The CVROS scanner can be adapted to applications; however, the effects of near object imaging need to be taken into account.
In order to preserve aberration-free imagery in the CVROS scanner, all sysem elements, including the object surface, must be concentric about the midpoint of the scan disc. For distant or “infinite conjugate” objects this condition is satisfied by the infinitely long object surface radius. For near objects with “finite conjugates” the difference between a flat object surface and the curvature of the ideal concentric object surface results in field curvature aberration. This degrades the imnage quality for off-axis points and needs to be corrected as described in the paper “Compact Video Rate Scanner (CVROS) for Finite Conjugate Applications”..
The paper also addresses other engineering issues including photometric efficiency, scan line distortion and the scan line location errors.due to scan disc and strip mirror manufacturing and alignment errors. These are all especially important considerations when the scanner is used to “write” as in a laser printer, rather than “read” as in the thermal imager camera.
A laboratory laser printer test bed employing the prototype CVROS scanner was assembled and tests were conducted. The optics fabrication and alignment issues cited in the study referenced above were confirmed and led to the development of a protype laser video rate raster scanner designed to deal with these issues..
This device employed a scan disc air bearing to minimize line wobble due to bearing run-out, a strip prism for flat field imagery, an electro-magnetic strip prism micropositioning device to achieve straight, parallel, evenly spaced scan lines in the presence of scan disc mirror radial location errors. A framing mirror was used to generate the raster scan from the series of line scans as in the thermal imaging camera..An objective mirror was repositioned electrically in the axial direction in synchronization with the framing mirror to compensate for the cylindrical “object” surface generated by the framing mirror at finite object distances. These components are shown below with the Scanner Assembly.