JP2015041024A - Lens device and stereoscopic image capturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stereoscopic image capturing device which offers higher AF focusing accuracy than conventional techniques when capturing 3D images using two lens devices having AF capability, and to provide a lens device for the same.SOLUTION: A stereoscopic image capturing device captures stereoscopic images using two lens devices, each having a focusing mechanism, including a focusing lens group, and phase difference-based focus detection means. The focus detection means detects a defocus amount and AF reliability value representing the reliability of the defocus amount for each of the two lens devices, compares AF reliability values of the two lens devices, determines a focal target position in accordance with the defocus amount corresponding to higher AF reliability, and drives the focusing lens group of each lens device to the determined focal target position.

Description

  The present invention relates to a lens device used for a television camera, a video camera, and the like, and in particular, a lens device used for a stereoscopic video imaging device that captures an image with parallax formed by left and right objective optical systems, and stereoscopic video imaging thereof. It relates to the device.

  2. Description of the Related Art Conventionally, stereoscopic video imaging apparatuses that capture stereoscopic video using left and right parallax are known. The stereoscopic imaging optical device disclosed in Patent Document 1 below alternately captures left and right parallax images formed through two optical systems, and focuses either one of the left and right parallax images. In other words, the focus position is obtained for each image, and the focus position on the middle point, the near distance side, and the far distance side is selected from the two focus points. As a result, it is possible to avoid the problem that the focal point cannot be found depending on the conditions of the respective subjects of the first image and the second image.

  In addition, the stereoscopic image capturing apparatus disclosed in Patent Document 2 below simultaneously drives the first and second focus lenses and captures the same subject at the same time in order to efficiently capture images in a short time, and a predetermined feed amount. An AF evaluation value is calculated for each, and the other focus lens is set at the position of the focus lens where the maximum value of the AF evaluation value is detected first.

JP 2005-173270 A JP 2006-162990 A

  However, in the prior art disclosed in Patent Document 1 described above, since the focusing operation for the first image and the focusing operation for the second image are performed separately, the time for detecting the in-focus position respectively. Is required. Also, if there is a difference between the in-focus position in the first image and the in-focus position in the second image, whether to adopt the long-distance side or the short-distance side, or to set in advance, There is a problem that the setting must be changed each time depending on the shooting situation. In addition, when there is a difference between the in-focus position in the first image and the in-focus position in the second image, when the intermediate position is set as the in-focus point, whichever of the in-focus positions is large, There is a risk of not focusing.

  In the prior art disclosed in Patent Document 1 and Patent Document 2 described above, the other focus lens is driven later to the position of the focus lens where the maximum AF evaluation value is detected. The focus accuracy of the focus target position thus obtained is not mentioned.

  Therefore, an object of the present invention is to provide a stereoscopic video imaging apparatus that can improve the focusing accuracy by AF when performing 3D imaging using two lens apparatuses equipped with an AF function, And providing a lens apparatus.

To achieve the above object, the present invention provides a focus mechanism including a focus lens group,
In a three-dimensional image photographing device for photographing a three-dimensional image using two lens devices having a phase difference type focus detection means,
The focus detection unit detects a defocus amount and an AF reliability value representing the reliability of the defocus amount, compares the AF reliability values of the two lens devices, and has high AF reliability. A focus target position is obtained based on the defocus amount of the other, and each of the focus lens groups is driven to the obtained focus target position.

  According to the present invention, it is possible to provide a stereoscopic video imaging apparatus and a lens apparatus that can improve the focusing accuracy of AF as compared with the prior art.

It is a block diagram which shows the structure of the three-dimensional video imaging device in the 1st Example and the 2nd Example. It is a figure explaining operation | movement of phase difference AF. It is a figure explaining AF reliability value. It is a figure showing the state which installed the two lens apparatuses in the 1st Example in the camera apparatus. It is a figure which shows arrangement | positioning of the line sensor in 1st Example, and arrangement | positioning of the phase difference sensor in an object field. It is a figure explaining the pattern of a to-be-photographed object and the clothes of the to-be-photographed object in a 1st Example. It is a figure which shows the direction of the phase difference sensor in the field of view of the two lens apparatuses in a 1st Example, and the image waveform detected by a phase difference sensor. It is a flowchart for demonstrating the focusing operation | movement in a 1st Example. It is a figure which shows arrangement | positioning of the line sensor in 2nd Example, and arrangement | positioning of the phase difference sensor in an object field. It is a figure showing the state which installed the two lens apparatuses in the 2nd Example in the camera apparatus. It is a flowchart for demonstrating the focusing operation | movement in a 2nd Example.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[Example 1]
Hereinafter, with reference to FIG. 1, a stereoscopic video imaging apparatus according to a first embodiment of the present invention will be described.

  FIG. 1 is a block diagram showing a main part configuration of a stereoscopic video photographing apparatus according to the present invention. Note that configurations not related to the present invention are omitted. In this figure, the stereoscopic image capturing apparatus is composed of two lens apparatuses 100A and 100B having the same specifications and equipped with a phase difference detection type AF mechanism.

  The lens devices 100A and 100B have the same specifications, and the lens device 100A will be described below. However, from 100 to 112, those with an A attached to a subscript and those with a B have the same functions and specifications.

  In the lens apparatus 100A, 101A is a focus lens group. A focus motor 102A is connected to the focus lens group 101A. The focus motor 102A is driven by the focus drive unit 103A, and the focus lens group 101A is moved in the optical axis direction. Reference numeral 104A denotes a focus position detector for detecting the position of the focus lens group 101A. A focus control unit 105A moves the focus lens group 101A in the optical axis direction via the focus drive unit 103A.

  106A is a spectroscope, and the light beam incident on the lens apparatus 100A passes through the focus lens group 101A and is split into a light beam transmitted through the spectroscope 106A and a light beam reflected by the spectroscope 106A. The spectroscope is, for example, a spectroscopic prism or a half mirror. The light beam that has passed through the spectroscope 106A is incident on an image sensor (not shown) (for example, a CCD sensor or a CMOS sensor) included in the camera device 113A.

  A focus detection unit 107A includes a secondary imaging lens and a phase difference sensor. The light beam reflected by the spectroscope 106A enters the focus detection unit 107A. The light beam incident on the focus detection unit 107A is divided into two light beams by the secondary imaging lens, and a pair of images (hereinafter referred to as two images) is formed on the phase difference sensor. The phase difference sensor photoelectrically converts two images and outputs them as two image signals. This is shown in FIG. FIG. 2 is a schematic diagram showing the focus detection unit 107A.

  Returning to the description of FIG. 1, reference numeral 108A denotes a focus information calculation unit, which calculates a phase difference according to the focus state of the lens device 100A based on two image signals output from the focus detection unit 107A, and calculates the phase difference. Based on this, the defocus amount is calculated. A method for calculating the defocus amount will be described later.

  A reliability value calculation unit 109A calculates a two-image coincidence degree (AF reliability value) that is a value indicating how much the image shapes of two images coincide. The AF reliability value will be described later.

  Reference numeral 110A denotes a target position determination unit that determines a target position for moving the focus lens group to the in-focus position based on the defocus amount and the focus position.

  111A is a communication unit that exchanges information according to the defocus amount, AF reliability value, and focus position of the lens device 100A, and the defocus amount, AF reliability value, and focus position of the lens device 100B. The communication unit 111A exchanges information by serial communication, for example. Reference numeral 112A denotes a mount, and the lens apparatuses 100A and 100B are connected to the camera apparatus 113 via the mounts 112A and 112B, respectively.

  Furthermore, this stereoscopic image capturing apparatus has two operation modes “stereoscopic image capturing mode” and “normal mode”. When the connection with the other lens apparatus can be confirmed, it operates as “stereoscopic image capturing mode”. When the connection with another lens device cannot be confirmed, the operation is performed in the “normal mode”.

  Here, a method of calculating the defocus amount will be described with reference to FIG. 2 again. As shown in FIG. 2, the distance between the two images on the phase difference sensor shows a specific value at the time of focusing, the distance between the two images is shorter than the specific value at the front pin, and the distance between the two images is specified at the rear pin. Longer than the value.

A state in which two images are superimposed on the right part of FIG. 2 is shown. Here, one of the two images is called an A image and the other is called a B image.
(a) At the time of rear pin, the A image is on the left side, the B image is on the right side, and there is an interval between the two images.
When focusing on (b), the A and B images overlap.
At the front pin of (c), the A image is on the right side, the B image is on the left side, and there is an interval between the two images.

  The interval between the two images is called a phase difference, and is obtained by using a correlation calculation for calculating how many pixels of the phase difference sensor the correlation is maximized. Further, the defocus amount is calculated based on the obtained phase difference.

  Therefore, in (a) and (c), the lens apparatus 100A is brought into focus by moving the focus lens group in the optical axis direction by an amount corresponding to the calculated defocus amount. In (c), the positional relationship between the two images is opposite to that in (a), and the direction in which the focus lens group is moved toward the in-focus state is also in (a). The opposite direction.

  Next, the AF reliability value will be described with reference to FIG. In the defocus amount calculation method based on the above correlation calculation, it is assumed that the image shapes of the A image and the B image coincide with each other. Therefore, if this assumption is broken, the reliability of the defocus amount obtained by the calculation is lowered. Therefore, the image shape coincidence between the A image and the B image is expressed as a two-image coincidence, which is referred to as an AF reliability value in this embodiment. Therefore, it is determined that the higher the AF reliability value is, the more correct focus is calculated.

  FIG. 3 (a) is an example of two images obtained from the focus detection unit 107A, in which an A image and a B image are superposed. FIG. 3 (b) shows the result of quantizing these in a certain unit. By using the ratio of the area of each of the A image and the B image and the area of the common part when superimposed, the degree of coincidence of the image shapes in the A image and the B image can be quantified.

  FIG. 4 is a schematic diagram when the lens devices 100A and 100B are installed in the camera device 113 in the present embodiment. The lens device 100A is rotated 90 degrees as usual and the lens device 100B is rotated 90 degrees, and the position of the phase difference sensor is on the upper side in the lens device 100A and on the right side in the lens device 100B.

  FIG. 5 shows the arrangement of the phase difference sensor and the lens devices 100A and 100B in the object field in the present embodiment. The phase difference sensor constituting the focus detection units 107A and 107B forms two images as described above. However, as shown in FIG. 5A, the phase difference sensor is composed of one set of two line sensors. A pair of images, that is, two images are formed. That is, focus detection of one area is performed by one set of two line sensors. FIG. 5 (b) shows the arrangement of the phase difference sensors in the object scene. As shown in the figure, let us consider a case in which AF operates on a subject in the center of the object scene.

  An image detected by the phase difference sensor when the subject shown in FIG. 6 is photographed by this stereoscopic image photographing device will be described. In order to simplify the explanation, the pattern of the subject's clothing is indicated by a vertical broken line (a) and a horizontal broken line (b).

  FIG. 7 is a diagram illustrating the orientation of the phase difference sensor in the field of view of the two lens apparatuses and the image waveform detected by the phase difference sensor in the present embodiment. The figure shows two images and the waveform after superposition.

  FIG. 7A shows the positional relationship between the vertical broken line, which is the pattern of the clothing of the subject shown in FIG. 6A, and the phase difference sensor in the object scene, and the detected image waveform.

  As shown in FIG. 7A, when a vertical broken line is detected, in the lens device 100A, a waveform with a sharp tip appears in a portion corresponding to the vicinity of the center detection pixel. In the lens apparatus 100B, since the direction of the phase difference sensor is 90 degrees, a waveform appears over almost all detection pixels. However, since the amount of light entering one pixel is smaller than in the case of the lens apparatus 100A, the waveform is relatively small. The height of becomes low.

  FIG. 7B shows the positional relationship between the horizontal broken line, which is the pattern of the clothing of the subject shown in FIG. 6B, and the phase difference sensor in the object scene, and the detected image waveform.

  As shown in FIG. 7B, when a horizontal broken line is detected, a waveform appears in almost all of the detection pixels in the lens device 100A, but the amount of light entering one pixel is smaller than in the case of the lens device 100B. The height of the waveform is relatively low. In the lens device 100B, a waveform with a sharp tip appears at a portion corresponding to the vicinity of the center detection pixel, as in the lens device 100A when detecting the vertical broken line.

  FIG. 7 also shows the waveform after superimposing the A and B images, but in the lens device 100B when detecting the vertical broken line and the lens device 100A when detecting the horizontal broken line, the influence of noise. Therefore, the image shapes of the A and B images are difficult to match. As described above, when the degree of coincidence between the A image and the B image is low, that is, when the AF reliability is low, the reliability of the defocus amount obtained by the correlation calculation also decreases.

  By installing the two lens devices installed at different angles in this way, there are edge directions that are easy to detect due to the inclination of the phase difference sensor, so that different results such as AF reliability values are obtained. By selecting the one with higher AF reliability, the correct defocus amount can be obtained even when shooting any subject. As a result, the focus lens group can be driven to the correct focal point.

  Next, a series of flows of the AF operation of the stereoscopic image capturing apparatus will be described with reference to the flowchart of FIG. The description is based on the lens device 100A. First, in S101, the focus information calculation unit 108A calculates the defocus amount based on the two image signals obtained by the focus detection unit 107A.

  In S102, the AF reliability value calculation unit 109A calculates an AF reliability value representing the reliability of the defocus amount based on the two image signals. In S103, the focus control unit 105A acquires the focus position from the focus position detection unit 104A.

  In S104, the connection with the lens device 100B is confirmed. When the connection is confirmed, in S105, the lens device 100A outputs the defocus amount, the AF reliability value, and the focus position obtained in S101 to S103 to the lens device 100B. In S106, when the defocus amount, AF reliability value, and focus position obtained in the lens apparatus 100B are acquired, the process proceeds to S107.

  In S107, the target position determination unit 110A compares the two AF reliability values and determines a lens device that indicates the target position to be adopted. In S108, the target position determination unit 110A determines the target position based on the defocus amount and the focus position indicated by the lens apparatus determined in S107. In S109, the focus control unit moves the focus lens group 101 to the target position calculated in S108 via the focus driving unit 103A.

  If the connection with the lens apparatus 100B cannot be confirmed in S104, the process proceeds to S111, and the target position determination unit 110A determines the target position based on the defocus amount and the focus position obtained in the lens apparatus 100A. In S112, the focus control unit moves the focus lens group 101A to the target position calculated in S111 via the focus driving unit 103A. That is, when connected to the lens device 100B, it operates as a stereoscopic video shooting mode, compares the AF reliability values of the two lens devices, and based on the defocus amount and the focus position of the one with higher AF reliability. Determine the target position. When not connected to another lens device, the operation is performed in the normal mode, and the target position is determined based on the defocus amount and the focus position obtained by the lens device.

  The lens device 100B operates in the same manner as described above. As described above, since the defocus amount used as the reference for the target position is determined using the AF reliability value, a more reliable target position can be selected and AF focusing accuracy is improved. It can be made. In addition, since each lens device determines a target position based on the same determination criterion, each lens device drives the focus lens group to the same position.

  In this embodiment, the target position is determined in S107, but the target position is determined between S103 and S104. In S104, the target position is output instead of the defocus amount and the focus position. Also good.

  In the present embodiment, the lens apparatus 100B is rotated about the optical axis and installed with an angle of 90 degrees. However, the lens apparatus 100B is installed with an angle of 45 degrees or as usual. Even in this case, the present invention can be applied. Even when both lens devices are installed at the same angle, it is possible to select the one with better optical performance each time, and the one with higher AF reliability can be selected. That is, by comparing the AF reliability values and determining the focus target position based on the defocus amount with higher AF reliability, the AF focusing accuracy can be improved.

[Example 2]
In the first embodiment, the phase difference sensor configured in the focus detection units 107A and 107B in FIG. 1 is the one shown in FIG. 5A configured by one set of two line sensors. In the second embodiment, as shown in FIG. 9A, a phase difference sensor composed of two sets of four line sensors is used.

  FIG. 10 is a schematic diagram when the lens devices 100A and 100B are installed in the camera device 113 in the present embodiment. The lens device 100A is shown in a state where the lens device 100B is rotated and installed by 45 degrees as usual, and the position of the phase difference sensor is in the upper part in the lens device 100A and in the upper right part in the lens device 100B.

  FIG. 9B shows the arrangement of the phase difference sensor in the object scene. As shown in the figure, let us consider a case in which AF operates on a subject in the center of an imaged area. Further, in the present embodiment, the phase difference sensor is arranged in a cross shape as shown in FIG. 9A, and therefore the lens device 100A has a configuration in which vertical and horizontal lines can be easily detected. In addition, the lens apparatus 100B installed with an angle of 45 degrees has a configuration in which oblique lines can be easily detected.

  The difference between the focal point detection method and the first embodiment will be described. In this embodiment, since there are two sets of phase difference sensors as described above, it is first determined which of the defocus amounts calculated by the two sets of phase difference sensors is to be used in each lens device. To do. Then, the lens device having the higher AF reliability value out of the defocus amounts indicated by the two lens devices is determined.

FIG. 11 is a flowchart showing a series of flows of the AF operation of the stereoscopic video imaging apparatus in the present embodiment. 8 differs from the first embodiment of FIG. 8 in that S201 to S203 instead of S101 and S102.
Is that. Hereinafter, description will be made from S201. The description is based on the lens device 100A.

  In S201, the focus information calculation unit 108A calculates two defocus amounts based on two sets of two image signals obtained by the focus detection unit 107A having two sets of phase difference sensors.

  In S202, the AF reliability value calculation unit 109A calculates two AF reliability values representing the reliability of the two defocus amounts based on the two sets of the two image signals.

  In S203, the target position determination unit 107A compares the two AF reliability values and selects a defocus amount with high AF reliability, thereby determining the defocus amount in the lens apparatus 100A. That is, in S203, the more reliable one of the two defocus amounts existing in each lens device is determined, and the defocus amount in the lens device is determined in the subsequent steps. In S107, the more reliable one of the defocus amounts indicated by the two lens devices is determined.

  The subsequent steps are the same as those in steps S103 to S112 in FIG. The lens device 100B operates in the same manner as described above.

  As described above, since the defocus amount used as the reference for the target position is determined using the AF reliability value, a more reliable target position can be selected and AF focusing accuracy is improved. It can be made. In addition, since each lens device determines a target position based on the same determination criterion, each lens device drives the focus lens group to the same position.

  In this embodiment, the target position is determined in S107, but the target position is determined between S103 and S104. In S104, the target position is output instead of the defocus amount and the focus position. Also good.

  In the present embodiment, the lens apparatus 100B is rotated about the optical axis and installed at an angle of 45 degrees. However, the present invention can be applied to a case where the lens apparatus 100B is installed as usual. Is possible. Even when both lens devices are installed at the same angle, it is possible to select the one with better optical performance each time, and the one with higher AF reliability can be selected. That is, by comparing the AF reliability values and determining the focus target position based on the defocus amount with higher AF reliability, the AF focusing accuracy can be improved.

  As mentioned above, although the preferable Example of this invention was described, this invention is not limited to these Examples, A various deformation | transformation and change are possible within the range of the summary.

100A lens unit
101A Focus lens group
102A focus motor
103A Focus drive unit
104A Focus position detector
105A Focus control unit
106A spectrometer
107A focus detector
108A Focus information calculator
109A Reliability calculator
110A target position determination unit
111A Communication Department
112A mount
113 Camera equipment

Claims (6)

A focus mechanism including a focus lens group;
In a three-dimensional image photographing device for photographing a three-dimensional image using two lens devices having a phase difference type focus detection means,
The focus detection unit detects a defocus amount and an AF reliability value representing the reliability of the defocus amount, compares the AF reliability values of the two lens devices, and has high AF reliability. A stereoscopic video imaging apparatus, wherein a focus target position is obtained based on the defocus amount of the other, and each of the focus lens groups is driven to the obtained focus target position. When there is an AF operation switching means and the AF operation switching means selects the stereoscopic image shooting side, the AF reliability values of the two lens devices are compared, and the defocus with the higher AF reliability is compared. A focus target position is determined based on the amount, and the focus target position is determined based on a defocus amount of the lens device when the AF operation switching unit selects the non-stereoscopic image capturing side. Lens device. The AF reliability value is a two-image coincidence degree that represents a coincidence degree between two images for determining a defocus amount, which is divided by a light beam on a phase difference AF sensor.
The stereoscopic video imaging apparatus or lens apparatus according to claim 1 or 2. 4. The phase difference AF sensor of the two lens devices has a rotation setting means capable of providing a rotation phase difference with respect to each optical axis as a reference. The three-dimensional image capturing device according to claim 1. 5. The stereoscopic image capturing apparatus according to claim 4, wherein when the phase difference AF sensor has detection pixels in a horizontal line, the phase setting AF sensor is set to a phase of 90 degrees by the rotation setting unit. 5. The stereoscopic image photographing apparatus according to claim 4, wherein when the phase difference AF sensor has detection pixels in each row in the vertical and horizontal directions, the phase setting AF sensor sets the phase to 45 degrees by the rotation setting unit.