Accurate control of contrast on microcomputer displays

Area of Science:

• Visual neuroscience
• Image display technology
• Instrumentation

Background:

• Microcomputers can display 8-bit images, but limitations in digital-to-analog converters (DACs) and video monitors hinder accurate control.
• Existing models address DAC and monitor calibration for vision experiments.
• Prior work suggests summing AC and DC signals for low-contrast rendering (Watson et al., 1986).

Purpose of the Study:

• To present a method for achieving high-accuracy low-contrast image display.
• To introduce an easy-to-build passive resistor network for video signal attenuation.
• To enable 12-bit accuracy in displaying low contrasts using standard microcomputers.

Main Methods:

• Development of a passive resistor network (video attenuator).
• Combination of outputs from three 8-bit DACs.
• Utilizing a summed AC and DC signal approach for signal generation.

Main Results:

• The proposed video attenuator successfully renders low contrasts.
• The system achieves 12-bit accuracy at the display.
• Experimental measurements confirm the 12-bit accuracy.

Conclusions:

• The passive resistor network provides an effective solution for accurate low-contrast display.
• This method enhances the capabilities of off-the-shelf microcomputers for vision research.
• The 12-bit accuracy achieved is validated by measurements.