Improve Delta Stage (reflection mode) image quality

[sgbaird]

We’re trying to improve the image quality from a Delta Stage Microscope in reflection mode (based on Test out optical microscopy on some dropcast battery slurry samples · Issue #142 · AccelerationConsortium/ac-training-lab · GitHub).

Below shows some images of the setup:

Below is a sample with some battery slurry deposited onto it (dried).

We’re trying to get images of the slurry. Below you can see the aluminum foil and then trying to focus on the slurry.

Some other notes someone mentioned from the corresponding github issue:

• only images with very poor quality. The contrast of back-reflections or dust on the lenses inside the beam path was always at least as high as contrast from the actual sample. (tried with 40x and 100x objective lenses)
• maybe the illumination was not adjusted correctly? I cleaned the condensor lens which helped a bit, but adjusting it nicely is super difficult or impossible.

@kenzoat suggested swapping out the pi camera and making sure the light isn’t too bright.

Do you have any tips or suggestions for increasing the quality (or if you think this is on par with expected quality) or doing additional troubleshooting? We will probably need to do some kind of 3D depth mapping to get a more in-focus image of the slurry.

[WilliamW]

The first image focused on the foil looks to be properly in focus. As it is a shiny surface the contrast is not high. The illumination is clearly not filling the field of view but it is well centred on the field of view. I don’t know whether the small illumated area will be positioning the illumination or the size of the small hole in the reflection illuminaton LED holder.

With a 40x or 100x lens the working distance and depth of focus will both be very small. In the Github comments you note that the slurry is quite thick/tall. That might well hit the 100x lens, and it will certainly mean that only parts of the stripe are in focus at any one z-position.
Apart from the focusing, matt black things are always difficult to image, as are shiny things - here you have one next to the other!