PURPOSE: To shorten the measuring time of the contrast of a display screen by projecting the Fourier transformation image of a parallel light beam transmitted through the display surface of the screen formed on the focal plane of a first objective lens upon a detector array through a second objective lens.

CONSTITUTION: All light rays transmitted through the blank display surface 9 of a screen 6 are converged on the focal plane Fi of an objective lens 12 and form the Fourier transformation image 19 of the blank surface 9 and the image 19 is projected upon the array 16 in which detectors 18 are distributed in a matrix-like state through a second objective lens 14 composed of a group of several convergent lenses. Electric signals supplied from the detectors 18 are proportional to the light intensity on the surface 9 in a given direction and received by means of a memory 21 connected to a microcomputer 22 and the microcomputer 22 converts each signal into luminance and calculates the relation between the luminance of white points and that of black points corresponding to the contract of the display screen.