Canon Patent: Quad Pixel Phase Detection Auto-Focus

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Here is a new and definitely interesting Canon patent application: Quad Pixel Phase Detection AF. It’s not the first patent for this technology.

Canon patent application 2023166867 (Japan, published 11/22/2023) discusses methods and technology for Canon’s next generation autofocus technology, Quad Pixel Detection AF.

From the patent literature:

  • [Problem] To improve the performance of focus detection in focus detection using an image plane phase difference method that uses signals output from image sensors having different vertical and horizontal lengths.
  • TECHNICAL FIELD
    The present invention relates to an image sensor in which a pixel section having a plurality of photoelectric conversion sections is two-dimensionally arranged, and an image sensor equipped with the image sensor.
  • BACKGROUND ART
    Conventionally, as one of the focus detection methods performed in an imaging device, a pair of pupil division signals are acquired using focus detection pixels formed on an image sensor, and a focus detection method using a phase difference method is used. A so-called imaging plane phase difference method for performing detection is known.
  • As an example of such an imaging surface phase difference method, there is an imaging device using a two-dimensional imaging element in which one microlens and a plurality of divided photoelectric conversion sections are formed for one pixel. It is disclosed in Patent Document 1. The plurality of photoelectric conversion units are configured to receive light transmitted through different regions of the exit pupil of the imaging lens via one microlens, and perform pupil division. Then, by calculating the amount of image shift from the phase difference signal that is a signal of each photoelectric conversion unit, focus detection using a phase difference method can be performed. Further, by adding up the signals of the individual photoelectric conversion units for each pixel, a normal image signal can be obtained. Further, Patent Document 1 discloses a configuration in which the saturation resistance of the pixel is increased by arranging a plurality of types of pixels having different heights of separation barriers between photoelectric conversion parts in the pixel.
  • In such an image sensor, in a configuration in which a plurality of photoelectric conversion units are arranged horizontally within a pixel and the pupil division direction is horizontal, for example, when the subject has a horizontal striped pattern, parallax is This may be difficult to see, and focus detection accuracy may deteriorate.
  • On the other hand, Patent Document 2 discloses a technique for improving focus detection accuracy by providing two types of arrangement directions of photoelectric conversion units for each microlens and two types of pupil division directions. There is. Furthermore, Patent Document 2 discloses a structure that separates vertically adjacent photoelectric conversion units and a structure that separates horizontally adjacent photoelectric conversion units, and has a structure that allows electric charges to leak to adjacent photoelectric conversion units. It is disclosed that the With this structure, supersaturated charges received in excess of the amount of charge that can be accumulated by one photoelectric conversion section leak and accumulate in different photoelectric conversion sections arranged in a predetermined direction. Even in the case of saturation, horizontal or vertical phase difference focus detection is possible.
  • Most conventional image sensors do not have an aspect ratio of 1:1. Therefore, when focus detection pixels using the image plane phase difference method in the vertical direction and focus detection pixels in the horizontal direction are arranged on the image sensor, focus detection using the image plane phase difference method is difficult, especially in the periphery of the image sensor. Performance is biased towards either the vertical or horizontal direction.
  • The image sensor described in Patent Document 1 changes the separation state of the photoelectric conversion unit depending on the saturation state of the pixel. Therefore, depending on the aspect ratio of the image sensor, the state of charge crosstalk (a phenomenon in which charge leaks to the adjacent photoelectric conversion unit) between the photoelectric conversion units in the vertical focus detection pixels and the horizontal focus detection pixels respectively occurs. It is not possible to control the above problems and cannot solve the above problems.
  • Furthermore, the image sensor of Patent Document 2 does not have a configuration that controls charge crosstalk when the photoelectric conversion section is not saturated, and also controls charge crosstalk between the photoelectric conversion sections according to the aspect ratio of the image sensor. Since there is no mention of the talk rate, the above problem cannot be solved.
  • The present invention has been made in view of the above problems, and is intended to improve the performance of focus detection in focus detection using an image plane phase difference method that utilizes signals output from image sensors having different lengths and widths. The purpose is to

More Canon patent applications are listed here.

[via asobinet]

Canon Patent: Quad Pixel Dual Cross Autofocus

Drawing From The Patent Literature
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For once a Canon patent application that is not for an RF mount lens. It’s for what could be a future generation of autofocus.

Canon patent application 2022-2383 (Japan) discusses methods and technology for a Quad Pixel Dual Cross autofocus system which one day might well be featured on a Canon mirrorless camera.

PROBLEM TO BE SOLVED: To increase the division direction of a pupil region while suppressing variation in sensitivity of an image signal.

As one of the focus detection methods of an image pickup device, a so-called image pickup surface phase difference method, in which a pupil division signal is acquired by using a focus detection pixel formed in an image pickup device and focus detection is performed by a phase difference method, is used. Are known. As a focus detection pixel, a configuration in which one microlens and a plurality of sensitivity regions are formed in each pixel is known, and each of the plurality of sensitivity regions is light that has passed through different pupil regions of the photographing optical system. The pupil division signal can be acquired by receiving light.

The patent application was spotted by asobinet.com. More Canon patent applications are listed here. Some particularly interesting patent applications we think might get into production are these:

Canon Patent: Quad Pixel Autofocus Imaging Sensor

Quad Pixel
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Dual Pixel AF was true innovation when first launched by Canon on the EOS 70D. It’s just common sense to assume Canon will develop it further. Welcome Quad Pixel AF.

Here is a Canon patent for a Quad Pixel AF imaging sensor, and it is not the first we spotted. Canon patent application 2020-171060 (Japan) discusses the technology. It’s hard to say when we will see the first commercial Quad Pixel AF sensor. But we know it is coming.

More Canon patent applications are listed here. Some particularly interesting patent applications we think might get into production are these:

Is Quad Pixel Autofocus The Upcoming Evolution Of Dual Pixel AF?

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A recently spotted Canon patent application suggests Canon might be at works to design the technological evolution of its patented Dual Pixel Auto Focus (DPAF).

Canon patent application 2019-041178 (Japan) describes a technology where pixels are split in four parts. This should allow for a more precise AF in all possible directions.

From the patent literature:

Therefore, there is the object of this invention in providing the image sensor which can always perform focus detection by an image surface phase difference system with high precision, and the imaging device using this image sensor. 

In order to achieve the above-mentioned object, the image sensor by the present invention, A plurality of optical waveguides which a unit pixel part provided with a plurality of pixels is the image sensor arranged by two-dimensional matrix form, and draw light to said plurality of pixels, respectively, It has the segregant formed among said plurality of waveguides, the height and position of the aforementioned segregant are changed according to image height, and the pupil distance of said plurality of pixels is changed in each of the aforementioned unit pixel part. 

The patent literature seems to describe an APS-C sensor with a resolution around 20MP:

A unit pixel has the 1st focus detection pixel 201, the 2nd focus detection pixel 202, the 3rd focus detection pixel 203, and the 4th focus detection pixel 204, and these pixels are arranged by two lines x two rows. In the illustrated example, although the pixel structure of four lines x four rows is shown, the many pixel is actually arranged by two-dimensional matrix form. For example, the image sensor is 4 micrometers in the cycle P of a pixel, and is side [ of 5575 lines ] x [ 3725 rows ] long = about 20,750,000 pixels in the pixel number N. The image sensor is 2 micrometers in the line writing direction cycle PAF of a focus detection pixel, and is side [ of 11150 lines ] x [ 7450 rows ] long = about 83,060,000 pixels in the focus detection pixel number NAF. 

No idea if this patent describes a technology that might get into production soon. More Canon patent applications are listed here. Some particularly interesting patent applications we think might get into production in the next few years are these: