SU1665246A1 - Test target - Google Patents

Abstract

The invention relates to the measurement of the modulation transfer function and its uniformity over the image field of an electron-optical and / or visual system. The aim of the invention is to improve the measurement accuracy. The test object contains a matrix of elements in the form of sinusoidal grids with a contrast smoothly varying from a maximum in the center to a minimum at the periphery. The average level of lattice density is equal to the matrix density. The grids in the matrix have a constant orientation, and the spatial frequency of the grids from matrix to matrix varies in the range of 0.01 - 60 cycles per angle degree and contrast in the range of 0.04 - 0.9. 2 Il.

Description

The invention relates to the measurement of the modulation transfer function and its uniformity over the image field of an electron-optical and / or visual system, allows to evaluate the quality of these systems and is intended for use in cinematography to study both a separate link of the cinematographic and photographic systems, and the entire system in In general, in television for the study of various television systems displaying video information, in ergonomics, medicine, in particular, for the study of the human visual system.

The aim of the invention is to improve the measurement accuracy.

FIG. Figure 1 shows the matrix element of the test object, which is a sinusoidal grating modulated according to Gauss law, in which the maximum contrast value in the center gradually decreases toward the periphery and the average density is equal to the density of the matrix; in fig. 2 is a test object matrix containing 3x3 lattices of the same spatial frequency 0) 18 and contrast K 0.8.

The test object is designed to study the uniformity of the transfer function over the image field of the electron-optical and / or visual system, since it is known that the system's spatial frequency band varies with eccentricity.

The test object contains l matrices, each of which consists of sinusoidal grids, the contrast of each of which varies from the maximum value in the center to the minimum at its periphery and the average density level of the grids coincides with the density of the matrices without visible borders.

Each such matrix consists of arrays of one spatial frequency, one contrast and orientation of the Matrix, as shown in FIG. 2, differ from one another in spatial frequency through an octave

BUT

ABOUT

oh you

Ј.

about

in the range of 0.01-6.0 cycle / degree and in contrast, changing according to a logarithmic law, i.e. with a variable step depending on the spatial frequency, the range of measurement of contrasts is 0 04-0.90.

The number of arrays in the matrix and the distance between the arrays both in the column and in the matrix row can be variable and vary depending on the research task. For example, when evaluating the projection optical system, the centers of the side lattices can be located from the edge of the matrix at a distance of 1 / 6 width of the floor image of the system. The number of matrices with the number of lattices in a 3x3 matrix is 24, which is sufficient to accurately study the system.

The measurement of the modulation transfer function of the system under study is carried out by successive presentation of the test object matrices, the number of matrices (n) depends on the tasks and type of research and can vary.

Each matrix consisting of grids with the same spatial frequency, contrast and orientation is sequentially presented to the observer at a given distance. The detection threshold of the test grids located in the matrix field is then determined by the observer's answers. Then deviations from the norm are determined in relative units,% or dB Normal is the contrast sensitivity of an ophthalmologically healthy observer.

The measurement of the uniformity of the transfer function over the image field, for example, an electron-optical system, is performed by successively presenting to the observer the image of each matrix of the test object, obtained on the screen of the system under study, for example, a television station.

To evaluate this system, the characteristics of the observation are compared with

five

0

tron-optical device and without it, l then get the difference in relative units,% or dB.

The test object allows, without additional technical means and devices, to visually determine the uniformity of the reproducing properties of the studied electro-optical and / or visual system in a wide range of spatial frequencies and contrasts.

The matrices of the test object can be made with a photo-method on transparent and non-transparent media, as well as using an offset printing method on printing paper. In this connection, the test object can be used both in transmitted and reflected light. Moreover, for the study of, for example, various cinematographic systems, you can use a test object in the form of a test film, each plan of which of a certain length should contain an image of one of n matrices, i.e. the plan from the plan of the test film must differ from the same parameters as the matrices from one another.

Claims (1)

Invention Formula A test object containing a matrix of elements in the form of sinusoidal grids, the average density level of which is equal to the density of the matrix, which differs By the fact that, in order to increase the accuracy, additional matrices are introduced into it, the contrast of each of the arrays forming the matrix smoothly changes from the maximum value in the center to the minimum by its periphery, while at a constant orientation of the gratings in the same matrix from the matrix to the matrix, the spatial frequency of the gratings varies in the range of 0.01–60 cycles per angle degree and contrast range 0.04-0.9 FY2 1