Line-based modulation transfer function measurement of pixelated displays

Abstract

This paper proposes a line-based method for measuring the modulation transfer function (MTF) of a display. In this method, the spatial distribution of a single line that is displayed in a small region of the screen is analyzed. This is performed by capturing the displayed line by a light measuring device (LMD). The square sampling grid of the LMD is set slightly slanted relative to the displayed line so that the line is recorded with various offsets with respect to the sampling positions. By analyzing a supersampled 1D line spread function generated from a small region of interest (ROI) in the image of the captured line, the display MTF is estimated. The convolution theorem is used to compensate the display MTF for the underestimation related to the spatial performance or MTF of the LMD. Thereby, accurate display MTF results are obtained for a wide range of pixel ratio, i.e., the number of pixels of the measurement device per display pixel interval. The proposed method was validated using computer-generated images of a model display with an RGB stripe subpixel arrangement and a model LMD. The utilization of a low pixel ratio enables the measurement to be performed using a small lens and long working distance. In addition, the small size of the employed ROI significantly reduces the computational cost and allows the use of a low-resolution camera.