SU1682950A1 - Reflection-interference light filter - Google Patents

Abstract

The invention relates to an optical instrument making and allows to increase the tuning range of the working length of the optical filter. The filter contains a substrate 1 in the form of a wedge or a reflective prism, on the working face of which a system of 2 layers is placed, made of a photo emulsion with equidistant translucent layers of silver salts located at a distance Y0 / 2 from each other. 4 il. (L o 00 th ate about

Description

FIG.

The invention relates to optical instrumentation, in particular to interference light filters.

The purpose of the invention is to increase the tuning range of the working wavelength of the light filter.

FIG. 1 and 2 show the constructions of the reflecting filter; Fig. 3 shows an installation for obtaining a system of transparent and translucent layers in a photographic emulsion layer; in fig. 4 shows the dependence of the reflection coefficient I in rel. units as a function of wavelength A,

The optical filter consists of a glass isosceles prism with an angle at the top equal to 90 °. The working face of the prism is contacted by a fine-grained emulsion about which a system of 2 equidistant layers of translucent silver salts is formed, located at a distance equal to half the wavelength of the length of the solar filter and the tuning of the working wavelength of the light filter. Another embodiment of the filter implementation is shown in FIG. 2. This filter consists of a glass wed-: ia 6, the working face of which is in contact with a fine-grained emulsion in which a system of 2 equidistant layers of translucent silver salts is formed.

The method of forming a layered system is based on the phenomenon that when a light wave is reflected from an optically more dense medium, the phase of the wave changes to the opposite one and as a result of the superimposed incident wave (standing wave and reflected in the medium are located on half-wave spacing each other.

The method is carried out as follows.

The transparent photosensitive material is optically tightly connected to a metal mirror, the resulting system is irradiated with collimated monochromatic light with a wavelength equal to the long wavelength boundary of the working wavelength of the filter being created, and then the physicochemical treatment of the photosensitive material is performed. As a result of the influence of standing light waves and processing, equidistant layers appear in the transparent photosensitive material, parallel to the mirror, the distance between which is equal to half the length of the wave.

This method is implemented in a plant shown schematically in FIG. 3; The coherent monochromatic beam from laser 7 passes through a diaphragm 8, then with a telescope formed by lenses 9 and 10, collimates and is directed onto glass substrate 11 with photo emulsion applied to it 12. Next, the beam is reflected from mirror 13 and interferes with the incident, as a result in which the standing waves form in the photoemulsion layer. After exposure, the photographic plate is subjected to a treatment that includes the following operations: development, washing in distilled water, fixation, washing in distilled water, bleaching, washing in distilled water, washing in ethanol and drying at room temperature. As a result of these operations, translucent layers of silver salts are formed in an optical emulsion at an optical distance equal to Y0 / 2.

Reflecting filter works as follows.

When a white light beam 3 is collimated onto the filter at an angle a, it is partially reflected in direction 4 from the face of the prism AC (Fig. 1) or the face of the sun wedge (Fig. 2). but mostly passes and falls on the emulsion. As a result of reflection from equidistant semitransparent layers, a beam of coherent rays 5 of practically the same intensity is formed. In this case, the optical path difference between adjacent beams is D 2ndcos p, where f is the angle of incidence of light on the photoemulsion, n is the refractive index of the photoemulsion, and d is the geometric distance between the layers of silver salts. As a result of the interference of coherent debugged rays, selective reflection occurs for a single wavelength I. Because the path length L depends on the angle of incidence with f / 7, the wavelength of the reflected radiation I changes as it changes, i.e., when the light filter is rotated wavelength.

Since the distance between the equidistant reflecting layers is equal to / 2, the filter is a filter of the first order

The table shows the parameters of the light filter corresponding to FIG. 1, containing about 60 equidistant layers.

As can be seen from the table, the tuning range of the working wavelength of the filter is 170 nm, with the filter remaining narrowband (A0.5.5 nm) in this entire area.

FIG. Figure 4 shows the reflection band spectrum of a filter containing a wedge-shaped substrate when it is irradiated with white light. From the graph shown in FIG. four,

It follows that at H 600 they have a spectral reflection bandwidth of approximately 2 nm. The position of this band changes in the spectrum within 50 nm as the position of the filter changes relative to the incident light.

The reflective interference filter allows to obtain a narrow (2-10 nm) reflection band, has a high contrast ratio, and the tuning range, depending on the filter design, covers 50 - 200 nm. Tunable filters can be used to irradiate various objects, for example biological, to selectively absorb light with a wavelength of the excitation source in obtaining Raman and luminescence spectra.

Claims (1)

Claims of the invention Reflecting interference city filter containing a substrate of a relatively transparent material and a system transparent and translucent alternating layers, characterized in that, in order to increase the filtering selectivity and to enable adjustment of the working wavelength of the light filter, the substrate is made in the form of a line or a reflective prism, on the working face of which a system of layers is placed - stanty translucent layers of salts silver, formed at the distance Ao / 2, where AO is the long wavelength limit of the tuning of the working wavelength, with the specified system of layers being the last in the direction of radiation. FIG. 2 eight pot j tt 12/3