Apparatus for dithering

• US 5,798,875 A
• Filed: 11/30/1995
• Issued: 08/25/1998
• Est. Priority Date: 03/13/1995
• Status: Expired due to Fees

• Current Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Original Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Inventors: Fortin, Jean, Chevrette, Paul
• Primary Examiner(s): Ben, Loha
• Application Number:
  US08/566,441
• Time in Patent Office: 999 Days
• Field of Search: 359/813, 359/814, 359/819, 359/822, 359/824, 358/474
• US Class Current: 359/813
• CPC Class Codes: G02B 26/0875 by means of one or more refracting elements
• CPC Class Codes: H04N 25/48 Increasing resolution by shifting the sensor relative to the scene

Abstract

An dithering system for implementation of a microscan that dithers an image on an array of sensing elements that defines an image plane by moving one or more lenses which displaces the image focused on the image plane. Piezoelectric positioners are provided to move the one or more lenses a predetermined amount and on a predetermined plane parallel to the image plane so that the image focused by the lensing system on the array of sensing elements is displaced on the image plane by the movement of the lensing system. As the lens is moved by the positioners and thus the optical axis of the lens, the image passing through the lens is also moved on the image plane. Moving the lens horizontally and vertically or in a predetermined pattern provides dithering of the image so that microscanning can be employed.

Claims

1. A dithering system comprising:

a stationary frame;

a movable lens mounted within the stationary frame;

two thin members disposed such that their longitudinal axes are orthogonal to one another, the members being either in a rest position or operable in one of a longitudinally rigid mode and a laterally flexible mode, said members for normally securing and holding the lens within the stationary frame in a fixed position in the rest position, in the presence of a force upon one of the members, one of said members being operable in the longitudinally rigid mode while the other member is operable in the laterally flexible mode of operation so as to guide and force the lens to move along one of the orthogonal axes; and

,

means for applying the force.

2. A dithering system as defined in claim 1, wherein the means for applying the force comprises two piezoelectric actuators, each actuator disposed at an end of one of the two thin members, and including circuitry for controlling the actuators so that only one actuator is enabled at a time, the moveable lens moving in the direction of the force applied by the actuator.

3. A positioning device comprising:

a stationary frame;

an optical element mounted to and movable within the stationary frame, said movement being confined to a plane;

flexure means comprising a pair of flexure elements, each element being rigid enough along a longitudinal axis, so that when a force is applied to an end thereof along the longitudinal axis, the element does not significantly bend, yet each element being sufficiently laterally flexible, such that when a force is applied across the longitudinal axis of the element, the element flexes, whereby the flexure elements in an unflexed position are for securing and holding the optical element within the staionary frame in a fixed position, and for allowing the optical element to move along at least one axis that lies on the plane, in the presents of an applied force; and

,

means for applying the force.

4. A positioning device as defined in claim 3, wherein the optical element is fixedly mounted within a holder, the holder and optical element being moveable within the stationary frame.

5. A positioning device as defined in claim 4, where in the flexure means further comprises two flexible s-shaped members coupling the holder to the stationary frame.

6. A positioning device as defined in claim 5, wherein the means for moving the optical element along one axis along the plane comprises a piezo-electric transducer.

7. A positioning device as defined in claim 6, wherein at least one of the s-shaped members is flexed as the piezo-electric transducer applies a force to the optical element.

8. A positioning device as defined in claim 4, wherein the flexure elements are each positioned to move the optical element along a different axis on the plane, the axes being orthogonal, each of said flexure elements having a stiffness that will allow a force applied to an end of one element to force the optical element to move in a direction along the longitudinal axis of the flexure elements, while the other flexure element laterally flexes.

9. A positioning device as defined in claim 8, wherein the optical element is comprised of a lens and wherein the flexure elements are in the form of flat steel blades.

10. A dithering system for positioning an optical element in a plurality of positions along two orthogonal axes defining a plane comprising:

a stationary frame;

a holder secured to the optical element and mounted to the stationary frame;

flexible joints for normally securing and holding the holder within the stationary frame in a fixed position and for allowing the holder holding the optical element to move friction-free along each of two orthogonal axes in the presence of force applied to the holder; and

means for applying the force to the holder.

11. A dithering system as defined in claim 10, wherein the optical element is a lens and wherein the holder securely frames the lens.