Camera cross-section
Camera exploded view
Render without front cover
A number of lessons were learned from the first SCENICC prototypes:
- For prototype systems, assembly difficulty and risk scales with the number of sensors that must be coupled to fiber bundles.
- Mating fiber bundle wedges to each other is possible but challenging without additional process development.
- The focus mechanism used in the early prototypes was challenging to assemble and a simpler solution was needed.
- It would be necessary to be able to seal the optical cavity to prevent contamination from particulates over time.
- The custom sensors that were intended to be used were not going to be available in time for use in the panoramic system.
To address this, a new system was designed that would use a single sensor to cover a full 96° horizontal x 96° vertical field of view (126° diagonal). This reduced the system complexity significantly. The optics were also redesigned, adding a static protective dome to the front that seals the optical cavity. A new, simpler to assemble focus mechanism was also designed that could accomodate the new lens design and all the previous lens designs as well. Finally, an electronics backend was also designed that would be flexible enough to build single cameras or groups of cameras with a remote controller and processing module.
Fiber Bundle
Fiber bundles in various states of processing
Using a single fiber bundle simplifies the assembly but presents new challenges for the machining. The large depth-of-cut (sag) of the spherical optical surface, along with a tight tolerance on the form of the parts and placement of the surface, required the development of new grinding strategies.
Focus
Assembled focus mechanism
The focus mechanism redesign used a motor with an eccentric cam instead of the pulley system that was in the original design. A stronger lever also replaced the original, taking advantage of the additional volume available due to the larger sensor footprint. Many other improvements were made to allow for easy calibration of the lens nominal focus position and the reading of the hall sensor. The result was a system that can be produced in larger quantities and with better consistency. There was also an improvement in the linearity of the focus motion, which simplifies implementation of autofocus algorithms.
Assembly Process
Bundle assembly process
Because of the much larger sensors and correspondingly larger fiber bundles, the fiber-coupling operation also had some new challenges. This was performed by DFC engineers in our cleanroom because it was much more critical to keep the sensor silicon clean after the coverglass was removed. A series of fixtures was used to place the bundle accurately on the sensor and to ensure the glue layer thickness was appropriately thick.
Later SCENICC Work:
Panoramic Photonic Mast (PMAST)
The compact size and high resolution of the monocentric lenses, coupled with a flexible backend electronics architecture, allows the sensor heads of the standard DFC Monocentric Camera to be reconfigured into an ultra-compact, high-resolution panoramic system. Five apertures image simultaneously, with the data being sent over fiber-optic cables to remote processing electronics where the individual images are stitched into a single image or video.
Earlier SCENICC Work:
Early Research
During the early phase of the program UCSD and DFC produced several prototype systems while exploring the monocentric lens architecture and the potential of fiber-coupled image planes. This includes a 30 megapixel, 6 sensor system that proved the potential of multiple-sensor fiber-coupled imaging systems.