What light stimulates PSP plates?

• A. Red light (~600 nm)
• B. Infrared light
• C. Blue light
• D. Ultraviolet light

Answer: (A)

PSP plates read out their stored image by being stimulated with light, which releases the trapped energy as luminescence. The active layer contains europium-doped barium fluorobromide (BaFBr:Eu2+), which traps electrons during X-ray exposure. When blue light hits the plate (around the blue region of the spectrum, roughly 450 nm), those trapped electrons are released and recombine, producing light that the scanner detects to form the image. Red light, infrared, or ultraviolet light don’t efficiently release those trapped electrons (or aren’t used in practice for readout), so blue light is the appropriate stimulating wavelength.