Optical filter and optical system

An optical stack comprising:

• a first optical filter comprising a plurality of alternating first and second polymeric layers numbering at least 50 in total, each polymeric layer having an average thickness less than about 500 nm, such that for substantially normally incident light and for a visible wavelength range extending from about 420 nm to about 550 nm and an infrared wavelength range extending from about 650 nm to about 800 nm and for at least a first polarization state, the first optical filter has an average optical transmission of greater than about 50% in the visible wavelength range, an average optical reflection of greater than about 90% in the infrared wavelength range, and an optical reflection of greater than about 80% at a first wavelength in a range of about 700 nm to about 900 nm;
• and
• a second optical filter disposed on the first optical filter and comprising a peak absorption at the first wavelength,
• wherein the optical stack has an optical density greater than about 2 throughout the infrared wavelength range.

An optical filter comprising a plurality of alternating first and second polymeric layers numbering at least 50 in total, each polymeric layer having an average thickness less than about 500 nm, such that for substantially normally incident light and for a visible wavelength range extending from about 420 nm to about 550 nm, a near infrared wavelength range extending from about 650 nm to about 800 nm, a far infrared wavelength range extending from about 950 nm to at least about 1050 nm, and for at least a first polarization state, the optical filter has:

• an average optical transmission of greater than about 50% in each of the visible and far infrared wavelength ranges;
• an optical density greater than about 2 throughout the near infrared wavelength range;
• and
• an optical transmission at a first wavelength between the near and far infrared wavelength ranges that is about 50% of the average optical transmission of the optical filter in the far infrared wavelength range;
• wherein at least one layer in the plurality of alternating first and second polymeric layers has an absorption peak at a second wavelength between the near and far infrared wavelength ranges, and wherein for light incident on the optical filter at an incident angle of at least about 45 degrees, the first wavelength shifts to a third wavelength less than the second wavelength.

An optical filter comprising a plurality of alternating first and second polymeric layers numbering at least 50 in total, each polymeric layer having an average thickness less than about 500 nm, such that for substantially normally incident light and for a visible wavelength range extending from about 450 nm to about 550 nm, a near infrared wavelength range extending from about 650 nm to about 800 nm, a far infrared wavelength range at least about 100 nm wide and disposed such that the near infrared wavelength range is between the visible and far infrared wavelength ranges, and for at least a first polarization state, the optical filter has:

• an average optical transmission of greater than about 75% in each of the visible and far infrared wavelength ranges;
• an optical density greater than about 2 throughout the near infrared wavelength range;
• and
• an optical transmission at a first wavelength between the near and far infrared wavelength ranges that is about 10% of the average optical transmission of the optical filter in the visible wavelength range;
• wherein at least one layer in the plurality of alternating first and second polymeric layers has an absorption peak at a second wavelength in a range from about 700 nm to about 900 nm, and wherein for light incident on the optical filter at an incident angle of at least about 45 degrees, the first wavelength shifts to a third wavelength less than the second wavelength.