Near-infrared absorbing filter and image sensor
The present disclosure provides a near-infrared absorbing filter, including an absorbing type infrared filtering medium having opposite first and second surfaces; an organic coating layer formed on the first surface of the absorbing type filtering medium for absorbing infrared rays; a first multi-layered film structure formed on the organic coating layer with the organic coating layer disposed between the first multi-layered film structure and the absorbing type infrared filtering medium; and a second multi-layered film structure formed on the second surface of the absorbing type infrared filtering medium. The near-infrared filter of the present disclosure is able to reduce the wavelength difference of T50 and T20 of the incident light within the range of from 0 to 30 degrees to less than 5 nm, thereby reducing chromatic aberration effectively and reducing ghost images of infrared reflections. The disclosure further provides an image sensor including the near-infrared absorbing filter.
1. A near-infrared absorbing filter, comprising:
an absorbing type infrared filtering medium having opposite first and second surfaces;
an organic coating layer formed on the first surface of the absorbing type filtering medium and configured to absorb infrared rays, wherein the organic coating layer has a central wavelength (T50) between 630 nm and 680 nm and has an average transmission (T avg ) of less than 8% for wavelength in a range of from 700 nm to 725 nm;
a first multi-layered film structure formed on the organic coating layer with the organic coating layer disposed between the first multi-layered film structure and the absorbing type infrared filtering medium, wherein the central wavelength of the first multi-layered film structure is between 700 nm and 730 nm; and
a second multi-layered film structure formed on the second surface of the absorbing type infrared filtering medium, wherein the central wavelength of the second multi-layered film structure is between 700 nm and 730 nm.
2. The near-infrared absorbing filter of claim 1 , wherein the absorbing type infrared filtering medium comprises at least one of P 2 O 5 and CuO.
3. The near-infrared absorbing filter of claim 1 , wherein the absorbing type infrared filtering medium is phosphate-based infrared filter glass.
4. The near-infrared absorbing filter of claim 3 , wherein the phosphate-based infrared filter glass is fluorophosphate-based infrared filter glass.
5. The near-infrared absorbing filter of claim 4 , wherein the fluorophosphate-based infrared filter glass comprises at least one of P 2 O 5 and CuO.
6. The near-infrared absorbing filter of claim 4 , wherein the fluorophosphate-based infrared filter glass has at least one fluoride selected from the group consisting of AlF 3 , LiF, MgF 2 , CaF 2 , SrF 2 , and BaF 2 .
7. The near-infrared absorbing filter of claim 1 , wherein the absorbing type infrared filtering medium has a thickness of from 0.15 mm to 1.5 mm.
8. The near-infrared absorbing filter of claim 1 , wherein the organic coating layer has a thickness of from 0.1 μm to 10 μm.
9. The near-infrared absorbing filter of claim 1 , wherein the organic coating layer comprises at least one of an organic pigment and a polymer.
10. The near-infrared absorbing filter of claim 9 , wherein the organic pigment is at least one selected from the group consisting of an azo compound, a diimmonium compound, a dithiophenol-metal complex, a phthalocyanine compound, a squaraine compound, and a cyanine compound.
11. The near-infrared absorbing filter of claim 9 , wherein the polymer is at least one selected from the group consisting of polyester, polyacrylate, polyolefin, polycarbonate, polycycloolefin, polyurethane, epoxy, polyether, and polyvinyl butyral.
12. The near-infrared absorbing filter of claim 1 , wherein at least one of the first multi-layered film structure and the second multi-layered film structure is one selected from the group consisting of an infrared reflecting multi-layered film, an ultraviolet-infrared reflecting multi-layered film, and an antireflective multi-layered film.
13. The near-infrared absorbing filter of claim 1 , wherein each of the first multi-layered film structure and the second multi-layered film structure comprises 4 to 50 layers of films.
14. The near-infrared absorbing filter of claim 13 , wherein each layers of the films is composed of at least one material selected from the group consisting of TiO 2 , SiO 2 , Y 2 O 3 , MgF 2 , Al 2 O 3 , Bi 2 O 3 , Gd 2 O 3 , LaF 3 , Nb 2 O 5 , AlF 3 , PbTe, Sb 2 O 3 , SiO, SiN, Ta 2 Os, ZnS, ZnSe, ZrO 2 , and Na 3 AlF 6 .
15. The near-infrared absorbing filter of claim 13 , wherein each layers of the films is composed of TiO 2 and SiO 2 alternately laminated to each other.
16. The near-infrared absorbing filter of claim 1 , wherein at least one of the first multi-layered film structure and the second multi-layered film structure has a thickness of from 0.2 μm to 5 μm.
17. An image sensor, comprising:
a lens module comprising a lens and the near-infrared absorbing filter of claim 1 arranged on a light transmission path of the lens; and
an image sensing element disposed at one side of the lens module with the near-infrared absorbing filter disposed between the lens and the image sensing element.