In a standard image sensor, the photodetectors are built on the silicon substrate with the interconnects on top. This means that some light is reflected, reducing the amount of light that reaches the photocathode layer. In a back-side illuminated (BSI) sensor, by flipping the silicon wafer during manufacturing and thinning its reverse side, light can strike the photocathode layer without passing through the wiring layer. This makes BSI sensors ideal where low-light performance is critical, such as in industrial sensors, security cameras, microscope cameras, and astronomy systems. It is also the ideal solution for detecting UV light and x-rays.