Sensitive imaging using a computer controlled back-illuminated screen with camera feedback.
- Screen lays flat on the table.
- Camera is placed above the screen.
- Samples are placed on a glass surface a couple cm above the screen.
We use a circle grid pattern to register the screen positions of each pixel on the camera. Then we have a mapping from camera coordinates to screen coordinates.
Objects between the screen and the camera are detected in the camera image. The mask of these objects is then mapped to the screen, creating am illusion of a shadow on the screen.
Run: shadow.py
The backlight screen is illuminated and imaged with moving stripes. Each pixel is averaged over images where it is in a dark stripe. This technique thereby simulates darkfield illumination, where the signal in each pixel is proportional to scattering, not transmission.
Example of a plastic bag taken in normal bright-field illumination and synthetic dark-field illumination:
Run: dark_field.py