Improving display quality by means of real-time image processing for multibeam CRTs

摘要

In this paper we address the correction of the convergence error of a monochrome multi-beam Cathode Ray Tube (CRT) by means of digital video-signal processing. Correction of the convergence (horizontal misalignment) of the three electron beams with respect to each other in the CRT, will improve the resolution and brightness of the CRT. We apply the theory of fractional delay filtering to design a digital Finite Impulse Response (FIR) filter that is capable of interpolating the digital video signal. Emphasis is on small four-tap filters, to reduce the necessary amount of processing power. The variable filter has been implemented on a TMS320C80 signal processor to assess the performance of standard DSP hardware on this type of filtering. The analysis of four-tap fractional delay filters has led to useful designs in our application. The implementation on the TMS320C80 processor shows that the variable filter can be implemented with about 10 (parallel) instructions, yielding a maximum throughput of 16 M pixels/s on the TMS320C80 DSP at 40 MHz. We demonstrate (results of) a real-time DSP (TMS320C80) implementation of a variable delay video processing for horizontal convergence correction. The image quality, MTF and brightness are quite satisfactory and well in the diagnostic application area.