Browse Prior Art Database

Variable Scale Vertical Expansion for Flat Panels

IP.com Disclosure Number: IPCOM000114618D
Original Publication Date: 1995-Jan-01
Included in the Prior Art Database: 2005-Mar-29

Publishing Venue

IBM

Related People

Fukuda, J: AUTHOR [+2]

Abstract

Disclosed is a method for enabling vertical screen expansion, which is required when existing low resolution display mode is displayed on a high resolution LCD panel, at a variable expansion scale. No additional mechanism is required to an existing video chip and therefore the size, complexity, and the cost of the video subsystem may be significantly reduced while providing a good front-of-screen quality. Two different algorithms are provided for the graphics modes and the text modes to get better front-of-screen quality. Additionally, there is an option which enables to adjust the position of the displayed screen area on Flat Panel, when displayed screen resolution is smaller than panel resolution.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 32% of the total text.

Variable Scale Vertical Expansion for Flat Panels

      Disclosed is a method for enabling vertical screen expansion,
which is required when existing low resolution display mode is
displayed on a high resolution LCD panel, at a variable expansion
scale.  No additional mechanism is required to an existing video chip
and therefore the size, complexity, and the cost of the video
subsystem may be significantly reduced while providing a good
front-of-screen quality.  Two different algorithms are provided for
the graphics modes and the text modes to get better front-of-screen
quality.  Additionally, there is an option which enables to adjust
the position of the displayed screen area on Flat Panel, when
displayed screen resolution is smaller than panel resolution.

      Unlike CRT monitors, flat panels have a fixed number of pixels
(e.g., 640x480, 800x600 or 1024x768 pixels).  Lower resolution
software running on a higher resolution panel only partially fills
the totally usable display area.  For instance, VGA 640x480 software
displayed on XGA 1024x768 panel would leave 384 pixels horizontally
and leave 288 lines vertically on the panel.  To increase the usable
display area when running lower resolution software on higher
resolution panel, the screen must be expanded both horizontally and
vertically.  This invention enables the vertical expansion at a
variable expansion scale rate.

In general, three methods are considered for the vertical expansion.
  o  Expansion inside the video chip
  o  RGB regeneration outside the video chip by using frame buffer
  o  Expansion inside the Flat Panel

      Some video chips have a control logic which controls both CRT
display timing and Flat Panel display timing with vertical expansion
(Fig. 1).  However, because Flat Panel has different display timing
from CRT, the resolution on CRT is changed in the CRT/Flat Panel
simultaneous display mode, compared with the CRT only mode.  CRT can
not retain original display mode resolution, when it is used in the
simultaneous display mode with Flat Panel.

      Another method is to capture the RGB data from the video chip
and, then, regenerate the RGB data onto Flat Panel with vertical
expansion and with different timing.  Fig. 2 shows its mechanism.
The generated RGB data, which is the output data of the video chip
and the input data to the DAC for CRT, is captured by the RGB
Capturing Logic at first.  Then, the RGB data is stored to the frame
memory, temporary.  Secondly, the stored RGB data is read by the RGB
Regeneration Logic with the different timing to display on high
resolution Flat Panel.  In this case, no resolution difference is
observed on CRT screen between in the CRT only mode and in the
CRT/Flat Panel simultaneous display mode.  However, very complex
logic and frame memory is additionally required for this buffering.

      The last method is to make vertical expansion inside the Flat
Panel (Fig. 3).  In this case, n...