Band-pass near-infrared (NIR) filter, method of production of a band-pass NIR filter and uses thereof
AssigneeSCHOTT Glass Technologies (Suzhou) Co. Ltd.
InventorsWei Xiao, Yigang Li, Guangjun Zhang
Life of this patent
Estimating the term…
Abstract
A band-pass near-infrared (NIR) filter has a glass substrate and at least one coating. The glass substrate has a scale factor that is smaller than 1500 kPa/K. The maximum internal stress of the glass substrate at an operating temperature TOT is smaller than 300 MPa. A method of production of such a band-pass NIR filter includes depositing a band-pass NIR coating that has alternating layers of high refractive index material and low refractive index material on at least one side of the glass substrate to form a coated glass substrate. Such a band-pass NIR filter can be used in an infrared sensor for object recognition.
Claims21
A method of producing a band-pass near-infrared (NIR) filter, the method comprising the following steps:
- a) providing a glass substrate having a length L0,GL at a temperature T0 and having a scale factor I that is smaller than 1500 kPa/K, wherein I is defined by the equation
- I
- =
- E
- 1
- -
- υ
- ·
- α
- ,
- wherein E is a Young's modulus of the glass substrate, v is a Poisson's ratio of the glass substrate, and a is a coefficient of thermal expansion (CTE) of the glass substrate in a range of 20° C. to 300° C.,
- b) depositing a band-pass NIR coating comprising alternating layers of a high refractive index material and a low refractive index material on at least one side of the glass substrate to form a coated glass substrate, so that the high refractive index material is in direct contact with the glass substrate and has a length LCT,HRF, wherein the glass substrate reaches a maximum temperature TCT and a maximum length LCT,GL during deposition of the coating,
- c) letting the coated glass substrate cool to the temperature T0, wherein T0 is lower than 30° C., and wherein the glass has a length L0,GL-LTS,GL when reaching T0, and wherein LTS,GL accounts for length reduction due to a decrease of fictive temperature,
- wherein the glass has a length LOT,GL-LTS,GL when being heated to an operating temperature TOT subsequent to step c) with T0<TOT<TCT,
- wherein the high refractive index material in direct contact with the glass substrate has a length LOT,HRF at temperature TOT, and
- wherein a difference
- L
- OT
- ,
- HRF
- L
- CT
- ,
- HRF
- -
- L
- O
-
- T
- ,
- G
-
- L
- -
- L
- T
-
- S
- ,
- G
-
- L
- L
- CT
- ,
- GL
- is smaller than 0.05.
A band-pass near-infrared (NIR) filter comprising:
- a glass substrate;
- and
- at least one coating,
- wherein the glass substrate has a scale factor I that is smaller than 1500 kPa/K, wherein I is defined by the equation
- I
- =
- E
- 1
- -
- υ
- ·
- α
- ,
- wherein E is a Young's modulus of the glass substrate, v is a Poisson's ratio of the glass substrate, and α is a coefficient of thermal expansion (CTE) of the glass substrate in a range of 20° C. to 300° C., and
- wherein a maximum internal stress of the glass substrate at operating temperature TOT is smaller than 300 MPa.
Dependencies are inferred from the claim text.