Imaging Flashcards
Pros and cons of directional illumination?
Pros: Bright, flexible, flexible packaging.
Cons: Glare, shadows
What is directional illumination and some applications?
Directional illumination is point source illumination from one or multiple sources, fairly simple, for inspection and measurement of flat and matte objects.
What is glancing illumination and what is it used for?
Glancing illumination is point source illumination at an extreme angle of incidence to the sample. It is used for identifying defects in objects with depth and examining the finish of opaque objects.
Pros and cons of glancing illumination?
Pros: Good for structural and topographical enhancement
Cons: Heavy shadows and hotspots.
What is diffuse illumination and some applications?
Diffuse illumination is illumination evenly (in intensity) applied across a sample. It is used for imaging large and/or shiny objects, or imaging with large working distances.
Pros and cons of diffuse illumination?
Pros: Reduces glare, consistent illumination across all spots of the sample
Cons: Requires physically large light source that may not be easy to fit in confines of system
What is ring illumination and some applications?
Ring illumination is (almost) coaxial illumination that is mounted directly onto the lens/detector. It is used for inspection and measurement of matte objects where uniform illumination is beneficial.
Pros and cons of ring illumination?
Pros: Reduced shadowing, easy system integration (just mount onto lens), and uniform illumination at proper distances
Cons: Not good for reflective surfaces (circular glare pattern present), only good for relatively short working distances.
What is coaxial illumination and applications?
Coaxial illumination is where diffuse light is incident onto the sample via a beamsplitter, such that the reflected light off the sample is transmitted through the beamsplitter onto the camera. It is used for measurement/inspection of very shiny objects
Pros and cons of coaxial illumination?
Pros: Very little glare and shadowing, very even, diffuse light.
Cons: Large and clumsy device needed, limited working distance, low throughput
What is structured illumination and some applications?
Structured illumination projects patterns (lines, dots, grids, etc) onto an object and get depth information from a sample based on that. Applications involve topographical measurements or 3D inspection.
Pros and cons of structured illumination?
Pros: Can obtain a lot of information from sparse scanning/small areas. Can get depth information
Cons: May cause blooming/saturation or absorption due to intensity of light.
What is darkfield illumination and what are some applications?
Darkfield illumination is inspection of a transparent/translucent object done perpendicular to the camera. Applications are defect detection in glass/plastic objects.
Pros and cons of dark field illumination?
Pros: Good for clear inspection of samples
Cons: Poor edge contrast and not useful for opaque objects.
What is brightfield illumination and some applications?
The simplest form of illumination. Object is illuminated from beneath, either imaging through transparent objects or silhouetting opaque objects. Applications are edge detection, opaque object measurement, test patterns/targets.
