JP2005175232A - Solid-state imaging device for imaging and focus detection - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-state imaging device which enables focus detection by a phase difference detection method by a CCD sensor which also enables moving video shooting. <P>SOLUTION: A pair of photodiodes 101-1, 101-2 are disposed adjacent in a horizontal direction, a pair of vertical CCD charge transfer paths 102-1, 102-2 are disposed alternately and one on-chip micro lens is disposed each pair of the photodiodes 101-1, 101-2. Furthermore, a barrier for isolation is not provided between the pair of photodiodes 101-1, 101-2 and cross talk of sensitivity is provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a solid-state image sensor for photographing of a photographing apparatus such as a digital still camera or a video camera, and is particularly used as an image sensor for focus detection.

Conventionally, an interline CCD sensor in which a light receiving unit (photo diode) and a vertical transfer unit (consisting of a CCD: Charge Coupled Device) are alternately arranged vertically with a storage charge readout gate interposed therebetween is a digital camera, video, etc. It is often used for shooting.

FIG. 5 is a schematic diagram of a conventional general interline CCD sensor. Reference numeral 101 denotes a photo diode which is a light receiving portion having an opening, and performs photoelectric conversion according to incident light to generate a charge signal. Reference numeral 102 denotes a vertical transfer unit which takes out a charge signal generated by the photodiode 101 as indicated by an arrow through a storage charge read gate (not shown).

  An area of one pixel unit in the light receiving area of the CCD sensor is 103 (a range surrounded by a wavy line) in the figure, and is actually arranged in a state of being in close contact vertically and horizontally. The charge signals taken out by the vertical transfer unit 102 are sequentially sent to the horizontal transfer unit 104 as indicated by the vertical arrows in the figure, and are sent out of the sensor by the horizontal transfer unit 104 as indicated by the horizontal arrows. The so-called on-chip microlens 105 is basically arranged so as to be aligned with the light receiving unit 101 as shown in the figure. However, in the peripheral region of the photographing region, it is general that the on-chip microlens is slightly shifted so that the photographing light flux is received without waste.

  On the other hand, as shown in FIG. 6, Patent Document 1 discloses an example in which two vertical transfer units 102-1 and 102-2 are disposed substantially on both sides of a light receiving unit for one photodiode 101. Yes. This is intended to eliminate the influence of dark current and smear by taking out charge signals of the same light receiving portion at different timings and taking the difference later. If the area of one pixel unit in the light receiving area of the CCD sensor is shown in the same manner as in FIG. 5, it becomes 103 (range surrounded by a wavy line), and the on-chip microlens 105 is also centered on the light receiving part 101 as shown in the figure. Will be arranged together.

  Further, in Patent Document 2, there is no disclosure of a plan view as shown in FIG. 7, but the vertical transfer units 102-1 and 102-2 are received on both sides of the pair of two photodiode light receiving units 101-1 and 101-2, respectively. An example in which one on-chip microlens is arranged for two photodiodes is also disclosed. As a result, the area of the photodiode is increased to improve the photosensitivity and prevent smear. Similarly, the area of one pixel unit in the light receiving area of the CCD sensor is 103 (a range surrounded by a wavy line), and the on-chip microlens 105 includes two light receiving units 101-1 and 101- as shown in the figure. 2 is arranged with the center in the middle. Incidentally, reference numeral 106 in the figure denotes a channel stop region for the purpose of separating adjacent pixel units.

On the other hand, Patent Document 3 is an imaging device and apparatus capable of focus detection by a phase detection method disclosed by the present applicant. Here, a sensor having a CMOS (Complementary Metal-Oxide Semiconductor) structure is characterized by an imaging mode in which one light receiving unit is divided into two parts, and each received light charge is added and read out separately, and a focus detection mode that is read out separately. .
JP 07-264491 A Japanese Patent Laid-Open No. 09-064329 JP 2001-083407 A

  Although the above-mentioned disclosure example by the present applicant is based on a CMOS sensor, the features of the CMOS sensor and the CCD sensor are both advantages and disadvantages. In particular, the electronic shutter function that maintains the synchronism of the entire shooting screen during moving image shooting has a significant advantage over the CCD.

  Therefore, an object of the present invention is to realize a solid-state imaging device capable of focus detection by a phase detection method using a CCD sensor capable of capturing beautiful moving images.

In order to solve the above problems, in the present invention, a photoelectric conversion element group formed two-dimensionally on the same semiconductor substrate, a vertical CCD register group for transferring signal charges from the photoelectric conversion element group in the vertical direction, A vertical CCD charge transfer path unit that is shared with a transfer gate of a vertical CCD register group and includes a selection gate that transfers a signal charge from the photoelectric conversion element group to the vertical CCD register group; In a solid-state imaging device having a horizontal readout unit that transfers signal charges in the horizontal direction, a pair of the photoelectric conversion elements and a pair of vertical CCD charge transfer paths are alternately arranged in the horizontal direction, and signals in the photoelectric conversion elements The charge is read out to the adjacent vertical CCD charge transfer path, and no cross-talk of sensitivity is provided between the pair of photoelectric conversion elements without providing an isolation barrier. Myself understood, employing a solid-state image sensor provided with one on-chip microlens for each of the pair of photoelectric conversion elements,
Furthermore, a solid-state imaging device is also proposed in which an on-chip microlens is provided for every four photoelectric conversion elements, and no barrier is provided between the four photoelectric conversion elements under the same microlens area. It is.

  The solid-state image sensor is used for both photographing and focus detection.

  As a result, even with a single solid-state imaging device, it is possible to achieve both an imaging function for moving images and still images and a ranging function.

  According to the present invention described above, even in a single-lens reflex camera using a CCD image sensor, a focus detection / adjustment operation by a deviation detection method can be performed without providing a dedicated focus detection sensor, and a distance measurement time can be reduced. The effectiveness of the short and light deviation detection method can be fully exploited.

  In addition, since the image pickup device itself is used, it is easy to check the focus with the blur AF, which is a general contrast detection method for a compact digital camera.

Examples of the present invention will be described below.
Hereinafter, a solid-state imaging device for imaging and focus detection according to an embodiment of the present invention will be described in detail with reference to the drawings.

In general, a method of automatically refocusing a light beam that has passed through a photographing lens by re-imaging on a sensor is roughly classified into two methods, which are called a blur method and a shift method.
Currently, a method of detecting a relative positional shift in image signals on a pair of sensors, called a shift method, is common in single-lens reflex cameras and the like.

Here, this shift method will be briefly described with reference to FIG. As shown in FIG. 8, the basic components are a field mask (MSK) and a field lens (FLDL) placed near the intended imaging plane where the subject image is formed by the photographic lens (LNS), and a porous film behind it. A secondary optical system (AFL-a, b) having a diaphragm (DP-a, b) and a secondary imaging lens, and a plurality of photoelectric conversion element arrays (SNS-a, b) arranged behind it Is.

  Then, with the above configuration, the two subject images formed by the light beams that have passed through the two pupil regions (PUP-a, b) of the photographing lens are re-imaged on different photoelectric conversion element arrays, and the two subject images. An automatic focus detection device is realized by utilizing the fact that the relative positional relationship, that is, “deviation” changes depending on the focus state of the photographing lens.

  The shift amount, which is the relative positional relationship between the two subject images, can be obtained by obtaining the correlation. An example of a calculation method for specifically obtaining this will be described with reference to FIG.

  The area U (the sum of the smaller values of the A and B images) of the AND region of the two subject images (A and B images) shown in FIG. 9 is converted into one image (A image in the figure) and one pixel of the photoelectric conversion element. Shift by (bits) and find the maximum value. If the two images coincide with each other, the maximum value is inevitably obtained. Therefore, the shift amount that causes the maximum value is the relative shift amount of the two images.

  When the shift method having the above-described configuration is realized by an image sensor, it is necessary to arrange two light receiving units adjacent to each other under one microlens as disclosed in Patent Document 3 above.

In the first embodiment, therefore, a pair of photoelectric conversion elements and a pair of vertical CCD charge transfer paths are alternately arranged in the horizontal direction, and signal charges in each photoelectric conversion element are read out to adjacent vertical CCD charge transfer paths. One on-chip microlens is provided for each photoelectric conversion element. FIG. 1 shows a specific example of the above configuration. In the following description, the notation conforming to FIG.

  As shown in FIG. 1, the photodiodes 101-1 and 101-2 which are light receiving parts having openings are arranged adjacent to each other, and perform photoelectric conversion according to incident light to generate a charge signal. The vertical transfer units 102-1 and 102-2 distribute and extract the charge signals generated by the photodiodes 101-1 and 101-2 to the left and right as indicated by arrows through a storage charge readout gate (not shown). is there.

  An area of one pixel unit in imaging in the light receiving area of the CCD sensor is 103 (a range surrounded by a wavy line) in the figure, and is actually arranged in a state of being in close contact vertically and horizontally.

  The charge signals taken out to the vertical transfer units 102-1 and 102-2 are sequentially sent to the horizontal transfer unit 104 as indicated by the vertical arrows in the figure, and the horizontal transfer unit 104 outputs the sensor signals as indicated by the horizontal arrows. Sent to the outside.

  In the imaging operation, the charge signals generated by the photodiodes 101-1 and 101-2 are externally added to obtain a charge signal in units of one pixel. Treated as signals constituting A and B images.

  Further, the on-chip microlens 105 is disposed so as to be aligned with the adjacent portion of the light receiving portions 101-1 and 101-2 as shown in the figure. However, it is effective to slightly shift the on-chip microlens in the peripheral area of the imaging area so as to receive the imaging light flux without waste.

  In the figure, reference numeral 106 denotes a channel stop region, but it is provided only between adjacent vertical transfer units because of the proposed configuration. As a result, sensitivity crosstalk occurs between the photodiodes 101-1 and 101-2. This has the effect of smoothing the shape of the pupil-divided image in the focus detection operation.

  In the second embodiment, an arrangement relationship between pixels and on-chip microlenses and a relationship between a visual field (base line length) direction in a focus detection operation will be described.

In the above-described first embodiment, two light receiving units are configured below one on-chip microlens. In this configuration example, the visual field (baseline length) direction detectable in the focus detection operation is the horizontal direction, that is, the pixel arrangement direction, and a vertical line can be detected as a signal.
FIG. 2 shows the relationship between the arrangement direction of the light receiving portions and the viewing direction.

  In the figure, (A) is an arrangement capable of detecting a vertical line, and (B) is an arrangement capable of detecting a horizontal line. In each case, the “shift” in the direction of the arrow can be detected, and therefore focus detection for the component in the vertical direction is effective.

  In order to be able to detect a focus on a general subject, it is not sufficient to detect only in the horizontal or vertical direction as described above, and focus detection capability (vertical and horizontal detection) in both directions is desired.

  In the second embodiment, as shown in FIG. 3, in order to enable simultaneous focus detection not only in the horizontal direction but also in the vertical direction with respect to the above problem, four light receiving portions are configured under one on-chip microlens. Is.

  In FIG. 3, the photodiodes that are light receiving portions are 101-1, 101-2, 101-3, and 101-4, which are arranged adjacent to each other as shown in the figure, perform photoelectric conversion according to incident light, and charge Generate a signal. Similarly to FIG. 1, vertical transfer units 102-1 and 102-2 are provided, and charge signals generated by the respective photodiodes 101-1, 101-3 and 101-2, 101-4 are not shown. The stored charge is sorted out to the left and right as indicated by the arrow through the readout gate for accumulated charges.

  Further, the on-chip microlens 105 is arranged so that the center and the center of the four light receiving units 101-1, 101-2, 101-3, and 101-4 are aligned as shown in the figure.

An area of one pixel unit in imaging in the light receiving area of the CCD sensor is 103 (a range surrounded by a wavy line) in the figure, and is actually arranged in a state of being in close contact vertically and horizontally as in FIG. In the figure, reference numeral 106 denotes a channel stop region. Also in this embodiment, it is provided only between adjacent vertical transfer units, and sensitivity crossing between the photodiodes 101-1, 101-2, 101-3, and 101-4. Generate talk. By adopting this configuration, as shown in FIG. 4, it is possible to set the focus detection visual field not only in the horizontal direction but also in the vertical direction. The focus detection area can be set by the method.

It is explanatory drawing of Example 1 of this invention. It is explanatory drawing of the focus detection visual field direction in Example 1 of this invention. It is explanatory drawing of Example 2 of this invention. It is explanatory drawing of the focus detection visual field direction in Example 2 of this invention. It is explanatory drawing of the prior art example which concerns on the Example of this invention. It is explanatory drawing of the prior art example which concerns on the Example of this invention. It is explanatory drawing of the prior art example which concerns on the Example of this invention. It is explanatory drawing of the focus detection method by a shift | offset | difference system. It is explanatory drawing of the focus detection method by a shift | offset | difference system.

Explanation of symbols

LNS lens
PUP pupil lens pupil area
SNS Photoelectric conversion element array for focus detection
MSK focus detection field mask
FLDL focus detection field lens
DP Aperture for focus detection
Secondary optical system for AFL focus detection
101-1, 101-2 Photo diode
101-3, 101-4 Photo diode
102 Vertical transfer section
104 Horizontal transfer section
105 On-chip micro lens
106 Channel stop area

Claims (3)

A photoelectric conversion element group formed two-dimensionally on the same semiconductor substrate, a vertical CCD register group for transferring signal charges from the photoelectric conversion element group in the vertical direction, and a transfer gate of the vertical CCD register group And a vertical CCD charge transfer path section having a selection gate for transferring signal charges from the photoelectric conversion element group to the vertical CCD register group, and signal charges from the vertical CCD charge transfer paths are transferred in the horizontal direction. In a solid-state imaging device having a horizontal readout unit,
A pair of the photoelectric conversion elements and a pair of the vertical CCD charge transfer paths are alternately arranged in the horizontal direction, and signal charges in the photoelectric conversion elements are read to the adjacent vertical CCD charge transfer paths,
Without providing a barrier for isolation between the pair of photoelectric conversion elements, to give a crosstalk of sensitivity,
A solid-state imaging device, wherein one on-chip microlens is provided for each pair of photoelectric conversion devices.   2. The solid-state imaging device according to claim 1, wherein an on-chip microlens is provided for every four photoelectric conversion elements, and no barrier is provided between the four photoelectric conversion elements under the same microlens area. A solid-state imaging device.   3. The solid-state image pickup device according to claim 1, wherein the solid-state image pickup device is used both for photographing and for focus detection.

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