The next generation of television broadcast format is moving in the direction of the 16:9 aspect ratio. However, broadcasters still must accommodate viewers who have TVs that work in the 4:3 aspect ratio. This requires broadcasters to maintain the existing format of the 4:3 aspect ratio. While adding equipment capable of the 16:9 aspect ratio. To serve in this mixed format environment, Canon has developed a crossover system for switchable CCD cameras that can switch between these two aspect ratios.

Aspects of the Canon crossover-system.

1. One of the common methods of 4:3 / 16:9 image switching by CCD is to cut off the image at both ends, leaving the centre portion as the effective image area. This results in a smaller image area for the switched 4:3 format (dia. 9mm) when compared to the 16:9 and conventiona1 4:3 formats (dia.11mm).

2. As the diameter of the image shortens under the condition of the switched 4:3 format (dia. 9mm), the ang1e of the lens becomes more telephoto. Consequently we lose about 20% of the angle at the widest focal length in comparison with the 16:9 format (dia.11mm).

3. To enable operations with the same picture angles in the two different format sizes, a 0.8x crossover unit is employed. This shortens the focal length of the lens to achieve the same angle as the conventional 4:3 format (dia. 11mm), under the switched 4:3 format (dia.9mm) condition. Accordingly a conventional 2.0x extender in the 16:9 format (dia.11mm) turns out to be a 2.4x extender under the switched 4:3 format (dia.9mm).

4. The extender unit of the crossover system includes a crossover lens in addition to conventional extenders.

Crossover-system for Box type lens.

Crossover-system for Portable lens.

There are 2 different types of Crossover ENG/EFP lenses available. One is the WRSD/WASD version which incorporates a 0.8x Crossover unit in addition to the 2x extender. The other is the VRSD/VASD version which has a 0.8x Crossover instead of a 2x extender.

The diagram shows how Canon’s exclusive Crossover Technology uses a 0.8x “Shrinker” to restore the loss of diameter and return the 4:3 image of a Switchable Camera to the same as a Standard Camera.