What solid-state detector is a silicon chip that converts light or X-ray photons to an electrical charge or signal?

What solid-state detector is a silicon chip that converts light or X-ray photons to an electrical charge or signal?

• A. Charge coupled device (CCD)
• B. Complementary metal oxide sensor (CMOS)
• C. Photomultiplier
• D. Scintillator

Answer: (A)

This question tests recognizing a solid-state detector that directly converts photons into an electrical signal on a silicon chip. The best fit is a Charge-Coupled Device. In a CCD detector, photons—whether light or X-ray photons—strike a silicon pixel array and generate electron-hole pairs. The resulting charge in each pixel is stored and then transferred through the chip to a readout stage, where it is converted into an electrical signal that forms the image. This direct conversion of photon energy into charge on a silicon substrate is the hallmark of CCDs used in digital radiography. CMOS sensors are also silicon-based detectors, but they differ in architecture because they use per-pixel amplifiers and a different readout scheme, which is why the term CCD is preferred for this direct chip-based charge transfer description. A photomultiplier is not a silicon chip but a vacuum-tube device that multiplies electrons, and a scintillator converts X-rays to light rather than directly to an electrical signal on a silicon chip.