International Journal of Research and Scientific Innovation (IJRSI) | Volume III, Issue VI, June 2016 | ISSN 2321–2705 www.rsisinternational.org Page 62 A New Non-Destructive Method for Retrieval of Completely Removed Printed Text on Thermal Papers Kapil Kumar, Parvesh Sharma, Ashesh Sen, Shobhana K. Menon* Department of Forensic Science, Gujarat University, Ahmedabad-380009, India *Corresponding Author - Shobhana K. Menon Abstract: Complete removal of printed text on thermal papers obtained from sources like ATM, fax machines and billing has always been a problem in recovery of evidential information out of it. This systematic non destructive technique exercised for the first time, on completely faded thermal paper allows recovering completely removed printed text. All the samples were introduced to different wavelengths of illuminations and exposure tools using Video Spectral Comparator 6000/HS and the results are subjected to image enhancement software available therein to retrieve the naturally removed text. No chemical treatment on document is required thereby retaining the evidential value of the paper even after examination. The method is non destructive, easy to perform and gives excellent resolution of developed text irrespective of the time elapsed after printing, making it completely readable. Key words - Thermal paper, Ultra violet light, VSC-6000/HS, Document analysis, Image processing tool. _______________________________________________________ I. INTRODUCTION xtensive use of thermal papers in facsimile copies, ATM transaction slips, billing at restaurant and shopping malls etc had attracted forensic examiners to extract evidential clues out of them. In spite of excellent source of transaction information, these thermal paper receipts pose a serious limitation that the thermally printed text gets faded or removed in due course of time naturally under ordinary environment conditions making them non readable and inaccessible. Thermal (Thermo-sensitive) recording paper was introduced by the National Cash Register Company in 1968. The chemistry of the thermal papers work is necessarily the same as that of carbonless papers [1] . Lot of research work have been done in forensic fraternity to develop fingerprints from thermal paper surfaces [2-9] and estimating the age of thermal papers has been done by FTIR [10] . But in cases where these thermal papers are produced as documental evidence, it becomes a real challenge for questioned document examiners to read and extract out information from faded or completely removed text on paper. Kelly et al. [11] proposed method for enhancing and retrieving text from faded thermally printed papers by using iodine fuming. Procedure is approvable however the method is destructive. This motivated us to develop a new non destructive and chemical free method for making the faded thermally printed contents visible and readable. The proposed method includes instrumental analyses whose outcome being subjectively improved by image enhancement techniques to make certain features easier to see by modifying the intensities. II. METHODOLOGY For the examination, a total of 50 samples of thermal receipts were collected from various sources viz. Point of Sale receipts (10), Fax copies (2), ATM transaction slip (20) and Card Payment receipts(18). All samples were faded over natural course of time and text is fully removed and is not visible to naked eyes and considered as naturally faded samples (NFS). Prior to any kind of exposure, samples were photographed in their natural state. All NFS were subjected to analysis in Video Spectral Comparator (VSC) 6000/HS (Foster and Freeman, UK). The process includes examination and illumination of samples to various light sources and filters to make completely faded thermal printed text visible. Following systematic step wise examinations were carried out on samples collected. Step. I – Examination under visible light illumination - In first step all NFS are photographed under flood light in VSC 6000/HS which is being obtained by 4x20W halogen lamps + 2xwhite 1W LEDs. Process is followed under other illuminating sources viz. transmitted light (4x12W incandescent lamps), spot light (20W halogen lamp, gives 25 mm), side light (4x20W halogen lamps + 2xwhite 1W LEDs). Step. II - Examination under Ultra Violet illuminations - All NFS analyzed across different spectral ranges from UV (a) Long wave 365nm peak wavelength (b) Medium wave 312 nm peak length and (c) Short wave 254 nm peak wavelength as some features respond at specific wavebands. Step. III - Image inversion and auto correction - In step II images, the thermally printed text was partially visible under background of fluorescence and appeared white, so an image inversion performed which turned text black in color and E