PIC Optical Inspection Using Linear Filter Wavelength Extraction
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Solution Overview
Problem
Existing inspection methods for photonic integrated circuits (PICs) cannot acquire wavelength information from light output, leading to inadequate inspection capabilities.
Innovation Solution
An inspection apparatus and method that utilizes an optical filter with a linearly varying transmittance characteristic to separate light by wavelength, capturing transmitted and reflected light to derive wavelength information through image data analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional inspection methods are used to capture scattered infrared light, then spatial positions of defects can be grasped, but wavelength information of light output cannot be obtained
Solution Approach 1:
The light from the optical output unit is segmented into multiple wavelength components using an optical filter with linearly varying transmittance. The filter divides the broadband light into spectral bands, allowing wavelength information to be extracted while maintaining spatial defect detection capabilities.
Solution Approach 2:
An optical filter with linearly varying transmittance is introduced as an intermediary between the photonic integrated circuit and the imaging unit. This filter mediates the interaction by selectively transmitting and reflecting different wavelengths, enabling wavelength information to be captured without compromising spatial defect detection.
2Loss of information
If an optical filter is introduced to obtain wavelength information, then wavelength information can be acquired, but the inspection system becomes more complex
Solution Approach 1:
The optical filter with linearly varying transmittance serves multiple functions simultaneously: it acts as a wavelength separator for spectral analysis, a beam splitter for creating multiple optical paths, and a means for deriving wavelength information through intensity ratio measurements. This multi-functionality reduces the need for additional separate components.
Solution Approach 2:
The inspection method utilizes changes in light intensity parameters at different wavelengths through the optical filter. By measuring intensity ratios of transmitted and reflected light, wavelength information is derived through parameter analysis rather than requiring complex spectral imaging equipment.
3Productivity
If only spatial defect detection is performed, then inspection speed is maintained, but comprehensive inspection of optical characteristics cannot be performed
Solution Approach 1:
The optical filter enables continuous wavelength analysis during the imaging process. By capturing both transmitted and reflected light intensities simultaneously through the filter, the system continuously derives wavelength information without requiring sequential measurements or additional processing steps that would slow down inspection.
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
Enables accurate acquisition of wavelength information from PICs, allowing for comprehensive inspection of defects and optical characteristics, including channel accuracy and light leakage detection.
Implementation Method 1
an optical filter having a transmission characteristic in which a transmittance varies linearly in a predetermined wavelength range and configured to transmit or reflect light
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
An inspection apparatus 1 includes a stage 10 holding a PIC 100, a PIC controller 20 controlling an operation of the PIC 100, an LRG filter 61 having a transmission characteristic in which a transmittance varies linearly in a predetermined wavelength range and configured to transmit or reflect light that has been guided by a waveguide 108 and output from at least one optical output unit 102 on the basis of the transmission characteristic, a camera 62 capturing light transmitted through the LRG filter 61 to output a transmission image and capturing light, which has arrived without passing through the LRG filter 61, to output a total light quantity image, and a computer 70 performing a first processing to derive wavelength information of the light output from the optical output unit 102 on the basis of the transmission image and the total light quantity image.