JP2012237831A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus that can be manufactured at a low cost.SOLUTION: An imaging apparatus 1 comprises: a polarization pupil division optical system 20 including a pair of pupil apertures 20 L and 20R, in which a polarization filter 21 L for a transmission polarization axis in a first direction and a polarization filter 21R for that in a second direction are provided, respectively; an azimuthal polarizer 31 including a plurality of transparent electrode rows 31EP arranged in parallel to each other, the azimuthal polarizer 31 capable of performing energization control of a voltage to be applied to each of the transparent electrode rows 31EP and capable of selecting the transmission polarization axis between the first direction and the second direction; a filter 32 having either the transmission polarization axis of the first direction or that of the second direction; and an image sensor 40 including pixel columns PL arranged along the transparent electrode rows 31EP. In addition, the imaging apparatus 1 comprises: a driving unit 51 for performing energization control for the transparent electrode rows 31EP; and a focus control unit 54 for detecting a focus state from a positional deviation between a first image by deflection in the first direction and a second image by deflection in the second direction.

Description

  The present invention relates to an imaging apparatus.

  In imaging devices that capture still images, so-called digital cameras that use a photoelectric conversion element such as a CCD to convert a subject image into an electrical signal and that process the electrical signal and record it on a recording medium have become mainstream. Yes. Most digital cameras have a so-called autofocus function that automatically performs focus adjustment. As a focus detection method for performing such autofocus, a method of performing focus detection of an imaging optical system by a pupil division method is known (see, for example, Patent Document 1).

  In the configuration disclosed in Patent Document 1, an aperture whose transmission polarization axes are orthogonal to each other is provided at the pupil position of the imaging optical system, each polarization is separated by a polarization separation element, and each image is detected by two imaging elements. Thus, the focal position is detected.

JP 2000-330012 A

  However, since the conventional imaging apparatus uses two imaging elements, there are problems of cost increase, size increase, and power consumption increase.

  The subject of this invention is providing the imaging device which can be manufactured cheaply.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this.

The invention according to claim 1 is a pair of pupil apertures (20L, 21R) each provided with a polarizing filter (21L, 21R) having a transmission polarization axis in a first direction and a second direction different from the first direction. 20R) and a plurality of transparent electrode rows (31EP) arranged in parallel with each other, and energization control of the applied voltage is possible for each transparent electrode row (31EP). , An optical rotator (31) whose transmission polarization axis can be changed or not changed between the first direction and the second direction, and the transmission polarization axis of the first direction or the second direction. A filter (32) that is any one of them, and an image sensor (40) having a pixel row (PL) arranged along the arrangement direction of the transparent electrode row (31EP), in order from the object side, In addition to the transparent electrode array (31EP) A drive unit (51) for controlling energization of voltage, a first image formed by light whose polarization axis is in the first direction when passing through the pupil opening in the image sensor (40), and A focus control unit (54) for detecting a focus state from a positional deviation between the second image formed by the light whose polarization axis is in the second direction when passing through the pupil opening, and That is, the imaging device (1).
Invention of Claim 2 is an imaging device (1) of Claim 1, Comprising: The said transparent electrode row | line | column (31EP) is arranged in parallel with the arrangement direction of said pair of pupil opening, An imaging device (1) characterized by
Invention of Claim 3 is an imaging device (1) of Claim 1 or 2, Comprising: The said drive part (51) sets the said transparent electrode row | line | column (31EP) to every 2 or more row | line | columns. The imaging apparatus (1) is characterized in that it is divided into two groups and the same energization control is performed on the transparent electrode rows (31EP) of the same group.
Invention of Claim 4 is an imaging device (1) of any one of Claim 1 to 3, Comprising: The said drive part (51) permeate | transmits the said optical rotator (31) at the time of imaging | photography. The imaging apparatus (1) is characterized in that the transparent electrode array (31EP) is driven so that the polarization axis is aligned in the same direction on the entire screen of the imaging element.
Invention of Claim 5 is an imaging device (1) of any one of Claim 1 to 3, Comprising: The said drive part (51) of the said optical rotator (31) is during exposure. The imaging apparatus (1) is characterized in that the transmission polarization axis is switched and the first image and the second image are captured by the same pixel.
Invention of Claim 6 is an imaging device (1) of any one of Claims 1-5, Comprising: The said drive part (51) is said 1st image in the said image pick-up element (40). Changing the position applied to the transparent electrode array (31EP) of the optical rotator according to a change in the state of the imaging device (1) that changes the position of the boundary between the second image and the second image; An imaging device (1) characterized by
Invention of Claim 7 is an imaging device (1) of Claim 6, Comprising: The said drive part (51) hold | maintains the boundary information of the test pattern imaged by the said image pick-up element (10). The imaging apparatus (1) is characterized in that a voltage applied to the transparent electrode array (31EP) of the optical rotator is controlled based on the boundary information.
Invention of Claim 8 is an imaging device (1) of any one of Claims 1-7, Comprising: A pixel row | line crosses the horizontal direction along the said transparent electrode row | line | column (31EP), and it The focusing control unit (54) includes a plurality of vertical pixel rows (PL) including boundaries between the first image and the second image at both ends in the horizontal direction. ) Is used for focus detection.

  Note that the configuration described with reference numerals may be modified as appropriate, and at least a part of the configuration may be replaced with another component.

  ADVANTAGE OF THE INVENTION According to this invention, the imaging device which can be manufactured cheaply can be provided.

It is a notional block diagram of the camera which is one embodiment of the present invention. It is a figure which shows the structure of a liquid crystal optical rotator unit. It is explanatory drawing which shows the state of polarization and optical rotation by a polarization pupil division filter and a liquid crystal optical rotator unit. It is explanatory drawing which shows the image formation state corresponding to each unit electrode of a liquid crystal optical rotator unit. It is explanatory drawing of imaging | photography which cancels an image shift. It is a figure which shows the liquid crystal optical rotator unit in 2nd Embodiment. It is explanatory drawing in the case of changing the unit electrode to drive when the pupil position of the imaging optical system changes due to zooming. It is explanatory drawing which sets the focus area, suppressing the influence of the error in an image sensor.

(First embodiment)
Embodiments of the present invention will be described below with reference to the drawings. Each figure shown below is provided with an XYZ orthogonal coordinate system for ease of explanation and understanding. In this coordinate system, the direction toward the left as viewed from the photographer at the position of the camera when the photographer shoots a horizontally long image with the optical axis OA horizontal (hereinafter referred to as a normal position) is defined as the X plus direction. Further, the direction toward the upper side in the normal position is defined as the Y plus direction. Further, the direction toward the subject at the normal position is defined as the Z plus direction.

FIG. 1 is a conceptual configuration diagram of a camera 1 that is a camera to which an embodiment of the present invention is applied.
The camera 1 includes an imaging optical system 10, a polarization pupil splitting optical system, a liquid crystal optical rotator unit 30, and an image sensor 40. The camera 1 also includes a control device 50, a focusing drive mechanism 60, an operation unit 70, a display unit 80, and a recording medium 90.

Although not shown in detail, the imaging optical system 10 is provided with a lens group including a focusing lens (represented by one lens in FIG. 1), and an imaging surface of an imaging element 40 to be described later for an object image. To form an image.
The polarization pupil splitting optical system and the liquid crystal optical rotator unit 30 perform a focus detection function in focusing control by the focusing control unit 54 described later together with the image sensor 40. This will be described in detail later.
The image sensor 40 photoelectrically converts the subject image formed by the imaging optical system 10 into an electric signal.

The control device 50 includes a CPU and the like, and performs overall control of the camera 1. The control device 50 includes functional units such as a liquid crystal driving unit 51, an imaging driving unit 52, an image processing unit 53, and a focusing control unit 54.
The liquid crystal drive unit 51 drives the liquid crystal optical rotator unit 30 by being controlled by a focus control unit 54 described later during focus control.

The imaging drive unit 52 drives the imaging element 40 at the time of shooting and at the time of focusing control by a focusing control unit 54 described later.
The image processing unit 53 amplifies the image signal photoelectrically converted by the image sensor 40 to a predetermined signal level, and performs image processing such as contour compensation, gamma correction, and white balance adjustment.

  The focus control unit 54 drives and controls the liquid crystal drive unit 51 and the imaging drive unit 52 during focus control, and performs focus detection (defocus amount calculation) based on the focus detection image information read from the image sensor 40. )I do. The focusing control unit 54 further performs a focusing operation by driving the focusing lens in the imaging optical system 10 via the focusing driving mechanism 60. The focus control by the focus control unit 54 will be described in detail later.

The focusing drive mechanism 60 includes driving means such as an ultrasonic motor that moves and drives a focusing lens (not shown) of the imaging optical system 10, a position sensor that detects the position of the focusing lens, and the like. The focusing drive mechanism 60 is controlled by the focusing control unit 54 and drives the focusing lens to focus. Further, the position information of the focusing lens by the position sensor is distance information with respect to the focused subject.
The operation unit 70 includes operation members that command the camera 1 such as a shutter button and various setting switches. The operation unit 70 inputs operation information of the operation member provided therein to the control device 50.

The display unit 80 is configured by an LCD panel or the like, and displays a real-time image (that is, a through image) captured by the image sensor 40, a captured image, various setting screens, and the like.
The recording medium 90 is a CF or SD memory card that can be attached to and detached from the camera 1 and records captured image data.

  The camera 1 is controlled by the control device 50 when the shutter button in the operation unit 70 is pressed (release operation), and the imaging element 40 converts the subject image light imaged by the imaging optical system 10 into an electrical signal. The image data is converted and recorded (that is, photographed) on the recording medium 90.

Here, the camera 1 performs focus control when the shutter button in the operation unit 70 is half-pressed (or the focus command switch is operated) prior to shooting.
In the focus control, the focus control unit 54 in the control device 50 controls the polarization pupil splitting optical system, the liquid crystal rotator unit 30 and the image sensor 40 via the liquid crystal drive unit 51 and the image capture drive unit 52. Focus detection (defocus amount calculation) is performed. Further, the focusing lens in the imaging optical system 10 is driven via the focusing driving mechanism 60 to perform the focusing operation.

Next, the configuration and operation of the polarization pupil splitting optical system, the liquid crystal optical rotator unit 30 and the image sensor 40 will be described in detail with reference to FIGS. 2 to 5 in addition to FIG. 1 described above.
2A and 2B show a liquid crystal optical rotator unit 30, wherein FIG. 2A is a longitudinal sectional view thereof, and FIG. 2B is a diagram showing electrode patterns 31A and 31B by unit electrodes 31EP corresponding to the AA sectional view of FIG. is there.

In the polarization pupil splitting optical system, as shown in FIG. 1, the polarizing filters 21L and 21R are arranged in a pair of pupil openings L and 20R in which the apertures are formed so that the transmission polarization axes are orthogonal (90 ° different). Has been.
The polarization pupil splitting optical system is disposed in the exit pupil of the imaging optical system 10 so that the pupil openings L and 20R are symmetrical on the X axis with the optical axis OA interposed therebetween.
In the present embodiment, the transmission polarization axis of the polarizing filter 21L in one pupil opening L is oriented in a direction orthogonal to the arrangement axis direction of the pupil openings L and 20R (that is, parallel to the Y-axis direction and the first direction). And the transmission polarization axis of the polarizing filter 21R at the other pupil opening R is set to be in a direction parallel to the arrangement axis direction of the pupil openings L and 20R (that is, parallel to the X-axis direction, the second direction). Has been.

  The thus configured polarization pupil splitting optical system polarizes the subject image light transmitted through the pupil apertures L and 20R into a pair of lights having polarization axes different by 90 °. The light transmitted through this polarization pupil splitting optical system includes both the vertical direction (Y-axis direction parallel to the paper surface of FIG. 2) and the horizontal direction (X-axis direction orthogonal to the paper surface of FIG. 2) in the same way. It is. For this reason, an image shift cannot be detected unless these are separated. Separation of subject image light having different polarization axes is performed by a liquid crystal optical rotator unit 30 described later.

As shown in FIG. 2A, which is a longitudinal sectional view of the liquid crystal optical rotator unit 30, a liquid crystal optical rotator 31 and a polarizing filter 32 that transmits only light having a polarization axis in a certain direction are integrally configured. ing.
In the liquid crystal optical rotator 31, two glass substrates 31F and 31R each having a transparent electrode 31E on one surface are arranged at a predetermined interval with the transparent electrode 31E facing each other, and the polarization axis of transmitted light is rotated between them. A possible liquid crystal 31L is enclosed.

  One of the opposing transparent electrodes 31E (the glass substrate 31F side) is a single electrode that covers the entire surface, while the other (the glass substrate 31R side) has a predetermined width in the Y-axis direction as shown in FIG. The rectangular unit electrodes 31EP that are long in the X-axis direction are arranged in parallel in the Y-axis direction. These unit electrodes 31EP form groups (electrode pattern 31A and electrode pattern 31B) every other Y-axis direction. The unit electrodes 31EP constituting the electrode patterns 31A and 31B are energized (ON / OFF) all at once. In addition, one (or both) of the electrode patterns 31A and 31B can be energized (ON / OFF).

  In the figure, there is a gap between the unit electrodes 31EP. However, this is based on the relationship shown in the drawing and is actually narrowed as much as possible. The transparent electrode 31E (unit electrode 31EP) can form a sensitive pattern by photolithography or the like, and the transmission polarization axis pattern can be controlled for each fine region accordingly. Thereby, it is not necessary to perform a very time-consuming operation such as attaching a polarizing film whose polarization axis is changed in a mosaic pattern to the front surface of the image sensor. Lithographic pattern formation has good accuracy and is technically easy to manufacture with much accumulation.

  The polarizing filter 32 is integrally provided on the outer surface (the surface on the image sensor 40 side) of the glass substrate 31R located on the image sensor 40 side in the liquid crystal optical rotator 31. The direction of the transmission polarization axis of the polarization filter 32 is aligned with the polarization axis of the polarization filter 21L or 21R in either pupil opening L or 20R of the polarization pupil splitting optical system.

  As shown in FIG. 2A, an IR cut filter 30C that prevents the incidence of infrared rays on the image sensor 40 may be provided on the outer surface of the liquid crystal rotator 31 on the subject side (the outer surface of the glass substrate 31F). Furthermore, a dust removing mechanism that vibrates the whole and drops the attached dust may be provided.

  The liquid crystal rotator unit 30 configured as described above transmits polarized light by changing the optical rotation state of the liquid crystal 31L by selecting the energization state of the electrode patterns 31A and 31B (energization of either one or both). Axis can be selected. Thereby, the subject image light transmitted through the pupil openings L and 20R of the polarization pupil splitting optical system is separated for each direction of the polarization axis.

Next, with reference to FIG. 3, the separation of the object image light in each direction of the polarization axis by the liquid crystal optical rotator unit 30 will be described.
FIGS. 3A and 3B are explanatory views showing the state of polarization and optical rotation by the polarization pupil division optical system and the liquid crystal optical rotator unit 30. FIGS. 3A and 3B show the relationship between the polarization state of the incident light, the optical rotation, and the image. (C) is explanatory drawing which forms the object image light isolate | separated for every polarization axis so that comparison is possible. 3 is a view as seen from the upper side (plus side) in the X-axis direction, in which the polarizing filter 21L is located on the upper side and the polarizing filter 21R is located on the lower side.

As described above, the light transmitted through the polarization pupil splitting optical system is the same in both the vertical direction (Y-axis direction parallel to the paper surface of FIG. 3) and the horizontal direction (X-axis direction orthogonal to the paper surface of FIG. 3). Included. The liquid crystal optical rotator unit 30 separates it by the following operation.
That is, as shown in FIG. 3A, when the optical rotator 31 does not rotate the light (OFF state = non-driven), the light is transmitted as it is, and only the incident light whose polarization axis matches the polarizing filter 32 is transmitted. . In contrast, when the liquid crystal rotator 31 rotates (ON state = drive), only incident light whose polarization axis is orthogonal to the polarizing filter 32 is transmitted as shown in FIG. That is, by selecting the optical rotation state in the liquid crystal optical rotator 31, it is possible to select which polarization component of the incident light is transmitted.

  FIG. 3C shows that half of the liquid crystal optical rotator 31 (one of the electrode patterns 31A and 31B shown in FIG. 2) is not driven (OFF) and half (the other of the electrode patterns 31A and 31B) is driven (ON). Shows the state. Of the incident light, each component parallel and orthogonal to the polarization axis of the polarizing filter 32 is selectively transmitted to form an image. As a result, it is possible to detect the image deviation = defocus amount by separating the respective components of the pupils divided by the polarization (the polarization filters 21L and 21R in the polarization pupil division optical system) and comparing the images. Become.

Next, with reference to FIG. 4, the imaging state and the in-focus state will be described.
FIG. 4 is an explanatory diagram showing an imaging state corresponding to each unit electrode 31EP of the liquid crystal optical rotator unit 30 (liquid crystal optical rotator 31).
As shown in FIG. 4A, the subject is a planar object having a single line at the center of the screen.
When the subject is in focus, the focal position does not change even if the polarization axes transmitted through the electrode patterns 31A and 31B in the liquid crystal rotator 31 are different, as shown in FIG. 4B. Accordingly, there is no deviation of the image (indicated by black solids in the figure) in the regions corresponding to the electrode patterns 31A and 31B.

FIG. 4C shows a slightly defocused state. In this state, a small image deviation: D1 is generated between the first image by the light transmitted through the electrode pattern 31A and the second image by the light transmitted through the electrode pattern 31B.
On the other hand, in a state where the focus is greatly defocused, as shown in FIG. 4D, a larger image shift: D2 is generated between the first image and the second image.
That is, the defocus amount can be detected by detecting the image shift amount. This principle itself is the same as that of a known general phase difference AF.

Next, with reference to FIG. 5, photographing (acquisition of image data) in which image displacement is canceled will be described. FIG. 5 is an explanatory diagram of photographing for canceling the image shift.
At the time of normal focusing control, as shown in FIG. 5A, the focal position is detected in a state where image deviation has occurred. If the image is taken in this state, the image will remain misaligned, so that an image is generated by thinning out the pixels in half, or image processing for correcting and synthesizing the image misalignment is required, which is not efficient.

  Therefore, as shown in FIG. 5B, both the two electrode patterns 31A and 31B are turned ON or OFF. As a result, only one of the polarization components is transmitted, and no image shift occurs. If shooting is performed in this state, it is not necessary to correct image displacement, and an image using all pixels can be generated.

  However, in the state shown in FIG. 5 (b), shooting is performed with either one of the polarized lights, the pupil opening area is substantially reduced and the depth of field is excessively deep, and the polarization effect causes the object to be captured. It is also possible that the light and darkness will be different from the naked eye. For this reason, during one exposure, ON-OFF is switched with respect to electrode pattern 31A, 31B. As a result, images with both polarizations are formed on the same pixel, the depth of field approaches that of the original optical system, and it is possible to suppress the possibility that the captured image differs from the naked eye impression by eliminating the polarization effect. .

(Second Embodiment)
Next, a second embodiment of the liquid crystal optical rotator unit 30 shown in FIGS. 6 to 8 will be described.
The liquid crystal optical rotator unit 30 shown in FIG. 6 includes a switch SW that can be turned on / off for each unit electrode 31EP in the liquid crystal optical rotator 31, and can be independently switched by a drive circuit 33. . Other configurations are the same as those of the first embodiment described above, and a description thereof will be omitted.

Since the unit electrode 31EP in the first embodiment shown in FIG. 2 is controlled collectively as the fixed electrode patterns 31A and 31B, the control is simple, but various controls cannot be performed.
In the second embodiment, the unit electrode 31EP to be energized can be dynamically changed by configuring the drive circuit 33 to perform switching for each unit electrode 31EP. Such control is common in matrix display type liquid crystal display devices.
With such a configuration, the unit electrodes 31EP are energized every other unit electrode 31EP as shown in FIG. 6A, or the unit electrodes 31EP are energized every other unit electrode 31EP as shown in FIG. 6B. It becomes possible.

  This makes it possible to select a polarization state with a fine pattern, and is suitable for a case where focus control is focused on a small area of a subject or a distance distribution of the entire screen is to be acquired in detail. For example, as shown in FIG. 6B, by energizing every second unit electrode 31EP, the region of the transmission polarization axis can be roughly divided. For example, the region corresponding to one pixel is expanded by pixel addition. Even so, the polarization region can be adjusted accordingly.

  Further, by shifting the unit electrode 31EP to be driven up and down, the position that becomes the boundary of the transmission polarization axis (the boundary of the polarization separation region) can be adjusted. As described above, by selectively switching the unit electrode 31EP, various focusing controls can be performed. For example, when the position at which the boundary of the polarization separation region on the light receiving surface of the image sensor 40 changes due to a change in camera settings, the imaging position is changed to correspond to the in-focus area. be able to. Here, the change in the camera setting that causes the change in the position where the boundary of the polarization separation region on the light receiving surface of the image sensor 40 is imaged is the change in the pupil position of the imaging optical system 10 due to zooming, the pixel readout setting of the image sensor 40 Switching (pixel switching), focusing area selection, and the like.

FIG. 7 is an explanatory diagram of a case where the unit electrode 31EP to be driven is changed when a change occurs in the pupil position of the imaging optical system 10 due to zooming.
In an actual camera, the shape of the electrode pattern (unit electrode 31EP) in the liquid crystal optical rotator 31 is not projected onto the image sensor 40 as it is. The imaging element 40 is reached by the positional relationship in the optical axis direction of the imaging optical system 10, the position of the polarization pupil splitting optical system, the liquid crystal rotator unit 30 (liquid crystal rotator 31), and the imaging element 40. The polarization region is enlarged or reduced about the optical axis OA. Further, the imaging optical system 10 may change its pupil position due to zooming, lens exchange, or the like.

  That is, in FIG. 7A, the boundary of the pupil division area overlaps with the focusing area 41, but in FIG. 7B in which the imaging optical system 10 is changed and the pupil position is moved, The boundary (indicated by the arrow in the figure) does not overlap the in-focus area 41. In this state, it becomes impossible to focus or the position of the focusing area 41 must be moved.

  Therefore, by changing the drive area (unit electrode 31EP) in the liquid crystal optical rotator 31 as already shown in FIG. 6, the boundary is moved as shown in FIG. On the other hand, try to stay in a certain position. Since the boundary of the polarization region projected onto the image sensor 40 is enlarged or reduced about the optical axis OA, the drive region (unit electrode 31EP to be driven) is also changed symmetrically about the optical axis OA. When the lens position is fixed, the pupil position may be read out by detecting the zoom position with a zoom encoder. In the case of the interchangeable lens system, the zoom encoder output and the lens characteristic value stored in the in-lens circuit may be similarly transmitted to the control device 50 (focus control unit 54). Regarding the correspondence to the pupil position fluctuation, the same processing is performed by the conventional phase difference AF, and the system is the same as them.

Next, the setting of the focusing area 41 including adjustment of the camera 1 will be described with reference to FIG. FIG. 8 is an explanatory diagram for setting the focusing area 41 while suppressing the influence of errors in the image sensor 40.
The pupil arrangement direction of the polarization pupil splitting optical system (the arrangement direction of the pupil openings L and 20R), the arrangement direction of the pattern corresponding to the unit electrode 31EP in the liquid crystal optical rotator 31, and the arrangement direction of the pixel column of the image sensor 40 are manufactured. There is a possibility of a slight inclination depending on the error. In particular, recent image sensors have been miniaturized, and the pixel pitch may be about 1 to 2 μm, so that manufacturing errors are easily affected.

  For this reason, the test pattern TP is defocused with the entire optical system assembled. When the test pattern TP is a straight line, as shown in FIG. 8A, the read image 100 has an image shift for each polarization region, and a step becomes clear at the boundary indicated by an arrow in the figure. By comparing the position of the image at the top and bottom of the step, the image shift amount can be detected. However, the arrangement direction of the pupil region divided by polarization, the pattern corresponding to the unit electrode 31EP of the liquid crystal optical rotator 31, and the arrangement direction (pixel row PL) of the pixels P of the image sensor 40 are slightly different due to manufacturing errors. It may be tilted. In that case, there is a possibility that the position of the pixel row PL that causes the image shift is different between the right side and the left side of the screen. In FIG. 8B, when the A column (PLA) and the B column (PLB) are compared, an image shift cannot be detected at the left end of the screen, but is detected at the right side of the screen.

In order to avoid such a state, it is necessary to read out pixel columns spaced apart from the inclination deviation Dx in FIG. 8B and use them for focus detection.
In FIG. 8B, if the A column (PLA) and the C column (PLC) are compared, the image shift can be detected in the same way on the left and right sides of the screen. When the space between the upper and lower pixel rows is increased, the same area of the subject is not seen and focusing becomes difficult. Therefore, adjustment is necessary when a certain inclination is detected. Alternatively, the adjustment may be performed while reading the image, and the image may be fixed at a position where the inclination is below a certain level. With the optical system assembled, the test pattern TP is imaged to detect the tilt and stored in the focusing control unit 54 of the camera 1, so that focus detection can be performed appropriately regardless of manufacturing errors. .

As described above, this embodiment has the following effects.
(1) The camera 1 polarizes subject image light into a pair of light beams whose polarization axes are different by 90 ° by the polarization pupil division optical system, and the liquid crystal rotator unit 30 separates each component and forms an image on the image sensor 40. . Then, the image shift = defocus amount is detected by comparing the image of each component from the image data captured by the image sensor 40. As a result, the entire screen can be set as a focus detection target (a focusing area is set on the entire screen). Further, since the focus information is obtained by the image sensor 40, a dedicated image sensor for detecting the focus, an optical path splitting element, and the like are not required, and a small and inexpensive configuration can be achieved.

(2) The camera 1 performs exposure in both polarization states by switching the polarization axis of the transmitted light of the liquid crystal rotator 31 in the liquid crystal rotator unit 30 during the exposure time at the time of photographing. Thereby, the image by both polarization forms on the same pixel, and it can suppress possibility that a photographed image and the impression of the naked eye differ.

(3) The camera 1 can adjust the position that becomes the boundary of the polarization separation region by changing the polarization region by changing the unit electrode 31EP that the liquid crystal optical rotator unit 30 drives. As a result, when the position at which the boundary of the polarization separation region on the light receiving surface of the image sensor 40 changes due to a change in camera settings, the imaging position changes to correspond to the in-focus area. Thus, focus detection can be performed.

(4) The camera 1 includes pixel rows that are spaced from an image inclination deviation Dx in a direction intersecting the arrangement direction at both ends of the pixel rows along the arrangement direction of the pupil openings L and 20R in the polarization pupil division optical system. Read out and used for focus detection. Accordingly, it is possible to obtain a high focusing accuracy while suppressing the influence of the tilt due to the manufacturing error of the pixel row of the image sensor 40.

(Deformation)
The present invention is not limited to the above-described embodiment, and various modifications and changes as described below are possible, and these are also within the scope of the present invention.
(1) In this embodiment, a digital still camera has been described. However, the present invention is not limited to this, and can also be applied to a digital video camera that can capture moving images.
In addition, although embodiment and a deformation | transformation form can also be used in combination as appropriate, detailed description is abbreviate | omitted. Further, the present invention is not limited to the embodiment described above.

  1: camera, 10: imaging optical system, 20: polarization pupil splitting optical system L, 20R: aperture, 21L, 21R: polarizing filter, 30: liquid crystal optical rotator unit, 31: liquid crystal optical rotator, 31E: transparent electrode, 31EP: Unit electrode, 32: Polarizing filter, 40: Image sensor, 50: Control device, 54: Focus control unit, TP: Test pattern, PL (PLA, PLB, PLC): Pixel array

Claims (8)

A polarization pupil splitting optical system having a pair of pupil apertures each provided with a polarizing filter having a transmission polarization axis in a first direction and a second direction different from the first direction;
It has a plurality of transparent electrode rows arranged in parallel to each other, and it is possible to control the application of voltage to be applied to each transparent electrode row, and the transmission polarization axis is between the first direction and the second direction. With an optical rotator that can be changed or not changed with
A filter whose transmission polarization axis is either the first direction or the second direction;
An image sensor having a pixel array arranged along the array direction of the transparent electrode array, and in order from the object side,
Furthermore, a drive unit that performs energization control of the voltage applied to the transparent electrode array;
A first image formed by light having a polarization axis in the first direction when passing through the pupil opening in the imaging device, and a polarization axis in the second direction when passing through the pupil opening. A focus control unit that detects a focus state from a positional deviation between the second image formed by the light, and
An imaging apparatus comprising: The imaging apparatus according to claim 1,
The transparent electrode rows are arranged in parallel with the arrangement direction of the pair of pupil openings;
An imaging apparatus characterized by the above. The imaging apparatus according to claim 1, wherein:
The drive unit divides the transparent electrode rows into two groups every other row, and performs the same energization control on the transparent electrode rows of the same group;
An imaging apparatus characterized by the above. The imaging apparatus according to any one of claims 1 to 3,
The driving unit drives the transparent electrode array so that the transmission polarization axis of the optical rotator is aligned in the same direction in the entire screen of the image sensor at the time of photographing;
An imaging apparatus characterized by the above. The imaging apparatus according to any one of claims 1 to 3,
The driving unit switches the transmission polarization axis of the optical rotator during exposure to capture the first image and the second image with the same pixel,
An imaging apparatus characterized by the above. The imaging apparatus according to any one of claims 1 to 5,
The driving unit controls a voltage applied to the transparent electrode array of the optical rotator according to a change in the state of the imaging device that changes a position of a boundary between the first image and the second image in the imaging element. To change by doing
An imaging apparatus characterized by the above. The imaging apparatus according to claim 6,
The driving unit holds boundary information of a test pattern imaged by the imaging device, and controls a voltage applied to the transparent electrode array of the optical rotator based on the boundary information;
An imaging apparatus characterized by the above. The imaging apparatus according to any one of claims 1 to 7,
The pixel columns are arranged in a matrix in the horizontal direction along the transparent electrode columns and in the vertical direction intersecting the transparent electrode columns,
The focus control unit uses the plurality of vertical pixel columns including the boundary between the first image and the second image at both ends in the horizontal direction for focus detection;
An imaging apparatus characterized by the above.

Images