Hadamard filter design

• US 4,007,989 A
• Filed: 09/29/1975
• Issued: 02/15/1977
• Est. Priority Date: 09/29/1975
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Wajda, Edward S.
• Primary Examiner(s): McGraw, Vincent P.
• Application Number:
  US05/618,308
• Time in Patent Office: 505 Days
• Field of Search: 356/96, 356/97, 356/98, 250/237 G, 350/167
• US Class Current: 356/310
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0208 using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction
• CPC Class Codes: G01J 3/0229 using masks, aperture plates, spatial light modulators or spatial filters, e.g. reflective filters
• CPC Class Codes: G01J 3/0256 Compact construction
• CPC Class Codes: G01J 3/2846 using modulation grid; Grid spectrometers

Abstract

An improved Hadamard filter is disposed between the dispersive element and detector of a Hadamard transform spectrometer. The detector has a series of linear photo-active diode elements arranged in the focal plane of an array of optical lenses. The lenses may be a series of Fly'"'"'s-Eye lenses with each series arranged to overlay the corresponding linear element of the detector, or may be a cylindrical lens overlying a corresponding detector element. Individual lenses of the Fly'"'"'s-Eye lens or individual elements of the cylindrical lens are selectively masked according to the desired matrix so as to perform the Hadamard transform spectrometry.

Claims

1. In a Hadamard transform spectrometer having a dispersive element arranged to disperse an elongated beam of spectral energy to be analyzed, the combination comprising:

a lens array disposed in the path of the dispersed beam and having a plurality of lens rows corresponding in number to at least the number of spectral elements to be analyzed, each row receiving spectral energy dispersed over a bandwidth containing such spectral elements, said array further comprising opaque means on said array providing a Hadamard mask in each lens'"'"' row,

and a photodiode array comprising a plurality of linear photodiode means corresponding to the number of lens'"'"' rows, said diode array being juxtaposed to said lens array whereby each lens'"'"' row directs the spectral energy incident thereon onto a different one of said photodiode means.

2. The combination of claim 1 wherein said lens array comprises an array of Fly'"'"'s-Eye lenses arranged with a plurality of lenses in each lens'"'"' row, and said opaque means blocks predetermined ones of said lenses.

3. The combination of claim 1 wherein said lens array comprises a plurality of elongated cylindrical lenses, and said opaque means blocks predetermined areas of said lenses.

4. The combination of claim 1 comprising:

scanning means connected to said photodiode array and operative to provide electrical signals proportional to the amount of light incident on each of said photodiode means.

5. The combination of claim 1 wherein said photodiode means comprises a semi-conductive base and an elongated area extending along a lens row and doped with a photoactive material.