A Fuzzy Algorithm for Auto-Focusing Laser Diode Products

The products of laser diode have been widely used, creating high profits. As there are only semi-auto-focus machines to do the focusing-jobs for the products of laser diode, it takes much work and increases the products’ cost. Therefore we developed a fully auto-focus machine for the products of laser diode to promote the quality of products and reduce the cost of the products. The AC servomotor was adopted to control the focus length. The image of the well-focused laser diode point can present more accurate information than the blurred laser point. It is helpful to get precise focus of laser diode. We adjusted the focus length of laser diode products by a fuzzy algorithm according to the feedback image information. The feedback image of laser diode spot was processed to distinguish the background, blurred region and bright region by a three-value thresholding method. The image information of the laser diode spot, the area of the bright region and the ratio between the blurred area and the bright area, were used as the criterion for the autofocusing job and to judge whether the focusing-job was well-done. In the meantime, we could also get the offsets in the x- and y- direction of the laser diode from the image of laser diode spot. Finally, we adjusted the focus length and the offsets of the laser diode products by a fuzzy imaging control algorithm to get the optimal focusing condition.