BALANCED TILTABLE, ROTATING MIRROR WITH ITS OPTICAL AXIS ANGULARLY OFFSET FROM ITS AXIS OF ROTATION

• US 3,733,133 A
• Filed: 03/13/1970
• Issued: 05/15/1973
• Est. Priority Date: 03/13/1970
• Status: Expired due to Term

• Current Assignee: Arthur S. Chapman
• Original Assignee: Arthur S. Chapman
• Inventors: Chapman, Arthur S.
• Primary Examiner(s): Feinberg, Samuel
• Assistant Examiner(s): Buczinski, S. C.
• Application Number:
  US05/019,374
• Time in Patent Office: 1,159 Days
• Field of Search: 356/152,141 244/3.13,3.16 350/289,307,285,7 250/236
• US Class Current: 356/141.4
• CPC Class Codes: F41G 7/303 Sighting or tracking devices especially provided for simultaneous observation of the target and of the missile

Abstract

The mirror, such as a mangin-mirror, is useful in a system which automatically detects a deviation between a target and an object moving towards the target by comparing the line of sight to the target and the line of sight to the object. The mirror has a first axis about which it rotates and an optical axis which is displaced at an angle from the rotational axis. The rotational axis is kept coaxial with the target line of sight. The mirror is selectively tiltable to one of two discrete positions about its optical axis so that, as the mirror rotates, the reflection from the object forms two images, corresponding to the two mirror positions which conically scan a detector plane. Two pairs of right-angled light detectors, one for each position, are located on the plane. By comparing the time intervals for each pair of detectors when the reflection crosses the detectors, the deviation can be calculated, and by other equipment corrections in the path of the object can be made.

Claims

1. Apparatus for sensing deviation of an object having a light source from a target comprising:

sensor means separated from the object and disposed at a particular detector plane;

imaging means for forming an image of the light source on the detection plane, said imaging means having a predetermined optical axis;

means for rotating said imaging means on an axis of rotation coaxial with a line extending to the target, the optical axis of said imaging means angled from the axis of rotation and crossing the axis of rotation at an intersection, to produce movement of the image generally in a circular path on the detector plane;

means responsive to said sensor means and the angular position of said imaging means about the axis of rotation, for sensing the deviation of the object from the target; and

mass means including said imaging means having a physical distribution of mass evenly distributed about the intersection of three substantially equal orthogonal moments of inertia.

2. The apparatus described in claim 1 including:

means for tilting said imaging means about the intersection during rotation thereof at a selected one of a plurality of angles different from the axis of rotation.

3. The apparatus described in claim 1 wherein:

said mass means including said imaging means comprises a mirror assembly including a mount and a mirror secured thereto;

said rotating means comprises a rotatably mounted wheel, said mirror mount being pivotally secured to said wheel for enabling pivoting of said mirror assembly about a predetermined pivot axis passing through the intersection; and

said mount having masses arranged in a manner to provide the substantially equal moments of inertia of said mirror assembly about the pivot axis, the optical axis of said mirror, and an axis mutually perpendicular to the pivot and optical axes.

4. The apparatus described in claim 1 wherein:

said said mass means including imaging means comprises a miRror assembly including a mirror and a mount, said mount including a frame portion for holding said mirror and an armature portion extending behind said mirror;

said rotating means comprises a rotatably mounted wheel, means for pivotally coupling said mirror mount to said wheel, a first stop on said wheel for limiting pivoting of said mirror assembly in a first direction, and means for biasing said mirror means towards and against said first stop; and

a solenoid disposed adjacent to said armature portion of said mount, for magnetically attracting said armature portion and to move said mirror means against said biasing means to pivot said mirror assembly to a position away from said first stop.

5. Apparatus for sensing deviation of an object having a light source from a particular target direction comprising:

a housing including a mirror mounted for pointing in the target direction;

detector means mounted in a predetermined detector plane on said housing;

means for rotating said mirror about an axis of rotation which is coaxial with the direction in which said housing is pointed;

means coupled to said mirror for tilting its optical axis at, at least, two angles from the axis of rotation, to focus light from the source substantially onto said detector plane;

means for measuring the time taken by light from said source to cross said detector means and for measuring the rotational angle of the optical axis for sensing deviation of the light source from the target direction; and

means including said mirror dynamically balancing said mirror at any of the angles of tilt.

6. The apparatus described in claim 5 wherein said sensor means comprises at least two pairs of elongated sensors;

and said mirror holding means includes means for pivoting said mirror about an axis crossing the axis of rotation to provide a plurality of angled positions of the optical axis from the axis of rotation.

7. The apparatus described in claim 5 wherein:

said means for rotating said mirror comprises a mount for rigidly holding said mirror, a wheel pivotally supporting said mount, said tilting means including means for pivoting said mount between selected positions to enable the change of angle between the axis of rotation and the optical axis, and means for rotatably supporting said wheel on said housing.

8. A tiltable and dynamically balanced mirror assembly comprising:

a mirror rotatable about an axis of rotation and tiltable about a second axis intersecting the axis of rotation, and having an optical axis angularly offset from the axis of rotation, and mass means including said mirror and dynamically balanced about the intersection of the axis of rotation and the second axis at all tilts of said mirror.

9. A mirror assembly as in claim 8 further including means for tilting said mirror about the second axis, said mass means including an element cooperable with said mirror tilting means for effecting the tilting of said mirror.

10. A mirror assembly as in claim 9 wherein said tilting means includes a solenoid and said element comprises an armature of magnetic material.

11. A mirror assembly as in claim 8 further including a rotatable support having pivot means disposed along the second axis, said mass means secured to said support by said pivot means, a pair of abutments on said support and positioned on opposite sides of said pivot means, biasing means secured between a first of said abutments and said mass means for tilting said mass means and said mirror into contact with the second of said abutments, and means secured between said mass means and said support for biasing and tilting said mass means and said mirror against said first of said abutments.

12. In a missile tracking system for directing a missile towards a target comprising a missile, having an electromagnetic signal, and a sensor and error correction apparatus having a detector plane with two pairs of orthogonally positioned detector elements, onE of said pair being longer than the second of said pair, a mechanism coupled to each of said detector pairs and to the missile for computing the error in missile trajectory to the target and for transmitting error correction signals to the missile for correcting the error in the missile trajectory, and a mirror assembly for directing the missile electromagnetic signal onto the detector plane and onto said pairs of detector elements, the improvement comprising:

target sighting apparatus having a target axis positionable on the target, a stationary housing secured to said target sighting apparatus and provided with a solenoid having a center pole and end poles, a rotatable support journalled in said housing on an axis of rotation coaxially positioned on the target axis, said support having opposed first and second faces and through bore means positioned on the axis of rotation and opening at said faces, a drive secured to said housing and operatively coupled to said rotatable support for imparting rotation thereto, a mount pivoted on a pivot axis to said rotatable support at said first face thereof, and having a rod extending through and beyond said bore means at said second face of said support and having an armature of ferromagnetic material secured to said rod, said armature being positioned adjacent to said solenoid and movable between a first position adjacent said center pole and a second position adjacent one of said end poles, a mirror affixed to said mount and having a curved reflective surface provided with an optical axis aimed towards the detector plane for focussing the missile electromagnetic signal onto the plane, said mirror being rotatable with said mount about the axis of rotation, and the optical axis being angularly offset to two discrete angles from the axis of rotation to provide two corresponding conical scans of the missile electromagnetic signal onto the detector plane, respectively for use with each said pair of detector elements, a pair of stops positioned on said first face of said support on opposed sides of the pivot axis of said mount for limiting the angular movement of said mount and said mirror to said discrete angles to provide the two conical scans, biasing means between a first of said stops and said mount for pivoting said mount into abutment with the second of said stops and for pivoting said armature in the position adjacent said solenoid center pole when said solenoid is deenergized, said solenoid when energized providing sufficient attractive force on said armature against the bias of said biasing means to pivot said mount into abutment with said first stop, and said mount having masses, including said mirror, said rod, and said armature, so distributed as to provide a dynamic balance of said mount and said mirror at any angular position thereof.

13. Apparatus for sensing deviation of an object having a light source from a particular target direction comprising:

a housing including a mirror mounted for pointing in the target direction;

detector means mounted in a predetermined detector plane on said housing;

means for rotating and pivoting said mirror about an axis of rotation which is coaxial with the direction in which said housing is pointed, said mirror rotating and pivoting means comprising a mount rigidly holding said mirror, said mounting including a frame portion attached to said mirror and an armature portion extending behind said frame portion to provide a dynamic balance, a wheel pivotally supporting said mount, a spring extending between said wheel and said mount for urging said mount toward a first pivotal position with respect to said wheel, and a solenoid coil mounted on said wheel adjacent said armature portion of said mount for urging said mount toward a second pivotal position against the bias of said spring to enable change of angle between the axis of rotation and the optical axis, and means for rotatably supporting said wheel on said housing;

means holdiNg said mirror so its optical axis is angled from the axis of rotation, to focus light from the source substantially onto said detector plane; and

means for measuring the time taken by light from said source to cross said detector means and for measuring the rotational angle of the optical axis for sensing deviation of the light source from the target direction.

14. A tiltable and dynamically balanced mirror assembly comprising:

a mirror rotatable about an axis of rotation and tiltable about a second axis intersecting the axis of rotation, and having an optical axis angularly offset from the axis of rotation; and

mass means secured to said mirror and dynamically balanced therewith about the intersection of the axis of rotation and the second axis for any tilt of said mirror, said mass means, when taken with said mirror, being physically distributed about the intersection to form the equivalent of a sphere of evenly distributed mass whose three orthogonal moments of inertia are substantially equal.