of wavelengths of infrared for the analysis) Also, this study could pave the way for the study of infrared by using a general digital camera under studying in a number of areas. Copyright 2015 SERSC 73

5 References 1. Har, D. W., Son, Y. H.: Infrared Photography Using Single Lens Reflex Digital Camera. Association of Image & Film Studies. Vol. 4, p. 401(2004) 2. Joo, J. W.: Researches in the Resolution of Digital Infrared Photography Acording to the relation between the size of an image sensor and the value of an aperture. Master s thesis. Chung-Ang University(2008) 3. Wueller, D.: Evaluating Digital Cameras. Paper presented at the Electronic Imaging Conference, Augustinusstr. 9D, Frechen, Germany(2006) 4. Williamson, J. C., et al.: Light and Color in nature and art. Jobn Wiley & Sons, Inc(1983) 5. Williams Robin, Williams Gigi.: Reflected infrared photography:optical considerations. RMIT University(2002) 6. Joo, J. W.: Improving the Resolution of an Infrared Image by using a Dual-pass Filter. The Society of Mordern Photography & Video. Vol. 17, pp (2014) 7. Joo, J. W.: Improve the resolution of digital infrared photography and study infrared RGB filter. PhD diss. Chung-Ang University(2014) 74 Copyright 2015 SERSC