High precision optical non-contact position measurement is a key technology in modern engineering. Laser trackers (LT) accurately determine x-y-z coordinates of passive retroreflectors. Next-generation systems answer the need to measure an object‘s rotational orientation (pitch, yaw, roll). So far, these devices are based either on photogrammetry or on enhanced retroreflectors. Here we present a new method to measure all six degrees of freedom in conjunction with a LT. The basic principle is to analyze the orientation to the LT’s beam path by coupling-out laser radiation. The optical design is inspired by a cat’s eye retroreflector equipped with an integrated beam splitter layer. The optical spherical aberration is compensated, which reduces the divergence angle for the reflected beam by one order of magnitude compared to an uncompensated standard system of the same size. The wave front distortion is reduced to less than 0.1 λ @ 633 nm for beam diameters up to 8 mm. Our active retroreflector is suitable for long-range measurements for a distance > 10 m.
High precision optical non-contact position measurement is a key technology in modern engineering. Laser trackers (LT)
can determine accurately x-y-z coordinates of passive retroreflectors. Next-generation systems answer the additional
need to measure an object‘s rotational orientation (pitch, yaw, roll). These devices are based either on photogrammetry
or on enhanced retroreflectors. However, photogrammetry relies on costly camera systems and time-consuming image
processing. Enhanced retroreflectors analyze the LT‘s beam but are restricted in roll angle measurements. In the past we
have presented a new method [1][2] to measure all six degrees of freedom in conjunction with a LT. Now we dramatically
optimized the method and designed a new prototype, e.g. taking into consideration optical alignment, reduced power
loss, highly optimized measuring signals and higher resolution. A method is described that allows compensating the
influence of the LT’s beam offset during tracking the active retroreflector. We prove the functionality of the active
retroreflector with the LT and, furthermore, demonstrate the capability of the system to characterize the tracking behavior of a LT. The measurement range for the incident laser beam is ±12° with a resolution of 0.6".
High precision optical non-contact position measurement is a key technology in modern engineering. Laser trackers (LT) can determine accurately x-y-z coordinates of passive retroreflectors. Next-generation systems answer the additional need to measure an object’s rotational orientation (pitch, yaw, roll). These devices are based on photogrammetry or on enhanced retroreflectors. However, photogrammetry relies on camera systems and time-consuming image processing. Enhanced retroreflectors analyze the LT’s beam but are restricted in roll angle measurements. Here we present an integrated laser based method to evaluate all six degrees of freedom. An active retroreflector directly analyzes its orientation to the LT’s beam path by outcoupling laser light on detectors. A proof of concept prototype has been designed with a specified measuring range of 360° for roll angle measurements and ±15° for pitch and yaw angle respectively. The prototype’s optical design is inspired by a cat’s eye retroreflector. First results are promising and further improvements are under development. We anticipate our method to facilitate simple and cost-effective six degrees of freedom measurements. Furthermore, for industrial applications wide customizations are possible, e.g. adaptation of measuring range, optimization of accuracy, and further system miniaturization.
In this paper we present a novel sensor device which can be used in a tracking system. Due to its unique design the device
can replace the often used assembly consisting of a beam splitter and a quadrant diode. So, it is cost effective and
eliminates the power loss introduced by the conventional assembly completely. The sensor array is not only restricted to
tracking units but can also be used in other applications where beam positioning without power loss is essential. So, e.g.
an online beam alignment during a measurement in microscopy is possible. Several beam profiles are supported due to
the possibility to adjust the sensing elements mechanically. Furthermore a miniaturized integrated version of the device
is achievable by the usage of microsystems technology.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.