Design team members: Adrian Spanu, Albert I Chen, Ashley Ee
Supervisor: Prof. John T.W. Yeow
Background
So there are two really cool things in this world: a) 2-D MEMS Micromirror b) Confocal Microscope. So the project we are working on is designing an elegant system that integrates the Micromirror with a Confocal Microscope.
To get a better understanding of our project, we shall first explain what a 2-D MEMS Micromirror is. As shown below is the actual mirror with the scale shown. The dimension is so small that the mirror can be driven by electric static force (note that the four corner frames are electrodes while the mirror itself is the smallest square piece at the centre.) Due to the size of the mirror, material cost could dramatically reduced, compared to, let’s say, galvanometer motor-driven mirror which approximates a 2 inch x 2 inch x .25 inch block. What also makes this mirror unique than competing cutting-edge technology is that it is able to actuate about two axes, thus allowing a two degree scanning.
Next, we will explain what a confocal microscope is. Unlike the conventional optical microscope, the confocal microscope sends one beam of light through the sample and only one beam of light is captured by a photosensor. This method would dramatically reduce light scattering effect which results an in-depth (3-D!) view of the specimen. Though it does prove to provide high resolution and in-depth selectivity, the confocal microscopy was not so popular in the industry because of the slow scanning rate and also the size.
However, by replacing the conventional mirror used for confocal microscopy with a MEMS Micromirror, we believe the problem of slow scanning rate and size can be solved. Since the micromirror is ridiculously small and can be driven by non-mechanical actuating force, the mirror has proven to have an incredible scanning rate and a satisfying scanning angle.
Project description
Aside from the actual mirror fabrication, our team is attempting to build a confocal microscopy system from scratch. We want to make it small, we want to make it elegant, and most importantly, we want the microscope to be able to clearly display images of specimen in micro-level (<2µm).
When the project first started, we were given confocal microscope system to play around with. The two photos below are the laser/lens/mirror system (left) and the control electronics (right). The schematics at the bottom shows the changes we want to make.
Design methodology
The new system will include the following components,
- Programmable Integrated Circuit (PIC)
- Signal generator
- Signal processor (amplifying & filtering)
- Sets of Lens
- Photosensor
- LCD
And the design is broken down to five parts:
- Optimize the control method for mirror movement,
- Replace I/O devices with a single PIC,
- Redesign the imaging software for optimized image capturing and processing,
- Display the captured data on the LCD.
- Synchronize the physical and software system
Requirement and constraint
| Task | Requirements | Constraints |
|---|---|---|
| Control and Synch |
System controller must exhibit precise and accurate timing in signal synchronization and data acquisition. Time for signal pass-through must be less than less than 5.2 microseconds (assuming input scan signal of 200 Hz) and drift between samples must be less than 1%. Pass-through is defined as the time it takes for the system to take in a data input from the imaging sensor once the current scan position has been inferred from tracking the input control signal. |
|
| Signal Generation |
The signal generator must generate four appropriate control signals based on the scanning requirements and amplify them to appropriate voltage levels (70 Vpp) with zero phase delay and no distortion. |
|
| Imaging |
The system must take in the sensor input, map it to corresponding visual data, and output it onto the LCD. |
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