Run time implementation of self-mixing laser interferometric sensor for vibration measurement
Self-mixing (SM) laser interferometry also recognized as optical feedback (OF) laser interferometry has been extensively demonstrated for past two decades, due to its ability to provide a cost-effective, compact and self-aligned setup for many industrial applications involving measurement of vibrati
2025-06-28 16:34:52 - Adil Khan
Run time implementation of self-mixing laser interferometric sensor for vibration measurement
Project Area of Specialization Artificial IntelligenceProject SummarySelf-mixing (SM) laser interferometry also recognized as optical feedback (OF) laser interferometry has been extensively demonstrated for past two decades, due to its ability to provide a cost-effective, compact and self-aligned setup for many industrial applications involving measurement of vibration, distance, displacement, and velocity. The self- mixing interferometry (SMI) phenomenon come into existence when emitted light from a laser diode (LD) strikes the surface of a moving target and a fraction of that laser beam reflect back from that target surface and reenters into the active laser cavity. This reentering beam interacts with the emitted beam, causing modulated kind of effect to the laser beam signal. This modulated change in a beam of light or also called SM signal is captured at photodiode embedded in the active laser cavity. This SM signal can be processed through some post-processing to extract the desired target motion. Therefore, many algorithms and methods were proposed to extract target motion from that SM Signal. But, most of them are only at simulation level and their real-time implementation is difficult to achieve due to extra-added optical components or long iterative and complex processing steps involved in different algorithms. However, a fast real-time nature algorithm known as direct phase unwrapping method (DFUM) was proposed and analyzed for FPGA based implementation, but its implementation is also at the simulation level. In this work, DFUM is analyzed and its Arduino based implementation is done using Arduino Due board. We tested our implemented system for various simulated and experimental signals acquired through SMI for displacement retrieval and found out that our system has the capability to retrieve target displacement with approximately ?/10 precision while utilizing only 25KB of programmable memory of Arduino Board. Furthermore, our Implemented system has the capability to process SM signals with speed up to 1MS/s. This low-cost implementation of such a fast algorithm is a key step towards an embedded sensor on a single chip capable of providing a solution for nano-metric displacement measurements.
Project ObjectivesThe purpose of this work is the real-time implementation for vibration retrieval algorithm direct phase unwrapping method for self-mixing interferometry.
Such an implementation of SMI based vibration retrieval paves the way towards:
- A complete digital SM sensor integration on chip
- Real-time measurements for vibration and displacement applications in an embedded, autonomous manner for many industrial applicaions.
Project implementation starts with Collection of Literature and Study of collected Literature from different sources. After basic understanding with the Self-mixing interferometry and its involvement in many industrial applications involving displacement, velocity and vibration measurement, the next step is to decide the algorithm to be implemented for real-time implementation.
- Once the scheme is selected (Direct phase unwrapping method is selected), the next step is its complete analysis before its real-time implementation.
- After the analysis, the next step is to propose an implementable model of DFUM.
- Next target is the selection of hardware (Arduino Board selected) to implement that proposed Model.
- Next step is Implementation of Schemes/Model
- Then Analysis & Simulation followed by Result Formulation
- The final phase is Write-up of the whole project
cost-effective self-aligned easy to use embedded system design capable of sensing any remote target motion, which is useful for many manufacturing industries, fluid flow rate measurements, a biomedical field involving blood flow measurements and disease identification sonar and range finding applications.
Technical Details of Final DeliverableAlgorithm and code
- Arduino IDE software is used to write script to program Arduino Board. DFUM is scripted in three different styles called as slow DFUM (SDFUM) medium DFUM (MDFUM) and fast DFUM (FDFUM) depending upon the sampling speed of SM signal.
Results
- Successful hardware implementation of SMI algorithm for vibration retrieval
- Vibration retrieval with capability of processing upto 1MS/s SM signals.
- This then means capability of retrieving target vibration upto maximum speed of 39.25 mm.
Hardware
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Arduino Due is used for real-time implementation of DFUM. Arduino Due is an Arm 32 bit microcontroller based Arduino board, which has total of 68 input/output pins out of which, 12 are analog input pins with 12 bit resolution, 54 digital I/O pins and two analog output pins with 12 bit resolution. Therefore, it has the capability of handling analog input and providing analog output.
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Arduino Due has total of 512 KB of flash memory available for user applications and has 96 KB of SRAM. Similarly, it has a clock speed of 84 MHz to support fast processing as compare to other Arduino boards.
| Item Name | Type | No. of Units | Per Unit Cost (in Rs) | Total (in Rs) |
|---|---|---|---|---|
| Total in (Rs) | 25000 | |||
| Arduino Due Board | Equipment | 1 | 5000 | 5000 |
| SM Sensor Interfacing Cables/Connectors and jumper wires | Equipment | 1 | 15000 | 15000 |
| printing etc | Miscellaneous | 1 | 5000 | 5000 |