Infographics / Digital Radiography

Display Technology: CRT vs LCD/TFT

A two-column comparison table. The CRT column describes a display formed by a focused electron beam scanning a phosphor screen: no polarizers, brightness set by beam current and phosphor output, susceptible to geometric distortion from deflection non-linearity, image quality that drifts over time with phosphor ageing and burn-in, high power from a tens-of-kilovolt electron gun in a deep evacuated tube, and grayscale that needs frequent recalibration. The LCD or AMFP TFT column describes fixed thin-film-transistor pixels modulating a backlight through liquid crystal and two crossed polarizers, brightness set by voltage-rotated crystal polarization, minimal distortion from fixed pixel geometry, stable luminance, low power in a flat panel a few centimetres thick, and grayscale that meets DICOM GSDF and maintains contrast, matching or beating CRT.

CRT versus LCD (AMFP/TFT) medical display monitors compared A two-column comparison table. The CRT column describes a display formed by a focused electron beam scanning a phosphor screen: no polarizers, brightness set by beam current and phosphor output, susceptible to geometric distortion from deflection non-linearity, image quality that drifts over time with phosphor ageing and burn-in, high power from a tens-of-kilovolt electron gun in a deep evacuated tube, and grayscale that needs frequent recalibration. The LCD or AMFP TFT column describes fixed thin-film-transistor pixels modulating a backlight through liquid crystal and two crossed polarizers, brightness set by voltage-rotated crystal polarization, minimal distortion from fixed pixel geometry, stable luminance, low power in a flat panel a few centimetres thick, and grayscale that meets DICOM GSDF and maintains contrast, matching or beating CRT. Property CRT electron beam + phosphor LCD / AMFP (TFT) backlight + liquid crystal Image formation Focused electron beam scans a phosphor-coated screen TFT pixels modulate the backlight through liquid crystal Polarizers None Two crossed polarizing sheets Brightness set by Beam current + phosphor output Voltage rotates crystal to set polarized-light transmission Geometric distortion Susceptible — beam-deflection non-linearity, pincushion/barrel Minimal — fixed pixel geometry Quality over time Drifts — ageing, burn-in, luminance fall-off Stable luminance and geometry Power & footprint Tens of kV gun + deep vacuum tube (tens of cm deep) Low power; flat panel, a few cm thick GSDF & low contrast Calibratable but drifts; needs frequent QA Meets DICOM GSDF, holds contrast; matches or beats CRT
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