Geometrical instruments – Straight-line light ray type – Rod or target
Reexamination Certificate
1999-07-09
2001-05-29
Bennett, G. Bradley (Department: 2859)
Geometrical instruments
Straight-line light ray type
Rod or target
C033S290000
Reexamination Certificate
active
06237235
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention is directed to an electronic level with a clinometer and a process for video sighting or targeting of a graduated staff of at least one target at a distance, from the level in accordance with the preamble of the first patent claim, wherein the level, as a dumpy level or quickset level, has a high degree of automation at low manufacturing cost.
b) Description of the Related Art
DD 291 141 discloses an arrangement for leveling the line of sight of levels, wherein the arrangement comprises a telescope with a sighting axis, including an objective with sliding lens, a graticule and an eyepiece. The arrangement further contains a photoreceiver device with a differential photoelement and a piezo-actuator by means of which the graticule can be adjusted in such a way, depending on the signals which are supplied by a clinometer and appropriately processed by a microprocessor, that a leveling of the telescope axis is achieved.
JP 60-25 413 describes a level with a digital graduated staff at the target. In this case, a light beam is sent to the graduated staff via a beam splitter from a light source arranged in the level and an image of the graduated staff is received by an optical television camera system and displayed on a screen. The determined data are stored in a computer and evaluated in a suitable manner. The screen itself is a liquid crystal display with elements arranged in a matrix. The objective can be focused manually by a sliding lens.
Further, JP 5-272 970 discloses an automatic level which comprises a matrix receiver with a screen, wherein image signals from a CCD-camera are converted into corresponding digital signals by an analog-to-digital converter and are stored in a data storage. The CCD-camera has a focusable objective with a sliding lens.
In the above-mentioned arrangements, focusable objectives are always provided for sharp imaging of the staff graduation on a photoreceiver arrangement or CCD arrangement.
In order to do without focusing, a device for leveling purposes (DE 195 04 039 C1) was provided with imaging optics and a spatially-resolving optoelectronic detector for image recording. In this case, the imaging optics are divided into pupil zones imaging in different ways for different depth of focus ranges; different partial areas of the detector are allocated to the pupil zones. While this device does avoid focusing, the different imaging optics are relatively uneconomical.
In a process for geometric height measurement according to DE 39 16 385, in a manner analogous to the signals of a clinometer arranged in a measurement device independent from a telescope, the reference point for the horizontal position of the measurement device is provided on the center pixel of a CCD array and, when the device is tilted, is displaced in such a way that its position corresponding to the respective inclination of the device determines the intersection point of the horizontal sighting axis for a pixel or for the area between two pixels.
OBJECT AND SUMMARY OF THE INVENTION
It is the primary object of the invention to provide an electronic level and a process for video sighting of a graduated staff which ensures a high degree of automation of measurements at low manufacturing costs and while economizing on optical and mechanical structural component parts and in which large inclinations of the vertical axis can be compensated.
This object is met, according to the invention, in an electronic level which comprises a clinometer, an image receiving device having a telescope with an objective and with a CCD receiver matrix and with a screen for displaying the image of a graduated staff which is set up at a target and provided with a coded graduation, a vertical axis which is rotatable about the level, a leveling device for alignment and rough leveling of the level with respect to the graduated staff, an input unit for entering measurement data and a power supply unit and a computer for processing the measurement data, calculating measurement values and for image evaluation. The image receiving device comprises a CCD receiver matrix which is operated in video clock. The objective or the CCD receiver matrix is arranged in a fixed position relative to the vertical axis. The objective and CCD receiver matrix is adjustable relative to one another. The clinometer is assigned in a fixed manner for measuring the deviation of the position of a sighting axis relative to the horizon. The sighting axis is formed by a center pixel of the CCD receiver matrix.
The invention also encompasses a process for using the electronic level.
The level according to the invention is a camera level, as it is called, which basically includes only the objective, the clinometer, the vertical axis and an endless slow-motion tangent screw for sighting the graduated staff, a leveling device (tribrach or ball joint) and an image detection and image display system. The image detection system includes a CCD receiver matrix with the center pixel which, together with the object-side principle point of the objective, serves to determine the line of sight which is assigned in a fixed manner to the clinometer which measures, in a known manner, the deviation of the position from the horizontal. The CCD receiver matrix itself is operated in pixel clock or video clock and accordingly supplies moving images of the distant target to be measured.
In order that the position of a vertical axis inclined in space can also be taken into account in measurements with the level, the data supplied by the clinometer are included in the processing by the computer. Therefore, it is possible that the level need no longer be exactly leveled. In a case such as this, the graduated staff image would appear inclined on the screen. For this reason, the level is provided not only with image evaluating electronics and corresponding software, but also with a computer which calculates an appropriate height correction by means of the data supplied by the clinometer and applies this to the reading of the graduated staff. In this way, with the aid of the data from the clinometer which supplies data in two axes, a crosshair on the screen can be adjusted so as to be vertical and moved in the horizon in order to simultaneously carry out an alignment of the line of sight in the same way as with a well-leveled level. Accordingly, it is possible to work with a skewed level in the same way as with a well-leveled level.
In order to obtain correction values in a particularly simple manner and to use these correction values for measurement correction in a corresponding manner, the forward, i.e., object-side, principal point of the objective advantageously lies in the intersection of the sighting axis and vertical axis or at a fixed distance from this intersection.
Further, it is advantageous when the CCD receiver matrix and the objective are displaceable relative to one another by adjusting means in the direction of the optical axis of the objective for focusing the graduated staff image, wherein the CCD receiver matrix or the objective is arranged in a fixed position relative to the vertical axis, and when the displacement path and the displacement direction of the matrix and/or of the objective can be determined from the image data supplied by the receiver elements of the matrix by means of an image evaluating system, known per se.
Further, the display unit is advantageously provided with a screen having a diaphragm for blocking out ambient light and an arrangement is provided which controls the contrast of the screen as a function of the ambient light and which is connected with the computer. In this way, the screen can be properly viewed even under unfavorable light conditions.
A process for video sighting with the level constructed according to the invention, wherein a graduated staff set up at a distant target point is sighted, is characterized in that when the vertical axis of the level is positioned so as to be inclined in space the correction of the sighting axis, with respect to amount
Feist Wieland
Kaschke Michael
Monz Ludwin-Heinz
Bennett G. Bradley
Carl Zeiss Jena GmbH
Reed Smith LLP
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