Optics: measuring and testing – Position or displacement
Reexamination Certificate
2001-11-30
2004-06-08
Rosenberger, Richard A. (Department: 2877)
Optics: measuring and testing
Position or displacement
C250S559310
Reexamination Certificate
active
06747745
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an optical displacement sensor for measuring a displacement such as a length of a measurement object according to a light section method, triangulation or the like, and in particular to an optical displacement sensor which allows the state of the surface of the measurement object to be observed on the screen of a video monitor.
BACKGROUND OF THE INVENTION
Two examples of sensor units for such optical displacement sensors are shown in
FIG. 43
(regular reflection surface type) and
FIG. 44
(irregular reflection surface type).
Referring to
FIG. 43
, a denotes a sensor head unit, b denotes measurement light (a red laser beam having a circular cross section or a linear cross section, for instance) which is emitted from the sensor head unit mounted at a prescribed position and impinged obliquely downward onto a measurement object, c denotes measurement light which is reflected by the surface of the measurement object and advances obliquely upward onto the sensor head unit, d denotes the measurement object of a regular reflection surface type such as a glass plate or a metallic plate having a smooth surface, and e denotes diffused reflected light produced by the reflection of the measurement light by the surface of the measurement object. The light axis of the measurement light exiting from the unit a and the light axis of the incident measurement light c directed to the unit a are arranged symmetric to each other at a same inclination angle.
Referring to
FIG. 44
, a denotes a sensor head unit, d denotes a measurement object of a irregular reflection surface type, f denotes measurement light (a red laser beam having a circular cross section or a linear cross section, for instance) which is emitted from the sensor head unit vertically downward onto the measurement object, g denotes measurement light which is reflected by the surface of the measurement object and advances obliquely upward onto the sensor head unit, and h denotes diffused reflected light produced by the reflection of the measurement light by the surface of the measurement object.
The reflected measurement light c and g received by the sensor head unit forms an image on the light receiving surface of the imaging device (such as a one dimensional CCD and a two dimensional CCD) via a light receiving optical system (such as a lens assembly), and is converted into a video signal including the radiated light image (a bright spot or line) of the measurement light by using the photoelectric conversion capability of the imaging device. The video signal thus obtained is forwarded to a controller unit now shown in the drawing, and is used for a computation for displacement measurement based on triangulation.
To accurately measure a displacement (such as a displacement in the vertical direction) of a desired position on the measurement object, it is necessary to coincide the radiated position of the measurement light b and f with the measurement position in a highly accurate manner. When the measurement light consists of visible laser light (such as red laser light), the registration between the measurement position and the radiated position of measurement light can be accomplished by moving the radiated light image of the measurement light to the desired measurement position while visually observing the radiated light image.
However, such conventional displacement sensors are known to have a number of problems.
(1) When the measurement has surface irregularities, the work of adjusting the radiated position of the measurement light right onto the measurement point, and the work of verifying that the measurement light is accurately radiating upon the measurement point involve some difficulty when performed with a direction observation using the naked eye.
(2) In
FIGS. 43 and 44
, if the measurement distance L which is a displacement measurement range is short, and the sensor head unit a and the measurement object are close to each other, because the sensor head unit a closely covers the measurement position from above, the field of view of the operator is obstructed by the sensor head unit a, and the operator experiences a difficulty in viewing the radiated light image of the measurement light, and is unable to properly carry out the work of achieving a registration between the measurement position and the radiated position of measurement light.
(3) Displacement sensors using a conventional two dimensional imaging device include those allowing the illuminated light image of the measurement light captured by the two dimensional imaging device to be displayed on an image monitor. However, the illuminated light image of the measurement light shows itself far brighter than the surrounding surface of the measurement object. This is because the intensity of the measurement light, the lighting timing of the measurement light and the shutter timing of the two dimensional imaging device are determined in such a manner that the illuminated light image of the measurement light is appropriately imaged but the surrounding surface of the measurement object appears substantially darker in comparison because the image of the shape and pattern of the surface of the measurement object surrounding the measurement point should not interfere with the measurement. Therefore, even though the image monitor allows the radiated light image of the measurement light to be observed, but because the surrounding surface of the measurement object is not shown on the screen, it is not possible to verify the positional relationship between the radiated light image and the surface of the measurement object on the image monitor.
The present invention was made in view of such problems, and its primary object is to provide a displacement sensor which allows the positional relationship between the radiated light image and the surface of the measurement object to be verified on the image monitor, and component technology to such a displacement sensor.
These and other objects, and advantages of the present invention will become apparent to a person skilled in the art in view of the following description.
BRIEF SUMMARY OF THE INVENTION
The sensor head of the present invention may have a sensor head and a controller either integrally or separately. The term “integral” as used herein means that the sensor head unit and the controller unit are accommodated in a common housing. The term “separately” as used herein means that the sensor head unit and the controller unit are accommodated in separate housings. As for the image monitor, it may be provided with a separate housing or may also be accommodated in the housing of the controller unit, for instance.
The sensor head may comprise a measurement light emitting optical system for emitting measurement light onto a measurement position of an measurement object from a prescribed angle, an image acquiring optical system for capturing an image by viewing the measurement position of the measurement object and a surrounding region from an angle different from that of the measurement light emitting optical system, and a two dimensional imaging device for photoelectrically converting an image obtained by the image acquiring optical system into a video signal corresponding to the image.
The “measurement light emitting optical system” as used herein may comprise a lens array defining a light emitting light path, and may also comprise other optical elements such as mirrors and filters. A light source for emitting light may be incorporated in the system or may be drawn from an external source via an optical fiber. An example of a light emitting light source consists of a red laser diode. The “emitting angle” may be either a regular reflective surface type described in connection with
FIG. 43
or an irregular reflective surface type described in connection with FIG.
44
.
The controller may be adapted to control an imaging condition associated with a brightness of the image in the form of the video signal, and to operate under a measurement mode and an observation mode.
When the contro
Ishikawa Nobuharu
Kawachi Masahiro
Nakashima Hirotaka
Oba Hitoshi
Shimada Koji
Barth Vincent P.
Omron Corporation
Rosenberger Richard A.
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