INFRARED-CUT FILTER WITH SAPPHIRE SUBSTRATE AND LENS MODULE

Abstract

An IR-cut filter includes a substrate and a film. The substrate made of sapphire. The film is covered on the substrate and is configured for increasing reflectivity of infrared lights and filtering the infrared lights. The film includes a plurality of high refractive index layers and a plurality of low refractive index layers alternately stacked on the substrate. The refractive index of the high refractive index layers is greater than about 2.0, and the refractive index of the low refractive index layers is lower than about 1.5.

Description

BACKGROUND

1. Technical Field

The present disclosure relates to infrared-cut (IR-cut) filters, and particularly, to an IR-cut filter and a lens module including the IR-cut filter.

2. Description of Related Art

Sapphires have excellent hardness and wear-resistance, and are used in optics and machinery. The sapphire can be used as a cover glass to protect lenses received in a lens module. However, quality of images captured by the lens module may be affected by infrared light, as the sapphire transmits infrared light.

Therefore, it is desirable to provide an IR-cut filter and a lens module, which can overcome the limitations described.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional schematic view of an IR-cut filter in accordance with an exemplary embodiment.

FIG. 2 is a graph showing a spectrum characteristic curve of the IR-cut filter of FIG. 1.

FIG. 3 is a cross-sectional schematic view of a lens module using the IR-cut filter of FIG. 1.

DETAILED DESCRIPTION

Embodiments of the disclosure will be described with reference to the drawings.

Referring to FIG. 1, an IR-cut filter 100, according to an exemplary embodiment is shown. The IR-cut filter 100 is configured to filter out (i.e., reject) infrared light and transmit (i.e., pass) visible light. The IR-cut filter 100 includes a substrate 10 and a film 20 formed on the substrate 10.

The substrate 10 is plate shaped and is made of sapphire. Sapphire is a gemstone variety of the mineral corundum, and has a hexagonal crystal structure. The main chemical component of sapphire is aluminum oxide, and the refractive index of the sapphire is from about 1.76 to about 1.78. A transmissivity of the substrate 10 at infrared wavelengths from about 825 nm to about 1300 nm is greater than 85%. The substrate 10 includes a first surface 11 and a second surface 12 opposite to the first surface 11.

The film 20 is configured to increase the reflectivity of the substrate 10 at the infrared lights, and is coated on the substrate 10 by a sputter method or an evaporation method. The film 20 includes a number of high refractive index layers and a number of low refractive index layers alternately stacked on the substrate 10. The refractive index of the high refractive index layer is greater than about 2.0, and the refractive index of the low refractive index layers is lower than about 1.5. In this embodiment, a material of the high refractive index layers can be selected from the group consisting of titanium dioxide (TiO₂), niobium pentoxide (Nb₂O₅), or tantalum pentoxide (Ta₂O₅), and a material of the low refractive index layers can be silicon dioxide (SiO₂).

The film 20 is comprised of about 60 to 70 layers. In this embodiment, the film 20 is stacked by a first layer to a seventieth layer in an order facing away from the first surface 11. The high refractive index layers are the odd number layers, and the low refractive index layers are the even number layers. The structure of the film 20 is (0.2 H, 0.3 L, 2 H, 0.3 L, 0.2 H, 2 L) (0.5 H) (0.2 L, 0.3 H, 2 L, 0.3 H, 0.2 L, 2 H) (2 L, 2 H)¹⁰ (0.2 L, 0.3 H, 2 L, 0.3 H, 0.2 L, 2 H)⁶ (1 L), wherein H represents as a quarter of thickness of a reference wavelength of the high refractive index layers, L represents as a quarter of thickness of a reference wavelength of the low refractive index layers, and the reference wavelength is about 463 nm.

In the embodiment, the film 20 is coated on the first surface 11 of the substrate 10. The material and thickness of each layer of the film 20 are shown in Table 1. The error of the optical thickness of each layer is ±0.01, and the error of the physics thickness of each layer is ±1.

TABLE 1
			Physics Thickness
Layers	Material	Optical Thickness	(nm)
First layer	TiO2	0.26	12
Second layer	SiO2	0.47	37
Third layer	TiO2	2.42	111
Fourth layer	SiO2	0.35	27
Fifth layer	TiO2	0.17	8
Sixth layer	SiO2	2.05	160
Seventh layer	TiO2	0.42	19
Eighth layer	SiO2	0.56	43
Ninth layer	TiO2	0.31	14
Tenth layer	SiO2	1.32	103
Eleventh layer	TiO2	0.17	8
Twelfth layer	SiO2	0.56	44
Thirteenth layer	TiO2	2.20	101
Fourteenth layer	SiO2	2.13	165
Fifteenth layer	TiO2	2.08	95
Sixteenth layer	SiO2	2.04	159
Seventeenth layer	TiO2	2.08	96
Eighteenth layer	SiO2	2.06	161
Nineteenth layer	TiO2	2.02	93
Twentieth layer	SiO2	2.06	160
Twenty first layer	TiO2	2.09	96
Twenty second layer	SiO2	2.05	159
Twenty third layer	TiO2	2.06	95
Twenty fourth layer	SiO2	2.10	163
Twenty fifth layer	TiO2	2.11	97
Twenty sixth layer	SiO2	2.07	161
Twenty seventh layer	TiO2	2.17	100
Twenty eighth layer	SiO2	2.25	175
Twenty ninth layer	TiO2	2.35	108
Thirtieth layer	SiO2	2.34	182
Thirty first layer	TiO2	2.43	112
Thirty second layer	SiO2	2.35	183
Thirty third layer	TiO2	2.30	106
Thirty fourth layer	SiO2	0.16	12
Thirty fifth layer	TiO2	0.17	8
Thirty sixth layer	SiO2	2.29	178
Thirty seventh layer	TiO2	0.56	25
Thirty eighth layer	SiO2	0.16	13
Thirty ninth layer	TiO2	2.00	92
Fortieth layer	SiO2	0.38	29
Forty first layer	TiO2	0.42	19
Forty second layer	SiO2	1.92	149
Forty third layer	TiO2	0.18	8
Forty fourth layer	SiO2	0.51	39
Forty fifth layer	TiO2	2.28	105
Forty sixth layer	SiO2	0.16	12
Forty seventh layer	TiO2	0.25	11
Forty eighth layer	SiO2	2.15	167
Forty ninth layer	TiO2	0.29	13
Fiftieth layer	SiO2	0.17	13
Fifty first layer	TiO2	2.24	103
Fifty second layer	SiO2	0.36	28
Fifty third layer	TiO2	0.28	13
Fifty fourth layer	SiO2	2.25	175
Fifty fifth layer	TiO2	0.33	15
Fifty sixth layer	SiO2	0.33	26
Fifty seventh layer	TiO2	2.30	106
Fifty eighth layer	SiO2	0.30	23
Fifty ninth layer	TiO2	0.31	14
Sixtieth layer	SiO2	1.99	155
Sixty first layer	TiO2	0.24	11
Sixty second layer	SiO2	0.35	27
Sixty third layer	TiO2	2.14	98
Sixty fourth layer	SiO2	0.20	15
Sixty fifth layer	TiO2	0.31	14
Sixty sixth layer	SiO2	1.97	153
Sixty seventh layer	TiO2	0.18	8
Sixty eighth layer	SiO2	0.31	24
Sixty ninth layer	TiO2	2.29	105
Seventieth layer	SiO2	1.17	91

In other embodiments, the high refractive index layer and the low refractive index layer can be other materials. The number of layers and the thickness of each layer can be designed according to actual requirement.

Referring to FIG. 2, a graph showing a spectrum of the IR-cut filter 100 is illustrated. The transmissivity of the substrate 10 at the infrared wavelengths from about 825 nm to about 1300 nm is lower than about 2%. The infrared lights are filtered after the lights passing through the IR-cut filter 100.

Referring to FIG. 3, a lens module 200, according to an exemplary embodiment, includes the IR-cut filter 100, a lens barrel 110, and at least one lens 120. The lens barrel 110 includes an object side 111 and an image side 112 opposite to the object side 111. A receiving room 113 is formed in the lens barrel 110 between the object side 111 and the image side 112. The lens barrel 110 defines a light entering hole 114 communicating with the receiving room 113 and positioned on the object side 111. The at least one lens 120 is received in the receiving room 113. The IR-cut filter 100 covers the object side 111, and the light entering hole 114 is sealed by the IR-cut filter 100. The IR-cut filter 100 not only can filter the infrared lights and transmit the visible light, but also can protect the lens module 200 from being damaged by an external force.

It should be understood that the IR-cut filter 100 can be received in the receiving room 113 or positioned on the image side 112 for filtering the infrared lights from the lights projected into the light entering hole 114.

Particular embodiments are shown and described by way of illustration only. The principles and the features of the present disclosure may be employed in various and numerous embodiments thereof without departing from the scope of the disclosure as claimed. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure.

Claims

1. An IR-cut filter, comprising: a substrate made of sapphire; anda film covered on the substrate and configured for increasing reflectivity of infrared lights and filtering the infrared lights; the film comprising a plurality of high refractive index layers and a plurality of low refractive index layers alternately stacked on the substrate, a refractive index of the high refractive index layers is greater than about 2.0, and a refractive index of the low refractive index layers is lower than about 1.5.

2. The IR-cut filter of claim 1, wherein a material of the high refractive index layers is selected from the group consisting of titanium dioxide (TiO2), niobium pentoxide (Nb2O5), and tantalum pentoxide (Ta2O5), and a material of the low refractive index layers is silicon dioxide (SiO2).

3. The IR-cut filter of claim 1, wherein the film is comprised of about 60 to 70 layers.

4. The IR-cut filter of claim 3, wherein the film is stacked by a first layer to a seventieth layer in an order facing away from the substrate.

5. The IR-cut filter of claim 4, wherein the structure of the film is (0.2 H, 0.3 L, 2 H, 0.3 L, 0.2 H, 2 L) (0.5 H) (0.2 L, 0.3 H, 2 L, 0.3 H, 0.2 L, 2 H) (2 L, 2 H)10 (0.2 L, 0.3 H, 2 L, 0.3 H, 0.2 L, 2 H)6 (1 L), wherein H represents as a quarter of thickness of a reference wavelength of the high refractive index layers, L represents as a quarter of thickness of a reference wavelength of the low refractive index layers, and the reference wavelength is about 463 nm.

6. A lens module, comprising: a lens barrel comprising an object side and an image side opposite to the object side, the lens barrel defining a receiving room between the object side and the image side, the lens barrel defining a light entering hole communicating with the receiving room and positioned on the object side;at least one lens received in the receiving room; andan IR-cut filter covering the light entering hole, the IR-cut filter comprising: a substrate made of sapphire; anda film covered on the substrate and configured for increasing reflectivity of infrared lights and filtering the infrared lights; the film comprising a plurality of high refractive index layers and a plurality of low refractive index layers alternately stacked on the substrate, a refractive index of the high refractive index layers is greater than about 2.0, and a refractive index of the low refractive index layers is lower than about 1.5.

7. The lens module of claim 6, wherein a material of the high refractive index layers is selected from the group consisting of titanium dioxide (TiO2), niobium pentoxide (Nb2O5), and tantalum pentoxide (Ta2O5), and a material of the low refractive index layers is silicon dioxide (SiO2).

8. The lens module of claim 6, wherein the film is comprised of about 60 to 70 layers.

9. The lens module of claim 8, wherein the film is stacked by a first layer to a seventieth layer in an order facing away from the substrate.

10. The lens module of claim 9, wherein the structure of the film is (0.2 H, 0.3 L, 2 H, 0.3 L, 0.2 H, 2 L) (0.5 H) (0.2 L, 0.3 H, 2 L, 0.3 H, 0.2 L, 2 H) (2 L, 2 H)10 (0.2 L, 0.3 H, 2 L, 0.3 H, 0.2 L, 2 H)6 (1 L), wherein H represents as a quarter of thickness of a reference wavelength of the high refractive index layers, L represents as a quarter of thickness of a reference wavelength of the low refractive index layers, and the reference wavelength is about 463 nm.