Multicolor infrared focal plane arrays

• US 5,157,258 A
• Filed: 08/21/1989
• Issued: 10/20/1992
• Est. Priority Date: 08/21/1989
• Status: Expired due to Fees

• Current Assignee: DRS Sensors & Targeting Systems, Inc. (Leonardo S.p.A.)
• Original Assignee: Rockwell International Corporation
• Inventors: Gluck, Natalie S., Gunning, William J. III
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US07/396,154
• Time in Patent Office: 1,156 Days
• Field of Search: 250/339, 250/332
• US Class Current: 250/339.02
• CPC Class Codes: G01J 2003/1213 Filters in general, e.g. dichroic, band
• CPC Class Codes: G01J 2003/516 with several stacked filters or stacked filter-detector pairs
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0259 Monolithic
• CPC Class Codes: G01J 3/36 Investigating two or more bands of a spectrum by separate detectors
• CPC Class Codes: G01J 5/602 using selective, monochromatic or bandpass filtering

Abstract

The multicolor focal plane array of this invention detects and distinguishes between incoming electromagnetic radiation within a first band of wavelengths and incoming electromagnetic radiation within a second band of wavelengths which includes the first wavelength band. The array includes a substrate and a two dimensional array of detectors disposed on the substrate and responsive to electromagnetic radiation within a predetermined range of wavelengths including the first and second wavelength bands. A first thin film filter is disposed on the substrate and interposed between the incoming radiation and a subset of the detectors in the array to prevent radiation outside of the first wavlength band from reaching the detectors. A second thin film filter is disposed on the substrate and interposed between the incoming radiation and all of the detectors in the array to prevent radiation outside of the second wavelength band from reaching the detectors in the subset. The filter design uses a double optimized approach that effectively reduces the thickness of the multilayer stack requiring lithographic patterning. A thickness of less than five microns is achieved which enables the use of a multilayer resist lift-off method. The detectors in the subset are thus made sensitive to wavelengths within the first wavelength band, while the remaining detectors are sensitive to wavelengths within both the first and second wavelength bands.

Claims

1. A multicolor focal plane array for detecting and distinguishing between incoming electromagnetic radiation within a first band of wavelengths and incoming electromagnetic radiation within a second band of wavelengths which includes the first wavelength band, comprising:

a substrate;

a two dimensional array of detectors disposed on the substrate and responsive to electromagnetic radiation within a predetermined range of wavelengths including the first and second wavelength bands;

a first thin film filter disposed on the substrate and interposed between the incoming radiation and a subset of the detectors in the array to prevent radiation outside of the first wavelength band from reaching the detectors; and

a second thin film filter disposed on the substrate and interposed between the incoming radiation and all of the detectors in the array;

thereby rendering the detectors in the subset sensitive to radiation within the first wavelength band and the remaining detectors sensitive to radiation within both the first and second wavelength bands.

2. The array of claim 1, wherein the first filter further comprises alternating layers of Ge and CaF₂ and the second filter further comprises alternating layers of Ge and ZnS.

3. A method of making a multicolor focal plane array for detecting and distinguishing between incoming electromagnetic radiation within a first band of wavelengths and incoming electromagnetic radiation within a second band of wavelengths which includes the first wavelength band, comprising the steps of:

providing a substrate;

fabricating on the substrate a two dimensional array of detectors which are responsive to electromagnetic radiation within a predetermined range of wavelengths including the first and second wavelength bands;

depositing a multilayer resist pattern on the substrate over the detector array;

depositing a first thin film filter on the substrate over the multilayer resist pattern;

lifting off the resist and portions of the first filter to leave the first filter interposed between the incoming radiation and a subset of the detectors in the array, thereby preventing radiation outside of the first wavelength band from reaching the detectors in the subset; and

depositing a second thin film filter on the substrate over the first filter and interposed between the incoming radiation and all of the detectors in the array,

thereby rendering the detectors in the subset sensitive to radiation within the first wavelength band and the remaining detectors sensitive to radiation within both the first and second wavelength bands.

4. A method of claim 3, wherein the step of depositing a first thin film filter further comprises the step of:

depositing alternating layers of Ge and CaF₂ on the substrate;

and wherein the step of depositing a second thin film filter further comprises the step of;

depositing alternating layers of Ge and ZnS on the substrate.