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 p.1 #1 · Nikon's patent: A Sensor using combined shutters - global shutter is AF only | |
Combining links etc from recent posts. This device could empower significant advances in photography - in Nikon's recent patent for a sensor combining the best of both shutter types (Rolling and Global).
https://asobinet.com/info-patent-nikon-global-shutter-for-af/
Submitted in March - Nikon's patent for a global shutter 
Excerpted report in Japanese,
The original patent is also in Japanese - JP,2021-100287,A
thanks be to google, translates in Chrome : EDIT: search for '2021-100287' in https://www.j-platpat.inpit.go.jp/ for
also: https://www.zsystemuser.com/nikon-z-system-news-and/did-nikon-just-provide-a-z9.html
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This long patent is rich in technical terminology and for a complex device! Nevertheless, it is clear Nikon's engineers have designed a sensor combining the best of both shutter types (Rolling and Global), and this design appears to be possible by exploiting the benefits of stacking the sensor layers.
The patent argues that when combined, these respective shutters operate at blindingly fast speeds to capture a focused image and store their readings within the duration of a single frame of the camera. The 2 dimensional layout of the integrated circuitry further allows their selections in different configurations of active AF sensors - aka AF Modes.
As I understand two of the prominent problems faced by an imaging sensor, typically exposed using a set of shutter curtains that sweep across the sensor. These respective challenges are implicit when using a Rolling line of light 'slides' across the photosites within the set fraction of a second, or a Global shutter reading the entire image in a narrow time-pulse by combining pulses of signals from millions of photosites, which is almost like one pulse of illumination.
1. As a very fast moving subject moves relative to pixels, even during the duration of its exposure (with a rolling shutter), sections [bands] of sensor sites read the image at different times, which results in an increasing lag between sites exposed first versus last. This can be overcome by driving the sensor read at very high speeds, but this uses more power.
2. Currently, almost all the sensors in MILCs can focus in the horizontal axis only; thus unlike dedicated cross-point "focus-sites" using its dedicated AF sensor in a DSLR (eg D5, D6 etc). These read inputs up and across the subject, which is more accurate, notably on moving subjects.
3. Activating the built-in Autofocus on a "mirrorless shutter" but with a global shutter focuses the entire set of dedicated/assigned photosites in a single pulse. It is amenable for designs to exploit the AF precision implicit in cross-type AF sensors.
4. However, a global electronic shutter that reads signals simultaneously across all the pixels generates high electronic noise (transferring the charge into each the photodiode). this can be rectified downstream but is complicated and inefficient.
Reading though the patent (link above):
5. It appears the original diagrams in Nikon's patent [Figs 21, 23, 25] are designed so the photographer can set up different areas of choice (similar to a D6) and these are then used by the global electronic shutter. These "include a subject recognition area and an AF area. When it is functionally more accurate to have pixel accumulation simultaneity in this way, it is preferable to use the global electronic shutter."
Thus, to maintain quality sensor output and performance, quoting Patent Paragraph 0088 is explicit: "...it is effective to arrange a plurality of circuits on a plane instead of arranging a plurality of circuits on a plane, and to stack a peripheral circuit, an intra-pixel switch, and the like on the pixel area 201.". Presumably, this means dedicated areas of the sensor have complementary functions of circuitry built into the stacked sandwich of sensor layers (?)
and it continues.... "According to the embodiment described above, the following effects can be obtained.
(1) The imaging element 101 has a pixel 220 including a photodiode PD for converting light into electric charge, and a reading unit 250 for reading an imaging signal generated by the electric charge photoelectrically converted by the photodiode PD. A control unit 206 of an imaging element 101 controls a reading unit 250 so as to read an imaging signal of a part of pixels 220 in a 1 electronic shutter system and read an imaging signal of another pixel 220 in a 2 electronic shutter system different from the 1 electronic shutter system. With such a configuration, it is possible to obtain an imaging signal using a plurality of electronic shutter systems within 1 frames."
and continues describing this integrated circuitry driving 2 different shutter systems:
"[0090]
According to the embodiment described above, the following effects can be obtained.
(1) The imaging element 101 has a pixel 220 including a photodiode PD for converting light into electric charge, and a reading unit 250 for reading an imaging signal generated by the electric charge photoelectrically converted by the photodiode PD. A control unit 206 of an imaging element 101 controls a reading unit 250 so as to read an imaging signal of a part of pixels 220 in a 1 electronic shutter system and read an imaging signal of another pixel 220 in a 2 electronic shutter system different from the 1 electronic shutter system. With such a configuration, it is possible to obtain an imaging signal using a plurality of electronic shutter systems within 1 frames."
7. Patent Paragraphs 0091 and 0092 are equally explicit: "(2) The 1 electronic shutter system is a global electronic shutter system, and the 2 electronic shutter system is a rolling electronic shutter system. By using a global electronic shutter system in an area which is better to store pixels and a rolling electronic shutter system in other areas, the disadvantages of the global electronic shutter system and the rolling electronic shutter system described above can be compensated.
[0092]
(3) The image pickup element 101 has a plurality of pixels 220 arranged 2 dimensionally in the row direction and the column direction."
bs kite wrote:
Hi to all.....
Why is this potentially exciting?
Would you please discuss/explain at your conveniences?
Thank you.
Edited on Dec 10, 2021 at 09:43 AM · View previous versions
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