Passive Autofocusing System for a Thermal Camera

Most of the Thermal (Infrared) cameras nowadays are equipped with a motorized lens for focusing a scene manually. The subjective nature of manual focusing makes it an inefficient and cumbersome process. In contrast, Autofocusing (AF) obtains the best focused image based on a quantitative measure with the benefits of convenience and intelligence. Various AF systems for visual cameras have been developed, but relatively less amount of work has been done for thermal imaging systems. This paper presents a Vision and Control based Autofocusing System (VCAFS) comprising: (1) an uncooled thermal camera with motorized lens, (2) a passive contrast-based focus measure, (3) a smoothing operator to avoid local extrema, and (4) two different lens motion controllers. Experimental results show the efficacy of the proposed system on live videos even when the scene and its depth are continuously changing.

[1]  Zhenming Peng,et al.  Accurate and Rapid Auto-Focus Methods Based on Image Quality Assessment for Telescope Observation , 2020, Applied Sciences.

[2]  Bradley J Nelson,et al.  Autofocusing in computer microscopy: Selecting the optimal focus algorithm , 2004, Microscopy research and technique.

[3]  Henry Pinkard,et al.  Deep learning for single-shot autofocus microscopy , 2019, Optica.

[4]  Anurag Kumar Srivastava,et al.  Design and Implementation of a Real-Time Autofocus Algorithm for Thermal Imagers , 2016, CVIP.

[5]  Sumon Dey,et al.  Autofocus Technologies in Digital Cameras: A Comparative Study , 2018 .

[6]  Joonki Paik,et al.  Robust focus measure for unsupervised auto-focusing based on optimum discrete cosine transform coefficients , 2011, IEEE Transactions on Consumer Electronics.

[7]  Li Chen,et al.  Robust passive autofocus system for mobile phone camera applications , 2014, Comput. Electr. Eng..

[8]  Tony Lindeberg,et al.  Scale Selection Properties of Generalized Scale-Space Interest Point Detectors , 2012, Journal of Mathematical Imaging and Vision.

[9]  Rey-Chue Hwang,et al.  A passive auto-focus camera control system , 2010, Appl. Soft Comput..

[10]  Larry S. Davis,et al.  AutoFocus: Efficient Multi-Scale Inference , 2018, 2019 IEEE/CVF International Conference on Computer Vision (ICCV).

[11]  Soo-Won Kim,et al.  Enhanced Autofocus Algorithm Using Robust Focus Measure and Fuzzy Reasoning , 2008, IEEE Transactions on Circuits and Systems for Video Technology.

[12]  Nasser Kehtarnavaz,et al.  Low-Light Auto-Focus Enhancement for Digital and Cell-Phone Camera Image Pipelines , 2007, IEEE Transactions on Consumer Electronics.

[13]  Arthur C. Sanderson,et al.  Implementation of Automatic Focusing Algorithms for a Computer Vision System with Camera Control. , 1983 .

[14]  C. Ortiz de Solórzano,et al.  Evaluation of autofocus functions in molecular cytogenetic analysis , 1997, Journal of microscopy.

[15]  I T Young,et al.  A comparison of different focus functions for use in autofocus algorithms. , 1985, Cytometry.

[16]  Jay Martin Tenenbaum,et al.  Accommodation in computer vision , 1971 .

[17]  Tom Drummond,et al.  Machine Learning for High-Speed Corner Detection , 2006, ECCV.

[18]  E. R. Davies,et al.  Machine vision - theory, algorithms, practicalities , 2004 .

[19]  Soo-Won Kim,et al.  Reduced Energy-Ratio Measure for Robust Autofocusing in Digital Camera , 2009, IEEE Signal Processing Letters.

[20]  Jirí Mekyska,et al.  On the focusing of thermal images , 2011, Pattern Recognit. Lett..

[21]  Homer H. Chen,et al.  Robust focus measure for low-contrast images , 2006, 2006 Digest of Technical Papers International Conference on Consumer Electronics.

[22]  Seong G. Kong,et al.  Focusing in thermal imagery using morphological gradient operator , 2014, Pattern Recognit. Lett..

[23]  Tom Drummond,et al.  Fusing points and lines for high performance tracking , 2005, Tenth IEEE International Conference on Computer Vision (ICCV'05) Volume 1.

[24]  Marcin Woźniak,et al.  Multi-focusing algorithm for microscopy imagery in assembly line using low-cost camera , 2019, The International Journal of Advanced Manufacturing Technology.

[25]  Gautam Srivastava,et al.  A Novel Auto-Focus Method for Image Processing Using Laser Triangulation , 2019, IEEE Access.

[26]  Eric Krotkov,et al.  Focusing , 2004, International Journal of Computer Vision.

[27]  Peter van Beek,et al.  Improving the accuracy and low-light performance of contrast-based autofocus using supervised machine learning , 2015, Pattern Recognit. Lett..

[28]  Jesús Chamorro-Martínez,et al.  Diatom autofocusing in brightfield microscopy: a comparative study , 2000, Proceedings 15th International Conference on Pattern Recognition. ICPR-2000.