UNDERSCAN
The underscan function in CRT (Cathode Ray Tube) monitors refers to a feature that adjusts the display area to ensure that the entire image being transmitted is visible on the screen. It addresses the issue of overscan, which occurs when the edges of the image extend beyond the visible area of the screen.
In CRT technology, overscan was a common occurrence due to the inherent limitations of the display technology. The electron beam used to draw the image on the screen had a slightly larger area of coverage than the visible screen area, resulting in a portion of the image being cut off or hidden outside the viewable boundaries.
To counter this, CRT monitors often included an underscan function. When enabled, the underscan feature reduces the size of the displayed image, effectively shrinking it so that the entire image fits within the visible screen area. This ensures that no part of the image is lost due to overscan.
The underscan function is particularly useful when working with content that contains important visual elements near the edges of the frame, such as user interfaces, graphics, or subtitles. By enabling underscan, users can ensure that these elements remain visible and prevent any critical information from being cut off.
It's important to note that the underscan function is more commonly associated with CRT monitors used in professional or specialized applications, such as video editing or broadcasting. In consumer-grade CRT televisions, overscan was typically used to hide potential noise or artifacts near the edges of the image, but underscan options were less prevalent.
Overall, the underscan function in CRT monitors was a practical solution to address the overscan issue, allowing users to see the full extent of the transmitted image and ensuring that no critical content is lost beyond the visible screen area.