Optics: measuring and testing – Range or remote distance finding – With photodetection
Reexamination Certificate
2001-06-11
2002-10-22
Tarcza, Thomas H. (Department: 3662)
Optics: measuring and testing
Range or remote distance finding
With photodetection
C356S005010
Reexamination Certificate
active
06469777
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a surveying instrument having an optical distance meter, and also relates to a surveying instrument having an optical distance meter and a focus detection device for detecting a focus state of a distance-measuring optical system such as a sighting telescope.
2. Description of the Related Art
When a surveyor measures the distance between two points, an electronic distance meter (EDM) designed as a surveying instrument is generally used. An electronic distance meter calculates the distance via the phase difference between a projecting light and a reflected light and via the initial phase of an internal reference light, or via the time difference between the projecting light and the reflected light.
A typical electronic distance meter is provided, behind the objective lens of a sighting telescope (distance-measuring optical system) thereof, with a light transmitting mirror positioned on the optical axis of the sighting telescope to project the measuring light toward a target (sighting object) through the center of the entrance pupil of the objective lens of the sighting telescope. The light which is reflected by the target and passed through the objective lens of the sighting telescope passes the peripheral space of the light transmitting mirror to be captured via a wavelength selection filter and a light receiving mirror.
In such an electronic distance meter, the light which is reflected by the target and passed through the objective lens of the sighting telescope is interrupted by the aforementioned light transmitting mirror by a greater amount as the target is closer to the electronic distance meter. If the light which is reflected by the target and passed through the objective lens of the sighting telescope is interrupted by the light transmitting mirror by a great amount, the light amount of the incident light upon the aforementioned light receiving mirror decreases, which deteriorates the precision in measuring the object distance or makes it impossible to perform a distance measuring operation. To prevent these problems from occurring, various methods have been proposed.
SUMMARY OF THE INVENTION
The present invention has been devised in view of the problems noted above, and accordingly, an object of the present invention is to provide a surveying instrument having an optical distance meter, wherein the aforementioned problems can be overcome in an easy manner without deteriorating the performance characteristics of the distance measuring operation of the optical distance meter when measuring the distance to a target at the maximum measurable distance.
Another object of the present invention is to provide a surveying instrument having an optical distance meter and a focus detection device for detecting a focus state of a distance-measuring optical system, wherein the aforementioned problems can be overcome in an easy manner without deteriorating the performance characteristics of the distance measuring operation of the optical distance meter when measuring the distance to a target at the maximum measurable distance.
To achieve the objects mentioned above, according to an aspect of the present invention, a surveying instrument is provided, including a distance-measuring optical system having an objective lens via which a distance from the surveying instrument to an object is measured; and an optical distance meter which includes a reflection member positioned behind the objective lens, a light-transmitting optical system for transmitting a measuring light toward the object via the reflection member and the objective lens, and a light-receiving optical system for receiving a portion of the measuring light which is reflected by the object, subsequently passed through the objective lens and not interrupted by the reflection member. The light-receiving optical system includes a plurality of light-guiding optical systems, so that the measuring light which is reflected by the object is selectively incident on an end of one of the plurality of light-guiding optical systems in accordance with the distance from the surveying instrument to the object.
In an embodiment, a diameter of at least one light-guiding optical system of the plurality of light-guiding optical systems, to which the measuring light reflected by the object is incident on, is greater as the object distance for which at least one light-guiding optical system is used is longer.
In an embodiment, the surveying instrument further includes a light shield mask having a plurality of apertures, wherein the measuring light reflected by the object is selectively incident on the end of the one of the plurality of light-guiding optical systems via one of the plurality of apertures.
In an embodiment, diameters of the plurality of apertures are different from one another, the diameters of the plurality of light-guiding optical systems being identical to one another.
In an alternative embodiment, diameters of the plurality of apertures are different from one another, wherein the diameters of the plurality of light-guiding optical systems correspond to the diameters of the plurality of apertures of the light shield mask.
The surveying instrument can further include a moving device for moving the light shield mask so that the measuring light reflected by the object can be selectively incident on the end of the one of the plurality of light-guiding optical systems.
Preferably, the distance-measuring optical system includes a focus adjustment lens which is moved to bring the object into focus; the surveying instrument further including a lens position detection device which detects an axial position of the focus adjustment lens, the moving device moving the light shield mask in accordance with the axial position of the focus adjustment lens that is detected by the lens position detection device.
Preferably, a controller is provided, which controls the moving device to move the light shield mask in accordance with a state of the light-receiving optical system when the light-receiving optical system receives the measuring light reflected by the object.
The controller can include a mask position detector for detecting a position of the light shield mask in which an amount of the measuring light reflected by the object and received by the light-receiving optical system becomes maximum. The controller controls the moving device to move the light shield mask in accordance with the position of the light shield mask that is detected by the mask position detector.
The controller can control, for example, the moving device to move the light shield mask so that the measuring light reflected by the object is incident on an end of another one of the plurality of light-guiding optical systems in the case where an amount of the measuring light reflected by the object and received by the light-receiving optical system via the one of the plurality of light-guiding optical systems, at a predetermined amount of time, is not greater than a predetermined amount of light.
In an embodiment, the central axes of the incident end surfaces of the plurality of light-guiding optical systems are positioned on a straight line.
In an alternative embodiment, the light-receiving optical system includes a light-receiving element on which the measuring light reflected by the object is incident via the plurality of light-guiding optical systems; wherein the central axes of the exit end surfaces of the plurality of light-guiding optical systems are positioned on a circle about an axis of the light-receiving element.
In an embodiment, the light-receiving optical system includes a plurality of light-receiving elements on which the measuring light reflected by the object is incident via the plurality of light-guiding optical systems, respectively.
Preferably, each of the plurality of light-receiving elements is an optical fiber.
The distance-measuring optical system can be a sighting telescope for sighting the object.
Preferably, the reflection member is made of a parallel-plate mirror ha
Andrea Brian
Asahi Kogaku Kogyo Kabushiki Kaisha
Greenblum & Bernstein P.L.C.
Tarcza Thomas H.
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