RETRACE LINES
Retrace lines in CRT (Cathode Ray Tube) technology refer to the faint horizontal lines that can be visible on the screen during the vertical retrace period. The retrace lines appear as a result of the electron beam returning to the top of the screen after completing a scan.
During the normal operation of a CRT, the electron beam scans horizontally across the screen, illuminating the phosphor dots that create the displayed image. Once the beam reaches the right edge of the screen, it quickly returns to the left side to begin the next line scan. However, during this retrace period, the electron beam is turned off or significantly dimmed, resulting in a lack of illumination on the screen.
The retrace lines become visible because the beam is not completely turned off during the retrace period. Although the beam is dimmed, it can still cause a residual glow on the phosphor coating of the CRT. This glow appears as faint horizontal lines that run parallel to each other, typically spanning the entire width of the screen.
Retrace lines are more noticeable on CRTs with higher brightness or contrast settings. They can be more pronounced in certain video content, such as scenes with bright backgrounds or solid colors.
While retrace lines are considered a characteristic of CRT technology, they are generally not considered a defect or malfunction. They are an inherent part of the CRT's scanning process and can be minimized by adjusting the brightness and contrast settings to optimal levels.