TW201512708A - Infrared cut filter - Google Patents

Abstract

The present disclosure relates to an infrared cut filter. The filter includes a substrate and a filter film formed on the substrate. The filter film includes a number of high refractive layers and low refractive layers alternately stacked on the substrate. The filter film can be represented by (aHbL)<SP>n</SP>, wherein aH represents the high refractive layer, bL represents the low refractive layer, a, b are coefficients, a ratio of a:b ranges from about 2 to about 15, H, L respectively represent high refractive material and low refractive material of a thickness of about 1/4 cut wavelength, and n is the number of (aHbL).

Description

Infrared cut filter

The present invention relates to a filter, and more particularly to an infrared cut filter.

The existing infrared cut filter shifts with the incident angle. Observed at a wavelength corresponding to a transmittance of 50% (indicated as T50), when the incident angle deviates from 0 degrees (normal incidence) to 30 degrees (30 degrees from the vertical direction), T50 may occur in the short-wave direction (blue end). 28 nm offset (ie blue-shift). That is to say, the infrared light of the short-wave portion originally cut off may pass through the infrared cut filter as the incident angle increases, thereby entering the imaging module applying the infrared cut filter, affecting the imaging quality.

In view of this, it is necessary to provide an infrared cut filter that improves quality.

An infrared cut filter comprising a substrate and a filter film disposed on the substrate, the filter film comprising a plurality of layers of high refractive index layers and a plurality of layers of low refractive index stacked on the substrate in sequence. The structure of the filter film is (aHbL) ⁿ , wherein aH is the high refractive index layer, bL is the low refractive index layer, a and b are coefficients and a:b is 2-15, and H and L respectively represent 1 /4 High refractive index material and low refractive index material of cutoff wavelength thickness, n represents the number of (aHbL).

The experiment proves that the wavelength corresponding to the transmittance of 50% (indicated as T50) is observed. When the incident angle is increased from 0 to 30 degrees, the offset of T50 to the short-wave direction is less than 15 nm, that is, the quality is obtained. improve.

1 is a schematic cross-sectional view of an infrared cut filter according to a preferred embodiment of the present invention.

2 is a graph showing a wavelength-transmittance characteristic of the infrared cut filter of FIG. 1.

Referring to FIG. 1 , an infrared cut filter 10 according to a preferred embodiment of the present invention includes a substrate 11 and a filter film 12 disposed on the substrate 11. The filter film 12 includes a stack of disks in sequence. A plurality of high refractive index layers 121 and a plurality of low refractive index layers 122 on the substrate 11. The structure of the filter film 12 is (aHbL) ⁿ , wherein aH is the high refractive index layer 121, bL is the low refractive index layer 122, a and b are coefficients and a:b is 0.6-1, H, L A high refractive index material and a low refractive index material each representing a 1/4 cutoff wavelength thickness, and n represents the number of (aHbL).

Referring to FIG. 2, the wavelength-transmittance characteristic curve A of the infrared cut filter 10 and the wavelength-transmittance of the infrared cut filter 10 when the incident angle is 0 degrees can be obtained experimentally. The characteristic curve B shows that the wavelength-transmittance characteristic curve of the infrared cut filter 10 is shifted in the short-wave direction after the incident angle is increased, however, the wavelength corresponding to the transmittance of 50% (indicated as T50) is observed. In the process of increasing the incident angle from 0 degrees to 30 degrees, the offset S of the T50 to the short-wave direction is less than 15 nm, that is, the quality is improved.

Specifically, the substrate 11 can be a glass substrate, a plastic substrate, a glass lens or a plastic lens. Among them, the substrate is flat and does not have an imaging function.

The high refractive index material is trititanium pentoxide or tantalum pentoxide. aH indicates that the optical film thickness of the high refractive index layer 121 is a/4 cutoff wavelength. The cutoff wavelength is generally defined as the wavelength at which the transmittance drops to about 3%. As an example, in the present embodiment, the cutoff wavelength is 700 nm.

The low refractive index material is cerium oxide. bL indicates that the optical film thickness of the low refractive index layer 122 is a b/4 cutoff wavelength.

A:b is 2-15 specifically indicating that the ratio of a to b is between 2 and 15, which is an important factor for improving the blue-end shift of the infrared cut filter of the present embodiment.

The multilayer high refractive index layer 121 and the plurality of low refractive index layers 122 are sequentially stacked on the substrate 11 to mean that the first layer of the high refractive index layer 121 is disposed on the substrate 11, and the first layer of the low refractive index layer 122 is disposed on the high refractive index layer 121 to constitute a first one (aHbL), and then a plurality of remaining (aHbL) are sequentially stacked on the first one (aHbL).

In the present embodiment, the value of n is between 10 and 20.

10‧‧‧Infrared cut filter

11‧‧‧Base

12‧‧‧Filter film

121‧‧‧High refractive index layer

122‧‧‧Low refractive index layer

no

10‧‧‧Infrared cut filter

11‧‧‧Base

12‧‧‧Filter film

121‧‧‧High refractive index layer

122‧‧‧Low refractive index layer

Claims (4)

An infrared cut filter comprising a substrate and a filter film disposed on the substrate, the filter film comprising a plurality of layers of high refractive index layers and a plurality of layers of low refractive index stacked on the substrate in sequence. The structure of the filter film is (aHbL) ⁿ , wherein aH is the high refractive index layer, bL is the low refractive index layer, a and b are coefficients and a:b is 2-15, and H and L respectively represent 1 /4 High refractive index material and low refractive index material of cutoff wavelength thickness, n represents the number of (aHbL). The infrared cut filter according to claim 1, wherein the high refractive index material is trititanium pentoxide or tantalum pentoxide. The infrared cut filter of claim 1, wherein the low refractive index material is cerium oxide. The infrared cut filter of claim 1, wherein n is 10 to 20.