1. Field of the Invention
The present invention relates to an optical mount.
2. Background Information
Mechanical mounts are commonly used to secure and vary the position of an optical element such as a mirror. The mount may be part of an optical system such as a laser or an interferometer. The system may be tuned or calibrated by varying the incident angle of the light reflected from the mirror. A conventional optical mount typically has a number of adjustment screws that can be manipulated to tilt the mirror and vary the angle of incidence.
There have been marketed gimbal optical mounts that can tilt the reflecting mirror and change the incident angle without spatially shifting the point at which the light is reflected from the mirror. This can be accomplished by reflecting light from the pivot points of the gimbal mount which are coincident with the mirror face. Gimbal mounts allow a scientist to vary the incident angle without introducing a phase shift in the reflected light.
Conventional gimbal optical mounts typically contain two concentric rings. The innermost ring holds the optical element and can rotate relative to an outer ring. The outer ring can rotate relative to an outer stationary housing about an axis that is perpendicular to the axis of rotation of the inner ring. Ring type gimbal mounts can be relatively expensive to produce.
U.S. Pat. No. 4,088,396 issued Edelstein and U.S. Pat. No. 3,357,268 issued to Richter disclose optical gimbal mounts which each have a first plate and a second plate. The first plate is typically mounted to a stationary surface such as a table. The second plate holds the optical element and has a spherical bearing surface. The spherical bearing surface cooperates with a spherical seat of the first plate to allow the second plate and optical element to pivot about a point. Unfortunately, the pivot point is located away from the optical surface of the optical element so that pivoting the element may introduce a phase shift in the reflected light.
There have been published articles which discuss the use of gimbal optical mounts that have kinematic type interfaces which pivot the optical element about a point on the optical surface. These mounts have three or four adjustment screws that are manipulated to pivot the optical element. Accurately pivoting the optical element typically requires manipulating two screws the same amount. Manipulating two screws can be both cumbersome and time consuming. For example, a gimbal mount with three or four screws requires the simultaneous manipulation of at least two screws to pivot the optical element about an axis. It would be desirable to provide an opto-mechanical mount that can tilt an optical element without introducing a spatial phase shift and which can pivot the element about an axis by manipulating only one screw.
One embodiment of the present invention is an optical mount for an optical element which has an optical surface. The mount includes a first plate, and a second plate which holds the optical element. The second plate may have a spherical bearing surface that cooperates with the first plate so that the optical element pivots about a point on the optical surface. The mount has a single first adjustment device to pivot the optical element about one axis and a single second adjustment device to pivot the element about a second perpendicular axis.