Holographic grating preparation system and method

Abstract

The invention discloses a holographic grating preparation system and method. The holographic grating preparation system comprises: a light source and a holographic material, a beam expanding device which is arranged on a light path between the light source and the holographic material and is used for expanding the passing light beam; a light splitting device which is used for splitting a source light beam emitted by the light source into a first split light beam and a second split light beam; a first light reflecting device and a second light reflecting device which are respectively used for reflecting the first split light beam and the second split light beam to the holographic material; a movable baffle plate which is arranged between the beam expanding device and the holographic material, wherein the movable baffle plate moves according to preset parameters to change the cross sectional areas of the light beams emitted to the holographic material by the first light splitting light beam and the second light splitting light beam; a control system which is used for controlling the movable baffle to move according to preset parameters; and a holographic material which is used for being exposed by interference fringes formed by the first split light beam and the second split light beam to form a holographic grating. According to the invention, the high-quality holographic grating with variable diffraction efficiency can be prepared.

Description

technical field [0001] The invention belongs to the field of holographic gratings, in particular to a preparation system and method of holographic gratings. Background technique [0002] Holographic waveguide refers to the attachment of multiple holographic gratings on a flat transparent plate medium. Holographic gratings can be divided into three types according to their functions: coupling-in grating, folded grating and coupling-out grating. The role of the coupling input holographic grating is to couple the light emitted by the optical machine into the waveguide substrate, and propagate in the waveguide substrate at an angle greater than the total reflection. After reaching the folded grating, part of the light changes the propagation angle, and the other part of the light continues to propagate in the original direction. The angled light passes to the coupling output grating, which outputs the light from the waveguide to the human eye. [0003] The holographic grating o...

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Problems solved by technology

[0004] At present, there are two commonly used methods to increase the diffraction efficiency along a certain direction. One is to control the thickness of the holographic grating to gradually change along one direction, which is usually achieved by using spacers. This method will lead to different surfaces of the waveguide. Parallel, the image resolution will decrease, and when the diffraction efficiency of the coupling output grating increases along the propagation direction and the coupling input grating does not need to change the diffraction efficiency, the design of the holographic waveguide is complicated and the preparation is difficult; the other is the preparation of the holographic grating. An attenuation film whose transmittance gradually changes along a certain direction is added to the optical path, and the efficiency of different areas is realized by controlling the exposure light intensity of different regions on the grating, but due to the self-interference of the attenuation film, such as figure 2 As shown, after a beam of laser light is irradiated on the attenuating sheet, the transmission direction of the light after passing through the attenuating sheet is the same as the original irradiation direction (the solid line part), and it is output again after being reflected by the attenuating sheet (the dotted line part). The virtual and real beams are coherent Light will interfere in the overlapping area, thereby forming an interference pattern, which affects the efficiency of the holographic grating, and when preparing holographic gratings of different sizes, the size of the attenuation sheet needs to be changed, and the attenuation of each part of the attenuation sheet needs to be redone. very low flexibility

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