Optical filter

Patent metadata

Field	Value
Publication number	US-2019137669-A1
Application number	US-201716095406-A
Country	US
Kind code	A1
Filing date	May 30, 2017
Priority date	Jun 9, 2016
Publication date	May 9, 2019
Grant date	—

Abstract

An optical filter including a polarizer and a visible light blocking filter is described. The polarizer is configured to transmit at least 60 percent of light in a first infrared wavelength range that is incident on the polarizer at normal incidence in a first polarization state, to transmit less than 30 percent of light in a second infrared wavelength that is incident on the polarizer at normal incidence in a second polarization state orthogonal to the first polarization state, and to transmit less than 30 percent of light in a third infrared wavelength range that is incident on the polarizer with a 50 degree angle of incidence in the second polarization state. The visible light blocking filter configured to transmit at least 60 percent of light in the first infrared wavelength range at normal incidence in the first polarization state.

First claim

1 . An optical filter comprising:
a polarizer configured to transmit at least 60 percent of light in a first infrared wavelength range that is incident on the polarizer at normal incidence in a first polarization state, the polarizer configured to transmit less than 30 percent of light in a second infrared wavelength range that is incident on the polarizer at normal incidence in a second polarization state orthogonal to the first polarization state, the polarizer configured to transmit less than 30 percent of light in a third infrared wavelength range that is incident on the polarizer with a 50 degree angle of incidence in the second polarization state; and a visible light blocking filter configured to transmit less than 30 percent of unpolarized light in a first visible wavelength range that is incident on the visible light blocking filter at normal incidence, the visible light blocking filter disposed such that light transmitted through the polarizer is incident on the visible light blocking filter, the visible light blocking filter configured to transmit at least 60 percent of light in the first infrared wavelength range that is incident on the visible light blocking filter at normal incidence in the first polarization state, wherein a wavelength range from 700 nm to 2500 nm comprises each of the first, second and third infrared wavelength ranges, and the first visible wavelength range includes at least 80 percent of a wavelength range from 400 nm to 700 nm.

2 . The optical filter of claim 1 being configured to transmit at least 60 percent of light in the first infrared wavelength range that is in the first polarization state and that is incident on the optical filter at normal incidence.

3 . The optical filter of claim 1 , wherein the first and second infrared wavelength ranges are from 800 nm to 1600 nm.

4 . The optical filter of claim 1 , wherein the third infrared wavelength range is from 800 nm to at least 1000 nm.

5 . The optical filter of claim 1 , wherein each of the second and third infrared wavelength ranges includes at least a 300 nm range.

6 . The optical filter of claim 1 , wherein the polarizer has a first order reflection band comprising the second infrared wavelength range and has at least one harmonic at least partially in the visible wavelength range.

7 . The optical filter of claim 1 , wherein the first infrared wavelength range has a width of less than 100 nm and the second infrared wavelength range is from 800 nm to 1600 nm.

8 . The optical filter of claim 7 being configured to provide a near-infrared passband for light having the first polarization state, the near-infrared passband comprising the first infrared wavelength range, the near-infrared passband having a full-width at half-maximum bandwidth of no more than 100 nm.

9 . The optical filter of claim 7 , wherein the visible light blocking filter comprises a notch filter, the notch filter configured to transmit at least 60 percent of unpolarized light in the first infrared wavelength range that is incident on the notch filter at normal incidence, the notch filter having a full-width at half-maximum bandwidth of no more than 100 nm.

10 . The optical filter of claim 7 , further comprising a notch filter disposed such that light transmitted through the polarizer is incident on the notch filter, the notch filter configured to transmit at least 60 percent of unpolarized light in the first infrared wavelength range that is incident on the notch filter at normal incidence, the notch filter having a full-width at half-maximum bandwidth of no more than 100 nm.

11 . The optical filter of claim 7 , wherein the polarizer comprises a notch filter and a broad-band polarizer, the notch filter configured to transmit at least 60 percent of unpolarized light in the first infrared wavelength range that is incident on the notch filter at normal incidence, the notch filter having a full-width at half-maximum bandwidth of no more than 100 nm, the broad-band polarizer configured to transmit at least 60 percent of light in a fourth infrared wavelength range that is incident on the broad-band polarizer at normal incidence in the first polarization state, and to transmit less than 30 percent of light in the second infrared wavelength range that is in the second polarization state and that is incident on the broad-band polarizer at normal incidence, the fourth infrared wavelength range comprising the first infrared wavelength range.

12 . The optical filter of claim 1 , wherein the first and second polarization states are circular polarization states.

13 . The optical filter of claim 1 , wherein the first and second polarization states are linear polarization states.

14 . The optical filter of claim 1 , further comprising a retarder disposed adjacent the polarizer.

15 . The optical filter of claim 14 , wherein the retarder is patterned.

16 . An optical filter comprising a polarizer, wherein the polarizer comprises a plurality of alternating polymeric layers and is configured to transmit at least 60 percent of light in a first infrared wavelength range that is incident on the polarizer at normal incidence in a first circular polarization state, the polarizer configured to transmit less than 30 percent of light in a second infrared wavelength range that is incident on the polarizer at normal incidence in a second circular polarization state orthogonal to the first polarization state, the polarizer configured to transmit less than 30 percent of light in a third infrared wavelength range that is incident on the polarizer with a 50 degree angle of incidence in the second circular polarization state, wherein a wavelength range from 700 nm to 2500 nm comprises each of the first and second infrared wavelength ranges.

17 . An optical device comprising a sensor and the optical filter of claim 1 disposed such that light entering an aperture of the sensor passes through the optical filter.

18 . The optical device of claim 17 , further comprising an near-infrared light source disposed proximate the sensor such that when the near-infrared light source emits near-infrared light though the optical filter towards a near-infrared retroreflector, the near-infrared light is reflected from the retroreflector towards the sensor.

19 . An optical system comprising at least one optical filter according to claim 1 , a near infrared light source, a sensor and a marker, wherein a light path extending from the near infrared light source to the marker and then to the sensor intersects the at least one optical filter.

20 . An optical system comprising the optical filter of claim 16 and at least one of a near infrared light source, a sensor, or a marker in optical communication with the optical filter.

Assignees

• 3M Innovative Properties Co

Inventors

• Wheatley John A
• Benoit Gilles J
• Ballen Todd A
• Smith Kenneth L
• Du Guanglei
• Kivel Edward J
• Biernath Rolf W
• Whitney Jordan D
• Schmidt Daniel J

Classifications

• G02B5/26

  Reflecting filters (G02B5/28 takes precedence) · CPC title

• G02B5/12

  Reflex reflectors · CPC title

• G02B27/281

  used for attenuating light intensity, e.g. comprising rotatable polarising elements · CPC title

• G02B5/281

  designed for the infrared light · CPC title

• G02B5/3025

  Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state (G02B5/3008, G02B5/3016 take precedence) · CPC title