Abstract:

Concerning the illumination changes and the low speed of pointer instrument detection which make it difficult for the existing algorithms to achieve readings quickly and accurately, we propose a new algorithm to solve these problems based on scan line processing. The new algorithm firstly extracts the illumination invariant image by single scale Retinex. In order to reduce the pointer detection time, we adopt the scan line processing to extract the characteristic pixels for Hough transform. Finally, we use the dual threshold Hough transform to detect straight lines. Experimental results show that the proposed algorithm cannot only solve the problem of illumination changes and the low speed of readings, but also has high precision and adjustable speed.

Key words: automatic reading of pointer instrument, single scale Retinex, scan line, Hough transform