1. Field of the Invention
The present invention relates to a surveying instrument having an auto-collimating function and a distance measuring function.
2. Description of the Related Art
Conventional high-end surveying instruments such as total stations have an auto-collimating function for automatically collimating the surveying instrument relative to a survey point (corner cube) in addition to an essential function of measuring the distance from the surveying instrument to the survey point and also horizontal and vertical angles. According to the auto-collimating function, auto-collimation light rays are projected toward the survey point (corner cube) through a telescope optical system of the surveying instrument, and are subsequently reflected back toward the surveying instrument from the survey point to be received by the surveying instrument to collimate the surveying instrument relative to the survey point.
On the other hand, according to the distance measuring function such as a distance measuring function of an EDM (electronic distance meter), distance measurement light rays are projected toward a survey point through the same telescope optical system, and subsequently reflected back toward the surveying instrument from the survey point to be received by the surveying instrument to measure the distance from the surveying instrument to the survey point.
Conventionally, the auto-collimation light rays and the distance measurement light rays are projected toward a survey point to travel on an optical axis of the telescope optical system. To project the auto-collimation light rays and the distance measurement light rays to a survey point while traveling on the same optical axis, the two different aforementioned light rays that are emitted from different directions must be combined with a beam splitter (half mirror). This beam splitter inevitably causes a substantial loss in the amount of light of each of the two different light rays; the amount of light of each of the two different light rays becomes less than half. This makes it more difficult to perform an auto-collimating operation and a distance measuring operation as the distance from the surveying instrument to the survey point increases, and also becomes a cause of deterioration in accuracy of distance measurement. This problem can be overcome if different wavelengths are given to the two different light rays when a wavelength-selective beam splitter is used. However, producing two different light rays which have different wavelengths is generally costly.
The present invention provides a surveying instrument having an auto-collimating function and a distance measuring function, wherein the auto-collimation light rays and the distance measurement light rays are projected toward a survey point through the same telescope optical system, and wherein loss in the amount of light of the two different light rays are reduced.
The present invention has been devised in view of the idea that the problem of loss in the amount of light of the two different light rays can be overcome if the auto-collimation light rays and the distance measurement light rays are projected toward a survey point on different light paths, respectively, which are offset from each other; this offset does not exerts any adverse effect on either auto-collimating operation or distance measuring operation.
According to an aspect of the present invention, a surveying instrument is provided, including a surveying instrument body which is rotatable about each of a vertical axis and a horizontal axis, the surveying instrument body including a telescope optical system for collimating the surveying instrument relative to a survey point; a collimator optical system, provided in the surveying instrument body, for projecting first light rays toward the survey point through the telescope optical system and for receiving the first light rays reflected at the survey point; an auto-collimating system which rotates the surveying instrument body about each of the vertical axis and the horizontal axis to position the survey point on an optical axis of the telescope optical system in accordance with information on a location of the survey point; a distance measuring optical system, provided in the surveying instrument body, for projecting second light rays toward the survey point through the telescope optical system and for receiving the second light rays reflected at the survey point; and a distance measuring device for calculating a distance from the surveying instrument to the survey point in accordance with information on the second light rays which are projected toward the survey point by the distance measuring optical system and reflected at the survey point. An optical axis of the collimator optical system on which the first light rays travel toward the survey point and an optical axis of the distance measuring optical system on which the second light rays travel toward the survey point are offset from each other in the telescope optical system.
It is desirable for one of the optical axis of the collimator optical system and the optical axis of the distance measuring optical system to be coincident with the optical axis of the telescope optical system.
It is desirable for the optical axis of the distance measuring optical system to be coincident with the optical axis of the telescope optical system.
The collimator optical system can include a first light source which emits the first light rays; and an off-axis mirror which is provided at a position offset from the optical axis of the telescope optical system. The distance measuring optical system can include a second light source which emits the second light rays; and an on-axis mirror which is positioned on the optical axis of the telescope optical system. The off-axis mirror is angled at approximately 90 degrees with respect to the on-axis mirror, and the on-axis mirror is angled at approximately 45 degrees with respect to the optical axis of the telescope optical system.
It is desirable for the distance measuring optical system to include a light receiving element; and a second on-axis mirror which is positioned behind the on-axis mirror to be substantially parallel to the on-axis mirror so that the second light rays which are reflected at the survey point back to the telescope optical system are reflected by the second on-axis mirror to be incident on the light receiving element.
It is desirable for the telescope optical system to include a half mirror positioned behind the second on-axis mirror on the optical axis of the telescope optical system in association with the second on-axis mirror.
It is desirable for the off-axis mirror, the on-axis mirror and the second on-axis mirror to be formed as a single member positioned behind an objective lens of the telescope optical system.
It is desirable for the single member is positioned in front of a beam splitter of the telescope optical system.
In another embodiment, a surveying instrument is provided, including a surveying instrument body rotatable about each of a vertical axis and a horizontal axis; a telescope optical system, provided in the surveying instrument body, for collimating the surveying instrument relative to a survey point; a collimator optical system, provided in the surveying instrument body, for projecting first light rays toward the survey point through the telescope optical system and for receiving the first light rays reflected at the survey point; and a distance measuring optical system, provided in the surveying instrument body, for projecting second light rays toward the survey point through the telescope optical system and for receiving the second light rays reflected at the survey point. An optical path of the first light rays projected toward the survey point through the telescope optical system and an optical path of the second light rays projected toward the survey point through the telescope optical system are offset from each other in the telescope optical system.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 2002-327068 (filed on Nov. 11, 2002) which is expressly incorporated herein by reference in its entirety.