I just found the United States Application US20100277637 which refers to a new Sony half-mirror patent (Click here to dowanload the pdf). It has been just published and it doesn’t reveal anything new. But I thought some of you might be interested to read the technical details of the SLT technology.
6 Responses
The patent contains one really interesting bit: The material of the SLT mirror seems to be Cyclo-Olefin-Copolymere. The patent already shows that the transmission over different wave-lengths is much better than the PET-film of the old Canon pellix cameras. If you look at the description of Cyclo-Olefin-Copolymere at wikipedia there is another interesting bit:
“Für optische Anwendungen ist die geringe Doppelbrechung interessant.”
Translation (me): “For optical applications the small double refraction is interesting”
Wouldn’t it be interesting if they could employ a mirror to direct the IR/UV light to the AF system (assuming that would allow AF), while keeping the visible spectrum going 100% to the sensor.
@Rob: that would be pretty much perfect, I guess! I don’t know if it would be possible and if it would allow AF!
does this patent concern tech already used in A33/55 or tech to be used in some upcoming SLT’s?
Would IR/UV wavelength light focus at different distances than visible light? I don’t think the apochromatic/achromatic designs in current lenses correct for this (they just correct for different wavelengths in the visible light spectrum), so just using IR/UV light to autofocus could result in consistent back or front focusing.
it’s just too complicated and difficult to make AF sensors work with IR/UV instead of visible light!! Simply reducing the percentage of reflected light from the mirror to the AF sensor would proportionally reduce any negative effects from light loss on IQ, (Currently that percentage is a considerable 30%).