INFRARED RECEIVER FOR OPTICAL RADAR

• US 3,746,454 A
• Filed: 03/03/1971
• Issued: 07/17/1973
• Est. Priority Date: 03/03/1971
• Status: Expired due to Term

• Current Assignee: Frank P. Pace, Frank R. Arams, Ronald A. Lange
• Original Assignee: Frank P. Pace, Frank R. Arams, Ronald A. Lange
• Inventors: Pace, Frank P., Lange, Ronald A., Arams, Frank R.
• Primary Examiner(s): Borchelt, Benjamin A.
• Assistant Examiner(s): Buczinski, S. C.
• Application Number:
  US05/120,564
• Time in Patent Office: 867 Days
• Field of Search: 350/167 250/83.3H,22M,204 62/DIG.9 356/152,4,5,141
• US Class Current: 356/139.08
• CPC Class Codes: G01J 1/0209 Monolithic
• CPC Class Codes: G01J 1/04 Optical or mechanical part supplementary adjustable parts
• CPC Class Codes: G01J 1/0411 using focussing or collimating elements, i.e. lenses or mirrors; Aberration correction
• CPC Class Codes: G01J 1/0422 using light concentrators, collectors or condensers
• CPC Class Codes: G01J 1/4228 arrangements with two or more detectors, e.g. for sensitivity compensation
• CPC Class Codes: G01S 17/06 Systems determining position data of a target
• CPC Class Codes: G02F 2/002 using optical mixing

Abstract

There is disclosed a receiver for an optical radar utilizing a two-dimensional array of microlens image dissectors which completely fills an area of an image plane. Each microlens is directly coupled to a mixer-detector element. The array is adapted to be illuminated with returned focus radiation from a remote reflecting target and with a planar wave of optical energy from a local oscillator. The output signals of the mixerdetectors are analyzed and utilized to orientate the array such that the maximum amplitude output signal corresponds to the central microlens of the array.

Claims

1. Apparatus for use in an optical radar system of the type employing a pulsed laser as the transmitting means, the combination of a multiplicity of microlenses arranged in a two-dimensional array such that the front radiant energy receiving surfaces of said microlenses completely fill an area of an image plane;

a mixer-detector element contacting the back surface of each microlens;

means for illuminating the front surfaces of said array of microlenses with a planar wave of optical radiation whose frequency differs from that of said pulsed laser, said planar wave of optical radiation acting within said mixer-detectors as a heterodyning signal with any laser radiation returned from any remote reflecting target within the field of view of said array and focused thereon; and

means responsive to the amplitude of the signals appearing in the outputs of said mixer-detector elements for positioning said array of microlenses such that the longitudinal axis of symmetry of a central microlens of said array is spatially aligned with said remote reflecting target.

2. In an arrangement as defined in claim 1 wherein the contacting area of each mixer-detector element is of the same size as the back surface of each microlens.

3. In an arrangement as defined in claim 1 wherein said microlenses are made of germanium and said detector-mixer elements are made of a germanium-copper mixture whenever the pulsed laser is operating in the 10.6 micron region of the spectrum.

4. In an arrangement as defined in claim 1 wherein the back surface of each microlens is planar and each mixer-detector element is of generally rectangular shape with its length considerably greater than its width.

5. In an arrangement as defined in claim 1 wherein said multiplicity of microlenses are arranged in horizontal rows and vertical columns and wherein a microstrip transmission line is connected to the output of each mixer-detector element, the microstrip transmission lines connected to those mixer-detector elements which contact a particular row of microlenses having a fanout pattern so as to minimize those portions of these microstrip transmission lines which are parallel to each other.

6. In an arrangement as defined in claim 5 wherein the microlenses, the mixer-detector elements and the microstrip transmission lines are conductibly cooled to a cryogenic temperature for minimizing thermionic noise and random interference.