Electro-optical Distance Meter Using Broadband Light Source
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Solution Overview
Problem
Existing electro-optical distance measurement methods using the Fizeau method are disrupted by additional polarization in the measuring light beam, requiring compensatory measures due to factors like beam deflection mirrors or retroreflectors, which complicate the measurement process.
Innovation Solution
An electro-optical distance meter employing a superluminescent diode as a light source with a wide spectrum, guided through a polarizing beam splitter, electro-optical modulator, and lambda/4 retarder, eliminates the need for optical isolators and compensatory devices by using broadband light, where the modulator modulates polarization, and the detector signal is processed to determine the measurement section length without significant influence from polarization disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a laser source with narrow spectrum is used for electro-optical distance measurement, then measurement precision can be improved, but the system requires optical isolators and is susceptible to polarization disturbances from beam deflection mirrors and retroreflectors
Solution Approach 1:
The patent changes the spectral parameter of the light source from narrow-band (laser) to broad-band (superluminescent diode). This parameter change eliminates the need for optical isolators and reduces sensitivity to polarization disturbances while maintaining measurement precision through the broadband characteristics that compensate for polarization effects
Solution Approach 2:
The patent replaces the expensive and complex laser source with a more economical superluminescent diode. While lasers provide coherent light, the SLED provides sufficient performance for distance measurement without requiring additional protective components like optical isolators, effectively using a simpler, more cost-effective light source
2Speed
If additional polarization elements are introduced in the measuring light beam, then beam direction control is improved, but measurement accuracy deteriorates due to polarization-induced shifts in the minimum position
Solution Approach 1:
The patent converts the harmful effect of polarization disturbances into a beneficial effect. The broadband spectrum of the superluminescent diode causes multiple wavelength components to experience different polarization effects that average out, transforming what would be a source of error into a compensating mechanism that maintains measurement accuracy despite the presence of polarization elements in the optical path
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach simplifies the distance meter structure and eliminates the need for compensation devices, as deviations in broadband light sources compensate for each other, maintaining measurement accuracy and stability regardless of polarization disturbances.
Implementation Method 1
an electro-optical modulator for modulation of a polarization state of the light
Implementation Method 2
a lambda/ 4 retarder (for temperature compensation of the modulator refractive coefficient)
Implementation Method 3
The light source has a wide spectrum of emitted light. Preferably the light source is a superluminescent diode (SLD or SLED)
Implementation Method 4
the emitted light in the distance meter is guided to a measuring section at least through a polarizing beam splitter
Implementation Method 5
Light returning along the measuring section passes through the elements mentioned to the polarizing beam splitter and is guided by it to a detector
Data Source
Figure 1~3
AI summary
An electro-optical distance-measuring unit (10) comprises a light source (1), the emitted light of which in the distance-measuring unit (10) is guided onto a measurement path (8) at least by one polarizing beam splitter (3), an electro-optical modulator (5) and a retarder (6). Light that is returned along the measurement path (8) is guided at least by the retarder (6), the electro-optical modulator (5) and the polarizing beam splitter (3) onto a detector (4). The distance-measuring unit (10) furthermore comprises a control and evaluation unit (11) for determining a length of the measurement path (8) in accordance with a modulation frequency of the electro-optical modulator (5) and a signal of the detector (4). The light source (1) has a broad spectrum of the emitted light and is preferably a super-luminescent diode.