Apparatus for image multispectral sensing employing addressable spatial mask

• US 5,867,264 A
• Filed: 10/15/1997
• Issued: 02/02/1999
• Est. Priority Date: 10/15/1997
• Status: Expired due to Fees

• Current Assignee: Pacific Advanced Technology, Inc. (PAT Industries, Inc.)
• Original Assignee: Pacific Advanced Technology, Inc. (PAT Industries, Inc.)
• Inventors: Hinnrichs, Michele
• Primary Examiner(s): EVANS, FANNIE L
• Application Number:
  US08/950,928
• Time in Patent Office: 475 Days
• Field of Search: 356/310, 356/326, 356/328, 356/330
• US Class Current: 356/310
• CPC Class Codes: G01J 3/04 Slit arrangements slit adjustment
• CPC Class Codes: G01J 3/2846 using modulation grid; Grid spectrometers
• CPC Class Codes: G01J 3/457 Correlation spectrometry, e.g. of the intensity G01J3/453 takes precedence

Abstract

An apparatus for spectral detection of remote objects. The apparatus consists of an input optic which focuses the field of view onto an image receiving surface consisting of an addressable spatial mask. The mask sequentially projects portions of the scene onto a diffractive optical element which focuses onto a photodetector array. The first image receiving surface of mask is partitioned into independently addressable and controllable subsurfaces, or gates, adapted to receive an electronic control signal from a programmable control signal generator. Each gate in the receiving mask directs a portion of the image incident thereon to a diffractive lens in response to a control signal communicated thereto. This gated image is dispersed by the diffractive lens and focused upon the photosensitive surface of a photodetector array. The photodetector array is partitioned into pixels having a number in ratio to the gates in the addressable mask. The signal output of a pixel within the optical path of the dispersed gated light is sampled and stored in a signal processor. A control signal generator sequentially or randomly addresses each gate in the mask causing the gate to direct that portion of the image thereon to the diffractive lens. The output signal from each pixel on the photodetector array corresponding to the addressed gate in the mask is sampled and stored until the entire image is recorded. This process is repeated as the diffractive optic is scanned through the spectral range of interest. The mask provides enhanced spectral and spatial resolution of the scene.

Claims

1. An apparatus for measuring the spectral composition of light emanating from a remote target comprising:

(a) an input optical element adapted to receive and transmit said light emanating from a remote target; and

(b) a diffractive optical element having an optical axis and disposed to receive said light transmitted by said input optical element and adapted to disperse spectral components of said light into a volume having an area A and a length L; and

(c) an addressable spatial mask disposed between said input optical element and said diffractive optical element comprising a sheet having a planar array of discrete addressable switchable apertures disposed thereon, said apertures being independently operable for directing a controllable portion of said light incident thereon to said diffractive optical element in response to a control signal; and

(d) a photodetector array with pixels having an area substantially equal to the pixel footprint at the addressable mask, said photodetector array being disposed to receive dispersed light from said diffractive optical element; and

(e) means for measuring said controllable portion of said light that is focused upon said photodetector array, said measured controllable portion comprising an image; and

(f) means for changing the distance between said diffractive optical element and said photodetector array in the direction of L; and

(g) means for controlling the direction of said light incident upon each of said plurality of apertures of said addressable spatial mask to impinge upon said diffractive optical element; and

(h) means for measuring said distance between said diffractive optical element and said photodetector array;

said spectral composition of light emanating from said remote target being determined by combining the images for each position along L.

2. The apparatus of claim 1, wherein said diffractive optical element is a diffractive lens.

3. The apparatus of claim 1, wherein said diffractive optical element is a diffractive mirror.

4. The apparatus of claim 1 wherein said diffractive optical element is a reflective mirror.

5. The apparatus of claim 1 wherein said diffractive optical element is a transmissive lens.

6. The apparatus of claim 1 wherein said addressable spatial mask comprises a plurality of discrete controllable optically reflective surfaces.

7. The apparatus of claim 1 wherein said addressable spatial mask comprises a plurality of discrete controllable optically transmissive surfaces.

8. The apparatus of claim 1 wherein said means for controlling the direction of said light incident upon each of said plurality of apertures of said addressable spatial mask is an electronic signal.