Calculating Laser Spot Center Position Using Centroid Algorithm

The centroid algorithm is a widely used image processing technique particularly suitable for calculating the center position of laser spots. This method analyzes the distribution of pixel intensity values to determine the spot's centroid, thereby obtaining precise center coordinates. The implementation typically involves weighting pixel coordinates by their brightness values to calculate the weighted average position.

Implementation workflow overview: Image Loading: The process begins by reading user-specified laser spot images, which can be selected through file paths or names using functions like imread() in MATLAB or OpenCV. Grayscale Conversion: If the input image is in color format, it should first be converted to grayscale using rgb2gray() or similar functions to improve computational efficiency. Binarization (Optional): Depending on requirements, threshold-based binarization can be applied using methods like Otsu's algorithm to emphasize the spot region by creating a binary mask. Centroid Calculation: The algorithm iterates through image pixels, computing weighted average coordinates of all valid pixels (e.g., those exceeding a brightness threshold). The x and y coordinates of the centroid are calculated separately using intensity-weighted averaging formulas: x_centroid = Σ(x_i * I_i)/ΣI_i, y_centroid = Σ(y_i * I_i)/ΣI_i, where I_i represents pixel intensity. Result Output: The calculated center coordinates (x, y) are returned for subsequent positioning or calibration procedures, often accompanied by visualization using plot() or imshow() functions.

Extension considerations: For noisy spot images, pre-processing with filtering algorithms like Gaussian filtering (using imgaussfilt() or GaussianBlur()) can improve accuracy. For non-uniform spots, modified weighting schemes such as squared intensity weighting (I_i²) can be implemented to enhance the contribution of brighter regions. This algorithm is equally applicable to center localization of other circular targets, including solder joints in industrial inspection or spot analysis in optical measurements, with adjustments to threshold parameters and region-of-interest selection.