Cut-off filter for frustrating wavelength shift

Abstract

The invention discloses a cut-off filter for frustrating wavelength shift. The cut-off filter comprises a substrate and a cut-off filter membrane plated on the substrate, wherein the cut-off filter membrane comprises a first matching secondary membrane system, a main membrane system and a second matching secondary membrane system which are sequentially arranged, wherein the first matching secondary membrane system is positioned between the main membrane system and the substrate; the main membrane system is formed by alternating high-refractivity membrane layers and low-refractivity membrane layers; the thickness of each high-refractivity membrane layer in the main membrane system is over three times that of each low-refractivity membrane layer; the first matching secondary membrane system is formed by alternating low-refractivity membrane layers and high-refractivity membrane layers; and the second matching secondary membrane system is formed by repeating high-refractivity membrane layers, low-refractivity membrane layers and intermediate refractivity membrane layers, and the closest membrane layers in the same type are separated by membrane layers in different types. According to the cut-off filter for frustrating the wavelength shift, a conventional optical glass substrate and an optical plastic substrate can be used to replace a blue glass substrate or a blue plastic substrate in a conventional optical filter.

Description

technical field [0001] The invention relates to a cut-off filter for a digital image sensor, belongs to the field of optical devices, and is mainly used in image acquisition systems such as digital cameras, mobile phone cameras, and monitoring cameras. Background technique [0002] The image sensor CCD (Charge-coupled Device, charge-coupled device) and the image sensor CMOS (Complementary Metal-Oxide Semiconductor, metal oxide semiconductor element) used in digital imaging technology are photodetectors of discrete pixels. When using CCD and CMOS cameras to acquire target images, the high-frequency harmonics in the image sensor will cause a moiré effect with the fundamental frequency, resulting in Moiré fringes, which will affect the image quality. Therefore, measures must be taken to eliminate the spatial high-frequency harmonics. The image interference of the image, the optical filter came into being like this. Optical filters are often placed in front of the image sensor ...

AI Technical Summary

Problems solved by technology

[0004] However, whether blue glass substrate or blue plastic substrate is used, there are some disadvantages

For the blue glass substrate: (1) In order to ensure that the transmission-cut transition region has sufficient steepness, the blue glass substrate is required to be thicker, but this will cause aberrations such as spherical aberration and chromatic aberration; (2) This blue glass is currently It is only available in Japan, and the price is very expensive due to the shortage of supply; (3) Some properties of blue glass are poor, such as large expansion coefficient, poor chemical stability, high mechanical stress, and brittleness, so it is easy to break when cut into small pieces after coating. It is also easy to corrode, which reduces the manufacturing yield; (4) It is heavy and bulky, and its application on smartphones is subject to some restrictions

For the blue plastic substrate, (1) Although the thickness of the blue plastic substrate used is relatively thin, while alleviating the aberration, the flexibility of the blue plastic brings the problem of deformation of the substrate caused by film stress; (2) ) The blue plastic substrate is an organic material, while the thin film is an inorganic material, the adhesion of the two is very easy to fail, or the film layer is difficult to plate on the blue plastic substrate; It is still difficult to apply to large-area image sensors such as cameras

[0005] In fact, people have been trying to replace the blue glass or blue plastic substrates used in existing optical filters with other glass or plastics with good performance and low price, but they have not been able to achieve this.

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