SU1365037A1 - Method of producing test-image of variable contrast - Google Patents

Abstract

The invention relates to an optical instrument making and allows to expand the area of contrast adjustment of the test image. The test object 7 is formed by applying a specularly reflecting pattern 8 onto an optically transparent substrate 9. The test object 7 is illuminated by sources 1 and 4 of polarized light with a mutually orthogonal polarization direction. The total luminous flux projected by lens 12 produces on the screen 11 an image of the original in the form of superimposed negative and positive images of it. By turning the analyzer 10, the contrast of the obtained image of the test object 7 is adjusted, determined by the e1 of the 1st lightness of the light source relative to the dark field created by the crossed polarizer 3 (6) and the 10 o 2 or o analyzer (O

Description

00

a :) ate

about

00

FIG.

The invention relates to optical instrumentation, and in particular to methods of controlling the frequency-contrast characteristics of optical elements and photographic materials.

The aim of the invention is to expand the area of contrast adjustment of the test image.

The figs represents the optical layout; FIG. 2 shows an optical circuit with a test object on a mica substrate;

The essence of the invention is that a transparent substrate applies a test pattern in the form of a specularly reflecting layer, illuminates the obtained test object from two sides with polarized light with a mutually orthogonal polarization direction and projects the total luminous flux through the analyzer to the screen as a result, an image of the original appears in the transmitted and reflected light fluxes on the screen, which is a superposition of negative and positive images of the original. The contrast of the obtained image is regulated from negative to positive by turning the analyzer and is determined by the magnitude of the light source relative to the dark field created by the crossed polarizer and analyzer, and is maximal due to the design of mirror image.

Example 1 Source of light 1 (Fig. O, condenser 2 and polarizer 3 are sequentially installed and aligned along the optical axis. A similar optical system with a light source 4, condenser 5 and polarizer 6 is installed so that the optical axes of the two systems are mutually orthogonal. The test object 7 is made in the form of a mirror-reflecting test-pattern 8, deposited on an optically transparent substrate 9, and installed at the intersection of the light fluxes from sources 1 and 4 of the light at an angle of 45 ° to the direction of each optical axis. The analyzer 10 and screen 11 are mounted on the continuation of the optical axis of one of the optical systems after the test object 7. A projection lens 12 is installed between the screen 11 and the analyzer 10, polarizers

3 and 6 orient the direction of polarization of light mutually orthogonal.

The light from source 1, which has vertical polarization, passes through the optically transparent portions of the test object 7. The light with horizontal polarization from source 4 is reflected from the mirror portions

test-picture 8 The total light flux going along one optical axis passes through the analyzer 10 and is projected by the lens 12 onto the screen 11. When the analyzer rotates

10, on screen 11, an image of the test object 7 appears in the transmitted, reflected light fluxes or their superposition,

The brightness of each part of the image

the test object can be changed from the zero level when the polarizer 3 (6) and the analyzer 10 are crossed to the maximum level when the polarizer 3 (6) is parallel and the analyzer 10, determined by the brightness of source 1 or

4 light, which does not limit the contrast of the resulting image, the light transmission of the optical device according to the given scheme is determined by the loss on the optical elements, absorption in the substrate 9 and the reflectance of the specular coating of the test picture 8 and is not less than 80% of the optical transmission of the optical device way, does not go beyond the value

10% about

Example 2 o The optical scheme is similar to that shown in example 1.

Test picture 8 is applied to a mica plate of a thickness of a multiple of I / 4, where A is the wavelength of the incident monochromatic light, and a specularly reflecting junction is applied on the reverse side of the mica plate. The test object on the basis of a mica plate is illuminated by polarized light, the polarization direction of which makes an angle of 45 with the direction of the crystal50.

mica plate axis

When the light flux from the light source 1, which passes the condenser 2 and the polarizer 3, gg with the test object 7, interacts, it is divided into two light fluxes, one of which is reflected from the mirror surface of the test figure 8, and the other passes through the optical transparent areas

mica plate 9, reflected from the rear mirror surface 13, passes through the mica plate and exits through the optically transparent areas. With the passage of a quarter-wave mica plate 9, the plane of polarization of the outgoing light flux rotates by 90 relative to the plane of polarization of the light flux incident on the test object. The total light flux propagates along a single optical axis. The formation of a variable in contrast image occurs as in Example 1. The quarter-wave mica plate silver-plated on the reverse side performs the function of a second light source for operation in a transmitted light flux, the polarization direction of which is orthogonal to the polarization direction of the incident light flux.

Taking into account the small change in the refractive indices of mica along the main optical axes in the visible region of the spectrum, mica plates with a thickness of 0.01–0.1 mm can be considered broad-cavity and working as phase plates in the entire visible region of the spectrum.

Compared to Example 1, the use of a quarter-wave phase plate simplifies the optical system and eliminates the need for precise alignment of the two optical systems for combining images of the test object in transmitted and reflected light fluxes.

The Frenee prism can be used as a phase plate.

ABOUT

0

five

l If the Fresnel prism has an angle of 74 ° 20, it operates as a quarter-wave plate in the visible light spectrum with a deviation from circularity of less than 5%. Tooe is an achromatic phase plate.

The proposed method allows to replace the set of certified stroke worlds of different contrast, used in practice to determine the frequency-contrast characteristics of the object being monitored, and also allows a continuous change in contrast during the control process, which reduces its duration and labor intensity. In addition, the continuity of the change in contrast allows the automation of the control process using machine readout.

Claims (1)

Invention Formula The method of obtaining a test image of variable contrast, including the illumination of the test object on a transparent substrate with polarized light, passing the light flux of the test object through a analyzer made with the possibility of rotation around its axis, and recording the image of the test object characterized in that in order to broaden the contrast adjustment area of the test image, the test object is illuminated from two sides with light with mutually orthogonal polarization, and the test object is mirrored by reflecting 1MOD FIG. 2