SU712686A1 - Device for measuring contrast-frequency characteristics of optical images - Google Patents

Description

The invention relates to instrumentation and can be used in television devices for measuring reproducible brightness values.

Known devices for measuring the contrast-frequency characteristics of optical images containing an optical system, a photodetector and an image scanning unit [1]. However, they are complex and not reliable enough.

The closest in technical essence to the invention is a device for measuring the contrast-frequency characteristics of optical images containing a lens, aperture diaphragm, a photodetector, an electromagnet, an image scanning unit [2].

A disadvantage of the known device is the lack of measurement efficiency and the complexity of the constructive implementation of the image scanning unit.

The purpose of the invention is to increase the measurement efficiency and simplify the design of the image scanning unit.

To achieve this goal, in the known device, a flexible optical fiber is installed in front of the photodetector, the free oscillating end of which is equipped with a nozzle of soft magnetic material located close to the electromagnet and combined with the end input part with the plane of the optical image.

In FIG. 1 presents a schematic diagram of the proposed device; in FIG. 2 is a diagram of the main characteristics of the image and the free oscillating end of the fiber.

The device contains a lens 1, a slit aperture 2, a photodetector 3, an elastic fiber 4, the free oscillating end of which has a nozzle 5 of magnetically soft material located near the electromagnet 6, and is aligned with the end input part with the plane of the optical image, and the other end of the fiber is fixed.

The device operates as follows.

2о From the area of the image under study, the light flux is projected by the lens 1 onto the input end of a flexible (for example, glass) fiber 4, with a slit diaphragm 2 fixed to it, through the slit diaphragm and the light guide onto the photodetector 3. Scanning by the slit aperture of the still image in the focal plane of the lens 1 is carried out by means of an alternating current electromagnet 6 located close to cradle 712686 5. An alternating magnetic field interacts with the nozzle material 5 and forces the free end of the optical fiber 4 make resonant oscillations in the direction specified by the orientation of the magnetic field 5 of the electromagnet 6 and the geometry of the fiber 4. The amplitude and frequency of oscillations, depending on the moving mass of the free input end, the cross section and elastic properties of the material of the light guide 4, the field strength of the electromagnet 6 and the frequency of the current supplying the electromagnet is determined by known methods.

The maximum deviation Ax of the free end of the fiber from the image plane 15 should not exceed the depth of field ε:

Δχ ε ζζ λ / Α ² , where λ is the wavelength of light; 20

A is the lens aperture.

If the length of the fiber / = x + Ax, then

Ax = I - ΥI ² - ^"2/4, where a is The size of the image, otsyuda25. α ² Λ ⁴ + 4λ ²

8Μ ² '

For example, for A = 0.11, λ = 0.6 μm, and = 2000 2000 μm and 1 ^ 14 mm.

This device allows to reduce the registration time and increase the scanning speed of the image by reducing the moving mass of the measuring device. Unlike the known device, in which the maximum scanning frequency of the image does not exceed a fraction of hertz, in this device it is tens of hertz. In addition, this device allows you to simplify the design of the image scanning unit, eliminating nodes subject to wear, which increases reliability and reduces the amount of power consumed by the electromagnet.

Claims (2)

charge 5. The variable magnetic field interacts with the material of the nozzle 5 and forces the free end of the light guide 4 to perform resonant oscillations in a direction which is determined by the orientation of the magnetic field of the electromagnet 6 and the geometry of the light guide 4. The amplitude and frequency of the oscillations depending on the moving mass of the free input end transverse The sections and elastic properties of the material of the light guide 4, the intensity of the field of the electromagnet 6 and the frequency of the current supplying the electromagnet are determined by known methods. Maximum deviation Ll: the free end of the fiber from the image plane should not exceed the depth of field of the lens e: YES; e: l / L% where K is the wavelength of light; A - lens aperture. If the fiber length is 1 x -} - / x, then YES: / -1 // - aV4, image size, hence + 4X ° For example, for L 0.11, 6 µm, and 2000 µm and mm. This device allows to reduce the recording time and increase the scanning speed of the image by reducing the moving mass of the measuring device. Unlike the known device, in which the maximum frequency of the image sweep does not exceed the fraction of Hertz, in this device it is ten Hertz. In addition, this device allows us to simplify the design of the image scanning unit, eliminating the nodes subject to wear, which increases reliability and reduces the amount of power consumed by the electromagnet. An apparatus for measuring the contrast-frequency characteristics of optical images, comprising a lens, a slit diaphragm, a photodetector, an electromagnet, an image scanning unit, characterized in that, in order to increase the measurement performance and simplify the design of the image scanning unit, a flexible light guide, free oscillating end, is installed in front of the photoreceiver which is equipped with a nozzle of a magnet of flexible material located near the electromagnet, and the end entrance is combined with the plane of the optical image. Sources of information taken into account at the examination 1.V. Babenko. Optics of television devices. L., “Energie, 1964, p. 5-41. 2. Krivosheev M. I. Basics of television measurements, M., “Sv, 1973, p. 268-270 (prototype).