Phase Modulator Constant Power Heating for Substrate Warpage
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Solution Overview
Problem
Phase modulators used in fringe projection systems face challenges due to thermal expansion differences between substrates and optical waveguides, leading to deformation and reduced measurement precision.
Innovation Solution
A phase modulator design with multiple heaters on a substrate, where the total electric power consumption is kept constant, allowing for controlled phase modulation while maintaining a stable substrate temperature, thus preventing warpage and ensuring precise interference fringe projection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the thermo-optic effect is employed to change the phase of the optical waveguide, then the phase modulator can be configured with only typical silica materials formed on a silicon substrate, but temperature change of the optical waveguide causes warpage of the substrate due to difference in thermal expansion rate between the substrate and the optical waveguide, leading to change of the interference fringe projection position
Solution Approach 1:
The patent changes the thermal parameter (temperature) of the substrate by applying heat uniformly across the entire substrate surface. This temperature change compensates for the thermal expansion differences between the silicon substrate and silica optical waveguide, preventing warpage and maintaining stable interference fringe projection position during phase modulation operations.
2Ease of operation
If a single heater is used to heat the waveguide for phase modulation, then the phase can be changed effectively, but the substrate temperature changes causing deformation and reduced measurement precision
Solution Approach 1:
The heating function is segmented into two independent heaters: a first heater that heats the optical waveguide for phase modulation, and a second heater that heats the substrate uniformly. This segmentation allows independent control of waveguide temperature (for phase change) and substrate temperature (for warpage prevention), resolving the contradiction between phase modulation capability and substrate shape stability.
Solution Approach 2:
The second heater acts as an intermediary element that mediates between the first heater's localized heating and the substrate's thermal expansion characteristics. By providing uniform background heating, it compensates for thermal gradients and prevents substrate warpage, enabling stable operation during phase modulation.
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 maintains the stability of the substrate temperature, preventing deformation and ensuring high precision in interference fringe projection patterns, enhancing the measurement accuracy in three-dimensional shape measurement techniques.
Implementation Method 1
in a case in which the thermo-optic effect is employed, such a phase modulator can be configured with only typical silica materials formed on a silicon substrate
Implementation Method 2
this arrangement has the potential to cause the occurrence of warpage of the substrate or the like due to the difference in the thermal expansion rate or the like between the substrate and the optical waveguide
Implementation Method 3
The plurality of heaters includes a first heater that heats the first waveguide and a second heater that heats a position away from the first waveguide. The plurality of heaters is driven such that the total electric power consumption of the plurality heaters is constant.
Data Source
AI summary
A fringe projector apparatus includes: a phase modulator having a first waveguide, a second waveguide, and a plurality of heaters including a first heater and a second heater, wherein the first and second waveguides and the plurality of heaters are provided on a single substrate, and wherein the first heater heats the first waveguide and the second heater heats a position away from the first waveguide; a light source that generates a light beam to be input to the first waveguide and the second waveguide; and a controller that controls a phase difference between the first waveguide and the second waveguide by changing an electric power consumption of the first heater under a condition that a total electric power consumption of the plurality of heaters is constant.