Optical inspection system detects defects of an object, such as an electronic device during manufacturing. The optical inspection system includes a first linear light source that irradiates a first light beam on a top surface of the object along a scan line across the width of the object. A second linear light source forms an angle with the first linear light source and irradiates a second light beam on a side surface of the object. A camera receives scattered light from the top surface and the side surface of the object and captures a subimage of the object along the scan line. An image processing system receives each subimage from the camera, stitches the subimages, and detects defects on the top surface and the side surface of the object.