Optical: systems and elements – Lens – With support
Patent
1996-09-12
1998-03-24
Nelms, David C.
Optical: systems and elements
Lens
With support
359822, 359696, G02B 702, G02B 1514
Patent
active
057319189
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a lens mounting for a high performance optical instrument.
BACKGROUND OF THE INVENTION
High performance optics often imply very tight tolerances for positioning lenses both axially and radially. To satisfy such tolerances lens carriages are often mounted on rolling element linear guides, and ball-screws provided for axially locating the lens carriages. The precision required in high performance optical instruments including such components gives rise to tight mechanical alignment requirements; errors in alignment of just a few microns can cause increases in friction sufficient to seize the mechanism.
Various methods are utilised to address this problem, generally utilising some means of careful alignment of the guides and ball-screw followed by fixation. Providing such accurate alignment adds considerably to the costs of the mechanism, and also the mechanism remains sensitive to small deformations in its structure, for example due to thermally induced stresses.
It is among the objects of the present invention to obviate and mitigate these disadvantages.
SUMMARY OF THE INVENTION
According to the present invention there is provided a lens mounting for a high performance optical instrument, the mounting comprising: substantially parallel to the linear guide, and a drive member follower being linked to the lens carriage such that actuation of the drive member or drive member follower moves the carriage axially along the guide,
one or more elements of the linear drive being mounted relative to the linear guide to permit a degree of relative movement therebetween to accommodate misalignment between the linear guide and the drive member.
Preferably, the linear drive is in the form of a ball-screw drive comprising a ball-screw extending substantially parallel to the linear guide and a ball-screw follower linked to the lens carriage such that rotation of the ball-screw moves the carriage axially along the guide.
Preferably also, the coupling between the ball-screw drive and the linear guide substantially precludes said relative movement in the axial direction to ensure accurate axial location of the lens carriage by the ball-screw drive.
The ball-screw may be mounted relative the body to accommodate a degree of relative movement therebetween, and thus between the ball-screw and the linear guide; one or more of the bearings supporting the ball-screw may be mounted to the body to permit such movement, for example by mounting an end bearing in an elastomeric compound. This arrangement allows provision of a substantially rigid coupling between the ball-screw follower and the lens carriage. Alternatively, a coupling may be provided between the ball-screw follower and the lens carriage that allows for a limited degree of relative movement therebetween; such a coupling may be in the form of a flexure, a spherical/bearing or an elastomeric element.
BRIEF DESCRIPTION OF THE DRAWINGS
This and other aspects of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is an end view of a lens mounting in accordance with a first embodiment of the present invention;
FIG. 2 is a perspective view from above of a flexure of the mounting of FIG. 1;
FIG. 3 is an end view of a lens mounting in accordance with a second embodiment of the present invention;
FIG. 4 is an end view of a lens mounting in accordance with a third embodiment of the present invention;
FIG. 5 is an end view of a lens mounting in accordance with a fourth embodiment of the present invention; and
FIG. 6 is a side view of parts of a lens mounting in accordance with a fifth embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Reference is first made to FIGS. 1 and 2 of the drawings which illustrate, somewhat schematically, a lens mounting 10 in accordance with a first embodiment of the present invention. The lens mounting 10 is itself mounted on a body or within a housing (not shown). The illustrated arrangemen
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Japanese Abstract 59 094 708, 31 May 1984, Toukiyou Kougaku Kikai, "Zoom Lens Moving Device".
Evans Graham
Gardam Allan
Parr-Burman Philip Michael
Mack Ricky
Nelms David C.
Pilkington P.E. Limited
Seltzer Bell
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