A patent showing a 2x teleconverter with a diffractive optic element (DO) has surfaced. The 2.0x teleconverter could use a little length reduction, though I'm not sure if DO would reduce the size of the current TC all that much.
Patent Publication No. 2014-145870 (Google Translated)
- Published Date 2014.8.14
- Filing date 2013.1.29
Example 1
- Focal length -109.09mm
- Magnification 2.00x
- 4 group 9-lens configuration
- One plane diffraction plane (the first group)
- Master lens
- Focal length f = 293.76mm
- Fno. 2.91
- Half angle ω = 4.21 °
- Image height Y = 21.64mm
- The overall length of the lens 275.41mm
- BF 53.79mm
- 15 sheets 11 groups lens configuration
- Protective glass 1
- Rear filter 1
- UD 2
- Fluorite 1
Canon Patents
- I and the diffraction plane cemented surface of the cemented lens closest to the object side
- This arrangement can suppress the flare
Source: [EG]
cr