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05-14-2015, 07:14 AM - 1 Like   #1
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Ricoh Patent: Improved DSLR AF system

The following patent appeared on the Egami Bog today. I'd be lying if I said I understood this fully, but what it seems to be showing is a new approach to DSLR focusing that allows the focus points to be spread more widely across the frame. The writer speculates that this might be introduced in the FF camera, since the patent was filed one and a half years ago and the timing would be about right.

Original Japanese
Ricoh ?????????AF?????????????????So-net???

English via Google
Google Translate

Can anyone smarter than me figure out what is described here?

05-14-2015, 07:26 AM   #2
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If this is the "expected" AF novelty from Ricoh/Pentax, there sure will be crowds of FF (only?) people interested !
05-14-2015, 08:16 AM   #3
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Very promising.
If they are introducing some AF hardware innovations, I trust they will also be investing in tuning up the AF software as well.
05-14-2015, 08:18 AM   #4
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QuoteOriginally posted by JPT Quote
Can anyone smarter than me figure out what is described here?
By using a concave secondary mirror for the AF sensor, the AF-points can cover wider area in the OVF. It also seems to suggest that both side of the main mirror are reflective, where the back side is using an "active" mirror".
It might also mean that they can use the same AF sensor for APS-C and FF, and by using the concave mirror on FF the AF point will cover the same percentage as on the APS-C camera.

The google translation is not very easy to understand, and as always, a lot of patents never reach production.
And if I got it right, the light have to travel a longer distance to the AF sensor, so it might not be possible to implement without a change in register distance (new lens mount).


Last edited by Fogel70; 05-14-2015 at 08:38 AM.
05-14-2015, 08:22 AM   #5
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QuoteOriginally posted by Fogel70 Quote
It might also mean that they can use the same AF sensor for APS-C and FF, and by using the concave mirror on FF the AF point will cover the same percentage as on the APS-C camera.
.
Let's hope the AF module on the FF is not a current APS-C transplant but new and with expanded points
05-14-2015, 08:45 AM   #6
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QuoteOriginally posted by jpzk Quote
If this is the "expected" AF novelty from Ricoh/Pentax, there sure will be crowds of FF (only?) people interested !
It would have to be extremely remarkable to get any back. In the time I've had my D810 I've not once wished I had a focus point outside of the ones it has. It is the one area that when I pick up my K-3 I am underwhelmed with now I am used to the Nikon.
05-14-2015, 08:56 AM   #7
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QuoteOriginally posted by Fogel70 Quote
By using a concave secondary mirror for the AF sensor, the AF-points can cover wider area in the OVF. It also seems to suggest that both side of the main mirror are reflective, where the back side is using an "active" mirror".
It might also mean that they can use the same AF sensor for APS-C and FF, and by using the concave mirror on FF the AF point will cover the same percentage as on the APS-C camera.

The google translation is not very easy to understand, and as always, a lot of patents never reach production.
And if I got it right, the light have to travel a longer distance to the AF sensor, so it might not be possible to implement without a change in register distance (new lens mount).
QuoteOriginally posted by Fogel70 Quote
The google translation is not very easy to understand, and as always, a lot of patents never reach production.
And if I got it right, the light have to travel a longer distance to the AF sensor, so it might not be possible to implement without a change in register distance (new lens mount).
My understanding is that this system has no need for the sub-mirror to reflect light down to the AF sensor. in conventional DSLRs, the maximum size of that mirror is limited by the flange distance and that is why AF points need to be more centralised, especially in FF DSLRs. Increasing the flange distance is only mentioned because the writer says this is what you would have to do to make the sub-mirror bigger. However, since this new system has no need for the mirror in the first place, it solves that problem. But I still don't understand quite how is works.
05-14-2015, 09:16 AM   #8
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As long as they don't fix the AF point selection (see istDS to see how it is done) I don't care, I'll only use the center point.

05-14-2015, 09:21 AM   #9
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With on.sensor PDAF coming soon via most every manufacturer of sensors, I would not expect this to be a fix worth pursuing. But R.Pentax sees further into the future than I do and by a long shot!
05-14-2015, 09:24 AM   #10
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QuoteOriginally posted by JPT Quote
My understanding is that this system has no need for the sub-mirror to reflect light down to the AF sensor. in conventional DSLRs, the maximum size of that mirror is limited by the flange distance and that is why AF points need to be more centralised, especially in FF DSLRs. Increasing the flange distance is only mentioned because the writer says this is what you would have to do to make the sub-mirror bigger. However, since this new system has no need for the mirror in the first place, it solves that problem. But I still don't understand quite how is works.
As I can see in the illustration, number 14-15 is the secondary concave mirror, 16 is the shutter and 17 is the image sensor.
The illustration also show (as far as I can see), that light travels through the main mirror and is reflected by the secondary mirror back to the back of the main mirror and then reflected down to the AF-sensor.
05-14-2015, 10:37 AM   #11
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QuoteOriginally posted by jimr-pdx Quote
With on.sensor PDAF coming soon via most every manufacturer of sensors, I would not expect this to be a fix worth pursuing. But R.Pentax sees further into the future than I do and by a long shot!
On-sensor PDAF doesn't work with a conventional OVF. EVF technology can't quite replace the OVF yet, so this Ricoh patent could be an interim solution.
05-14-2015, 10:41 AM   #12
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QuoteOriginally posted by Fogel70 Quote
As I can see in the illustration, number 14-15 is the secondary concave mirror, 16 is the shutter and 17 is the image sensor.
The illustration also show (as far as I can see), that light travels through the main mirror and is reflected by the secondary mirror back to the back of the main mirror and then reflected down to the AF-sensor.
You're describing the PDAF mechanism, except that the secondary mirror is angled so it's projects directly into the phase detect sensor. In the patented diagram the secondary mirror seems to stay vertical, the phase detection unit extrapolates the data from the once refracted and one reflected image. I don't know know if the diagram is overly-simplified (and not 100% true) or the whole design is new.
05-14-2015, 10:59 AM   #13
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QuoteOriginally posted by jimr-pdx Quote
With on.sensor PDAF coming soon via most every manufacturer of sensors, I would not expect this to be a fix worth pursuing. But R.Pentax sees further into the future than I do and by a long shot!
A cool technology for sure, but only works with mirrorless cameras or SLRs having a stationary pellicle mirror


Steve
05-14-2015, 11:12 AM   #14
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QuoteOriginally posted by Stavri Quote
You're describing the PDAF mechanism, except that the secondary mirror is angled so it's projects directly into the phase detect sensor. In the patented diagram the secondary mirror seems to stay vertical, the phase detection unit extrapolates the data from the once refracted and one reflected image. I don't know know if the diagram is overly-simplified (and not 100% true) or the whole design is new.
The new in this patent is that the secondary mirror is concave, and that the main mirror is reflective on both sides. By placing the secondary mirror vertically makes it possible make this mirror larger.

On conventional design the secondary mirror is in approx 90 degree angle from the main mirror, which would need more space behind the main mirror if made larger.
05-14-2015, 11:19 AM   #15
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That sounds pretty good! So many cameras have many, many AF points, but all clustered around the centre, which highly limits their use (except of course for AF.C, tracking). Having AF points around the rule of thirds focal points and other such locations would be great. I hope this tech will be used in APSC cameras as well
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