The Otsu thresholding algorithm represents a fundamental technique in image segmentation, yet its computational efficiency is severely limited by exhaustive search requirements across all possible threshold values. This work presents an optimized implementation that leverages the bisection method to exploit the unimodal characteristics of the between-class variance function. Our approach reduces the computational complexity from O(L) to O(log L) evaluations while preserving segmentation accuracy. Experimental validation on 48 standard test images demonstrates a 91.63% reduction in variance computations and 97.21% reduction in algorithmic iterations compared to conventional exhaustive search. The bisection method achieves exact threshold matches in 66.67% of test cases, with 95.83% exhibiting deviations within 5 gray levels. The algorithm maintains universal convergence within theoretical logarithmic bounds while providing deterministic performance guarantees suitable for real-time applications. This optimization addresses critical computational bottlenecks in large-scale image processing systems without compromising the theoretical foundations or segmentation quality of the original Otsu method.