A prior art survey apparatus has been generally provided with a centering telescope optical system (centering telescope), and has utilized a centering telescope optical system when deploying a survey apparatus directly above a point of measurement. The centering telescope optical system is able to carry out an accurate centering operation because an operator looks directly into the centering telescope optical system. However, since the centering telescope optical system is located at a lower position than that of a collimation telescope used for measurement, the operator looks into the optical system in a half-sitting posture (in a squatted state), which creates a burden on the operator. In particular, work for installing a survey apparatus on an inclined site becomes a large burden on an operator.
Therefore, recently, survey apparatuses such as a survey apparatus provided with a laser centering device, by which a visible laser beam is emitted directly therebelow, and a survey apparatus having a centering telescope optical system and a laser centering device are made available in addition to the centering telescope optical system.
A survey apparatus having such an optical centering system and a laser centering device is disclosed in Japanese Unexamined Patent Publication No. Hei-6-213664. The survey apparatus is shown in FIG. 6. The survey apparatus 1 is provided with a laser centering device formed of a centering telescope optical system 5, a laser beam source 3, a collimate optical system 4, a mask member 41, and a transparent member 6.
In order to use a laser centering device, a laser beam is emitted from the laser beam source 3, and the laser beam is collimated to be a parallel beam by the collimate optical system 4. Next, light beams other than the laser beam, which are made incident into a reflection portion 61 of the transparent member 6, are cut off by the mask member 41. Then, the laser beam is reflected directly below by the reflection portion 61, and irradiates a stake 10 showing a point of measurement. And, an operator adjusts the position of a survey apparatus body 2 so that the point irradiated by the laser beam, that is, the laser spot becomes coincident with the point of measurement on the stake 10. Thus, it is remarkably easy to carry out centering operations since it is sufficient that for the laser centering device the operator only look at the vicinity directly below the survey apparatus 1.
However, for work in bright sunlight, the laser centering device is inconvenient in that it is difficult to see the laser spot. During such times, a centering telescope optical system 5 is used. At this time, when an operator looks into an eyepiece portion 51 of the centering telescope optical system 5, the point of measurement on the stake 10 can be seen through a prism 7 and the transparent member 6. Therefore, the position of the survey apparatus body 2 is adjusted so that the cross line of the centering telescope optical system is made coincident with the point of measurement on the stake 10.
In the survey apparatus shown in FIG. 6, usually, it is possible to easily carry out survey work using the laser centering device. When it is difficult to see the laser spot in bright sunlight work, the centering telescope optical system 5 can be used, and this is convenient.
However, a survey apparatus in which a centering telescope optical system is detachably mounted is widely used at present. FIG. 7 shows an example of a structure of attaching such a centering telescope optical system to a survey apparatus. The centering telescope optical system 20 is formed of an outer barrel 136 in which a Dachprisma 22 and an object lens 24 are fixed at one end thereof, and an inner barrel 132 that is slidable in the outer barrel 136, and is provided with a focusing plate 26 and a diopter-adjustable eyepiece lens 28 in the inner barrel 132. The outer barrel 136 of the centering telescope optical system 20 is fixed at the fixing portion 38 of the centering telescope optical system by being pressed by the tip end of a screw screwed in the fixing portion 38 of the centering telescope optical system in the survey apparatus 1. The centering telescope optical system 20 can be easily detached from the survey apparatus 1 by the unit of the outer barrel 136 if a side plate 11 is removed from the survey apparatus 1 and the screw 62 is loosened.
Although a survey apparatus provided with both a centering telescope optical system and a laser centering device as shown in FIG. 6 is desirable, there is a problem in that the apparatus becomes complicated and becomes expensive. Therefore, since a survey apparatus provided with a detachable centering telescope optical system has been widely used, it is considered, in order to facilitate centering operations, that in such a survey apparatus, the centering telescope optical system and laser centering device are replaced.
However, if, in a laser centering device as shown in FIG. 6, there is an error in the attaching position and angle of the laser beam source 3 and reflection portion 61, a centering error occurs. In particular, even if an error in the angle of the reflection portion 61 is only slight, the position of the laser spot largely changes due to a principle of the optical lever, wherein there is a problem in that a large centering error occurs. However, adjustment of the emission direction of the laser beam requires various steps of adjustment for each of the many components such as the laser beam source 3, reflection portion 61, etc., and it is very cumbersome.
Therefore, in order to solve the above-described problems, it is an object of the present invention to provide a laser centering device for which the emission direction of a laser beam can be simply adjusted.