An Improved Gradient-Based Image Sharpness Evaluation Method for Variable Focusing Window

To address the focusing challenges of varying scales at different time points of moving target images in space, we propose an improved gradient-based image sharpness evaluation method for variable focusing window. The method obtains the target focusing window adaptively and computes the sharpness evaluation value by convolving the image within the focusing window with a multi-directional gradient operator weighted factor. Experiments show that the method exhibits strong sensitivity and anti-interference capabilities, contributing to the improved performance of the space imaging autofocus system.