Auto-Focus System for HDTV Field Lenses

The operation of a contemporary high-definition television (HDTV) lens-camera for sports and special events is a multifaceted task entailing close coordination of the camera operator with a program director and utilization of honed skills in picture framing, panning, and tilting, while maintaining a sharp focus on chosen objects within complex three-dimensional scenes The latter is made especially difficult by the absence of any true HDTV viewfinder; far higher focus sensitivity in HDTV than in standard-definition television (SDTV); and widely varying scene-lighting conditions calling for lens aperture settings that can shorten depth of field, all compounded at times by having to maintain that accurate focus on fast-moving objects within the scene. This imposes a significant strain on the camera operator, which can lead to considerable fatigue during extended shoots. This paper describes a powerful new auto-focus technology recently incorporated into two long zoom HDTV field lenses (today's zoom ranges for such lenses are on the order of 100:1 for sports coverage). The system borrows from a technology that has become central to digital still image single lens reflex cameras—called Secondary Image Registration Phase Difference technology. Sensing capabilities have been added that ensure a high accuracy in image-focus, while precisely maintaining that focus when tracking a fast-moving subject within the scene. Consistent HDTV sharpness is maintained thus freeing the camera operator to pay full attention to the important creative aspects of image framing and lens-camera positional manipulation with a lowering of fatigue.

Print ISSN

1545-0279

Electronic ISSN

2160-2492

Published

2008-03

Content type

Original Research

DOI

10.5594/J16000