Focuser for optical instrument

• US 6,069,754 A
• Filed: 04/23/1999
• Issued: 05/30/2000
• Est. Priority Date: 04/23/1999
• Status: Active Grant

• Current Assignee: Starlight Instruments, LLC
• Original Assignee: Starlight Instruments, Inc.
• Inventors: Schmidt, Detlef W. P.
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): Seyrafi, David
• Application Number:
  US09/296,379
• Time in Patent Office: 403 Days
• Field of Search: 359/825, 359/826, 359/828, 359/830, 359/819, 359/822, 359/823
• US Class Current: 359/825
• CPC Class Codes: G02B 7/08 adapted to co-operate with a remote control mechanism

Abstract

A device for focusing optical instruments, for example a telescope or microscope, includes a drive assembly having a fine and a coarse control knob. The knobs operatively connect with a drive shaft that extends transversely through a concave shaped support area of the drive. Seated in this support area is a tubular-shaped housing having an opening that fits over the drive shaft. Respective pairs of longitudinally spaced apart bearings then are attached to an inside wall of the housing to proximately align one each with ends of the housing shaft opening. A tubular-shaped drawtube then movably fits in the housing where a friction plate carried by a bottom portion of the drawtube engages the drive shaft. In an outer surface of the drawtube on each side of the friction plate is a longitudinal slot. Each slot has a bottom offset for a self-locating rail. Respective upper flat segments of the rails are in rolling contact with one each of the bearing pairs. During use an eyepiece of the optical instrument, for example, is inserted in a support collar carried inside an outer end of the drawtube. Lens of the eyepiece then are focused by rotation of the drive assembly knobs. The connecting drive shaft moves the drawtube and eyepiece to a position where the eyepiece lens display a distinct image.

Claims

1. A focuser particularly adapted for adjusting focusing means of an optical system of an instrument, said focuser comprising:

a housing having a body formed with an opening prepared for disposition of a drive shaft of a drive assembly of said focuser, said opening allowing said drive shaft to extend through an inside wall of said housing,

a first and a second set of bearings rotatively attached to said housing inside wall, and

a drawtube having a body prepared to connect with said instrument focusing means, said drawtube body defined in part by a lower portion, a plate attached to said drawtube body lower portion to movably fit over said housing opening, and a first and second slot formed in said drawtube body bottom portion on respective sides of said plate, said first bearing set operatively engaging a rail carried in an offset of said first slot and said second bearing set operatively engaging a rail carried in an offset of said second slot,

wherein, during operation of said focuser, said focuser maintains optical alignment of said instrument focusing means with a reminder of said instrument optical system.

2. A focuser as defined by claim 1 and further characterized by including,

an eyepiece support collar carried by an outer end of said drawtube body so that set screws threadedly secured to said collar locate in slots in said drawtube outer end.

3. A focuser as defined by claim 1 and further characterized by,

said each drawtube slot offsets having sidewalls positioned to form a V-like shape, and

said rails having deflection resistant, cylindrical body portions adjustably fitting against said sidewalls of said respective slot offsets and flat segments squarely fitting against said bearings of said respective sets,

wherein during said adjustment of said focuser said rails self-locate in said slot offsets to maintain said square fits between said bearings and said rail flat segments.

4. A focuser as defined by claim 1 and further characterized by,

said plate being deflection resistant and secured in a longitudinal recess formed in said drawtube bottom portion.

5. A focuser as defined by claim 1 and further characterized by including,

a drive assembly attached to said housing and having a drive shaft positioned in said housing opening, and

a spring carried on said drive shaft to operatively connect said drive shaft to said drive assembly,

wherein said spring may be preloaded to produce a torsional force that acts to counterbalance gravity induced forces placed on said drawtube.

6. A method of operating a focuser particularly adapted for delineating images observable with an optical instrument, said method comprising the steps of:

rotating a drive shaft of a drive mechanism of said focuser by selectively winding adjustment knobs carried by said drive mechanism,

interacting a friction plate carried by a lower portion of a drawtube of said focuser with said drive shaft to convert said drive shaft rotational movement into a linear force driving said drawtube in a path-of-movement, and

controlling said drawtube path-of-movement with wedging action from sets of bearings secured to a housing attached to said drive mechanism as one said bearing set rolls on a rail carried by said drawtube lower portion on one side of said friction plate and another bearing set rolls on a rail carried by said drawtube lower section on an opposite side of said friction plate,

wherein said wedging action maintains said drawtube path-of-movement aligned with an optical axis of said instrument during operation of said focuser.

7. A device for focusing an optical instrument, said device comprising:

a drive assembly,

a housing having a body carried by said drive assembly, said housing body formed with an opening located next to said drive assembly to receive a drive shaft of said assembly that extends through an inside wall of said housing,

a drawtube having a body movably carried by said housing, a deflection resistant plate carried in a longitudinal recess in a bottom portion of said drawtube body to operatively engage said drive assembly drive shaft,

a first and a second longitudinal slot formed in said drawtube body bottom portion on respective sides of said plate recess with each said slot having a V-like shaped offset,

a first and second deflection resistant rail adjustably fitting in said respective drawtube slot offsets with each said rail having an outward facing flat segment, and

a first and a second set of bearings attached to said housing inside wall to fit respectively in said drawtube slots with said bearings of said first set in rolling contact with said flat segment of said first rail, and said bearings of said second set in rolling contact with said flat segment of said second rail,

wherein during use of said device, selective operation of said drive assembly rotates of said drive shaft, said drive shaft rotation converts to a linear driving force that moves said drawtube in a path-of-movement, said path-of-movement of said drawtube being controlled by a three-directional wedging action generated as said bearings roll on said rails, said wedging action remaining uniform from said bearings staying squarely seated on said rail flat segments, and said bearing-rail square seating being self-generating by said adjustable fits between said rails and said drawtube slot offsets.

8. A device as defined by claim 7 and further characterized by said drive assembly including,

a spiral-type spring fitting about said drive shaft with respective ends of said spring operatively attached to said shaft and said drive assembly to allow preloading of said spring to counterbalance gravity loading of said drawtube.