Optical: systems and elements – Lens – With support
Reexamination Certificate
2000-03-21
2001-10-02
Epps, Georgia (Department: 2873)
Optical: systems and elements
Lens
With support
C359S823000, C359S703000
Reexamination Certificate
active
06297917
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to optical instruments, and more particularly to a device for focusing an optical instrument that achieves focus by effecting relative movement along an optical axis between two components of an optical system. Although the invention has wide utility in the field of optical devices, it has proven particularly useful in the context of focusing a telescope.
BACKGROUND OF THE INVENTION
A conventional reflecting telescope, it will be appreciated, employs a system of mirrors contained within an optical tube to gather and focus rays of light at a focal point. Typically, a primary mirror gathers and reflects light to a secondary mirror that reflects and focuses the light at a focal point. The light reflected from the secondary mirror can be viewed through an eyepiece. The telescope is focused by causing the optical tube focal point to coincide with the focal point of the eyepiece. A photographic plate or CCD sensor may be used instead of an eyepiece in certain applications to “view,” or capture the light reflected from the secondary mirror.
Effecting relative movement between the focal points of the optical tube and eyepiece is the general method used to focus a reflecting telescope. This may be accomplished by moving the primary and secondary mirrors to change the position of the optical tube focal point. In this method, the optical tube and eyepiece remain in fixed positions relative to one another. A problem with this method is that moving the optical tube mirrors can cause the viewed image to shift, requiring that the telescope be re-aimed in order to view the original image.
Various mechanisms have been designed that allow a telescope to be focused without moving the optical tube mirrors. These include sliding drawtubes, threaded focusing tubes, rack and pinion systems, all of which are configured to move an eyepiece longitudinally relative to an optical tube. An example of such a focussing apparatus may be found in U.S. Pat. No. 5,303,090, the disclosure of which is incorporated herein by this reference thereto.
Known optical focuser designs are effective under most circumstances, though they do suffer from various problems and disadvantages. Some designs require use of components machined to within precise tolerances, making the focuser costly to manufacture and difficult to maintain. Where equipment does not meet these tolerances, whether due to poor construction or to inevitable wear, the telescope may suffer from problems related to jamming, rocking, or slippage of the moving parts. This, in turn, may result in poor alignment of the eyepiece relative to the optical tube. These failures can lead to difficulty in bringing the telescope into focus.
A problem common to drawtube designs is that they typically require supporting structures surrounding the drawtube to hold the drawtube aligned as it moves with respect to the optical tube. These supporting structures can decrease access to the drawtube, making it more difficult to integrate certain types of optical components into the focuser. For example, a flip mirror system, an optical component frequently used in conjunction with CCD sensors, cannot easily be integrated into known drawtube designs. Instead, the flip mirror system is provided as a separate component that must be affixed to the end of the focuser, increasing the size and weight of the structure attached to the optical tube of the telescope. Bulky and/or heavy attachments to the optical tube may imbalance the telescope, place unnecessary strain on the structure supporting the optical tube, decrease portability, and/or make the telescope difficult to aim or focus.
SUMMARY OF THE INVENTION
The focuser of the present invention includes an eyepiece holder that is adapted to be fixedly secured to an eyepiece and movably secured to a telescope's optical tube so that the eyepiece can be moved along the telescope's optical axis relative to the optical tube for purposes of focusing the telescope. The eyepiece holder includes spaced opposing surface portions located to one side of a plane bisected by the optical axis. The opposing surface portions are configured such that, when the eyepiece holder is movably secured to the optical tube of the telescope, the optical tube is held in alignment by opposing forces exerted upon the surface portions.
The configuration of the spaced opposing surface portions and the way that the surface portions are used to align the eyepiece holder provide an improvement over known focuser designs. Not only is the eyepiece holder firmly aligned as it moves and carries the eyepiece, but it is aligned without the opposed supporting structures required in previous eyepiece holder designs. As a result, the design offers increased access to the eyepiece holder, allowing additional optical accessories to be integrated with the invented focuser.
The focuser also may be provided with a base adapted to be mounted to the optical tube of the telescope. The eyepiece holder may include a drawtube movably engaged with the base and a track fixed to, and spaced apart from, the drawtube. In this embodiment, an advancement mechanism may be secured to the base and operatively engaged with the track to selectively cause the eyepiece holder to move relative to the base. The advancement mechanism may take the form of a shaft rotatably secured to the base and frictionally engaging the track such that rotation of the shaft effects relative movement between the eyepiece holder and base.
In another embodiment of the invention, the eyepiece holder may be fitted with a mirror rotatably disposed within the drawtube. The mirror typically is pivotal between a reflecting position wherein the mirror reflects light travelling through the drawtube out through an opening formed in a wall of the drawtube, and a retracted position wherein the mirror does not obstruct light travelling through the drawtube.
REFERENCES:
patent: 3851952 (1974-12-01), Werz et al.
patent: 4478491 (1984-10-01), Kawai
patent: 4640578 (1987-02-01), Turner et al.
patent: 4929073 (1990-05-01), La Plante et al.
patent: 4961115 (1990-10-01), Jessop
patent: 4993801 (1991-02-01), Sarraf
patent: 5053794 (1991-10-01), Benz
patent: 5303090 (1994-04-01), Burr et al.
patent: 6069754 (2000-05-01), Schmidt
Advertisement entitled “CCD-Photo-Visual Flip-Mirror Systems”.
Epps Georgia
Kolisch, Hartwell, Dickinson, McCormack & Hueser
Seyrafi Saeed
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