Optical Power Sensor Using Polarization Filtering for Laser Diodes
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Solution Overview
Problem
Existing methods for measuring optical power in scanning laser devices are often bulky and costly, and struggle with variability in laser diodes with poor polarization extinction ratios, which affects measurement accuracy.
Innovation Solution
The use of a polarizing component, beam splitter, and photodiode configuration that filters and directs a consistent percentage of the laser beam for accurate power measurement, allowing for compact and cost-effective optical power monitoring in scanning laser devices, even with laser diodes having variable polarization extinction ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional optical power measurement techniques are used, then measurement capability is provided, but device size becomes excessively bulky and cost increases
Solution Approach 1:
The patent combines the optical power measurement function with the existing scanning laser optical path by integrating a beam splitter and photodiode detector into the same optical path. This merging eliminates the need for separate, bulky measurement devices while maintaining measurement capability within the compact scanning laser architecture.
Solution Approach 2:
The optical path components (beam splitter, photodiode) are designed to serve multiple functions: they enable optical power measurement while coexisting with the primary scanning laser function. This multi-functionality reduces overall system complexity and cost by avoiding dedicated separate measurement subsystems.
2Ease of manufacture
If laser diodes with poor polarization extinction ratios are used, then cost and efficiency are improved, but measurement accuracy deteriorates due to variability
Solution Approach 1:
The patent changes the measurement approach from direct intensity measurement to polarization-based measurement. By using a polarizing beam splitter and measuring the difference in intensity between orthogonal polarization components, the system can accurately determine total optical power even when the laser diode has poor or variable polarization extinction ratios. This parameter change in measurement methodology enables accurate measurement while allowing use of cost-effective laser diodes.
Solution Approach 2:
The patent implements a feedback mechanism where the measured optical power (derived from polarization component differences) is used to control the laser diode drive current. This feedback loop compensates for variations in polarization extinction ratio and ensures accurate power control, enabling the use of laser diodes with variable polarization characteristics without sacrificing measurement accuracy.
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 configuration ensures accurate and consistent optical power measurement, enabling reliable feedback for controlling laser light sources and maintaining power efficiency in scanning laser projectors.
Implementation Method 1
a polarizing component configured to filter the first portion of the laser beam for one polarization state
Implementation Method 2
a beam splitter configured to receive the laser beam and split the laser beam into a first portion and a second portion
Implementation Method 3
a photodiode configured to receive the filtered first portion of the laser beam
Data Source
AI summary
Devices and methods are described herein to measure optical power in scanning laser projectors. In general, the devices and methods utilize a polarizing component and photodiode to measure optical power being generated by at least one laser light source. The polarizing component is configured to polarize at least a portion of the laser beam in a way that improves the accuracy and consistency of this optical power measurement. Specifically, the polarizing component filters at least a portion of the laser beam for one polarization state in a way that facilitates improved reliability in the amount of laser light directed into the photodiode.