Microscope Image Analysis
 | Resolutions down to an atom |
| Programmable oscillator frequency |
| Low noise synchronous detection of surface image |
| Programmable bandwidth using a DSP |
An instrument was developed to modulate the cantilever of a microscope at high frequencies while monitoring changes in amplitude and phase to extract surface image information.
Since the instrument drives the cantilever directly with a magnetic field, the need to drive the cantilever mounting mechanism was eliminated, thus resulting in an increase in control. The resulting increase in control allows for smaller amplitudes, and therefore much smaller vertical forces on the sample.
The amplitude of the cantilever is amplified over a programmable range and is synchronously detected and converted to digital information with two16-bit analog-to-digital converters. The DSP then extracts phase and amplitude information while providing a programmable bandwidth and filter attenuation, so that a tradeoff of scanning speed versus noise level can be made.
The phase and amplitude information, which is the image, is converted back to 16-bit analog data for transfer to a computer for image capture.
An operator interface can be provided for control of parameters such as gain of input stages, current drive of the cantilever, frequency of the cantilever oscillation, amplitude of the image signal, and bandwidth of the signals.
All parameters were stored in non-volatile FLASH memory for easy configuration of the instrument.
Among the technologies used in the design are:
| Digital Signal Processing |
| Direct Digital Synthesis |
| Low Noise Data Acquisition |
| Synchronous Detection of Low Level Signals |
| Programmable Logic |
