Which layer of the PSP plate tends to emit light in a forward direction when read?

• A. Reflective
• B. Active phosphor
• C. Conductor
• D. Support

Answer: (A)

Light produced by the phosphor is isotropic, meaning it would go in all directions. The key is the layer directly behind the phosphor: a reflective layer. This layer bounces light that would otherwise travel backward back toward the front, so more of the emitted light makes it toward the reader. In other words, the reflective layer doesn’t generate light itself, but it redirects most of the light forward, enhancing forward emission during readout. The protective, conductor, and support layers mainly serve protection and electrical/structural roles and don’t bias the emission direction the way the reflective layer does.