A device includes a holding device, a first camera module, a second camera module, a driving device, and an image processor. The holding device is configured for holding a plurality of lens elements, each of which includes lenses. The driving device is connected to the first camera module and the second camera module and configured for driving the first camera module and the second camera module to move such that the first camera module and the second camera module aim at and capture an image of each lens. The image processor is in communication with the first camera module and the second camera module and configured for processing the images to detect defects of the lenses, if any.