[Leica] Glass IR cover on sensor

[lrzeitlin at optonline.net (Lawrence Zeitlin)]

On Mar 8, 2009, at 1:32 PM, Goeff wrote:

> Frank, as you say, I think that is so about sensors in general. If  
> you are
> curious there are some other differences with this new sensor  
> discussed in
> the blog and the L Camera forum thread. I noted that the  Kodak  
> sensor uses
> angled micro lenses around the periphery like the M8 arrangement.  
> Also the
> lens formulations take into account the cover glass (and I guess the  
> IR
> filter component ?) in their formulation. They are describing a mm  
> of glass
> over the sensor vs. I think half a mm on the M8 sensor.


I dimly recall from an optics class that a flat glass slab behind a  
lens doesn't add any aberrations, and, if the entrance angle is not  
too extreme, moves the focal plane back about 1/3 the thickness of the  
glass. This might introduce a problem is switching lenses between  
cameras. The shift in focal plane would be quite small, about 1/3 mm  
but that's enough to rile RF camera users. Of course with DSLRs or  
autofocus the point is moot.

Larry Z