Abstract: There is described a picture quality control system for use with a multi-beam cathode ray tube raster scan display device. The display device generates an image comprising a multiplicity of parallel, nonoverlaping bands of pixels, each band of pixels comprising a set of parallel lines of pixels.The control system includes a linearity correction circuit and a dynamic detwist correction circuit. The linearity correction circuit adjusts the distance between neighboring bands of pixels. The dynamic detwist correction circuit adjusts the relative positions of the electron beams generated by the cathode ray tube.The control system further includes a dynamic astigmatism correction circuit and a dynamic focus correction circuit for correcting astigmatism and focus imperfections in the image generated by said cathode ray tube. A dynamic size correction circuit adjusts the size of the pixels generated by the electron beams.The display is organized as an array of tiles.