JP2002303785A - Focus detecting device and image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform focus detection of an object having any contrast whatever by a phase difference detection system which is of simple constitution and precise. SOLUTION: The focus detecting device has a photoelectric converting element 100 constituted by arranging in a two-dimensional area a plurality of photodetection parts each composed of a 1st photoelectric conversion part which photoelectrically converts 1st luminous flux among pieces of luminous flux separating the exit pupil of an image formation system 1 and a 2nd photoelectric conversion part which photoelectrically converts 2nd luminous flux different from the 1st luminous flux and computes focus detection information according to phase differences between the output parts of the 1st photoelectric conversion parts and 2nd photoelectric conversion parts. Pupil splitting means 7 and 8 which divide the exit pupil of an image pickup optical system obliquely to the separation direction of the exit pupil of the 1st luminous flux and 2nd luminous flux are arranged in the optical path of the image formation optical system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an improvement in an imaging device to which a solid-state imaging device such as a focus detection device, a digital camera or a video camera is applied.

[0002]

2. Description of the Related Art In a digital camera, a solid-state image sensor such as a CCD or CMOS sensor is exposed to a subject image for a desired time in response to pressing of a release button, and a still image of one screen obtained from this is obtained. Is converted into a digital signal and subjected to predetermined processing such as YC processing to obtain an image signal of a predetermined format. A digital image signal representing a captured image is recorded in a semiconductor memory for each image, and the recorded image signal is read out at any time, reproduced into a displayable or printable signal, and output to a monitor or the like. Is displayed.

Conventionally, in a digital camera, focus detection of a contrast detection method using an imaging device has been performed. In general, in such focus detection of the contrast detection method, a position on an optical axis of an imaging optical system is determined. Since the extreme value of the contrast is obtained while slightly moving, there is a problem that a considerable amount of time is required for focus adjustment until focusing.

Therefore, it has been proposed to perform focus detection of a phase difference detection method used in a single-lens reflex camera using a silver halide film by using an image sensor of a digital camera. Since the defocus amount can be obtained in the focus detection using the phase difference detection method, there is an advantage that the time required for focusing can be greatly reduced as compared with the contrast detection method.

As an example of such a focus detection system, a pair of photoelectric conversion units is provided for each two-dimensionally arranged microlens array, and a light receiving unit including the pair of photoelectric conversion units is imaged by the microlens. A method has been proposed in which a pupil is separated by projecting the pupil onto a system pupil and focus detection is performed by a phase difference method. Further, an imaging device using a solid-state imaging device capable of arbitrarily adding and non-adding a pair of photoelectric conversion unit output signals in one microlens for each pixel unit has been proposed as this light receiving unit (Japanese Patent Application Laid-Open No. H9-1997). -465
No. 96).

In this proposed imaging apparatus, in the case of imaging, the output signals of a pair of photoelectric conversion units in one microlens are added and read out. In the case of focus detection, the output signals of each photoelectric conversion unit are independently output. By reading out, focus detection of the phase difference detection method by the image sensor is realized. Also, since the addition of the output signal of the photoelectric conversion unit at the time of imaging is performed in the pixel unit, the same level as the image obtained by the image sensor originally designed to obtain the image using the entire luminous flux of the pupil of the imaging optical system is used. It is possible to obtain an image excellent in S / N.

[0007]

However, in the case of performing the focus detection by the phase difference method with the configuration as in the conventional example, the moving direction of the image on the image sensor is the separating direction of the pair of photoelectric conversion units. For example, when the pupil separation direction of the taking lens is horizontal by a pair of photoelectric conversion units, that is, when the pair of photoelectric conversion units is separated in the horizontal direction, the contrast difference is in the same direction as the separation direction of the photoelectric conversion units. Although the focus detection (vertical line detection) of a subject having a contrast can be easily performed, the focus detection (horizontal line detection) of a subject having a contrast difference in a direction orthogonal to the separation direction of the photoelectric conversion unit cannot be performed. Therefore, the configuration as in the conventional example has a disadvantage that the focus detection performance differs depending on the direction in which the contrast difference on the subject occurs.

(Object of the Invention) It is an object of the present invention to provide a focus detection device capable of performing a focus detection by an accurate phase difference detection method with a simple configuration for an object or a subject having any contrast. It is intended to provide a device and an imaging device.

[0009]

In order to achieve the above object, according to the present invention, the first light beam among the light beams obtained by splitting the exit pupil of the imaging optical system into a plurality of light beams is photoelectrically converted. A first photoelectric conversion unit for conversion, and a second photoelectric conversion unit different from the first light flux.
A photoelectric conversion element in which a plurality of light receiving units each configured of a second photoelectric conversion unit that photoelectrically converts the light beam of the first and second photoelectric conversion units are arranged in a two-dimensional area, and output signals of the first photoelectric conversion unit and the second photoelectric conversion unit are provided. In a focus detection device that calculates focus detection information based on a phase difference, an exit pupil of the imaging optical system is divided into a direction obliquely intersecting a direction in which the exit pupil is separated by the first light beam and the second light beam. The pupil dividing means is a focus detection device arranged in the optical path of the imaging optical system.

According to another aspect of the present invention, there is provided an imaging optical system, wherein a first light beam of a light beam obtained by dividing an exit pupil of the imaging optical system into a plurality of light beams is photoelectrically converted. A solid-state imaging device in which a plurality of light receiving units including a second photoelectric conversion unit that photoelectrically converts a second light flux different from the first light flux are arranged in a two-dimensional area; An image pickup apparatus comprising: a first photoelectric conversion unit and focus detection means for calculating focus detection information based on a phase difference between output signals of the second photoelectric conversion unit. A pupil dividing unit that divides an exit pupil of the imaging optical system in a direction obliquely intersecting with a separation direction of the exit pupil,
The image pickup apparatus is arranged in an optical path of the image pickup optical system.

In the above arrangement, the photoelectric conversion outputs of the first and second light fluxes via the exit pupil divided by the pupil dividing means are obtained from the first and second photoelectric conversion units, respectively. Based on each output, focus detection is performed on an object or a subject having a contrast difference in a direction orthogonal to the direction in which the exit pupil is separated by the first and second photoelectric conversion units.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments.

FIG. 1 is a configuration diagram showing an image pickup optical system according to an embodiment of the present invention, which is a zoom optical system of a digital color camera using a solid-state image pickup device 100, wherein the image pickup optical system and the camera body are integrated. Is provided. The left side of the figure is the object side, and the right side is the image plane side.

In FIG. 1, an imaging optical system includes a negative lens,
A first positive lens unit (grp1) including a positive lens and a positive lens,
The negative second group (g) including a negative lens and a negative and positive cemented lens.
rp2), aperture ST, positive third lens unit (g)
rp3), a fourth unit (grp) including a cemented lens of negative and positive lenses
4). F1 is an infrared (IR) cut filter, LPF is an optical low-pass filter, L
Reference numeral 1 denotes an optical axis of the imaging optical system.

As indicated by the arrow in the drawing, as the focal length changes from wide angle to telephoto due to zooming, the negative second
The group grp2 moves to the image plane side, and the positive fourth group grp4 moves to the object side. The imaging optical system has a lens driving mechanism (not shown), and uses a motor and a gear train to generate a negative second group grp2.
Is moved in the optical axis direction to adjust the focus so that the object image is focused on the image sensor 100.

FIG. 2 is a perspective view showing a main part of the image pickup apparatus.

In FIG. 1, reference numeral 1 denotes a first group (grp) on the object side of the stop ST in the imaging optical system shown in FIG.
1 is a front lens group collectively showing a second group (grp2). Reference numeral 2 denotes a rear lens group collectively showing a third group (grp3) and a fourth group (grp4) on the image plane side of the stop ST, and an object on the image sensor 100 by a light beam passing through the opening of the stop ST. Form an image. Note that, in order to eliminate the complexity of the drawing, the infrared cut filter F1 and the optical low-pass filter LPF are omitted. Aperture ST
Rotates about the axis L2, selectively takes six positions by the driving force of a motor (not shown), and has openings 3 to 6 of different shapes and a pair of openings 7 to 8 (mainly used for horizontal line focus detection). The details will be described later).

Next, the image sensor 100 will be described.

The image sensor 100 is a CMOS process compatible sensor (hereinafter, referred to as a CMOS sensor), which is one of amplification type solid-state image sensors. This type of sensor is IEEETRANSACTIONS ON ELECTRON DEVICE, VOL
41, PP452-453, 1994. One of the features of the CMOS sensor is that since the MOS transistor of the photoelectric conversion unit and the MOS transistor of the peripheral circuit can be formed in the same step, the number of masks and the number of process steps can be significantly reduced as compared with the CCD. By taking advantage of this feature, in this embodiment, two photoelectric conversion units are formed for one pixel, and a floating diffusion region (hereinafter, referred to as an FD region) and a source follower amplifier, which are conventionally provided for each photoelectric conversion unit, are provided. Only one photoelectric conversion part is formed, and two photoelectric conversion
It is connected to the FD region via an OS transistor switch.

Therefore, the charges of the two photoelectric conversion units can be transferred to the FD region simultaneously or separately, and the signal charges of the two photoelectric conversion units can be summed up only by the timing of the transfer MOS transistor connected to the FD region. Non-addition can be easily performed.

Utilizing this structure, a first output mode for performing photoelectric conversion output by a light beam from the entire exit pupil of the imaging optical system and a photoelectric conversion output by a light beam from a part of the exit pupil of the imaging lens are performed. The second output mode can be switched. In the first output mode in which signals are added at the pixel level, a signal with less noise can be obtained as compared with a method in which signals are read and then added.

FIG. 3 is a circuit diagram of an area sensor section in the image sensor 100 in which addition and non-addition of signal charges of the two photoelectric conversion sections as described above can be easily performed.

FIG. 1 shows a two-dimensional area sensor having 2 columns × 2 rows of pixels. In practice, the image sensor 1 shown in FIG.
As shown in FIG. 00, the number of pixels is increased to 1920 columns × 1080 rows or the like to obtain a practical resolution.

In FIG. 3, reference numerals 101 and 102 denote MOS transistors.
The first and the first, consisting of a transistor gate and a depletion layer below the gate,
The second photoelectric conversion units 103 and 104 are photogates,
05 and 106 are transfer switch MOS transistors, 1
07 is a reset MOS transistor, 108 is a source follower amplifier MOS transistor, 109 is a vertical select switch MOS transistor, 110 is a source follower load MOS transistor, and 111 is a dark output transfer MOS.
Transistor, 112 is a bright output transfer MOS transistor, 113 is a dark output storage capacitor CTN, 114 is a bright output storage capacitor CTS, 115 and 116 are vertical transfer MOS transistors, 117 and 118 are vertical output line reset MOs.
The S transistor, 119 is a differential output amplifier, 120 is a vertical scanning unit, 121 is a horizontal scanning unit, and constitutes a light receiving unit 122. Here, the first photoelectric conversion unit 101 and the second photoelectric conversion unit 102 adjacent to each other are grouped together as a light receiving unit, and the other light receiving units 123 to 125 have the same configuration.

FIG. 4 is a sectional view of the light receiving section 122.

In the figure, 126 is a P-type well, 12
7 and 128 are gate oxide films, 129 and 130 are first layer poly-Si, 131 and 132 are second layer poly-Si, and 133 is n.
+ FD area. The FD region 133 is connected to the first photoelectric conversion unit 101 via the transfer MOS transistors 105 and 106.
And the second photoelectric conversion unit 102. In FIG. 1, the first photoelectric conversion unit 101 and the second photoelectric conversion unit 102 are drawn apart from each other. However, the boundary portion is extremely small in practice, and the first photoelectric conversion unit 101 and the second photoelectric conversion unit are practically used. The unit 102 may be considered to be in contact. Reference numeral 9 denotes a color filter that transmits light in a specific wavelength range, and reference numeral 10 denotes a microlens for efficiently guiding a light beam from the imaging optical system shown in FIG. 1 to the first and second photoelectric conversion units.

With the above-described configuration, the imaging device 100 according to the present embodiment can separately transfer charges generated in the first photoelectric conversion unit 101 and the second photoelectric conversion unit 102 to the FD region 133, The addition and non-addition of the signal charges of the two photoelectric conversion units 101 and 102 are realized only by the timing of the transfer MOS transistors 105 and 106 connected to 133. Although a detailed timing chart and the like are disclosed in JP-A-9-46596, they are not directly related to the present invention and will not be described in detail.

FIG. 5 shows the structure shown in FIG.
4 out of the image sensor 100 having columns × 1080 rows of pixels
FIG. 4 is an enlarged plan view showing only columns × 4 rows.

The pixels including the light receiving section and the MOS transistor are laid out in a substantially square shape, and are arranged adjacent to each other in a lattice.

The light receiving units 122 to 122 described above with reference to FIG.
Numerals 125 are located in the pixels 11 to 14 in the figure, and therefore, each pixel has a light receiving section composed of two adjacent photoelectric conversion sections as shown in FIG. Further, this area sensor unit is provided with R
(Red), G (green), and B (blue) color filters are alternately arranged to form a so-called Bayer array in which four pixels constitute one set. In the Bayer array, the overall image performance is improved by arranging more G pixels that are easily felt by an observer when viewing an image than R and B pixels. Generally, in an image sensor of this type, a luminance signal is mainly generated from G, and a color signal is generated from R, G, and B.

As described above, each pixel section has a light receiving section composed of two photoelectric conversion sections. Attached to the figure,
R, G, and B are light receiving units provided with red, green, and blue color filters, and the numbers 1 or 2 following R, G, and B indicate whether the first photoelectric conversion unit or the second photoelectric conversion unit. Represents the distinction. For example, R1 is a first photoelectric conversion unit having a red color filter, and G2 is a second photoelectric conversion unit having a green color filter. Further, the ratio of the light receiving portion in each pixel is about several tens of percent. In order to effectively use the light flux emitted from the imaging optical system, a condensing lens is provided for each pixel, and the light receiving portion other than the light receiving portion is provided. It is necessary to deflect the light that is going to reach the light receiving unit, which is the microlens 10 shown in FIG.

FIG. 6 is a cross-sectional view showing the optical positional relationship between the microlens provided on the front surface of the image sensor and the light receiving section, and is an enlarged view of a part near the photographing optical system L1.

The microlenses 10-1 to 10-4 are axially symmetrical spherical lenses or aspherical lenses in which the center of the light receiving section substantially coincides with the optical axis. Are convexly arranged in a grid pattern. The imaging optical system shown in FIG. 1 is located on the left side of the figure.
1. First, the light enters the microlenses 10-1 to 10-4 through the optical low-pass filter LPF. Color filters 9-1 to 9-4 are arranged behind each microlens, where only a desired wavelength range is selected and reaches each light receiving unit. The color filters constitute a Bayer array as described with reference to FIG. 5, and there are three types of R, G, and B. Also, because of the Bayer arrangement, only two of them appear on the cross section, 9-1 and 9-3 are green transmission color filters, and 9-2 and 9-4 are red transmission color filters. .

Here, the power of each micro lens is set so that each light receiving portion of the image sensor is projected on the exit pupil of the image pickup optical system. At this time, the projection magnification is set so that the projected image of each light receiving unit is larger than the exit pupil of the imaging optical system when the aperture is opened, and the difference between the amount of light incident on the light receiving unit and the opening degree of the aperture ST of the imaging optical system is set. Make the relationship roughly linear. In this way, when the luminance of the subject and the sensitivity of the image sensor are given, the aperture value and the shutter speed can be calculated by the same method as that of a film camera. That is, the amount of incident light is proportional to the aperture area of the stop, and the APEX-type calculation is established. The exposure amount can be calculated using a general light meter as in the case of a film camera, and the photographing operation is extremely easy. When the object image formed by the imaging optical system is located on the microlens, the image obtained from the imaging device 100 is sharpest.

It is preferable that the imaging optical system be a telecentric system so that the angle of incidence of the principal ray on the imaging device is 0 ° from the viewpoint of pupil projection accuracy by the micro lens.
It is difficult to make it completely telecentric because of the demand for miniaturization and high magnification of the zoom ratio. In this case, the microlens and the light receiving unit may be slightly decentered, and the amount of eccentricity may be a function of the distance from the optical axis of the imaging optical system to the light receiving unit.

In general, if the amount of eccentricity is monotonically increased in accordance with the distance, the light receiving portion around the screen can be correctly projected on the exit pupil of the imaging optical system. However, in the present embodiment, the microlenses are uniformly decentered for each block of 10 columns × 10 rows. By doing so, the manufacturing process of the microlens can be simplified, and there is an effect of cost reduction.

FIGS. 7 (a) and 7 (b) show the light flux incident on the first photoelectric conversion unit and the second photoelectric conversion for one micro lens 10-1 shown in FIG. 6 for easy understanding. It is the figure which showed each of the light beam which injects into a part separately.

FIG. 7 showing a light beam incident on the first photoelectric conversion unit.
In FIG. 7A, a light beam from below is incident on the first photoelectric conversion unit, and FIG. 7B is a light beam incident on the second photoelectric conversion unit.
In the figure, it can be seen that the light flux from above in the figure is incident on the second photoelectric conversion unit. Therefore, in the entire image sensor, the second
The luminous flux incident on the photoelectric conversion unit is as shown in FIG. 7.
This is a light beam that passes through the upper half of T. FIG. 8 is a configuration diagram of an imaging optical system showing a light beam passing through the upper half of the exit pupil. On the other hand, the light beam incident on the first photoelectric conversion unit of the entire image pickup device may be considered as being inverted up and down with the optical axis L1 of the image pickup lens as a symmetric axis. Therefore, the state of separation of the exit pupil of the imaging optical system is as shown in FIG.

In FIG. 9, reference numeral 15 denotes an opening pupil of the image pickup optical system at the aperture 3 in FIG. 2, that is, a virtual image of the aperture ST of the aperture ST when viewed through the rear lens group 2. . A hatched portion 16 is a first area on an exit pupil through which a light beam incident on the first photoelectric conversion unit of the imaging device 100 passes, and a hatched portion 17 is an emission region through which a light beam incident on the second photoelectric conversion unit of the imaging device 100 passes. This is the second area on the pupil. Reference numerals 18, 19, and 20 denote exit pupils when the stop ST is stopped down, and are virtual images of the apertures 4 to 6 of the stop ST viewed through the rear lens group 2.

With the above-described configuration, the output signals from the first photoelectric conversion unit and the second photoelectric conversion unit of the image sensor 100 are read out independently, so that the light beams passing through different exit pupils of the photographing optical system can be received. Is possible.

Next, the focus detection method will be described.
In this embodiment, the exit pupil is divided vertically by using the apertures 3 to 6 of the stop ST in FIG. 2, and the exit pupil is divided obliquely by using a pair of apertures 7 to 8. There are two types of focus detection when performing this.

First, focus detection using the former openings 3 to 6 will be described.

For example, when focus detection is performed at the aperture 3 of the stop ST, the exit pupil of the imaging optical system is vertically separated as shown by the arrow A in FIG. When the imaging optical system is defocused, the object image is shifted in phase in the pupil separation direction. Therefore, as shown in FIG. 10, the focus detection area is defined by the pupil separation direction of the imaging optical system and the longitudinal direction. Set as a rectangle. Then, the first photoelectric conversion unit and the second
The phase shift amount can be detected by a well-known correlation operation or the like, which is a phase shift amount detection means, using the image signal obtained by independently reading the output signal from the photoelectric conversion unit, and the focus adjustment state of the imaging optical system is known. be able to. In the same manner, the focus adjustment state of the imaging optical system can be detected by setting the focus detection area 21 in FIG. Further, the focus detection area 21 is composed of two sets of pixel rows, which extract image signals of each color (green, red, blue) from the image sensor 100 configured with the Bayer arrangement described with reference to FIG. The details will be described later.

Next, focus detection using a pair of openings 7 and 8 of the stop ST will be described.

For example, when focus detection is performed with a pair of apertures 7, the exit pupil of the imaging optical system is as shown in FIG. In addition,
In the same figure, the components denoted by the same symbols as those in FIG. 9 indicate the same functions, and the description is omitted.

The exit pupil of the image pickup optical system is connected to the first photoelectric conversion unit and the second photoelectric conversion unit of the image pickup device 100 and a pair of apertures 7.
Are separated as shown by hatched portions 24 and 25. Here, the line segment 26 is a line segment that intersects the optical axis L1 and is inclined at 45 degrees to the exit pupil separation direction in FIG.

Since the hatched portions 24 and 25 are set so as to be symmetrical with respect to the line segment, the centers of gravity of the hatched portions 24 and 25 exist on the line segment 26, respectively. The phase shift direction of the object image when the imaging optical system is defocused is the direction of separation of the exit pupil, that is, the direction of the line connecting the centers of gravity of the hatched portions 24 and 25 of the exit pupil.
The pixel array having a longitudinal direction along the direction 6
With the above setting, the amount of phase shift due to defocus of the imaging optical system can be detected. Therefore, in the case of focus detection by the opening 7, a focus detection area is set by a pixel row in an oblique direction as shown by 22 in FIG.

As described with reference to FIG. 4, pixels having a pair of photoelectric conversion units are laid out in a square shape.
The 0 focus detection area 22 becomes a pixel row inclined at 45 degrees to the focus detection area 21 and coincides with the phase shift direction at the time of defocusing of the imaging optical system. Then, the phase shift amount can be detected by a well-known correlation operation or the like, which is a phase shift amount detection means, using the image signals obtained by independently reading the output signals from the first photoelectric conversion unit and the second photoelectric conversion unit. It is possible to know the focus adjustment state of the imaging optical system. In the case of focus detection by the aperture 8, the exit pupil separation direction is a direction orthogonal to the line segment 26, and focus detection can be performed in the same manner using the focus detection area 23 in FIG.

Next, at the time of image pickup, the output signals of the first photoelectric conversion unit and the second photoelectric conversion unit are added at the pixel level using the apertures 3 to 6 of the stop ST, so that an unnatural image blur is generated. Does not occur, and it is possible to obtain a high-quality image excellent in S / N at the same level as an image obtained by an imaging device originally designed to obtain an image using the entire luminous flux of a pupil of an imaging optical system. it can. The hatched portions 16 and 17 in FIG.
There is a gap between them, but the amount is very small, so there is almost no effect on the imaging, and the exposure calculation of the APEX method is almost established.

Next, the circuit configuration of the electric system according to the present embodiment will be described.

FIG. 12 is a block diagram showing an internal configuration including peripheral circuits of the image sensor 100. Image sensor 100
Inside, the timing generator 134 and the area sensor 13
5. A vertical scanning unit 136 and a horizontal scanning unit 137 for selecting an output of a pixel, an analog signal processing unit 138, an A / D conversion unit 139 for performing analog / digital conversion, and a digital signal for converting a digitized signal into an output signal Processing unit 14
0, an interface (IF) unit 141 for outputting a digital image signal to the outside and receiving command data from the outside.

The area sensor unit 135 is provided with the above-mentioned C
It is a MOS sensor. The timing generation unit 134 generates a timing signal for reading out the image signal photoelectrically converted by each photoelectric conversion unit based on a master clock which is a reference frequency from the outside, and generates a vertical and horizontal scanning unit 136,1.
37 performs necessary scanning control in accordance with the timing signal to read out charges. Note that the timing generator 13
4 outputs a vertical synchronizing signal and a horizontal synchronizing signal to the outside, and supplies a synchronizing signal for a system requiring a timing signal outside the image sensor. The analog signal processing unit 138 is for outputting the image signal read from the area sensor unit 135 to the A / D conversion unit 139 after performing noise reduction processing, amplification processing, gamma processing, and clamping processing. The A / D converter 139 converts the image signal into a digital signal and outputs the digital signal. The digital signal processor 140 converts the image signal into a digital signal.
And outputs the digitally converted image signal to the interface unit 141. The interface unit 141 outputs a digital image signal output from the digital signal processing unit 139 to the outside of the image sensor 100. Further, the image sensor 10
0 can control a mode, an output signal form, a signal output timing, and the like of the image sensor 100 in response to a command from the outside, and when a required command for obtaining a captured image or a focus detection image is externally given to the interface unit 141, Each component is controlled so as to perform control corresponding to the command received by the interface unit 141.

FIG. 13 is a block diagram showing the internal configuration of the digital signal processing section 140 shown in FIG. 12. In order to easily obtain a focus detection image, signal processing 1 (140-140) is performed.
An output position designation command is prepared as 1),..., Signal processing n (140-n).
8, the focus detection area 21 shown in FIG.
23 correspond to any one of them, and by designating an arbitrary focus detection area, a pair of focus detection image signals in the first photoelectric conversion unit and the second photoelectric conversion unit is obtained. I have.

On the other hand, in the case of imaging, similarly, any one of signal processing 1 (140-1),..., Signal processing n (140-n) of the digital signal processing unit 140 corresponds to an imaging command. By specifying an imaging command, it is possible to obtain an imaging image signal obtained by adding the image signals of the first photoelectric conversion unit and the second photoelectric conversion unit in the imaging region of the area sensor unit 138 at the pixel level. it can. Note that the lines including these focus detection areas are configured to output an image in which the charge accumulation level is optimized for focus detection, and to obtain an appropriate signal level within the focus detection area. The electronic shutter can be set for each detection area.

In general, the CCD type image pickup device has the same charge accumulation time for all pixels. However, the image pickup device 100 of the present embodiment takes advantage of the features of a CMOS sensor to make pixel-by-pixel or line-by-line use. It is easy to adopt a structure that performs reading in block units.
The start and end of the accumulation time can be made different for each unit. Here, the charge accumulation time is changed for each vertical line, so that an image in the focus detection area can effectively use the A / D conversion range. In the present embodiment, only three focus detection areas are set. However, instead of selecting from predetermined areas, a pointing device such as a trackball is prepared, and about several hundred focus detection areas are provided. Some of the regions may be arbitrarily specified. By doing so, it is also possible to perform focus detection in a wide area in the imaging area.

FIG. 14 is a block diagram showing an electric circuit of the imaging apparatus according to the present embodiment.

In FIG. 14, a microcomputer 142 is connected to the image sensor 100 shown in FIG. 12 via an IF unit 141, and the microcomputer 142 gives a required command to the IF unit 141,
The imaging device 100 is controlled. Microcomputer 1
65 is a CPU (Central Processing Unit) 143, ROM 14
4, RAM 145, EEPROM 146, ROM
Various operations are executed in accordance with the program stored in 144. Information such as image signal correction processing information is stored in the EEPROM 164 in advance.

Finally, signal processing for focus detection using a pair of image signals will be described.

First, the apertures 3 to 6 of the stop ST in FIG.
The focus detection using is described. FIG.
6 is an enlarged view of a focus detection area 21 corresponding to No. 6; FIG. As shown in the figure, the focus detection area 21 includes two sets of pixel columns 27 and 28 each composed of twelve light receiving units. However, the actual focus detection area 21 has, for example, a large number of 300 rows × 2 columns. Although composed of pixels, the description will be made using only 12 rows × 2 columns in order to eliminate the complexity of the drawing.

Since the color filters of the area sensor section 135 have a Bayer arrangement, two types of color filters are alternately arranged in each pixel row. Therefore, for focus detection, each pixel row is classified by the type of the color filter, and each pixel row is further composed of a signal from the first photoelectric conversion unit and a signal from the second photoelectric conversion unit.
Generate a pair of image signals. Therefore, the focus detection area 2
Four pairs of image signals are generated from one. Note that one focus detection area has a substantially uniform accumulation time.

FIGS. 17 to 20 show these four pairs of image signals, which are image signals of the focus detection area 21 when a horizontal solid line chart on a black background as shown in FIG. 16 is used as a subject. . Here, the horizontal single line on the white background is orthogonal to the exit pupil separation direction of the imaging optical system in FIG.

FIG. 17 shows a pair of image signals of every other pixel having a green color filter in the pixel row 27 shown in FIG. 15, and 29 shown by a black circle plot is the first signal shown by G1.
The signal 30 from the photoelectric conversion unit and the white circle plot 30 are the signals from the second photoelectric conversion unit indicated by G2. Similarly, FIG.
20 is a pair of image signals of every other pixel provided with a green color filter in the pixel row 28 shown in FIG. 5, and FIG. 19 is a pair of image signals of every other pixel provided with a red color filter in the pixel row 27. Indicates a pair of image signals of every other pixel having a blue color filter in the pixel column 28. Also in FIGS. 18 to 20, similarly to FIG. 17, image signals 31, 33, and 35 shown by black circle plots shifted to the right are signals by the first photoelectric conversion unit, and white circle plots shifted to the left. The image signals 32, 34, and 36 indicated by are signals from the second photoelectric conversion unit.

These are examples in which the object image formed on the focus detection area 21 by the imaging optical system is an object image according to the chart of FIG. 16. The image signal corresponding to a black background has a low intensity, and the white line Has a strong intensity. Here, in FIGS. 17 and 19, as shown in FIG. 15, the sampling points in the pixel signal 27 in the phase shift direction of the image signal are shifted by ピ ッ チ pitch.
The same applies to FIGS. 18 and 20. Conversely, the image signals of FIGS. 17 and 20, and FIGS. 18 and 19 have the same sampling points in the phase shift direction, so that the image signals of FIGS. 17 and 20, and FIGS. The signal has been obtained. These figures show a state where the object image is defocused, and the signal of the first photoelectric conversion unit and the second
It can be seen that the phase is shifted from the signal of the photoelectric conversion unit. When the object is in focus, the phase of the signal of the first photoelectric conversion unit and the phase of the signal of the second photoelectric conversion unit match. Therefore, focus detection can be performed using a pair of image signals.

Further, the amount of defocus can be obtained by detecting the amount of phase shift using a known method using a correlation operation. If the obtained defocus amount is converted into an amount to drive the second group grp2 of the imaging optical system in FIG. 1, automatic focusing can be performed. Since the driving amount of the lens can be known in advance, it is usually sufficient to drive the lens to the in-focus position almost once, and an extremely high-speed focus adjustment can be realized.

Although the color-separated signal is used here, when color separation is not performed, this corresponds to obtaining a signal obtained by adding the image signals of the respective colors. It is easy to fall into an impossible state. On the other hand, if the color-separated signal is used,
Although high contrast does not always appear in all of the R, G, and B signals, a high-contrast signal is obtained in any of R, G, and B, and focus detection can be performed in most cases.

On the other hand, as shown in FIG. 21, a vertical solid line chart on a black background and a white background and the vertical single line is parallel to the exit pupil separation direction of the imaging optical system in FIG. A pair of image signals in the focus detection area 21 using the apertures 3 to 6 is a uniform pair of image signals 37 and 38 as shown in FIG.
become. There is a level difference between the R, G, and B image signals obtained by color separation depending on which part of the chart, a black background or a white background, is received by the pixel columns 27 and 28 of the focus detection area 21. Signal, the phase shift amount of the image signal cannot be detected even if the imaging optical system is defocused.

Therefore, the focus detection in the focus detection area 21 using the apertures 3 to 6 of the stop ST in FIG. 2 is mainly performed in the direction parallel to the exit pupil separation direction of the imaging optical system (arrow A in FIG. 9). Is particularly good at focus detection of an object having a contrast, and in particular, an object having a contrast difference only in a direction orthogonal to the exit pupil separation direction of the imaging optical system has a feature that focus detection is impossible.

Next, focus detection using a pair of openings 7 and 8 in the stop ST in FIG. 2 will be described.

FIG. 23 shows a focus detection area 2 corresponding to the opening 7.
2 is an enlarged view of FIG. As shown in FIG.
2 is an oblique pixel array 39, 40 composed of 12 light receiving sections.
Although the actual focus detection area 22 is composed of a large number of pixels of, for example, 300 rows × 2 diagonal columns, in order to eliminate the complexity of the drawing, only the 12 rows × 2 diagonal columns are used. explain.

Since the color filters of the area sensor section 135 have a Bayer arrangement, only the green color filters are arranged in the diagonal pixel rows 39 and the diagonal pixel rows 40 are arranged.
, Blue and red color filters are alternately arranged.
The image signal of the focus detection in the focus detection area 21 described above is obtained by classifying each pixel row according to the type of the color filter, and further dividing the image signal from the signal from the first photoelectric conversion unit and the signal from the second photoelectric conversion unit. Although four pairs of image signals were obtained by generating a pair of image signals, the focus detection area 2
In the second diagonal pixel column 39, only the green color filter is used.
It is configured to obtain a pair of image signals. Therefore, from FIG. 23, the sampling pitch of the image signal of the green color filter in the pixel array 39 is の of the sampling pitch of the image signal of the blue and red color filters in the pixel array 40. Since the focus detection area 22 is composed of a 45-degree oblique pixel row, the focus detection area 21 has a smaller sampling pitch than the focus detection image signal sampling pitch.
The sampling pitch of blue and red color filters is √
(2) It is twice as large as that of the image signal sampling pitch of the green color filter of the pixel row 39, and therefore smaller than the sampling pitch in the focus detection area 21. Therefore, the G image signal of the oblique pixel row 39 can be resolved to a higher frequency subject.

FIGS. 24 to 26 show three pairs of image signals when the chart of FIG. 21 is used as a subject.

FIG. 24 shows a pair of image signals of a diagonal pixel array 39 provided with a green color filter. A black circle plot 41 indicates a signal of the first photoelectric conversion unit indicated by G1, and a white circle plot 42 indicates G2. It is the signal of the 2nd photoelectric conversion part shown. Similarly, FIG. 25 shows a pair of image signals of every other pixel having a blue color filter in the diagonal pixel row 40.
Reference numeral 6 denotes a pair of image signals of every other pixel provided with a red color filter in the diagonal pixel row 40, respectively. In FIGS. 25 and 26, similarly to FIG. 24, image signals 43 and 45 indicated by black circle plots shifted to the right are signals from the first photoelectric conversion unit, and white circle plots shifted to the left. Image signals 44, 46 shown
Is a signal from the second photoelectric conversion unit.

FIG. 24 is an image signal of the green color filter in the diagonal pixel row 39, so that the number of sampling points is doubled as compared with the image signals of FIGS. 25 and 26. In addition, the chart shown in FIG. 21 in which the focus cannot be detected in the focus detection area 21 can also be obtained by detecting a diagonal pixel row to obtain a pair of image signals that are phase-shifted. Note that FIG.
24, the pair of image signals detected in the focus detection area 22 are the same as those in FIGS.

Therefore, in the focus detection by the focus detection area 22 using the aperture 7 of the stop ST in FIG. 2, even an object whose focus cannot be detected in the focus detection area 21 using the openings 3 to 6 can be detected. . However, a subject having a contrast difference only in a direction orthogonal to the exit pupil separation direction of the imaging optical system by the aperture 7 shown in FIG. 11, for example, a black background as shown in FIG. In the case of a chart, a pair of image signals are uniform image signals like the image signals 37 and 38 in FIG. 22, and a phase shift due to defocus of the imaging optical system cannot be detected.

However, in such a case, if focus detection is performed by the focus detection area 23 using the aperture 8, the contrast difference in the chart of FIG. 27 is parallel to the exit pupil separation direction of the imaging optical system by the aperture 8. Therefore, the amount of phase shift due to defocus of the imaging optical system can be detected.

As is clear from the above, conventionally,
Since each pixel unit of the imaging device 100 has only a pair of photoelectric conversion units, the exit pupil of the imaging optical system can be divided only in one direction indicated by an arrow A in FIG. In the present embodiment, the pair of apertures 7 and 8, which are means for dividing the pupil in the oblique direction, and the focus detection areas 22 and 23 set in the oblique direction are combined. Even if each pixel unit has only a pair of photoelectric conversion units, a phase difference type automatic focus adjustment that can detect a phase shift of an object image in a plurality of directions, that is, a so-called cross AF is realized.

Further, the image signals obtained by the color-separated green color filters in the focus detection areas 22 and 23 are:
In the Bayer array as in the present embodiment, the sampling pitch can be made finer than in the focus detection area 21, and focus detection can be performed on a higher-frequency subject.

Although the present embodiment has been described by taking an example of an image pickup apparatus in which an image pickup optical system is integrally provided, the present embodiment can also be applied to an image pickup apparatus using a so-called interchangeable lens system in which the image pickup optical system is detachable. . Furthermore, the present invention can be applied to a focus detection device.

According to the above-described embodiment, the first light beam (FIG. 7) of the light beams obtained by separating the exit pupil of the imaging optical system into a plurality of light beams.
(A) first photoelectric conversion unit 101 for performing photoelectric conversion
The solid-state imaging device 100 includes a plurality of light receiving units including a second photoelectric conversion unit 102 configured to photoelectrically convert a second light flux (see FIG. 7B) different from the first light flux in a two-dimensional area. As shown in FIG. 2, apertures 7 and 8 serving as pupil dividing means for dividing the exit pupil of the imaging optical system in a direction obliquely intersecting with the direction of separation of the exit pupil by the first light beam and the second light beam. , In the optical path of the imaging optical system. Therefore, the following effects were obtained. (1) The focus detection of the phase difference detection method by the image sensor 100 becomes possible, and high-speed focus adjustment based on the detected defocus amount can be realized. (2) At the same time, it is possible to obtain a high-quality image excellent in S / N at the same level as an image obtained by an image sensor originally designed to obtain an image using the entire luminous flux of the pupil of the imaging optical system. Was. (3) An imaging device 1 including a pixel portion having a pair of light receiving portions
By using 00, it is possible to detect a phase shift of an object image in a plurality of directions due to defocusing of the imaging optical system, so that it is possible to realize focus detection of a wide range of subjects (with any contrast) with a simple configuration. did it.

[0080]

As described above, according to the present invention,
It is possible to provide a focus detection device or an imaging device capable of performing focus detection by an accurate phase difference detection method with a simple configuration for an object or a subject having any contrast.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an imaging optical system according to an embodiment of the present invention.

FIG. 2 is a perspective view illustrating a configuration of a main part of the imaging device in FIG. 1;

FIG. 3 is a circuit diagram showing an electrical configuration of an area sensor unit according to one embodiment of the present invention.

FIG. 4 is a sectional view of an area sensor light receiving unit according to one embodiment of the present invention.

FIG. 5 is a partially enlarged view showing an arrangement of a color filter according to one embodiment of the present invention.

FIG. 6 is a configuration diagram illustrating a projection relationship between a microlens and a light receiving unit according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating a light beam incident on a first photoelectric conversion unit and a light beam incident on a second photoelectric conversion unit according to an embodiment of the present invention.

8 is a configuration diagram of the imaging optical system showing a light beam passing through an upper half of an exit pupil of the imaging optical system of FIG. 1;

FIG. 9 is an explanatory diagram illustrating a state of separation of an exit pupil according to the embodiment of the present invention.

FIG. 10 is a schematic diagram showing a focus detection area on an image sensor according to one embodiment of the present invention.

FIG. 11 is an explanatory diagram illustrating a state of separation of an exit pupil by a pair of openings 7 according to the embodiment of the present invention.

FIG. 12 is a block diagram showing an internal configuration including a peripheral circuit of an image sensor according to an embodiment of the present invention.

FIG. 13 is a diagram for explaining an output position designation command according to the embodiment of the present invention.

FIG. 14 is a block diagram illustrating a main part of an electrical configuration of the imaging device according to the embodiment of the present invention.

15 is a partially enlarged view of a focus detection area 21 in FIG.

FIG. 16 is a diagram illustrating a horizontal single line chart as an example of a contrast subject.

FIG. 17 shows a pair of image signals in a light receiving unit having a green color filter in the pixel column 27 of FIG.

FIG. 18 shows a pair of image signals in a light receiving unit having a green color filter in the pixel column 28 of FIG.

FIG. 19 shows a pair of image signals in a light receiving section provided with a red color filter in the pixel column 27 of FIG.

20 illustrates a pair of image signals in a light receiving unit including a blue color filter in the pixel column 28 of FIG.

FIG. 21 is a diagram illustrating a vertical solid line chart as another example of a contrast subject.

22 is an image signal when the chart in FIG. 21 in the focus detection area 21 in FIG. 10 is set as a subject.

23 is a partially enlarged view of a focus detection area 22 in FIG.

24 is a pair of image signals in a light receiving unit including a green color filter of the pixel array 39 in FIG.

FIG. 25 is a pair of image signals in a light receiving section provided with a blue color filter in the pixel array 40 of FIG. 23;

26 illustrates a pair of image signals in a light receiving unit including a red color filter in the pixel array 40 of FIG.

FIG. 27 is a diagram illustrating a diagonal solid line chart as another example of a contrast subject.

[Explanation of symbols]

 L1 Optical axis of imaging optical system ST Stop 100 Image sensor 3 to 6 Opening 7, 8 A pair of openings 9 Color filter 10 Micro lens 101, 102 First and second photoelectric conversion units 15, 18, 19, 20 Exit pupil 16, 17, 24, 25 Separated areas on exit pupil 21 to 23 Focus detection area

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/225 G02B 7/11 C 5/232 N // H04N 101: 00 G03B 3/00 A F term ( Reference) 2F065 AA06 DD04 DD06 FF01 FF10 GG09 HH03 HH13 JJ03 JJ09 JJ26 KK03 LL22 LL26 LL30 LL59 NN03 QQ03 QQ24 QQ25 QQ27 UU07 2H011 BA23 BB01 2H051 BA03 BA07 CB06 AC42 ACB22 5CB22

Claims (8)

[Claims] 1. A first photoelectric conversion unit for photoelectrically converting a first light beam among light beams obtained by separating an exit pupil of an imaging optical system into a plurality of light beams, and a second light beam different from the first light beam. A photoelectric conversion element in which a plurality of light receiving units each including a second photoelectric conversion unit that performs photoelectric conversion are arranged in a two-dimensional area; and a phase difference between output signals of the first photoelectric conversion unit and the second photoelectric conversion unit is determined. A focus detection device that calculates focus detection information based on the pupil division unit; a pupil division unit that divides an exit pupil of the imaging optical system in a direction obliquely intersecting a direction in which the exit pupil is separated by the first light flux and the second light flux. Is disposed in the optical path of the imaging optical system. 2. The pupil dividing means has a pair of openings for dividing an exit pupil of the imaging optical system in a direction obliquely intersecting a direction in which the exit pupil is separated by the first light beam and the second light beam. The focus detection device according to claim 1, wherein: 3. The pupil splitting means sets an exit pupil of the imaging optical system in first and second directions obliquely intersecting a direction in which the exit pupil is separated by the first light beam and the second light beam. The focus detection device according to claim 1, further comprising a pair of openings to be divided. 4. The focus detection device according to claim 3, wherein the first direction and the second direction are orthogonal to each other. 5. An imaging optical system, a first photoelectric conversion unit for photoelectrically converting a first light beam among light beams obtained by dividing an exit pupil of the imaging optical system into a plurality of light beams, and a first light beam different from the first light beam. A solid-state imaging device in which a plurality of light receiving units each including a second photoelectric conversion unit that photoelectrically converts two light beams are arranged in a two-dimensional area; and a position of an output signal of the first photoelectric conversion unit and the output signal of the second photoelectric conversion unit. An imaging device having focus detection means for calculating focus detection information based on a phase difference, wherein the imaging optical system emits light in a direction obliquely intersecting a direction in which the exit pupil is separated by the first light flux and the second light flux. An imaging apparatus, wherein pupil division means for dividing a pupil is arranged in an optical path of the imaging optical system. 6. The pupil dividing means has a pair of openings for dividing an exit pupil of the imaging optical system in a direction obliquely intersecting a direction in which the exit pupil is separated by the first light flux and the second light flux. The imaging device according to claim 5, wherein: 7. The pupil splitting means sets an exit pupil of the imaging optical system in first and second directions obliquely intersecting a direction in which the exit pupil is separated by the first light beam and the second light beam. The imaging device according to claim 5, further comprising a pair of openings to be divided. 8. The imaging device according to claim 7, wherein the first direction and the second direction are orthogonal to each other.