SU1569788A1 - Method of manufacturing diffraction cylindrical lenses - Google Patents

Abstract

The invention relates to the field of optical instrumentation, in particular, to the technology of producing focusing and correcting diffractive optical elements. The purpose of the invention is to increase the diffraction efficiency. For this, the photomask in the form of a circular amplitude binary zone plate 4 is calculated, the strip of the photomask is symmetric about the diameter by means of the diaphragm 5, the image of the selected strip of the photomask on the photoresist layer deposited on the substrate 7 is formed with the aid of lens 6, and the photoresist layer is exposed, moving substrate 7 in the direction perpendicular to the axis of symmetry of the selected photomask strip, followed by chemical treatment of the layer. In this case, the width of the selected strip of the photomask is chosen equal to 2√2Fλ, where F is the focal length of the photomask

λ is the working wavelength of radiation for manufactured lenses. 2 Il.

Description

The invention relates to optical instrumentation, in particular, to the technology for producing focusing and correcting diffractive optical elements.

The aim of the invention is to increase the diffraction efficiency of diffractive cylindrical lenses by forming an asymmetric profile of their zones.

FIG. 1 shows an optical device diagram for implementing the proposed method; in fig. 2 - a fragment of a dedicated photogaben strip, the distribution of the exposure value E (x) within each zone of the lens produced and the profile h (x) of the surface of the diffractive lens made on the layer of positive photoresist.

The method consists in that a computer calculates a photo mask according to the parameters of a diffraction cylindrical lens produced and forms it as a circular amplitude binary zone plate, isolates the band symmetric with respect to its diameter, forms an image of a selected part of a photo mask on a photoresist layer using an objective lens deposited on the substrate, and expose a layer of photoresist, moving the substrate in the direction perpendicular to the axis of symmetry of the selected band of the photomask, by an amount equal to forming from the prepared lens, with the subsequent chemical processing of a layer of photoresist. In this case, the width of the selected strip of the photomask is chosen to be 2 V 2f A ,, where f is the focal distance of the photomask, L is the working length of the water radiation for the lenses being manufactured.

The width of the selected photomask strip, established from the above condition, ensures that the exposure value within each zone is distributed over the asymmetrical gauge, since the exposure value at each point on the axis perpendicular to the photoresist's direction of movement is directly proportional to the length of the segments formed when the track is straight, parallel to the direction photoresist movements, with the passable zones of the photomask. The asymmetry of the law of exposure

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after processing the photoresist to the formation of an asymmetrical profile of the zones close to ideal. Depending on the type of diffractive cylindrical lens (focusing or diffusing), a positive or negative photoresist is used, respectively.

A device for implementing the method comprises a radiation source 1, a spectral light filter 2, a capacitor 3, a photomask 4, a diaphragm 5, a separating strip of the photomask, a lens 6 and a substrate 7 coated with a photoresist layer mounted for movement in an installation plane in a direction perpendicular to the axis symmetry of the selected “photomask strip”.

The method is carried out as follows.

Using the parameters of a cylindrical diffractive lens made on an EBM, a binary amplitude circular zone plate is calculated, all dimensions of which are increased by a factor of K, where K is the multiplicity of the lens used, and made it, for example, on a soft metal film on a quartz substrate . Next, using a diaphragm 5, a 2 G2GL width symmetric about the diameter is distinguished. The radiation from a source 1 (for example, a mercury lamp) that passes through a spectral optical filter 2 is concentrated by a capacitor 3 on the band of the photomask 4 selected by a diaphragm 5, the image of which is formed by an objective 6 on a positive layer photoresist deposited on the substrate 7. The substrate 7 is uniformly moved in the direction perpendicular to the axis of symmetry of the selected strip of the photomask, for a distance determined by the length of the forming fabrication ivaemoy lenses. The photoresist layer exposed in this manner is chemically treated.

Example. Samples of diffractive cylindrical lenses with a light hole of 5 mm and a focal length of 30 mm on the layers of negative photoresist are obtained. The diffraction efficiency of the manufactured lenses is 60-75%. The photomask is made in the form of a zone plate with a diameter of 52 mm with a stroke ratio

Claims (1)

Claim A method of manufacturing diffractive cylindrical lenses, which consists in calculating and forming a photomask in the form of a circular amplitude binary zone plate, isolating the photomask band symmetrical with respect to the diameter, the photomask formolos on the resist deposited by ku, and exposing that layer of the photon with a substrate photoresis By moving the substrate in the direction perpendicular to the axis of symmetry of the selected strip of the photomask, followed by chemical processing of the layer, the difference is that, in order to increase the diffraction efficiency of the manufactured lenses, the width of the selected band of the photomask is chosen equal to 2 V 2fλ, where f is focal distance of the photomask, ή - working radiation wavelength