Continuous AF in video mode/live view patent (used in the upcoming Nikon D3100)

As some readers already noted, this previously covered patent application could be the base of the new continuous AF in video mode/live view feature which will first be implemented in the new Nikon D3100 DSLR camera. As you can see from the drawings, Nikon produced various camera configuration as a possible implementations of this patent, which could indicate that this solution will spread across all future Nikon cameras, including the EVIL system.

Nikon patent application 20100150539 is for a focus adjustment solution (see wikipedia's explanation of the two different passive focus solutions: phase detection and contrast measurement). Different implementations are shown in this patent application: the first drawing is a camera with a half mirror, the second is mirrorless (EVIL) camera, the third implementations is without a prism (Pellix camera?) and in the last drawing the sensor is located under the mirror (instead of behind the mirror):

Quotes from the patent application after the break:

"Field of the invention: The present invention relates to a device that adjusts the focus of an imaging optical system, an imaging device equipped with the focus adjustment device and a focus adjustment method.

Abstract: A focus adjustment device includes an image sensor that includes imaging pixels for capturing an image formed via an imaging optical system and focus detection pixels for detecting a focus adjustment state at the imaging optical system through a first pupil division-type image shift detection method, a focus detector that detects a focus adjustment state at the imaging optical system through a second pupil division-type image shift detection method different from the first pupil division-type image shift detection method, and a focus adjustment controller that executes focus adjustment for the imaging optical system based upon the focus adjustment states detected by the image sensor and the focus detector.

Description of the related art: There is a digital camera known in the related art (see Japanese Laid Open Patent Publication No. 2001-281530) that includes a focus detection sensor adopting a phase difference detection method and an image sensor. This digital camera first drives the imaging optical system to a point near the focus match position based upon the results of detection executed by the focus detection sensor, then detects the focus match position through a contrast detection method by using the output from the image sensor and executes fine adjustment to the focus match position. However, the contrast detection method and the phase difference detection method adopted in the camera in the related art described above are not perfectly compatible with each other since their focus detection principles are different and, for this reason, the correspondence of the focus detection results obtained through the two methods tends to be poor. For instance, there may be a photographic subject for which the focus can be detected successfully through the phase difference detection method but the focus detection cannot be executed successfully through the contrast detection method. In addition, while the focus may be detected with a high level of accuracy through the phase difference detection method for a given photographic subject, the accuracy of the focus detection for the same photographic subject executed through the contrast detection method may be poor. Under such circumstances, the imaging optical system may hunt for, and fail to reach the focus match point, the imaging optical system may be driven to an unexpected position or the imaging optical system may not move at all when the camera attempts to fine-adjust the position of the imaging optical system through the contrast detection method after driving the lens to a point near the focus match position through the phase difference detection method."

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  • Now we’re cookin’ I’m not big on shooting videos then but a new camera sounds great by me!

    • Anonymous

      All of the patents show the focus motor being in the lens, not the body. Perhaps to save room and cost?

      • WoutK89

        Focus motor in lens = SWM = AF-s Lens

  • i am waiting, for D400, i believe here it will be also the AF for the movie mode..
    I dont think that d700 will be replaced, … not now … here, the stocks are already full of d700 …

  • rawrf

    It seems like the patent was filed in 2007…? So that could mean it’s probably had plenty of time to test/perfect!! =D To me that’s good news.

  • Indeed Nikon will come with interesting (if not really great) movie/video features on upcoming DSLRs. They know what trends are and won’t miss the opportunity.

    Canon is still the leader in the field of “HDSLR” (Hybrid DSLR), but for how long?

    As we already said many times at our Blog when requesting many features that CAN be implemented via Firmware updates to the existing EOS line of HDSLRs (such as Focus Rack/Preset/Program, etc.) , it won’t last forever…

    We’re sure that lot of the ideas suggested and requested to Canon will be taken by Nikon (in fact they probably they were already taken and in development… as any smart company would do)

    Some of those ideas were compiled and listed here (but also requested long before):

    Ironically is not so easy to make a company listen to their customers, it takes LOT of time and big efforts. It should be easier though, since they are receiving suggestions and feedbacks for free to improve their products and increase sales…

    • Toxicab

      Nice post.

      What worries me is the current lack of pro-model update news. Though I am optimistic, but not a pixel or video fiend though as a UK user the VAT increase is substantially worrying me as I am going to update before the increase, so price drops on the D700 for another back up body or gawd knows what would be a huge relief.

  • NikoDoby


    • Johan

      Agreed. Why would you want to do away with it? A mirror will give you a true picture unlike a small LED in the view finder. They will always look back lit.

      • Anonymous

        You’ve never looked through a high quality EVF have you?

        Death to the mirror! Long Live Live View!

      • David Hasselblaff

        As good as an electronic view finder can be – it makes things quite difficult if you are trying to safe power. This may not be big of an issue for most photographers, but out in the field I often find myself a bit worried whether or not the batteries will last. I won’t be carrying extra spares because of the electronics.

      • John

        Are you kidding? Have you ever compared the DOF that an OVF has with the actual depth of field the lens actually gives – they are quite different below f/5.6 on my D300. I would love an EVF that gave me no focus errors (beyond the usual ones not associated with mis-alignment of the mirrors and sensors) and accurate depth of field preview. EVFs have come a long way and are ready for prime time in my opinion. Time for the mirrors and prisms to go on some digital camera models.


  • alvix

    well perfect: a D3X with 32Mp @iso800 and 12Mp @iso12800 plus 1920/30/24 P , this AF magic something ..and .17mm PC/E…and that’s it,,i’m done (included NX3 thankyou..)

    • preston

      Hell yes to the 17mm PC/E! That’s the only reason I would possibly switch to Canon right now.

    • Canon Fangirly

      I have to agree here. The independent TS rotation on the new Canon 17mm and 24mm is one thing I’d love to see on Nikon’s PC-E line. It’s almost like working with a view camera.

  • Brian Davis

    To hell with these stupid entry-level pieces of garbage. The photo community is waiting for a D700 replacement…it’s coming up on 2 years old and needs refreshed. This is supposed to replace the D3000? It’s only 1 year old and is being oversold by the D5000 and D90, so who cares about it? The soccer moms have enough choices.

    • NikoDoby

      Be thankful you’re not waiting on the Fuji S5 Pro replacement! That’s based on the Nikon D200 and still hasn’t been replaced!

      Or be thankful you’re not waiting on the Olympus E-3 replacement.
      Or be thankful you’re not waiting on the Sony A700 replacement.
      Or be thankful you’re not waiting on the canon 1DsMk3 replacement.
      Or be thankful you’re….oh you get the idea

    • Chris P

      By ‘photo community’ you must mean those who don’t actually own a D700, I, and others I know who also own one, aren’t interested as it does all we need.

  • Blckcat

    Is that “black square” between the lens and the body (213) what I think it is?

    • WoutK89

      I think so too (whatever you think it is)

      • WoutK89

        The body CPU 214 and the lens drive control circuit 206 exchange various types of information, such as the lens information and information indicating the defocus amount based upon which the focusing lens is driven, via an “ELECTRICAL CONTACT POINT PORTION” 213 present at the mount unit 204.

  • Rob

    With 12mp CMOS sensor? Would keeping the ol 10mp CCD be better for video?

  • Adam

    I think thy should make upgradeable sensors like CPU’s in computers..

  • @adam, yes I agree.

    Figure #1 is a winner IMO, you can have the focus detection unit active while doing video and live view, and do enhanced focus as described in the paragraph starting “Description of the related art”. (The focus detectors assist contrast based focusing.)

    What you would lose is (a) optical TTL, but you could do it all with live view, and (b) an unobstructed path to the sensor, and (c) some light loss, light has to go to the focus detection unit too. (b) isn’t so important because the sensor is behind the Bayer grid and low pass filter anyway, flat mirrors are easy to make well. (c) isn’t important either, I think the focus detection units in current SLRs only get about 1% of the light. so the sensor will only lose a similar amount.

    I forgot, (d), if this is supposed to be an EVIL camera competitor, Nikon won’t be able to reduce the flange distance, not by 50% as most EVIL cameras do. They could reduce it by 30% however, the 46.5mm flange distance gives 1mm clearance to the reflex mirror in its “up” position on SLRs, laid back at 45 degs there’s probably a good 10mm clearance.

    I suspect this is then “new concept DSLR” that was reported in Bloomberg, and it looks great, but I would miss optical TTL and only a 30 or 35mm flange distance would be a shame (compared to 20-25mm for other EVIL cameras).

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