A display device includes a display part made of a roll-up sheet-like direct-view display element; a take-up part attached on one end of the display part, the take-up part allowing the display part to be rolled up; a pulling part attached on the other end of the display part, the pulling part allowing the display part to be roll out; and a holding part for holding the display part from behind. The method includes providing an article having a feature to be measured, the article having a surface; measuring the surface of the article with a measuring instrument to obtain article surface data; and analyzing the article surface feature data such that data on the feature to be measured is developed. The output quantization index is determined by repeated decoding of the quantization indices in order to minimize the error between the input signal and the prediction signal, and the predictor uses a recursive autocorrelation estimate for the error minimization. A dispersive lens is arranged between the reflector and the converging lens.