Dynamic expansion of a distance measuring device having a variable optical attenuation element in the transmitting channel

1. A measuring device for scanning uncooperative objects, the measuring device comprising:

an electronic laser distance measuring module including:

an optical transmitting channel having a transmitting unit for generating laser measuring radiation,

an attenuation unit in the optical transmitting channel for attenuating the laser measuring radiation generated by the transmitting unit, and

an optical receiving channel having a receiving unit for reflected laser measuring radiation,

wherein the beam guiding in the electronic laser distance measuring module is implemented by means of a fiber optic,

wherein, during the scanning, the transmitting unit progressively generates modulated signals having a modulation rate greater than 100 kHz,

wherein an electrically controllable setting of at least two different attenuation factors is provided,

wherein the attenuation unit is continuously activatable from transmitted signal to transmitted signal, wherein during the scanning, setting of the attenuation unit is performed using different attenuation factors in such a way that the receiving unit is supplied a received signal having an amplitude in a linear dynamic range of the receiving unit, based on a single immediately preceding received signal pulse or based on multiple successive immediately preceding received signal pulses,

wherein the attenuation unit is designed such that the attenuation is performed by means of an optically active crystal based on an effect from at least one of the groups consisting of:

electro-optical effects,

acousto-optical effects, and

magneto-optical effects, and

wherein the attenuation unit has a functional relationship between attenuation factor and electrical activation, wherein the functional relationship is known over a temperature range between −20° C. and 50° C.

2. A measuring device according to claim 1 , wherein the optically active crystal is a solid optical crystal and the functional relationship between attenuation factor and electrical activation is known over a temperature range between −40° C. and 70° C.

3. A measuring device according to claim 1 , wherein the attenuation unit is configured to operate using:

the attenuation setting rate defined by a setting time between two successive attenuation factors of less than 1000 ns, and

a settable ratio between a minimum and a maximum attenuation factor of a factor of 10 3 or more.

4. A measuring device according to claim 1 , wherein the attenuation unit is designed such that a hysteresis effect in the optically active crystal is automatically calibrated.

5. A measuring device according to claim 4 , wherein the hysteresis effect in the optically active crystal is progressively calibrated.

6. A measuring device according to claim 1 , wherein the laser distance measuring module and the attenuation unit are designed such that a distance error is automatically corrected as a function of the attenuation factor.

7. A measuring device according to claim 6 , wherein the distance error is progressively corrected as a function of the attenuation factor.

8. A measuring device according claim 1 , wherein the attenuation unit is designed as polarization-free.

9. The measuring device according to claim 1 , wherein the optically active crystal is an electro-optically active crystal, wherein the attenuation unit comprises:

a first polarizing beam splitter for generating a first and a second partial beam each having different polarization, wherein the electro-optically active crystal changes the polarization of at least the first partial beam by means of an electro-optical effect, and

a second polarizing beam splitter to guide the two partial beams back together.

10. The measuring device according to claim 9 , wherein the electro-optically active crystal is an optical nonlinear crystal and/or a phase-shifting crystal.

11. The measuring device according to claim 1 , wherein the attenuation unit is designed such that it comprises:

an acousto-optically active crystal comprising the optically active crystal to generate an intensity change between the incident laser measuring beam and a partial beam deflected by diffraction by means of an acousto-optical diffraction effect as a function of an applied activation voltage and an order of diffraction, and

a monitoring unit to compensate for the temperature dependence of an angle of diffraction by means of tracking of a high frequency which generates the acoustic wave.

12. The measuring device according to claim 11 , wherein the first order of diffraction is used for the attenuation of the deflected beam.

13. A measuring device according to claim 1 , wherein the optically active crystal is a magneto-optically active crystal, and wherein the attenuation unit comprises:

a first polarizing beam splitter for generating a first and a second partial beam each having different polarization,

a magneto-optically active crystal comprising the optically active crystal to generate a spatial rotation of a polarization vector of at least the first partial beam by means of a magneto-optical Faraday effect, as a function of a set magnetic field, and

a second polarizing beam splitter to generate an output signal based on at least the modified first partial beam,

wherein a runtime difference between the first and the second partial beam less than 1 ps.

14. The measuring device according to claim 13 , wherein the attenuation unit comprises at least one element of the group consisting of:

another optically active crystal, and

an absorber element to reduce internal scattered light.

15. The measuring device according to claim 1 , wherein the attenuation unit comprises at least one element of the group consisting of:

a calibration unit for calibrating a transit time as a function of the set attenuation factor,

a fixed attenuation unit for reducing multiple reflections,

a fiber having an angled fiber end, in particular at an angle of 8°, for reducing multiple reflections,

an absorber element for extinguishing the deflected light and for generating a constant transit time independently of the set attenuation factor, and

a circulator upstream from an optically active crystal for absorbing back reflections.