Patent Description:
A surveying instrument such as a laser scanner or a total station has an electronic distance meter which detects a distance to an object which is to be measured by the prism distance measurement using a reflecting prism having the retro-reflective property as the object or the non-prism distance measurement using no reflecting prism.

In a conventional surveying instrument, to coincide an optical axis of a distance measuring light projected toward the object with a reflected distance measuring light reflected from the object, the optical axis of the distance measuring light or the optical axis of the reflected distance measuring light is deflected by a mirror or the like. Further, to miniaturize an optical system of the surveying instrument, the optical axis of the distance measuring light or the optical axis of the reflected distance measuring light may be deflected more than once.

Some surveying instruments are capable of both the prism distance measurement and the non-prism distance measurement. On the other hand, since the non-prism distance measurement may have a low reflectance of an object, it is necessary to use a distance measuring light with a large light amount in order to obtain a reflected distance measuring light with a sufficient light amount. However, in a case where the prism distance measurement is performed using the distance measuring light with a large light amount, a light amount of the reflected distance measuring light may become excessive, and a light receiving system may be saturated, which makes it impossible to measure.

State of the art surveying instruments are disclosed in <CIT> and <CIT>.

It is an object of the present invention to provide a surveying instrument which is capable of adjusting a light amount of a distance measuring light.

To attain the object as described above, a surveying instrument according to the present invention is defined in claim <NUM>.

Further, a preferred embodiment is defined in claim <NUM>.

A description will be given below on embodiments of the present invention by referring to the attached drawings.

First, by referring to <FIG>, a description will be given on a surveying instrument according to a first embodiment of the present invention.

A surveying instrument <NUM> is, for instance, a laser scanner. The surveying instrument <NUM> is constituted of a leveling module <NUM> mounted on a tripod (not shown) and a surveying instrument main body <NUM> mounted on the leveling module <NUM>.

The leveling module <NUM> has leveling screws <NUM>, and the surveying instrument main body <NUM> is leveled up by the leveling screws <NUM>.

The surveying instrument main body <NUM> includes a fixing unit <NUM>, a frame unit <NUM>, a horizontal rotation shaft <NUM>, a horizontal rotation bearing <NUM>, a horizontal rotation motor <NUM> as a horizontal rotation driving module, a horizontal angle encoder <NUM> as a horizontal angle detector, a vertical rotation shaft <NUM>, a vertical rotation bearing <NUM>, a vertical rotation motor <NUM> as a vertical rotation driving module, a vertical angle encoder <NUM> as a vertical angle detector, a scanning mirror <NUM> which is a vertical rotation module, an operation panel <NUM> which serves as both an operation module and a display module, an arithmetic control module <NUM>, a storage module <NUM>, a distance measuring unit <NUM> and others. It is to be noted that, as the arithmetic control module <NUM>, a CPU specialized for this instrument or a general-purpose CPU is used.

The horizontal rotation bearing <NUM> is fixed to the fixing unit <NUM>. The horizontal rotation shaft <NUM> has a vertical axis 6a, and the horizontal rotation shaft <NUM> is rotatably supported by the horizontal rotation bearing <NUM>. Further, the frame unit <NUM> is supported by the horizontal rotation shaft <NUM>, and the frame unit <NUM> integrally rotates with the horizontal rotation shaft <NUM> in the horizontal direction.

The horizontal rotation motor <NUM> is provided between the horizontal rotation bearing <NUM> and the frame unit <NUM>, and the horizontal rotation motor <NUM> is controlled by the arithmetic control module <NUM>. The arithmetic control module <NUM> rotates the frame unit <NUM> around the axis 6a by the horizontal rotation motor <NUM>.

A relative rotation angle of the frame unit <NUM> with respect to the fixing unit <NUM> is detected by the horizontal angle encoder <NUM>. A detection signal from the horizontal angle encoder <NUM> is input to the arithmetic control module <NUM>, and the horizontal angle data is calculated by the arithmetic control module <NUM>. The arithmetic control module <NUM> performs the feedback control of the horizontal rotation motor <NUM> based on the horizontal angle data.

Further, in the frame unit <NUM>, the vertical rotation shaft <NUM> having a horizontal axis 11a is provided. The vertical rotation shaft <NUM> can rotate via the vertical rotation bearing <NUM>. It is to be noted that an intersection of the axis 6a and the axis 11a is a projecting position for a distance measuring light, and the intersection is an origin of a coordinate system of the surveying instrument main body <NUM>.

A recess portion <NUM> is formed in the frame unit <NUM>. One end portion of the vertical rotation shaft <NUM> extends to the inside of the recess portion <NUM>. Further, the scanning mirror <NUM> is fixed to the one end portion, and the scanning mirror <NUM> is accommodated in the recess portion <NUM>. Further, the vertical angle encoder <NUM> is provided at the other end portion of the vertical rotation shaft <NUM>.

The vertical rotation motor <NUM> is provided on the vertical rotation shaft <NUM>, and the vertical rotation motor <NUM> is controlled by the arithmetic control module <NUM>. The arithmetic control module <NUM> rotates the vertical rotation shaft <NUM> by the vertical rotation motor <NUM>. Further, and the scanning mirror <NUM> is rotated around the axis 11a.

A rotation angle of the scanning mirror <NUM> is detected by the vertical angle encoder <NUM>, and a detection signal is input to the arithmetic control module <NUM>. The arithmetic control module <NUM> calculates the vertical angle data of the scanning mirror <NUM> based on the detection signal, and performs the feedback control of the vertical rotation motor <NUM> based on the vertical angle data.

Further, the horizontal angle data and the vertical angle data calculated by the arithmetic control module <NUM>, and the measurement results are stored in the storage module <NUM>. As the storage module <NUM>, various types of storage devices are used. These storage devices include: an HDD as a magnetic storage device, a CD or DVD as an optical storage device, a memory card and a USB memory as a semiconductor storage device, and other storage devices. The storage module <NUM> may be attachable to and detachable from the frame unit <NUM>. Alternatively, the storage module <NUM> may enable transmitting the data to an external storage device or an external data processing device via a not shown communicating means.

In the storage module <NUM>, various types of programs are used. These programs include: a sequence program for controlling a distance measuring operation, a calculation program for calculating a distance by the distance measuring operation, a calculation program for calculating an angle based on the horizontal angle data and the vertical angle data, a calculation program for calculating three-dimensional coordinates of a desired measuring point based on a distance and an angle, and other programs. Further, when the various types of programs stored in the storage module <NUM> are executed by the arithmetic control module <NUM>, various types of processing are performed.

The operation panel <NUM> is, for instance, a touch panel. The operation panel <NUM> serves as both an operation module which performs, for instance, changing distance measurement instructions or measurement conditions such as a measuring point interval and a display module which displays distance measurement results, images and the like.

Next, a description will be given on the distance measuring unit <NUM> by referring to <FIG> and <FIG>.

The distance measuring unit <NUM> has a distance measuring light projecting module <NUM> and a distance measuring light receiving module <NUM>. It is to be noted that, the distance measuring light projecting module <NUM> and the distance measuring light receiving module <NUM> configure a distance measuring unit.

The distance measuring light projecting module <NUM> has a distance measuring optical axis <NUM>. Further, the distance measuring light projecting module <NUM> has a light emitter <NUM> such as a laser diode (LD), a collimator lens <NUM>, a pinhole plate <NUM> as a spread angle adjusting member, and a reflecting prism <NUM> provided on the distance measuring optical axis <NUM> sequentially from a light emission side. Further, the scanning mirror <NUM> is provided on a reflected optical axis of the reflecting prism <NUM>. Further, a window unit <NUM> which is formed of a transparent material and integrally rotates with the scanning mirror <NUM> is provided on a reflected optical axis of the scanning mirror <NUM>. It is to be noted that the window unit <NUM> is provided in <FIG>, but the window unit <NUM> may be omitted.

It is to be noted that the collimator lens <NUM>, the pinhole plate <NUM>, the reflecting prism <NUM>, and the like configure a light projecting optical system <NUM>. Further, in the present embodiment, the distance measuring optical axis <NUM> and the distance measuring optical axis <NUM> reflected by the reflecting prism <NUM> are generically referred to as the distance measuring optical axis <NUM>.

The light emitter <NUM> is configured to project a laser beam having a predetermined wavelength as a distance measuring light <NUM>, and the collimator lens <NUM> is configured to turn the distance measuring light <NUM> to a parallel light flux.

The pinhole plate <NUM> is, for instance, a black plate material having a pinhole <NUM> drilled in a central portion. The pinhole plate <NUM> is insertable into or removable from the distance measuring optical axis <NUM> via a driving mechanism <NUM>, for instance, a solenoid. In a state where the pinhole plate <NUM> is being inserted onto the distance measuring optical axis <NUM>, the center of the pinhole <NUM> is placed on the distance measuring optical axis <NUM>. It is to be noted that a diameter of the pinhole <NUM> is appropriately set in the range of ϕ = <NUM> to <NUM>, for instance.

In case of performing the prism measurement, which the object is a prism or the like having the retroreflective property, the pinhole plate <NUM> is inserted onto the distance measuring optical axis <NUM>. Further, in case of performing the non-prism measurement, which the object is other than the prism, the pinhole plate <NUM> is removed from the distance measuring optical axis <NUM>.

When the pinhole plate <NUM> has been inserted onto the distance measuring optical axis <NUM>, regarding to the distance measuring light <NUM> which has entered the pinhole plate <NUM>, only the distance measuring light <NUM> which has entered the pinhole <NUM> passes through the pinhole plate <NUM>, and the distance measuring light <NUM> which has entered other than the pinhole <NUM> is blocked by the pinhole plate <NUM>. Therefore, the distance measuring light <NUM> is decreased the light amount by the pinhole plate <NUM> and projected from the pinhole <NUM> while diverging (diameter-expanding) at a predetermined spread angle by a diffraction effect. It is to be noted that a diameter of the pinhole <NUM> is set in such a manner that the spread angle ϕ which is expanded by the diffraction is, for instance, <NUM> minutes. Preferably, the diameter of the pinhole <NUM> is appropriately set in the range of <NUM> to <NUM> minutes.

Further, in the present embodiment, the pinhole plate <NUM> is provided between the collimator lens <NUM> and the reflecting prism <NUM>. On the other hand, the pinhole plate <NUM> may be provided between the light emitter <NUM> and the collimator lens <NUM>.

The reflecting prism <NUM> is formed by joining two trapezoidal prisms. The reflecting prism <NUM> has a rectangular parallelepiped shape with the two prisms being joined. An incidence surface of the distance measuring light <NUM> is orthogonal to the distance measuring optical axis <NUM>, and a joined surface <NUM> of the reflecting prism <NUM> tilts at a predetermined angle with respect to the distance measuring optical axis <NUM>. Further, a projecting surface of the reflecting prism <NUM> is configured in such a manner that the distance measuring optical axis <NUM> reflected on the joined surface <NUM> enters while slightly tilting at, for instance, approximately <NUM>°. That is, the distance measuring light <NUM> enters the reflecting prism <NUM> at a slight tilt with respect to the projecting surface of the reflecting prism <NUM>. Therefore, the projecting surface of the reflecting prism <NUM> prevents the distance measuring light <NUM> internally-reflected by the projecting surface from being received by a photodetector <NUM> (to be described later). It is to be noted that a tilt angle of the joined surface <NUM> is an angle causing the deflection (the reflection) of the distance measuring optical axis <NUM> in such a manner that the distance measuring optical axis <NUM> coincides with a light receiving optical axis <NUM> (to be described later) and the axis 11a. Alternatively, the tilt angle of the joined surface <NUM> may be set to <NUM>°, and the distance measuring light <NUM> may enter the reflecting prism <NUM> with the distance measuring optical axis <NUM> being tilt with respect to the incidence surface of the reflecting prism <NUM> in such a manner that the distance measuring optical axis <NUM> coincides with the light receiving optical axis <NUM> and the axis 11a.

A beam splitter film <NUM> is formed at a central portion of the joined surface <NUM>, and an antireflective film <NUM> is formed on entire front surface and back surface of the reflecting prism <NUM>. The beam splitter film <NUM> has an elliptic shape in conformity with a light flux of the distance measuring light <NUM>. Further, a size of the beam splitter film <NUM> is equivalent to or slightly larger than a light flux diameter of the distance measuring light <NUM> diverged by the pinhole <NUM>. Further, for instance, the beam splitter film <NUM> has optical characteristics to reflect a light which is approximately <NUM>% and transmit through a light which is approximately <NUM>%.

It is to be noted that a ratio of a reflectance and a transmittance in the beam splitter film <NUM> is appropriately set in correspondence with applications or a distance to the object. For instance, in a case where the distance to the object is close, it is desirable to select the reflectance and the transmittance of the beam splitter film <NUM> from the range of the <NUM>% to <NUM>% reflectance and the <NUM>% to <NUM>% transmittance. Further, in a case where the distance to the object is far, it is desirable to select the reflectance and the transmittance of the beam splitter film <NUM> from the range of the <NUM>% to <NUM>% reflectance and the <NUM>% to <NUM>% transmittance.

The distance measuring light receiving module <NUM> has the light receiving optical axis <NUM>. Further, the distance measuring light receiving module <NUM> has the photodetector <NUM>, a light amount adjusting plate <NUM>, and a receiving prism <NUM> provided on the light receiving optical axis <NUM> sequentially from a light reception side, and has a light receiving lens <NUM> with a predetermined NA (Numerical Aperture) provided on the light receiving optical axis <NUM> reflected by the receiving prism <NUM>.

It is to be noted that the light amount adjusting plate <NUM>, the receiving prism <NUM>, the light receiving lens <NUM>, the reflecting prism <NUM>, and the like configure a light receiving optical system <NUM>. Further, in the present embodiment, the light receiving optical axis <NUM> and the light receiving optical axis <NUM> reflected by the receiving prism <NUM> are generically referred to as the light receiving optical axis <NUM>.

The distance measuring unit <NUM> is controlled by the arithmetic control module <NUM>. In a case where the pinhole plate <NUM> is not present on the distance measuring optical axis <NUM>, the pulsed distance measuring light <NUM> is projected onto the distance measuring optical axis <NUM> from the light emitter <NUM>, then the distance measuring light <NUM> is turned to a parallel light flux by the collimator lens <NUM>. Further, in a case where the pinhole plate <NUM> is present on the distance measuring optical axis <NUM>, since the pinhole plate <NUM> blocks lights other than the distance measuring light <NUM> which passes through the pinhole <NUM>, a total light amount of the distance measuring light <NUM> is reduced, Furthermore, the distance measuring light <NUM> is projected at a predetermined spread angle due to the diffraction effect when it passes through the pinhole <NUM>.

The distance measuring light <NUM> which has passed through the pinhole <NUM> enters an incidence surface of the reflecting prism <NUM> at a right angle, and the distance measuring light <NUM> is transmitted through the reflecting prism <NUM> and reflected on the joined surface <NUM> (the beam splitter film <NUM>) in such a manner that the distance measuring optical axis <NUM> becomes coaxial with the light receiving optical axis <NUM> and the axis 11a. The distance measuring light <NUM> projected from the reflecting prism <NUM> is deflected at a right angle by the scanning mirror <NUM> and irradiated to the object via the window unit <NUM>. By rotating the scanning mirror <NUM> around the axis 11a, the distance measuring light <NUM> becomes orthogonal to the axis 11a, and the distance measuring light <NUM> is rotated (scanned) within a plane including the axis 6a.

It is to be noted that the window unit <NUM> is tilted at a predetermined angle with respect to the distance measuring optical axis <NUM> in such a manner that the distance measuring light <NUM> reflected by the window unit <NUM> does not enter the photodetector <NUM>.

The distance measuring light <NUM> reflected by the object (hereinafter a reflected distance measuring light <NUM>) is reflected at a right angle by the scanning mirror <NUM>, and the reflected distance measuring light <NUM> is received by the photodetector <NUM> through the light receiving optical system <NUM>. The photodetector <NUM> is, for instance, an avalanche photodiode (APD) or an equivalent photoelectric conversion element.

The arithmetic control module <NUM> performs the distance measurement for each pulse of the distance measuring light <NUM> based on a time lag between a light emission timing of the light emitter <NUM> and a light reception timing of the photodetector <NUM> (that is, a round-trip time of a pulsed light) and a light velocity (Time Of Flight). It is to be noted that the operation panel <NUM> can change the light emission timing of the light emitter <NUM>, that is, a pulse interval.

It is to be noted that an internal reference light optical system (to be described later) is provided in the distance measuring unit <NUM>. By performing the distance measurement based on a time lag between the light reception timing for an internal reference light (to be described later) received from the internal reference light optical system and the reception timing of the reflected distance measuring light <NUM> and the light velocity, the distance measuring unit <NUM> enables the further accurate distance measurement.

The frame unit <NUM> and the scanning mirror <NUM> are rotated at a constant speed, respectively. A two-dimensional scan by the distance measuring light <NUM> is performed by the cooperation between the vertical rotation of the scanning mirror <NUM> and the horizontal rotation of the frame unit <NUM>. Further, the distance measurement data (a slope distance) is acquired by the distance measurement for each pulsed light, by detecting a vertical angle and a horizontal angle for each pulsed light by the vertical angle encoder <NUM> and the horizontal angle encoder <NUM>, the arithmetic control module <NUM> enables calculating the vertical angle data and the horizontal angle data. Three-dimensional coordinates of the object and the three-dimensional point cloud data corresponding to the object can be acquired based on the vertical angle data, the horizontal angle data, and the distance measurement data.

Next, a description will be given on the light receiving optical system <NUM>. It is to be noted that, in <FIG> and <FIG>, only a chief ray (the distance measuring optical axis <NUM>) of the distance measuring light <NUM> and a chief ray (the light receiving optical axis <NUM>) of the reflected distance measuring light <NUM> are shown.

The receiving prism <NUM> is a quadrangular prism having a predetermined refractive index. The receiving prism <NUM> has a first surface 42a which the reflected distance measuring light <NUM> transmitted through the light receiving lens <NUM> enters, a second surface 42b which reflects the reflected distance measuring light <NUM> transmitted through a plane of the first surface 42a, a third surface 42c which the reflected distance measuring light <NUM> reflected by the second surface 42b and the first surface 42a enters, and a fourth surface 42d as a transmission surface which the reflected distance measuring light <NUM> reflected by the third surface 42c is transmitted through. The reflected distance measuring light <NUM> transmitted through the fourth surface 42d is configured to enter the photodetector <NUM>. It is to be noted that, the third surface 39c reflects the reflected distance measuring light <NUM> in such a manner that the reflected distance measuring light <NUM> crosses the reflected distance measuring light <NUM> entered the first surface 39a.

The light amount adjusting plate <NUM> is a plastic disk, for instance. A circular gradation film is formed as a light amount adjusting surface on a surface of the light amount adjusting plate <NUM>, and a part of the gradation film is arranged to be orthogonal to the light receiving optical axis <NUM>. Further, the light amount adjusting plate <NUM> is rotatable around a rotation shaft <NUM> by a motor <NUM>. An incidence position of the reflected distance measuring light <NUM> with respect to the light amount adjusting plate <NUM> (the light amount adjusting surface) is configured to change based on the rotation of the light amount adjusting plate <NUM>.

The gradation film is configured in such a manner that a transmittance gradually increases (or decreases) in the range of θ = <NUM>° to <NUM>°. Therefore, by driving the motor <NUM> and controlling an incidence position of the reflected distance measuring light <NUM> with respect to the light amount adjusting plate <NUM> (the light amount adjusting surface), the arithmetic control module <NUM> is capable of changing the transmittance of the reflected distance measuring light <NUM> in the range of <NUM>% to <NUM>%, for instance. The transmittance of the light amount adjusting plate <NUM> is appropriately set in correspondence with a type of the object or a distance to the object.

Further, a reference prism <NUM> having the retroreflective property is provided below the scanning mirror <NUM>. In a process of the rotational irradiation of the distance measuring light <NUM> via the scanning mirror <NUM>, a part of the distance measuring light <NUM> enters the reference prism <NUM>. The distance measuring light <NUM> retro-reflected by the reference prism <NUM> is configured to enter the light receiving optical system <NUM> via the scanning mirror <NUM>, and to be received by the photodetector <NUM>.

Here, an optical path length from the light emitter <NUM> to the reference prism <NUM> and an optical path length from the reference prism <NUM> to the photodetector <NUM> are known. Therefore, the distance measuring light <NUM> reflected by the reference prism <NUM> can be used as internal reference light <NUM>. The scanning mirror <NUM> and the reference prism <NUM> configured an internal reference light optical system <NUM>.

Next, a description will be given on a case where the measurement is performed by the surveying instrument <NUM> having the distance measuring unit <NUM>. Various types of operations of the distance measuring unit <NUM> are performed when the arithmetic control module <NUM> executes various types of programs stored in the storage module <NUM>. It is to be noted that a case where the prism measurement is performed will be described below.

The distance measuring light <NUM> emitted from the light emitter <NUM> is turned to a parallel light flux by the collimator lens <NUM>, and then enters the reflecting prism <NUM> at a right angle while being dimmed and spreading at a predetermined spread angle via the pinhole <NUM> of the pinhole plate <NUM>. Alternatively, the distance measuring light <NUM> emitted from the light emitter <NUM> directly enters the reflecting prism <NUM> at a right angle via the collimator lens <NUM>.

The distance measuring light <NUM> which has entered the reflecting prism <NUM> is transmitted through the reflecting prism <NUM>, and deflected (reflected) such that the distance measuring optical axis <NUM> becomes coaxial with the light receiving optical axis <NUM> and the axis 11a by the beam splitter film <NUM> of the joined surface <NUM>. At this time, since the beam splitter film <NUM> has an elliptic shape with a size equivalent to or slightly larger than a light flux diameter of the distance measuring light <NUM>, the entire distance measuring light <NUM> enters the beam splitter film <NUM>. Further, since a projecting surface of the reflecting prism <NUM> tilts with respect to the distance measuring optical axis <NUM>, the distance measuring light <NUM> internally reflected on the projecting surface is not received by the photodetector <NUM>.

The distance measuring light <NUM> reflected on the beam splitter film <NUM> is transmitted at a slight tilt with respect to the projecting surface of the reflecting prism <NUM> and irradiated to the object, for instance, a prism having the retroreflective property via the scanning mirror <NUM>.

The reflected distance measuring light <NUM> reflected by the prism is reflected at a right angle by the scanning mirror <NUM>, transmitted through the reflecting prism <NUM>, and enters the light receiving optical system <NUM>. Here, a light of a center part of the reflected distance measuring light <NUM> enters the beam splitter film <NUM> on the joined surface <NUM>. Further, the reflected distance measuring light <NUM> is totally transmitted through portions other than the beam splitter film <NUM> via the antireflective film <NUM>. On the other hand, a part of the reflected distance measuring light <NUM> which has entered is transmitted through a portion where the beam splitter film <NUM> is provided. In the present embodiment, since the beam splitter film <NUM> has a transmittance of <NUM>%, <NUM>% of the reflected distance measuring light <NUM> which has entered the beam splitter film <NUM> is transmitted through the beam splitter film <NUM>.

The reflected distance measuring light <NUM> which has been transmitted through the reflecting prism <NUM> and has entered the light receiving optical system <NUM> is refracted in a process of being transmitted through the light receiving lens <NUM> and the first surface 42a. The reflected distance measuring light <NUM> is internally-reflected sequentially by the second surface 42b and the first surface 42a in the receiving prism <NUM>, and enters the third surface 42c. Further, the reflected distance measuring light <NUM> is reflected on the third surface 42c toward the fourth surface 42d, that is, in a direction crossing the reflected distance measuring light <NUM> which has entered from the first surface 42a. The reflected distance measuring light <NUM> transmitted through the fourth surface 42d is received by the photodetector <NUM> while being decreased the light amount in a process of being transmitted through the light amount adjusting plate <NUM>.

The arithmetic control module <NUM> calculates three-dimensional coordinates of the prism based on a distance measurement result of the distance measuring unit <NUM> and detection results of the horizontal angle encoder <NUM> and the vertical angle encoder <NUM>.

It is to be noted that the measurement of the prism may be performed by scanning a whole circumference or a periphery of the prism with the distance measuring light <NUM> and determining a position at which the reflected distance measuring light <NUM> has been received as a position of the prism.

As described above, in the first embodiment, the pinhole plate <NUM> insertable and/or removable with respect to the distance measuring optical axis <NUM> is provided, and the dimming of the distance measuring light <NUM> and the expansion of the spread angle are enabled via the pinhole <NUM> of the pinhole plate <NUM>.

Here, regarding to the non-prism distance measurement, the distance measuring light <NUM> which a large light amount is used in such a manner that a received light amount of the reflected distance measuring light <NUM> is obtained sufficiently even if a reflectance of the object is low. On the other hand, in a case where the prism measurement is performed using the distance measuring light <NUM> with a large light amount, a received light amount of the reflected distance measuring light <NUM> becomes excessive, and the photodetector <NUM> is saturated.

Therefore, in a case where the prism measurement is performed, by inserting the pinhole plate <NUM> onto the distance measuring optical axis <NUM> and decreasing the receiving light amount of the distance measuring light <NUM>, it is possible to prevent the photodetector <NUM> from being saturated. That is, by inserting or removing of the pinhole plate <NUM>, the arithmetic control module <NUM> enables changing a light amount and a spread angle of the distance measuring light <NUM>.

Further, when the distance measuring light <NUM> passes through the pinhole <NUM>, since the distance measuring light <NUM> diverges at a predetermined spread angle by the diffraction effect, it is possible to easily irradiate the distance measuring light <NUM> to the prism, and the workability can be improved.

Further, the pinhole <NUM> is a hole, and the distance measuring light <NUM> does not refract when the distance measuring light <NUM> passes through the pinhole <NUM>. Therefore, since the pinhole plate <NUM> does not have to be precisely arranged in such a manner that the pinhole plate <NUM> becomes orthogonal to the distance measuring optical axis <NUM> and a surface of the pinhole plate <NUM> does not have to be a precise flat surface, a manufacturing cost can be reduced, and the workability can be improved.

Further, in a first embodiment, the reflecting prism <NUM>, which is a combination of two prisms, is used as an optical member configured to coincide the distance measuring optical axis <NUM> with the light receiving optical axis <NUM>, and the distance measuring light <NUM> is deflected by the beam splitter film <NUM> formed on the joined surface <NUM> of the reflecting prism <NUM>.

Here, a light amount at a central portion of the reflected distance measuring light <NUM> increases if a distance to the object is short, and a light amount at a peripheral portion of the reflected distance measuring light <NUM> increases if a distance to the object is long.

Therefore, since a part of the reflected distance measuring light <NUM> which has entered the beam splitter film <NUM> is transmitted through the beam splitter film <NUM> having a predetermined transmittance, it is possible to reduce the vignetting of the reflected distance measuring light <NUM> due to the beam splitter film <NUM> and obtain a sufficient received light amount which enables the distance measurement even in the short-distance measurement.

Further, since it is possible to reduce the vignetting of the reflected distance measuring light <NUM> passing through the beam splitter film <NUM>, a small corner cube or the like is used as the object, and performing the measurement is enabled even if a beam diameter of the reflected distance measuring light <NUM> is small.

Further, the light amount adjusting plate <NUM> having a light amount adjusting surface capable of changing a transmittance by the rotation is provided between the receiving prism <NUM> and the photodetector <NUM>, and the rotation of the light amount adjusting plate <NUM> enables adjusting a light amount of the reflected distance measuring light <NUM> received by the photodetector <NUM>.

Therefore, even in a case where the light amount of the reflected distance measuring light <NUM> is so large that the photodetector <NUM> is saturated, it is possible to attenuate the light amount of the reflected distance measuring light <NUM> to an appropriate light amount by the light amount adjusting plate <NUM>.

Further, since the projecting surface of the reflecting prism <NUM> slightly tilts with respect to the distance measuring optical axis <NUM> deflected by the beam splitter film <NUM>, it is possible to prevent the distance measuring light <NUM> internally reflected on the projecting surface is received by the photodetector <NUM>, which reduces measurement errors.

Further, since the receiving prism <NUM> is provided and the reflected distance measuring light <NUM> is internally reflected in the receiving prism <NUM> more than once, it is possible to be shorten an optical path length in a direction of the axis 11a (a left-and-right direction with respect to a plane of paper), downsize an optical system of the distance measuring unit <NUM>, and reduce a weight of the surveying instrument <NUM>.

Next, by referring to <FIG>, a description will be given on a second embodiment of the present invention. It is to be noted that, in <FIG>, the same components as shown in <FIG> are referred by the same symbols, and detailed description thereof will be omitted.

In the second embodiment, by being deflected a distance measuring optical axis <NUM> twice, the distance measuring optical axis <NUM> is configured to coincide with a light receiving optical axis <NUM> and an axis 11a. That is, in the second embodiment, a reflecting mirror <NUM> which deflects (reflects) the distance measuring optical axis <NUM> at a right angle is provided between a pinhole plate <NUM> and a reflecting prism <NUM>.

The distance measuring light <NUM> which has been emitted from a light emitter <NUM> and passed through a pinhole <NUM> is deflected at a right angle by the reflecting mirror <NUM> and then perpendicularly enters with respect to a reflecting prism <NUM>. That is, the distance measuring light <NUM> enters with respect to an incidence surface of the reflecting prism <NUM> perpendicularly. Processes after incidence upon the reflecting prism <NUM> are the same as the processes in the first embodiment.

In the second embodiment, since the reflecting mirror <NUM> which deflects the distance measuring optical axis <NUM> at a right angle is provided, it is possible to be shorten an optical path length in a direction of an axis 6a (an up-and-down direction with respect to a plane of paper, see <FIG>) and downsize an optical system of a distance measuring unit <NUM>.

Next, by referring to <FIG>, a description will be given on a third embodiment of the present invention. It is to be noted that, in <FIG>, the same components as shown in <FIG> are referred by the same symbols, and detailed description thereof will be omitted.

The third embodiment, like the second embodiment, is configured to coincide a distance measuring optical axis <NUM> with a light receiving optical axis <NUM> and an axis 11a, by deflecting the distance measuring optical axis <NUM> twice. On the other hand, in the third embodiment, a reflecting prism <NUM> is a trapezoidal prism with two prisms joined together.

The reflecting prism <NUM> has a reflecting surface <NUM>, the reflecting surface <NUM> reflects (deflects) a distance measuring light <NUM> which entered at a right angle with respect to the reflecting prism <NUM> toward a joined surface <NUM>. The distance measuring light <NUM> reflected on the reflecting surface <NUM> is deflected by a beam splitter film <NUM> on the joined surface <NUM> in such a manner that the distance measuring optical axis <NUM> coincides with a light receiving optical axis <NUM> and an axis 11a. Processes after incidence upon the beam splitter film <NUM> are the same as the processes in the first embodiment.

In the third embodiment, the reflecting prism <NUM> has the reflecting surface <NUM> which deflects a distance measuring optical axis <NUM> toward the beam splitter film <NUM>. Therefore, it is possible to be shorten an optical path length in a direction of an axis 6a (an up-and-down direction with respect to a plane of paper, see <FIG>) and downsize an optical system of a distance measuring unit <NUM>.

Further, since the prism is used instead of a mirror as an optical member configured to deflect the distance measuring optical axis <NUM> toward the beam splitter film <NUM>, it is possible to suppress a deviation of the optical axis (a deflection angle error) based on temperature changes with respect to a surveying instrument main body <NUM> and improve a measurement accuracy.

Next, by referring to <FIG>, a description will be given on a fourth embodiment of the present invention. It is to be noted that, in <FIG>, the same components as shown in <FIG> are referred by the same symbols, and detailed description thereof will be omitted.

The fourth embodiment is a configuration that a tracking function added to the surveying instrument of the first embodiment, and a distance measuring unit <NUM> has a tracking light projecting module <NUM> and a tracking light receiving module <NUM>.

The tracking light projecting module <NUM> has a tracking optical axis <NUM>. Further, the tracking light projecting module <NUM> has a tracking light emitter <NUM>, a collimator lens <NUM>, a dichroic mirror <NUM>, and a reflecting prism <NUM> sequentially provided on the tracking optical axis <NUM> from a light emission side. It is to be noted, in the present embodiment, the tracking optical axis <NUM> and the tracking optical axis <NUM> reflected by the reflecting prism <NUM> are generically referred to as the tracking optical axis <NUM>. Further, a distance measuring light projecting module <NUM>, that is, a light emitter <NUM>, a collimator lens <NUM>, and a pinhole plate <NUM> are provided on a reflection side of the dichroic mirror <NUM>.

The tracking light emitter <NUM> is, for instance, a laser diode (LD), and configured to project a tracking light <NUM> having a near-infrared wavelength different from a wavelength of a distance measuring light <NUM>. Further, the dichroic mirror <NUM> is configured to transmit through the tracking light <NUM> and reflect the distance measuring light <NUM>.

That is, the dichroic mirror <NUM> is provided on a common optical path of the distance measuring light <NUM> and the tracking light <NUM> (an intersecting position of a distance measuring optical axis <NUM> and the tracking optical axis <NUM>), and deflects (reflects) the distance measuring optical axis <NUM> in such a manner that the distance measuring optical axis <NUM> coincides with the tracking optical axis <NUM>. Therefore, the distance measuring light <NUM> and the tracking light <NUM> are coaxially irradiated toward an object.

The tracking light receiving module <NUM> has a tracking light receiving optical axis <NUM>. Further, the tracking light receiving module <NUM> has a tracking photodetector <NUM>, a receiving prism <NUM>, and a light receiving lens <NUM> sequentially provided on the tracking light receiving optical axis <NUM> from a light reception side.

The receiving prism <NUM> has a configuration in which a first prism <NUM> which is a quadrangular prism having a predetermined refractive index and a second prism <NUM> which is triangular prism having a predetermined refractive index are joined and integrated with each other. In an integrated state, the receiving prism <NUM> has the same outer shape as the outer shape of the receiving prism <NUM> in the first embodiment. A dichroic filter film is provided on a joined surface <NUM> of the first prism <NUM> and the second prism <NUM>, and the joined surface <NUM> is configured to transmit through a reflected distance measuring light <NUM> and reflect the tracking light <NUM> (a reflected tracking light <NUM>) reflected on an object. That is, the joined surface <NUM> is a separating surface for separating the reflected distance measuring light <NUM> (a light receiving optical axis <NUM>) and the reflected tracking light <NUM> (the tracking light receiving optical axis <NUM>) from each other. It is to be noted that a first surface, a second surface, and a third surface in the receiving prism <NUM> have the same configurations as the configurations of the first surface 42a, the second surface 42b, and the third surface 42c of the receiving prism <NUM> in the first embodiment.

Further, a light amount adjusting plate <NUM> and a photodetector <NUM> are provided on a transmission side of the joined surface <NUM>, and the tracking photodetector <NUM> is provided on a reflection side of the joined surface <NUM>. That is, the joined surface <NUM> is placed on a common optical path of the reflected distance measuring light <NUM> and the reflected tracking light <NUM> (an intersecting position of the light receiving optical axis <NUM> and the tracking light receiving optical axis <NUM>), and separates the reflected distance measuring light <NUM> and the reflected tracking light <NUM> from each other which have coaxially entered the receiving prism <NUM>.

The tracking photodetector <NUM> is a CCD or a CMOS sensor which is an aggregation of pixels, and a position of each pixel on the tracking photodetector <NUM> can be identified. For instance, each pixel has pixel coordinates in a coordinate system with the center of the tracking photodetector <NUM> as an origin, and its position on the tracking photodetector <NUM> can be identified by the pixel coordinates. Each pixel outputs pixel coordinates together with a light reception signal to the arithmetic control module <NUM>.

When tracking an object, an arithmetic control module <NUM> irradiates the tracking light <NUM> coaxially with the distance measuring light <NUM>, calculates an incidence position of the reflected tracking light <NUM> which reflected by the object with respect to the tracking photodetector <NUM>, and calculates a deviation between the incidence position and the center of the tracking photodetector <NUM>. Based on the deviation, the arithmetic control module <NUM> controls a horizontal rotation motor <NUM> and the vertical rotation motor <NUM> in such a manner that the incidence position of the reflected tracking light <NUM> coincides with the center of the tracking photodetector <NUM>. Thereby, the surveying instrument main body <NUM> tracks the object.

In the fourth embodiment, optical components for the distance measurement and optical components for the tracking are partially shared, and the distance measuring light <NUM> and the tracking light <NUM> are configured to irradiate the object coaxially. Therefore, even if a tracking function is added to the surveying instrument <NUM>, it is possible to downsize an optical system of the distance measuring unit <NUM>.

It is to be noted that a transmission side of the dichroic mirror <NUM> may be set as a distance measuring light projecting module <NUM>, and a reflection side of the dichroic mirror <NUM> may be set as the tracking light projecting module <NUM>. Further, a transmission side of the joined surface <NUM> may be set as the tracking light receiving module <NUM>, and a reflection side of the joined surface <NUM> may be set as the distance measuring light receiving module <NUM>.

Next, by referring to <FIG>, a description will be given on a fifth embodiment of the present invention. It is to be noted that, in <FIG>, the same components as shown in <FIG> are referred by the same symbols, and detailed description thereof will be omitted.

In the fifth embodiment, in addition to a distance measuring light projecting module <NUM>, a distance measuring light receiving module <NUM>, a tracking light projecting module <NUM>, and a tracking light receiving module <NUM> similar to those in the fourth embodiment, a laser pointer light projecting module <NUM> and an image pickup module <NUM> are coaxially provided.

The laser pointer projecting module <NUM> has a laser pointer light emitter <NUM>, a light projecting lens <NUM> and a beam splitter <NUM> provided on an optical axis of a laser pointer light projected from the laser pointer light emitter <NUM> (a laser pointer optical axis <NUM>), a mirror <NUM> provided on a reflected optical axis of the beam splitter <NUM>, and a short-pass filter plate <NUM> provided on a reflected optical axis of the mirror <NUM>. It is to be noted, in the present embodiment, the laser pointer optical axis <NUM>, and a laser pointer optical axis <NUM> reflected by the mirror <NUM> and the short-pass filter plate <NUM> are generically referred to as the laser pointer optical axis <NUM>.

The laser pointer light emitter <NUM> is, for instance, a laser diode which projects a laser beam in a visible light range. The beam splitter <NUM> deflects the laser pointer optical axis <NUM> coaxially with an image pickup optical axis <NUM> (to be described later). That is, the beam splitter <NUM> is arranged at an intersecting position of the laser pointer optical axis <NUM> and the image pickup optical axis <NUM>. Further, the mirror <NUM> reflects the laser pointer optical axis <NUM> toward the short-pass filter plate <NUM>.

The short-pass filter plate <NUM> has optical characteristics to transmit through a visible light and reflect a distance measuring light <NUM> (a reflected distance measuring light <NUM>) and a tracking light <NUM> (a reflected tracking light <NUM>). Further, the short-pass filter plate <NUM> deflects a distance measuring optical axis <NUM> and a tracking optical axis <NUM> in such a manner that the distance measuring optical axis <NUM> and the tracking optical axis <NUM> become coaxial with a laser pointer optical axis <NUM> transmitted through the short-pass filter plate <NUM>. Further, the short-pass filter plate <NUM> separates the image pickup optical axis <NUM> from the light receiving optical axis <NUM> and a tracking light receiving optical axis <NUM>. That is, the short-pass filter plate <NUM> is arranged on a common optical path of the distance measuring light <NUM> (the tracking light <NUM>) and a laser pointer light.

The image pickup module <NUM> has an image pickup element <NUM>, a light receiving lens group <NUM>, the beam splitter <NUM>, the mirror <NUM>, and the short-pass filter plate <NUM> provided on an optical axis of a background light received by the image pickup element <NUM> (the image pickup optical axis <NUM>).

The image pickup element <NUM> is a CCD or a CMOS sensor which is an aggregation of pixels, and a position of each pixel on the image pickup element <NUM> can be identified. For instance, each pixel has pixel coordinates in a coordinate system with the center of the image pickup element <NUM> as an origin, and its position on the image pickup element <NUM> can be identified by the pixel coordinates. Each pixel outputs pixel coordinates together with a light reception signal to the arithmetic control module <NUM>.

The reflected distance measuring light <NUM>, the reflected tracking light <NUM>, and a reflected laser pointer light which have been coaxially irradiated and coaxially reflected enter the distance measuring unit <NUM> together with the background light, and each light are separated when the reflected laser pointer light and the background light are transmitted through the short-pass filter plate <NUM>.

Further, the reflected laser pointer light and the background light which have been transmitted through the short-pass filter plate <NUM> are reflected by the mirror <NUM>, and imaged on the image pickup element <NUM> via the beam splitter <NUM> and the light receiving lens group <NUM>, and an image is acquired.

In the fifth embodiment, the laser pointer light projecting module <NUM>, the image pickup module <NUM>, the distance measuring optical axis <NUM> and the tracking optical axis <NUM> are provided in such a manner that each module and axis becomes coaxial with each other. Therefore, since it is possible to share some of optical members used in the distance measurement, the tracking, the image pickup, and others, which achieves downsizing an optical system and a reduction in the number of components.

Next, by referring to <FIG>, a description will be given on a sixth embodiment of the present invention. It is to be noted that, in <FIG>, the same components as shown in <FIG> are referred by the same symbols, and detailed description thereof will be omitted.

In the sixth embodiment, in addition to a distance measuring light projecting module <NUM>, a distance measuring light receiving module <NUM>, a tracking light projecting module <NUM>, and a tracking light receiving module <NUM>, an image pickup module <NUM> is added.

Further, in the sixth embodiment, a reflecting prism <NUM> tilts at approximately <NUM>° with respect to an axis 11a, and a long-pass filter surface <NUM> having a long-pass filter provided is formed on a projecting surface of the reflecting prism <NUM> (a left surface with respect to a plane of paper). Further, a lower portion of the reflecting prism <NUM> is formed a chamfered portion.

The long-pass filter surface <NUM> has optical characteristics to reflect a visible light and transmit through an infrared light and a near-infrared light. That is, the long-pass filter surface <NUM> is a separating surface which reflects a background light and transmits through a reflected distance measuring light <NUM> and a reflected tracking light <NUM> which have entered coaxially.

An optical axis of the background light separated and reflected by the long-pass filter surface <NUM> is the image pickup optical axis <NUM>, and a light receiving lens group <NUM> and an image pickup element <NUM> are provided on the image pickup optical axis <NUM>. Therefore, the background light which has entered the reflecting prism <NUM> is reflected on the long-pass filter surface <NUM>, and enters the image pickup element <NUM>. The other structures are substantially the same as the structures in the fourth embodiment.

In the sixth embodiment, the long-pass filter surface <NUM> provided on the projecting surface of the reflecting prism <NUM> is used as a separating surface by which the background light is separated. Therefore, since a mirror or a prism does not have to be additionally provided in order to separate the background light, which achieves a reduction in the number of components and the downsizing of an optical system.

Claim 1:
A surveying instrument comprising: a distance measuring light projecting module (<NUM>) configured to project a distance measuring light (<NUM>) to an object, a distance measuring light receiving module (<NUM>) having a photodetector (<NUM>) configured to receive a reflected distance measuring light (<NUM>) from said object, and an arithmetic control module (<NUM>) configured to control said distance measuring light projecting module and calculate a distance to said object based on a light reception result of said reflected distance measuring light with respect to said photodetector, wherein said distance measuring light projecting module has a pinhole plate (<NUM>) which is insertable or removable with respect to an optical axis (<NUM>) of said distance measuring light, a pinhole (<NUM>) having a predetermined diameter is formed in said pinhole plate, and a light amount and a spread angle of said distance measuring light are changeable based on the insertion or removable of said pinhole plate, characterized in that said distance measuring light projecting module (<NUM>) has a reflecting prism (<NUM>, <NUM>, <NUM>) having two prisms joined together, a beam splitter film (<NUM>) having a predetermined reflectance and transmittance is formed on a joined surface (<NUM>) of said reflecting prism, and said reflecting prism is configured to deflect said optical axis (<NUM>) of said distance measuring light (<NUM>) via said beam splitter film so as to coincide with an optical axis (<NUM>) of said reflected distance measuring light (<NUM>), wherein said reflecting prism is tilted with respect to said optical axis of said reflected distance measuring light, such that said distance measuring light, reflected by the beam splitter film, transmits at a slight tilt through a projecting surface of said reflecting prism.