Backlighting is ideal for inspecting for defects in solar cells. The narrow directivity angle OPF series illuminates workpieces with a narrow directivity light angle, allowing for chips and small cracks in a solar cell to be captured with a camera. In addition, the optimized arrangement of LEDs with OPF series lighting minimizes decreases in brightness of peripheral components, ensuring proper inspection of even general solar cells (150 mm square size) when using an OPF series light with a light-emitting surface of 210 × 200 mm.