SU1141373A1 - Method of producing relief holograms having step-like profile of bands - Google Patents

Abstract

A METHOD FOR MANUFACTURING RELIEF HOLOGRAMS WITH A STEPPED BAND PROFILE, which consists of: that the working and protective layers are applied to the substrate, and then the relief is formed by selectively removing layers, the next protective layer is applied and the operations of selectively removing the layers and applying the next protective layer are repeated successively until the desired number of relief levels is reached. y sch. and Ys by the fact that, in order to simplify the process of making holograms while maintaining their high diffraction efficiency, additionally, before applying a protective layer, after each successive stage, remove. Neither the layers, except the last one, are applied to the working layer, and etching is carried out each time before the substrate.

Description

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The invention relates to the field of optical instrumentation, and more than KoliKpeTHo to the technology of manufacturing synthesized holograms, which are used as fusing and correcting optical elements in optical devices for various purposes.

A known method of making relief holograms by bleaching an amplitude optical hologram l

The disadvantage of this method is the need to form a real light field when recording a hologram, which is not always possible,

Closest to the invention is a method for producing embossed holograms with a step profile of strips. A working SiOj and protective (positive photoresist) layers are deposited on the Si substrate, and then the relief is formed by selectively removing the layers, the next protective layer is applied, and the operations of selectively removing the layers and applying the next protective layer are successively repeated until the desired number of relief levels is reached 2J ..

The disadvantage of the known method is its complexity due to the need to apply the process of exposing a layer of photoresist through amplitude masks, the accuracy of the fabrication of which depends on X1, the quality of the resulting hologram. The process of manufacturing masks is very time consuming. In addition, according to this method, the etching depth of the working layer is controlled by time (indirectly), which requires high stability of the parameters (temperature of the production room, concentration of solutions, etc.). The deviation of the height of the profile of a hologram from a given value leads to a decrease in the diffraction efficiency of the resulting hologram

The aim of the invention is to simplify the process of making embossed holograms with a stepped profile of the bands while maintaining their high diffraction efficiency.

This goal is achieved by the fact that, according to the method of producing relief holograms with a stepped profile of strips, in which working and protective layers are applied to the substrate, and then the relief is formed by

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selective removal of layers, the next protective layer is applied and the operations of selective removal of layers and the application of the next protective layer are repeated successively until the required number of relief levels is reached, additionally before applying the protective layer after each next layer removal stage, the working layer is etched, and etching each time, before the substrate.

The thickness of the layers is chosen from the condition

d, (n, -1) -f d, (n2.-1) -, (1)

where d, d is the thickness of the working and protective layers, respectively, o, with d. d,;

n, P2 are the refractive indices of the materials of the working and protective layers, respectively;

L is the length of the light wave;

M - number of profile levels

hologram stripes.

FIG. 1-6 show the structure for making a two-level (binary) hologram; in fig. 7-9 structure for making a three-level hologram.

The method is implemented as follows ..

A two-layer coating is applied on the substrate 1, consisting of working 2 and protective 3 layers (Fig. 1), the thickness of the layers is chosen in accordance with the formula

d, (n, - 1) + d, (n, - 1) | -,

In this case, for a binary hologram the number of levels N 2. Then mechanically, for example using a diamond cutter, the protective and part of the working layers are removed in the hologram strips (Fig. 2). In this case, each strip (ring) of the hologram is made in the form of a group of cut stripes (rings) with a constant width and a tracking pin, and the width of each strip (ring) is greater than the pitch of the same strip (ring). The working layer remaining in the strips is removed by etching it to the substrate surface with an etchant, to whose action the protective layer is resistant. As a result of these operations, a hologram with a two-level (binary) profile of the strips is obtained (Fig. 3). To produce a hologram with a three-level profile of the strips, the thickness of the working 2 and protective 3 layers (Fig. 4) is chosen from the same level as for the two-level hologram, substituting the number of levels N 3 into it. The whole process is repeated one more time (Fig. 4 -9). To obtain a hologram with an N-level profile of the strips, the entire manufacturing process is repeated N-1 times, changing only the width of the strip to be removed (Fig. 1) of the protective layer and part of the working layer, on the assumption that all N-1 steps in each strip are N - The level hologram has either an equal width, or it can vary according to a certain law, taken into account when calculating the hologram. The proposed method can be used to produce both reflective and transmissive holograms, and transmissive holograms can be made either by using transparent materials as the protection and working layers, or by obtaining a copy of the relay from the hologram that was used as the protective and working layers. opaque materials. Copies are produced on a transparent material, such as a cold cured polyester resin. In the case of copying on a resin, the formula by which the thickness of the protective and working layers is determined takes the form. N (n-1) where d dn + is the total thickness of the working and protective layers; n is the refractive index of the polyester resin. If the hologram is intended for use in reflected light, then after making a stepped profile, a reflective coating is additionally applied to it, and the formula by which the thickness of the protective and working layers is determined taking into account the condition n Hj takes the form d -2 2 2N achieving a constant diffraction efficiency of holograms used in light beams with a large angular aperture. In this case, in order to ensure the constancy of the optical paths in the adjacent strips of the hologram, the working and protective layers must be applied with a variable thickness, which makes it possible to compensate for the change in the difference of the optical paths, while changing the angle of the beam on the hologram, intended for use as a corrective and exemplary optical elements in holographic interferometers in the quality control of optical elements and systems (including aspherical Coy optics). Of particular practical interest is the use of embossed synthesized holograms as a test glass, where both high diffraction efficiency (at least 30%) and significant values of light diameters (130 mm and more) are required.

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Claims (1)

METHOD FOR PRODUCING RELIEF HOLOGRAMS WITH A STEPPED STRIP PROFILE, which consists in applying the working and protective layers to the substrate, and then forming the relief by selective removal of the layers, applying the next protective layer and the operations of selective removing layers and applying the next protective layer are repeated successively until the desired layer is reached the number of relief levels, characterized in that, in order to simplify the process of manufacturing holograms while maintaining their high diffraction efficiency, additionally before by applying a protective layer after each subsequent step of removing layers, except the last one, a working layer is applied, and etching is carried out each time to the substrate. Ί