Firearms – Implements – Sight devices
Reexamination Certificate
1999-10-14
2001-07-31
Jordan, Charles T. (Department: 3641)
Firearms
Implements
Sight devices
C089S203000, C250S201200, C359S426000
Reexamination Certificate
active
06266911
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an autofocusing apparatus suitable for a sighting telescope incorporated in a surveying instrument such as an automatic level, a transit, a theodolite, etc.
2. Description of the Related Art
A conventional surveying instrument such as an automatic level (auto-level), a transit, or a theodolite, etc., is generally provided with a sighting telescope, a level and a measuring device which measures a rotational angle, a descending angle, and a ascending angle, etc. When this type of surveying instrument is used, the sighting telescope is positioned horizontally, and subsequently the horizontal and vertical adjustments for the sighting telescope are performed. Thereafter, the sighting telescope is aimed at a reference object or a reference point so that the reference object is sighted by a surveyor.
For instance, the optical system of the sighting telescope of an automatic level includes an objective lens group, a focusing lens group and an eyepiece, arranged in that order from the object side. The position of the focusing lens group is adjusted depending on the object distance, so as to form a sharp object image on a reticle provided on the focal plane. The object image formed on the reticle can be viewed through the eyepiece.
In a conventional sighting telescope provided with an autofocusing system, immediately after the AF start button of the autofocusing system is depressed by the user, the focusing lens group of the system is driven from a current position (e.g., initial position) to another position to bring a sighting object into focus. According to a phase-difference detection AF system, a focal point which is firstly detected by the AF system is regarded as an actual focal point for the sighting object, so that the AF system drives the focusing lens group to an axial position thereof which corresponds to the initially detected focal point to stop the focusing lens group thereat.
A sighting telescope is different from a telephoto-photographic lens used for cameras or regular observational telescopes; namely, that the focus detection range of sighting telescope from an infinite distance to the close-up extremity is much greater (e.g., by a number of centimeters). When such an excess detection range is converted into the amount of movement of the focal point, the distance of movement exceeds from 100 mm through 200 mm. The focus detection range of an AF unit of a phase-difference detection type is approximately ±15 mm from an assuming focal point, so that the focus detection range of the AF unit can cover merely a fraction of the whole focus detection range of a sighting telescope. Accordingly, the phase-difference detection AF unit is used for a sighting telescope, wherein there is a high probability that an actual focal point (target focal point) of the sighting object be positioned out of the focus detection range. Therefore, specifically in the case of the conventional sighting telescope being provided with an AF system having a phase-difference detection AF unit, there is a probability that other objects (non-target objects) rather than the sighting object (target object) be brought into focus if the AF system moves the focusing lens to an axial position thereof which corresponds to the initial detected focal point.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide an autofocusing apparatus of a sighting telescope which makes it possible to bring a sighting object into focus in a quick manner via a simple operation.
Other objects of the present invention will become apparent to one skilled in the art from a reading of the following disclosure and the appended claims.
To achieve the object mentioned above, according to an aspect of the present invention, there is provided an autofocusing apparatus of a telescope, including: a telescopic optical system which includes a focusing lens group guided along an optical axis; a focus detector which detects a focus state of the telescopic optical system; a lens driver which drives the focusing lens group along the optical axis; an AF switch which is manually operated; and a controller which performs a first AF operation to control the lens driver to move the focusing lens group to an in-focus position on the optical axis in accordance with a result of detection of the focus detector each time the AF switch is operated. The controller performs a second AF operation when the AF switch is operated more than once within a predetermined period of time, after the first AF operation is performed, the second AF operation including the movement of the focusing lens group by the lens driver to move the focusing lens group until the focusing lens group is moved to a second in-focus position other than the in-focus position, upon a later operation of the AF switch within the predetermined period of time; the second in-focus position being determined in accordance with the result of detection of the focus detector that is repeatedly actuated during the movement of the focusing lens group.
Preferably, there is further provided a lens position memory which stores a position of the focusing lens group on the optical axis after the focusing lens group is moved each time the AF switch is operated; wherein the controller controls the lens driver to move the focusing lens group to a position other than the position stored in the lens position memory in the second AF operation.
Preferably, the controller erases all the positions stored in the lens position memory if the AF switch is not operated more than once within the predetermined period of time.
Preferably, the autofocusing apparatus is incorporated in a surveying instrument.
Preferably, the focus detector includes a photosensor of a phase-difference detection type which includes a pair of line sensors.
Preferably, the lens position memory includes a RAM in which positional data of the focusing lens group is stored.
According to another aspect of the present invention, there is provided an autofocusing apparatus of a telescope, including: a telescopic optical system which includes a focusing lens group guided along an optical axis; a focus detector which detects a focus state of the telescopic optical system; a lens driver which drives the focusing lens group along the optical axis; and a controller which controls the lens driver in either one of a first control and a second control. In the first control, the controller controls the lens driver to move the focusing lens group to an in-focus position on the optical axis in accordance with a result of detection of the focus detector; and wherein in the second control, after the first control has been performed, the controller performs an operation to control the lens driver to move the focusing lens group until the focusing lens group is moved to a second in-focus position other than the in-focus position, the second in-focus position being determined in accordance with the result of detection of the focus detector that is repeatedly actuated during the movement of the focusing lens group.
Preferably, there is further provided an AF switch which is manually operated, wherein the first control is executed every time the AF switch is operated.
Preferably, the second control is executed when a predetermined operation that is different from the operation of the AF switch in the first control is performed.
Preferably, the predetermined operation includes operating the AF switch more than once within a predetermined period of time; and wherein the operation to move the focusing lens group to the second in-focus position is executed by a later operation of the AF switch.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 10-291937 (filed on Oct. 14, 1998) which is expressly incorporated herein by reference in its entirety.
REFERENCES:
patent: 3782822 (1974-01-01), Spence
patent: 5180875 (1993-01-01), Berry, Jr. et al.
patent: 5276554 (1994-01-01), Nassivera
patent: 5388005 (1995-02-01),
Asahi Kogaku Kogyo Kabushiki Kaisha
Buckley Denise J
Greenblum & Bernstein P.L.C.
Jordan Charles T.
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