JP2009092909A - Imaging apparatus, focus control method, program, and integrated circuit - Google Patents

Abstract

Since the position of the subject cannot be recognized as an absolute value in video AF, it is necessary to move the focus lens before and after the focus peak in order to obtain a contrast peak. It took time to do so, missed shooting opportunities, acquired images of unexpected moments, and video cameras were sometimes forced to shoot images that were out of focus even though shooting was started .
A light separation unit 3 that divides a subject image into three and three image sensors that photoelectrically convert the divided subject images, one of which acquires only the luminance signal of the subject image. The other two acquire the color signal, and the image sensor that acquires the color signal is disposed before and after the optical distance from the imaging optical system of the image sensor that acquires the luminance signal.
[Selection] Figure 1

Description

  The present invention relates to a technique for realizing an autofocus function in an imaging apparatus (such as a camera) that acquires an image using a plurality of imaging elements, using the contrast value of a subject acquired by each imaging element.

2. Description of the Related Art Recently, a digital camera that converts an optical image into an electrical signal and digitizes and records the converted electrical signal using an image sensor such as a CCD (Charge Coupled Device) type sensor or a CMOS (Complementary Metal-Oxide Semiconductor) type sensor. Imaging devices such as digital video cameras have become widespread.
In such an imaging apparatus, the autofocus function is widely recognized by general consumers as an essential function. The high speed / high accuracy of the autofocus function of the imaging apparatus is an index for evaluating user satisfaction (customer satisfaction). Generally, in most compact digital cameras, an autofocus function is realized by a method called video AF (Automatic Focusing). The video AF method is a method for obtaining the peak value of the contrast value by detecting the contrast value of the subject while driving the focus lens of the compact digital camera. Specifically, once the focus lens is driven to pass the just focus position (focus position of the compact digital camera), and the focus lens is further driven to return to the just focus position, the peak value of the contrast value is obtained. It is a method to seek.

In digital video cameras, the focus lens is moved by minute vibrations (wobbling), so that the focus lens continues to be driven to a higher contrast value while detecting changes in contrast in time series. This realizes an autofocus function that supports moving images.
Since video AF in a compact digital camera cannot recognize the position information of the subject in the three-dimensional space as absolute position information, it is focused before and after the focus peak (front and rear direction of the optical axis) to obtain the peak value of the contrast value. The lens needs to be moved and reciprocated. For this reason, in a compact digital camera, it takes time from when the photographer presses the release button until it is focused, and it is possible to miss a photographing opportunity or to acquire an image of an unexpected moment that the photographer does not intend. is there.

Even in a digital video camera, since the position information of the subject in the three-dimensional space cannot be recognized as absolute position information at the beginning of shooting, the positional relationship between the digital video camera and the subject is specified in the three-dimensional space. In order to find the peak value of the contrast value before performing the wobbling operation, it is necessary to move the focus lens back and forth (in the front-rear direction of the optical axis) and move it back and forth. As in the case, the photographer may be unsatisfactory.
Also, when acquiring high-definition video signals (for example, HDTV format video signals) in a digital video camera, if the autofocus function is realized by the wobbling method, focus change and image magnification change due to wobbling the focus lens The fluctuation component due to is generated on the video signal acquired by the digital camera. When this video signal is displayed on the display device, there is a problem that a fluctuation component of a level that can be visually confirmed on the displayed video (fluctuation component due to focus change or image magnification change) occurs.

On the other hand, a method has been proposed in which an external light passive module is separately provided in a camera (compact digital camera or digital video camera) to detect the direction of the focus position. However, in this method, a separate module must be arranged in the camera, and the size is increased in a compact digital camera that is required to be downsized. Also, in the digital video camera, each focal length of the high magnification zoom is also increased. Therefore, it is difficult to realize an autofocus function at a level that satisfies the photographer. Furthermore, since a separate module is attached to the camera, there is a problem that the cost increases.
Further, as a technique that can realize an autofocus function without adding a separate module, there is an imaging apparatus (automatic focusing apparatus) disclosed in Japanese Patent Laid-Open No. 2001-61155.

In this imaging apparatus, a color separation prism that separates light from a subject into R color component light, G color component light, and B color component light, an R color image sensor, a G color image sensor, and a B color image sensor. The three image sensors are arranged so that the optical path lengths are different from each other, and the blur characteristic information is calculated for each color, thereby realizing an autofocus function.
JP 2001-61155 A (FIG. 5)

  However, the conventional imaging apparatus has a problem that the acquired image (video) is blurred. That is, in the conventional imaging apparatus, after separating light from the subject into R component light, G component light, and B component light, the R component, R color image sensor, G color image sensor, and B color image sensor A signal, a G component signal, and a B component signal are acquired. Then, the video signal is acquired by combining the R component signal, the G component signal, and the B component signal. Since the three image pickup devices of the R color image pickup device, the G color image pickup device, and the B color image pickup device are arranged so as to have different optical path lengths, for example, when the G color image pickup device is focused. As for the R color image sensor and the B color image sensor, the R component signal and the B component signal are acquired in a state where they are not in focus. In this state, the video signal obtained by synthesizing the R component signal, the G component signal, and the B component signal includes a blur component.

In particular, when a high-definition video signal (for example, a video signal in HDTV format) is acquired in the imaging apparatus, there is a problem in that display video degradation due to the blur component becomes significant.
Therefore, in view of the above problems, the present invention provides an imaging device, a focus control method, a program, and an integrated circuit that realize a high-precision and high-speed autofocus function without blurring an acquired image (video). The purpose is to do.

  The first invention includes a condenser lens, a focus lens, a light separation unit, a first color signal acquisition imaging unit, a luminance signal acquisition imaging unit, a second color signal acquisition imaging unit, and focus control. And an imaging device. The condenser lens collects light from the subject. The focus lens is a lens for adjusting the focus position of the light collected by the condenser lens. The light separation unit separates light that has passed through the focus lens into at least three paths. The first color signal acquisition imaging unit includes a first color imaging element disposed at a position where the distance from the condenser lens is the first optical path length, and photoelectrically converts the light separated by the light separation unit To obtain the first color signal. The luminance signal acquisition imaging unit includes a luminance imaging element disposed at a position where the distance from the condenser lens is the second optical path length, and the light separated by the light separation unit is converted into a luminance signal by photoelectric conversion. get. The second color signal acquisition imaging unit has a second color imaging element disposed at a position where the distance from the condenser lens is the third optical path length, and photoelectrically converts the light separated by the light separation unit To obtain the second color signal. The focus control unit obtains a first color contrast value corresponding to a contrast value of light incident on the first color image pickup device from the first color signal acquired by the first color signal acquisition image pickup unit, and outputs a luminance signal. A luminance contrast value corresponding to the contrast value of the light incident on the luminance imaging element is obtained from the luminance signal acquired by the acquisition imaging unit, and the second color signal acquired by the second color signal acquisition imaging unit is obtained. A focus lens for a second color corresponding to the contrast value of the light incident on the image sensor for the second color is obtained, and based on the contrast value for the first color, the contrast value for luminance, and the contrast value for the second color light, the focus lens Adjust the position.

In this imaging apparatus, the first color imaging device, the second color imaging device, and the luminance imaging device are arranged at positions having different optical path lengths, and the relationship between the contrast values acquired from the respective imaging devices ( Based on the magnitude relationship, the focus control unit adjusts the position of the focus lens. In other words, this imaging device realizes a high-speed and high-precision autofocus function because the direction and amount of movement of the focus lens can be determined from the relationship of contrast values acquired from image sensors placed at different optical path lengths. Can be made.
In this image pickup apparatus, the first color image sensor, the second color image sensor, and the luminance image sensor need only be arranged at different optical path lengths. In the above description, the optical path length measurement reference point ( The starting point is a condensing lens (preferably the central point on the optical axis of the condensing lens (group)), but is not limited to this, and is another point on the optical axis. Needless to say.

Further, the optical path length from the reference point on the optical axis to the luminance image sensor is the optical path length from the reference point on the optical axis to the first color image sensor, and the second color image from the reference point on the optical axis. The value is preferably between the optical path length to the element, but is not limited thereto. For example, the optical path length from the reference point on the optical axis to the first color image sensor is on the optical axis. The optical path length from the reference point to the luminance image sensor and the optical path length from the reference point on the optical axis to the second color image sensor may be arranged.
2nd invention is 1st invention, Comprising: A focus control part adjusts the position of a focus lens so that the contrast value for brightness | luminance may become a peak value.
In this imaging apparatus, the focus control unit adjusts the position of the focus lens so that the luminance contrast value becomes the peak value, so that a highly accurate image (video) can be acquired. In this imaging apparatus, focus control is performed so that the luminance contrast value becomes a peak value. That is, in this imaging apparatus, focus control is performed so as to focus on the luminance imaging element, so that signals in a state where the first color imaging element and the second color imaging element are not in focus are acquired. Will be. Since the sensitivity on the human visual characteristic with respect to the color information is lower than the sensitivity with respect to the luminance information, the luminance signal acquired in such a state (signal acquired in the in-focus state), the first color signal (in-focus) The image (video) acquired from the second color signal (signal acquired in a state slightly deviated from the in-focus state) and the second color signal (video acquired in a state slightly deviated from the state) can be highly accurate. .

The “peak value” is a concept including a maximum value and a maximum value.
3rd invention is 1st or 2nd invention, Comprising: The imaging part for 1st color signal acquisition is the color filter for 1st colors installed on the image pick-up element surface of the image pick-up element for 1st colors. Have. The second color signal acquisition imaging unit includes a second color filter disposed on the imaging element surface of the second color imaging element. The luminance signal acquisition imaging unit includes a luminance signal imaging element in which no color filter is provided on the imaging element surface.
In this imaging apparatus, since a color filter is not provided on the imaging element surface of the luminance imaging element, a luminance signal without light loss can be obtained by the color filter. As a result, an image (video) acquired by the imaging apparatus has high accuracy (particularly, high accuracy in luminance information).

The fourth invention is any one of the first to third inventions, wherein the first color imaging device, the luminance imaging device, and the second color imaging device have a first optical path length LC1; When the second optical path length is LY and the third optical path length is LC2,
LC1 <LY <LC2
Or LC2 <LY <LC1
Are arranged at positions satisfying the above relationship.
Accordingly, the position on the optical axis of the luminance image sensor is between the position on the optical axis of the first color image sensor and the position on the optical axis of the first color image sensor. The focusing operation can be performed more quickly and accurately.

A fifth invention is any one of the first to fourth inventions, wherein the luminance image pickup device has the first number of pixels, and the first color image pickup device has the first number of pixels. The second color imaging element is a third number less than or equal to the first number.
In this imaging apparatus, since the number of pixels of the color imaging element is small, the manufacturing cost of the imaging apparatus can be reduced. In addition, since the sensitivity on the human visual characteristic with respect to the color information is lower than the sensitivity with respect to the luminance information, even if the number of pixels of the color image sensor is reduced, an image (video) acquired by this imaging device is It can be of sufficient accuracy.
A sixth invention is any one of the first to fifth inventions, wherein the focus control unit detects a first color contrast detection unit and a luminance contrast value. Based on the contrast detection unit for luminance, the second color contrast detection unit for detecting the second color contrast value, the first color contrast value, the luminance contrast value, and the second color light contrast value, A focus lens drive amount determination unit that determines a drive amount to be driven and a drive direction of the focus lens; and a focus lens drive unit that drives the focus lens in the drive direction based on the drive amount.

The seventh invention is the sixth invention, wherein the focus lens drive amount determination unit includes a corrected first color contrast value obtained by adding a first offset value to the first color contrast value, and a second color contrast. The driving amount for driving the focus lens and the driving direction of the focus lens are determined based on the corrected second color contrast value obtained by adding the second offset value to the value and the luminance contrast value.
The eighth invention is the seventh invention, wherein when the condensing lens collects light from the same subject, the maximum value of the corrected first color contrast value and the corrected second color contrast. The first offset value and the second offset value are set such that the maximum value and the luminance contrast value are substantially the same value.
In this imaging apparatus, the corrected first color contrast value and the corrected second color contrast value are corrected so as to be at the same level as the luminance contrast value. The direction in which the focus lens is moved can be determined simply by comparing the magnitude relationship between the second color contrast value and the luminance contrast value.

A ninth invention is any one of the first to eighth inventions, and further includes a Lab conversion unit and an image data generation unit. The Lab conversion unit performs Lab conversion on the first color signal, the second color signal, and the luminance signal, thereby converting the a component signal and the b component signal from the first color signal and the second color signal into the luminance signal. L component signals are respectively generated. The image data generation unit generates captured image data from the L component signal, the a component signal, and the b component signal.
In this imaging apparatus, an L component signal is acquired from a signal acquired from an in-focus luminance image sensor, and an a component signal and a b component signal are acquired from a signal acquired from a color image sensor that is slightly out of focus. To get. Since the captured image data is acquired from the high-accuracy L-component signal and the a-component signal and the b-component signal, which are color signals that do not require so high accuracy in terms of human visual characteristics, sufficiently high accuracy is obtained. Captured image data can be acquired.

Further, in this imaging apparatus, the captured image data is generated by a synthesis process of luminance information and color information, that is, a so-called Lab synthesis process, so that it is not necessary to align pixel positions. In other words, for example, an image pickup apparatus having three conventional RGB image pickup elements needs to have a precise pixel position alignment, but this image pickup apparatus does not need to have an exact pixel position adjustment as in the past.
A tenth aspect of the invention is any one of the first to ninth aspects of the invention, in which the first color image pickup device and the second color image pickup device have an optical distance from the condenser lens of the luminance image pickup device. It is arrange | positioned in the position within 1-4Fdelta before and behind the optical axis direction.
An eleventh invention includes a condensing lens, a focus lens, a light separation unit, a first color signal acquisition imaging unit, a luminance signal acquisition imaging unit, and a second color signal acquisition imaging unit. This is a focus control method used in an imaging apparatus. The condenser lens collects light from the subject. The focus lens is a lens for adjusting the focus position of the light collected by the condenser lens. The light separation unit separates light that has passed through the focus lens into at least three paths. The first color signal acquisition imaging unit includes a first color imaging element disposed at a position where the distance from the condenser lens is the first optical path length, and photoelectrically converts the light separated by the light separation unit To obtain the first color signal. The luminance signal acquisition imaging unit includes a luminance imaging element disposed at a position where the distance from the condenser lens is the second optical path length, and the light separated by the light separation unit is converted into a luminance signal by photoelectric conversion. get. The second color signal acquisition imaging unit has a second color imaging element disposed at a position where the distance from the condenser lens is the third optical path length, and photoelectrically converts the light separated by the light separation unit To obtain the second color signal. In this focus control method, the first color contrast value corresponding to the contrast value of the light incident on the first color image sensor is obtained from the first color signal acquired by the first color signal acquisition imaging unit. . Then, a luminance contrast value corresponding to the contrast value of the light incident on the luminance imaging element is obtained from the luminance signal acquired by the luminance signal acquisition imaging unit. Then, a second color contrast value corresponding to the contrast value of the light incident on the second color image sensor is obtained from the second color signal acquired by the second color signal acquisition imaging unit. Then, the position of the focus lens is adjusted based on the first color contrast value, the luminance contrast value, and the second color light contrast value.

Accordingly, an imaging apparatus including a condenser lens, a focus lens, a light separation unit, a first color signal acquisition imaging unit, a luminance signal acquisition imaging unit, and a second color signal acquisition imaging unit. By being used, it is possible to realize a focus control method that exhibits the same effect as the first invention.
A twelfth invention includes a condenser lens, a focus lens, a light separation unit, a first color signal acquisition imaging unit, a luminance signal acquisition imaging unit, and a second color signal acquisition imaging unit. A program for causing a computer to execute a focus control method used in an imaging apparatus.
The condenser lens collects light from the subject. The focus lens is a lens for adjusting the focus position of the light collected by the condenser lens. The light separation unit separates light that has passed through the focus lens into at least three paths. The first color signal acquisition imaging unit includes a first color imaging element disposed at a position where the distance from the condenser lens is the first optical path length, and photoelectrically converts the light separated by the light separation unit To obtain the first color signal. The luminance signal acquisition imaging unit includes a luminance imaging element disposed at a position where the distance from the condenser lens is the second optical path length, and the light separated by the light separation unit is converted into a luminance signal by photoelectric conversion. get. The second color signal acquisition imaging unit has a second color imaging element disposed at a position where the distance from the condenser lens is the third optical path length, and photoelectrically converts the light separated by the light separation unit To obtain the second color signal. In the focus control method, the first color contrast value corresponding to the contrast value of the light incident on the first color image sensor is obtained from the first color signal acquired by the first color signal acquisition imaging unit. Then, a luminance contrast value corresponding to the contrast value of the light incident on the luminance imaging element is obtained from the luminance signal acquired by the luminance signal acquisition imaging unit. Then, a second color contrast value corresponding to the contrast value of the light incident on the second color image sensor is obtained from the second color signal acquired by the second color signal acquisition imaging unit. Then, the position of the focus lens is adjusted based on the first color contrast value, the luminance contrast value, and the second color light contrast value.

Accordingly, an imaging apparatus including a condenser lens, a focus lens, a light separation unit, a first color signal acquisition imaging unit, a luminance signal acquisition imaging unit, and a second color signal acquisition imaging unit. By being used, it is possible to realize a program that causes a computer to execute a focus control method that exhibits the same effect as the first invention.
According to a thirteenth aspect of the present invention, there is provided a condensing lens for condensing light from a subject, a focus lens for adjusting a focus position of light collected by the condensing lens, and at least three light beams that have passed through the focus lens. It is an integrated circuit used for an imaging device provided with the light separation part which isolate | separates into one path | route.
The first color signal acquisition imaging unit includes a first color imaging element disposed at a position where the distance from the condenser lens is the first optical path length, and photoelectrically converts the light separated by the light separation unit To obtain the first color signal. The luminance signal acquisition imaging unit includes a luminance imaging element disposed at a position where the distance from the condenser lens is the second optical path length, and the light separated by the light separation unit is converted into a luminance signal by photoelectric conversion. get. The second color signal acquisition imaging unit has a second color imaging element disposed at a position where the distance from the condenser lens is the third optical path length, and photoelectrically converts the light separated by the light separation unit To obtain the second color signal. The focus control unit obtains a first color contrast value corresponding to a contrast value of light incident on the first color image pickup device from the first color signal acquired by the first color signal acquisition image pickup unit, and outputs a luminance signal. A luminance contrast value corresponding to the contrast value of the light incident on the luminance imaging element is obtained from the luminance signal acquired by the acquisition imaging unit, and the second color signal acquired by the second color signal acquisition imaging unit is obtained. A focus lens for a second color corresponding to the contrast value of the light incident on the image sensor for the second color is obtained, and based on the contrast value for the first color, the contrast value for luminance, and the contrast value for the second color light, the focus lens Adjust the position.

Thus, an integrated circuit that exhibits the same effect as that of the first invention can be realized by being used in an imaging apparatus including a condenser lens, a focus lens, and a light separation unit.
14th invention is provided with the condensing lens, the focus lens, the light separation part, the imaging part for 1st color signal acquisition, the imaging part for luminance signal acquisition, and the imaging part for 2nd color signal acquisition. It is an integrated circuit used for an imaging device.
The condenser lens collects light from the subject. The focus lens is a lens for adjusting the focus position of the light collected by the condenser lens. The light separation unit separates light that has passed through the focus lens into at least three paths. The first color signal acquisition imaging unit includes a first color imaging element disposed at a position where the distance from the condenser lens is the first optical path length, and photoelectrically converts the light separated by the light separation unit To obtain the first color signal. The luminance signal acquisition imaging unit includes a luminance imaging element disposed at a position where the distance from the condenser lens is the second optical path length, and the light separated by the light separation unit is converted into a luminance signal by photoelectric conversion. get. The second color signal acquisition imaging unit has a second color imaging element disposed at a position where the distance from the condenser lens is the third optical path length, and photoelectrically converts the light separated by the light separation unit To obtain the second color signal.

The focus control unit obtains a first color contrast value corresponding to a contrast value of light incident on the first color image pickup device from the first color signal acquired by the first color signal acquisition image pickup unit, and outputs a luminance signal. A luminance contrast value corresponding to the contrast value of the light incident on the luminance imaging element is obtained from the luminance signal acquired by the acquisition imaging unit, and the second color signal acquired by the second color signal acquisition imaging unit is obtained. A focus lens for a second color corresponding to the contrast value of the light incident on the image sensor for the second color is obtained, and based on the contrast value for the first color, the contrast value for luminance, and the contrast value for the second color light, the focus lens Adjust the position.
Accordingly, an imaging apparatus including a condenser lens, a focus lens, a light separation unit, a first color signal acquisition imaging unit, a luminance signal acquisition imaging unit, and a second color signal acquisition imaging unit. By being used, it is possible to realize an integrated circuit having the same effects as those of the first invention.

  In the present invention, it is possible to provide an imaging device, a focus control method, a program, and an integrated circuit that realize a high-precision and high-speed autofocus function without blurring an acquired image (video).

Hereinafter, embodiments of an imaging apparatus according to the present invention will be described with reference to the drawings.
[First Embodiment]
<1.1: Configuration of Imaging Device>
FIG. 1 shows a schematic configuration diagram of an imaging apparatus 100 according to the first embodiment. In FIG. 2, the imaging lens system LEN, the light separation unit 3, the luminance signal acquisition imaging unit 40, the first color signal acquisition imaging unit 41, and the second color signal acquisition imaging unit 42 of the imaging apparatus 100 are illustrated. The schematic block diagram is shown.
The imaging apparatus 100 includes a photographic lens system LEN including a condenser lens 1 that collects light from a subject and a focus lens 2 for adjusting focus, and light that separates light from the photographic lens system LEN into three paths. The separation unit 3, the luminance signal acquisition imaging unit 40 that acquires the light separated by the light separation unit 3 as a luminance signal by photoelectric conversion, and the light separated by the light separation unit 3 as a first color signal by photoelectric conversion A first color signal acquisition imaging unit 41 to acquire, and a second color signal acquisition imaging unit 42 to acquire the light separated by the light separation unit 3 as a second color signal by photoelectric conversion. In addition, the imaging apparatus 100 includes a luminance contrast detection unit 50 that detects a luminance contrast value from the luminance signal acquired by the luminance signal acquisition imaging unit 40 and the first color signal acquisition imaging unit 41. The first color contrast detection unit 51 that detects the first color contrast value from the one color signal, and the second color contrast value is detected from the second color signal acquired by the second color signal acquisition imaging unit 42. A second color contrast detection unit 52. Furthermore, the imaging apparatus 100 includes a focus lens drive amount determination unit 6 that determines a focus lens drive amount based on the luminance contrast value, the first color contrast value, and the second color contrast value, and a focus lens drive amount determination. A focus lens driving unit 7 that drives the focus lens 2 based on the focus lens driving amount determined by the unit 6. In addition, the imaging apparatus 100 includes a Lab conversion unit 8 and a captured image data generation unit 9.

The photographic lens system LEN has a condenser lens 1 for condensing light from the subject and a focus lens 2 for adjusting the focus, condenses the light from the subject, and outputs it to the light separation unit 3. . The condenser lens 1 and the focus lens may be composed of a single lens or may be composed of a plurality of lens groups.
The focus lens 2 is installed so that it can be moved in the front-rear direction of the optical axis by the focus lens driving unit 7. Then, the focus lens driving unit 7 moves the focus lens 2 in the front-rear direction of the optical axis, thereby realizing a focus adjustment function in the imaging apparatus 100.
The light separation unit 3 separates the light from the photographing lens system LEN into three different paths, and the separated light is the luminance signal acquisition imaging unit 40, the first color signal acquisition imaging unit 41, and the second color signal acquisition. Each is output to the imaging unit 42. An optical prism is preferably used as the light separation unit 3.

  The luminance signal acquisition imaging unit 40 includes an imaging device, receives the light separated by the light separation unit 3, acquires the luminance signal by photoelectric conversion, and acquires the acquired luminance signal as a luminance contrast detection unit 50. And output to the Lab converter 8. Then, the luminance signal acquisition imaging unit 40 has a point F that is the center point (point orthogonal to the optical axis) of the imaging surface of the imaging element of the luminance signal acquisition imaging unit 40 shown in FIG. 2 and a point B shown in FIG. Are arranged at positions where L1 + L2. Further, the luminance signal acquisition imaging unit 40 is configured such that no color filter is provided on the imaging surface of the imaging element of the luminance signal acquisition imaging unit 40. Thereby, in the luminance signal acquisition imaging unit 40, since there is no light loss due to the color filter, it is possible to increase the photoelectric conversion efficiency in the luminance signal acquisition imaging unit 40, and the luminance signal acquisition imaging unit 40. The luminance signal acquired by the above can be a highly accurate signal (a signal capable of realizing a high contrast and a high S / N ratio). Note that it is preferable to use a CCD type image sensor or a CMOS type image sensor as the imaging element of the luminance signal acquisition imaging unit 40.

  The first color signal acquisition imaging unit 41 includes an imaging device, receives the light separated by the light separation unit 3, acquires the first color signal by photoelectric conversion, and acquires the acquired first color signal. The data is output to the first color contrast detection unit 51 and the Lab conversion unit 8. Then, the first color signal acquisition imaging unit 41 has a G point that is the center point (a point orthogonal to the optical axis) of the imaging surface of the imaging element of the first color signal acquisition imaging unit 41 shown in FIG. The optical path length with respect to the point B shown in FIG. In addition, the first color signal acquisition imaging unit 41 is configured to install a color filter on the imaging surface of the imaging element of the first color signal acquisition imaging unit 41. In addition, as an image pick-up element of the image pick-up part 41 for 1st color signal acquisition, it is preferable to use a CCD type image sensor and a CMOS type image sensor. In addition, since the image sensor of the first color signal acquisition imaging unit 41 is for color signal acquisition, accuracy as high as that of the luminance signal is not necessary. Therefore, the luminance signal is used as the image sensor of the first color signal acquisition imaging unit 41. An image sensor having a smaller number of pixels than the image sensor of the acquisition imaging unit 40 may be used. For example, a Bayer color filter is preferably used as the color filter.

  The second color signal acquisition imaging unit 42 includes an imaging device, receives the light separated by the light separation unit 3, acquires the second color signal by photoelectric conversion, and obtains the acquired second color signal. The data is output to the second color contrast detection unit 52 and the Lab conversion unit 8. The second color signal acquisition imaging unit 42 has a point D which is the center point (a point orthogonal to the optical axis) of the imaging surface of the imaging element of the second color signal acquisition imaging unit 42 shown in FIG. The optical path length with respect to the point B shown in FIG. In addition, the second color signal acquisition imaging unit 42 is configured to install a color filter on the imaging surface of the imaging element of the second color signal acquisition imaging unit 42. In addition, as an image pick-up element of the image pick-up part 42 for 2nd color signal acquisition, it is preferable to use a CCD type image sensor and a CMOS type image sensor. In addition, since the image sensor of the second color signal acquisition imaging unit 42 is for color signal acquisition, accuracy as high as that of the luminance signal is not necessary. Therefore, the luminance signal is used as the image sensor of the second color signal acquisition imaging unit 42. An image sensor having a smaller number of pixels than the image sensor of the acquisition imaging unit 40 may be used. For example, a Bayer color filter is preferably used as the color filter.

The luminance signal acquisition imaging unit 40, the first color signal acquisition imaging unit 41, and the second color signal acquisition imaging unit 42 are:
L1 + C1 <L1 + L2 <C2 + C3
Or
C2 + C3 <L1 + L2 <L1 + C1
Are arranged at positions satisfying the above.
The luminance contrast detection unit 50 receives the luminance signal acquired by the luminance signal acquisition imaging unit 40, detects the luminance contrast value from the luminance signal, and uses the detected luminance contrast value as the focus lens drive amount determination unit 6 To the focus lens drive amount calculation unit 63.

The first color contrast detection unit 51 receives the first color signal acquired by the first color signal acquisition imaging unit 41, detects the first color contrast value from the first color signal, and detects the detected first color signal. The color contrast value is output to the first color adder 61 of the focus lens drive amount determination unit 6.
The second color contrast detection unit 52 receives the second color signal acquired by the second color signal acquisition imaging unit 42, detects the second color contrast value from the second color signal, and detects the detected second color signal. The color contrast value is output to the second color adder 62 of the focus lens drive amount determination unit 6.
The focus lens drive amount determination unit 6 includes a first color adder 61, a second color adder 62, and a focus lens drive amount calculation unit 63.
The first color adder 61 receives the first color contrast value and the first offset value output from the first color contrast detection unit 51, and adds the first color contrast value and the first offset value. The addition result (hereinafter referred to as “corrected first color contrast value”) is output to the focus lens driving amount calculation unit 63. The first offset value is preferably stored in advance in a storage device (not shown) such as a ROM of the imaging apparatus 100. The first offset value will be described later.

The second color adder 62 receives the second color contrast value and the second offset value output from the second color contrast detection unit 52, and adds the second color contrast value and the second offset value. , And outputs the result (hereinafter, referred to as “corrected second color contrast value”) to the focus lens driving amount calculation unit 63. The second offset value is preferably stored in advance in a storage device (not shown) such as a ROM of the imaging device 100. The second offset value will be described later.
The focus lens driving amount calculation unit 63 includes a luminance contrast value output from the luminance contrast detection unit 50, a corrected first color contrast value output from the first color adder 61, and a second color adder. The direction of moving (driving) the focus lens based on the luminance contrast value, the corrected first color contrast value, and the corrected second color contrast value is input using the corrected second color contrast value output from 62 The driving amount is calculated. Then, the focus lens drive amount calculation unit 63 outputs information about the calculated direction and drive amount of the focus lens to the focus lens drive unit 7.

The focus lens drive unit 7 receives information about the direction and drive amount for moving (driving) the focus lens output from the focus lens drive amount calculation unit 63, and the focus lens 2 is moved by the focus lens drive amount calculation unit 63. The focus adjustment in the imaging apparatus 100 is performed by moving the determined movement (drive) direction by the drive amount determined by the focus lens drive amount calculation unit 63.
The Lab converter 8 outputs the luminance signal output from the luminance signal acquisition imaging unit 40, the first color signal output from the first color signal acquisition imaging unit 41, and the second color signal acquisition imaging unit 42. The luminance signal output from the luminance signal acquisition imaging unit 40 is converted into an L component signal in the Lab color space (the luminance signal may be used as it is as an L component signal). Then, the Lab conversion unit 8 converts the first color signal output from the first color signal acquisition imaging unit 41 into an a component signal in the Lab color space, and is output from the second color signal acquisition imaging unit 42. The second color signal is converted into a b component signal in the Lab color space. Alternatively, the first color signal output from the first color signal acquisition imaging unit 41 and the second color signal output from the second color signal acquisition imaging unit 42 are combined, and then the a component signal and the b component signal are combined. May be converted to The Lab conversion unit 8 outputs the L component signal, the a component signal, and the b component signal to the captured image data generation unit 9.

The captured image data generation unit 9 receives the L component signal, the a component signal, and the b component signal output from the Lab conversion unit 8, and synthesizes the L component signal, the a component signal, and the b component signal to obtain captured image data. Is generated. The imaging device 100 stores the captured image data generated by the captured image data generation unit 9 in a storage unit (not shown) of the imaging device 100. In addition, the imaging device 100 displays the captured image data generated by the captured image data generation unit 9 on a display unit (not shown) of the imaging device 100.
<1.2: Operation of Imaging Device>
Hereinafter, the operation of the imaging apparatus 100 configured as described above will be described.
Light from the subject is collected by the condenser lens 1, passes through the focus lens 2, and enters the light separation unit 3. Here, as shown in FIG. 2, the light separation unit 3 will be described below as being composed of a prism 3a, a prism 3b, and a prism 3c.

As shown in FIG. 2, the light that has passed through the focus lens 2 is guided upward to the second color signal acquisition imaging unit 42 by the prism 3 a with its optical path bent upward. Further, the light transmitted through the joint surface of the prism 3a and the prism 3b by the prism 3b is bent downward and guided to the first color signal acquisition imaging unit 41. Further, the light transmitted through the joint surface between the prism 3b and the prism 3c is guided to the luminance signal acquisition imaging unit 40 by the prism 3c.
The center point (point perpendicular to the optical axis) of the image pickup device surface of the image pickup device of each image pickup unit (point D in FIG. 2) with reference to point B, which is the point where the joint surface of the prism 3a and prism 3b intersects the optical axis , F point and G point) have the following relationship.
That is, the distance from the point B to the point G (the optical optical path length from the point B to the image sensor of the first color signal acquisition imaging unit 41) is L1 + C1, and the distance from the point B to the point D (from the point B to the first point). The optical optical path length from the image pickup unit 42 for acquiring the two-color signal to the image pickup device is C2 + C3, and the distance from the point B to the point F (the optical optical path from the point B to the image pickup device of the image pickup unit 40 for obtaining the luminance signal) Since the length) is L1 + L2, the sizes and shapes of the prisms 3a, 3b and 3c constituting the light separating unit (prism) 3 are determined so that these optical optical path lengths have the following relationship.

L1 + C1> L1 + L2> C2 + C3
Or L1 + C1 <L1 + L2 <C2 + C3
As described above, the relationship between the optical optical path lengths is the optical up to the image sensor of the two color signal acquisition imaging units (the first color signal acquisition imaging unit 41 and the second color signal acquisition imaging unit 42). As long as the optical path length satisfies the condition for sandwiching the optical optical path length to the image sensor of the luminance signal acquisition imaging unit 40, the positional relationship between the image sensors is limited to the position shown in FIG. Needless to say, other combinations may be used. Further, the configuration of the light separating section (prism) 3 that separates the light from the photographic lens system LEN into three is not limited to the configuration shown in FIG.

The three lights separated by the light separation unit 3 are respectively converted into luminance signals by the luminance signal acquisition imaging unit 40, to the first color signal by the first color signal acquisition imaging unit 41, and to the second color signal acquisition imaging. The unit 42 converts it into the second color signal.
The luminance signal is input to the luminance contrast detection unit 50, and the luminance contrast detection unit 50 detects the luminance contrast value that is the contrast value of the luminance signal.
The first color signal is input to the first color contrast detection unit 51, and the first color contrast detection unit 51 detects the first color contrast value that is the contrast value of the first color signal.
The second color signal is input to the second color contrast detection unit 52, and the second color contrast detection unit 52 detects the first color contrast value which is the contrast value of the second color signal.

Here, as a method for detecting the contrast value, for example, the contrast value is obtained by integrating the signal value acquired from a certain number of pixels (pixels existing in a certain region) on the imaging surface of the imaging element of each imaging unit. The value can be detected.
The first color contrast value is added to the first offset value by the first color adder 61 and output to the focus lens drive amount calculation unit 63 as the corrected first color contrast value.
The second color contrast value is added to the second offset value by the second color adder 62 and output to the focus lens drive amount calculation unit 63 as the corrected second color contrast value.
Further, the luminance contrast value is output to the focus lens drive amount calculation unit 63.
(1.2.1: About the first offset value and the second offset value)
Here, the first offset value and the second offset value will be described.

FIG. 3 is a graph showing the relationship between the position in the optical axis direction and the contrast value.
4 to 6, the positional relationship between the imaging lens of each imaging unit (the luminance signal acquisition imaging unit 40, the first color signal acquisition imaging unit 41, and the second color signal acquisition imaging unit 42) and the focus lens 2. The schematic diagram which showed was shown. 4 to 6 show the optical path to be bent as a straight line and display it for convenience so that the optical path length and the positional relationship between the imaging element of each imaging unit and the focus lens 2 can be easily compared. . Then, the optical axis direction is set as shown in FIGS.
FIG. 3 shows the relationship between the position in the optical axis direction and the contrast value when the positional relationship between the imaging units 40, 41 and 42 and the focus lens 2 is in the state shown in FIG.
3A to 3C are graphs in which the horizontal axis represents the position on the optical axis and the vertical axis represents the contrast value. FIG. 3A is a graph showing the relationship between the contrast value (first color contrast value) by the second color signal acquisition imaging unit 42 and the optical axis position. FIG. 3B is a graph showing the relationship between the contrast value (luminance contrast value) by the luminance signal acquisition imaging unit 40 and the position on the optical axis. FIG. 3C is a graph showing the relationship between the contrast value (first color contrast value) by the first color signal acquisition imaging unit 41 and the position on the optical axis.

Further, the optical axis is assumed to be as shown in FIGS. 4 to 6, and in the imaging apparatus 100, the position on the imaging surface of the imaging element of the imaging unit 40 for obtaining the luminance signal is the focal point on the optical axis. As the origin of, the following will be described. For convenience of explanation, as shown in FIG. 4, the position on the optical axis of the imaging surface of the imaging element of the second color signal acquisition imaging unit 42 is “−α” (α is a positive number), The following description will be made assuming that the position on the optical axis of the imaging surface of the imaging element of the first color signal acquisition imaging unit 41 is “β” (β is a positive number). That is, the relationship of the optical path length is L1 + C1> L1 + L2> C2 + C3
And
(L1 + C1) − (L1 + L2) = β
(L1 + L2)-(C2 + C3) = α
This will be described below.

The solid line in FIG. 3A indicates the contrast value (for the first color) acquired by the second color signal acquisition imaging unit 42 when the focus lens 2 is moved and the focal position (focus point) is moved in the optical axis direction. An example of a change (contrast value) of (contrast value) is shown.
The solid line in FIG. 3B indicates the contrast value (luminance contrast value) acquired by the luminance signal acquisition imaging unit 40 when the focus lens 2 is moved and the focal position (focusing point) is moved in the optical axis direction. An example of changes (characteristics) is shown.
The solid line in FIG. 3C indicates the contrast value (for the first color) acquired by the first color signal acquisition imaging unit 41 when the focus lens 2 is moved and the focal position (focus point) is moved in the optical axis direction. An example of a change (contrast value) of (contrast value) is shown.
As can be seen from FIG. 3, since no color filter is provided on the imaging surface of the imaging device of the luminance signal acquisition imaging unit 40, the contrast value is high. On the other hand, since the color filters are respectively provided on the imaging surfaces of the imaging elements of the first color signal acquisition imaging unit 41 and the second color signal acquisition imaging unit 42, the first color signal acquisition imaging unit 41 Contrast value (the maximum value is the contrast value at point B, and the contrast value at point B corresponds to the contrast value when the imaging surface of the imaging element of the first color signal acquisition imaging unit 41 is located at the focal point) Is a value lower than the contrast value acquired by the luminance signal acquisition imaging unit 40. Further, since the first color signal acquisition imaging unit 41 is located farther on the optical axis than the second color signal acquisition imaging unit 42, the contrast acquired by the first color signal acquisition imaging unit 41. The value is the contrast value of the second color signal acquisition imaging unit 42 (the maximum value is the contrast value of the C point, and the contrast value of the C point is the imaging surface of the imaging element of the second color signal acquisition imaging unit 42). This corresponds to the contrast value in the case of being located at the focal point.)

Therefore, as shown in FIG. 3, the difference between the contrast value at point A and the contrast value at point C is obtained, and that value is set as the second offset value, and the difference between the contrast value at point A and the contrast value at point B is calculated. And the value is obtained as the first offset value.
For example, when the imaging apparatus 100 is manufactured (or after manufacture), the first offset value and the second offset value are the maximum contrast values (a contrast value at point A in FIG. (The contrast value of the point and the contrast value of the point C) are calculated, and the above-described calculation (calculation for calculating a difference) is performed on the calculated maximum value. Then, the calculated first offset value and second offset value together with the maximum value of each contrast value (contrast value at point A, contrast value at point B and contrast value at point C in FIG. 3), for example, an imaging device The data is stored in a storage device (not shown) such as 100 ROM. Note that data of the first offset value, the second offset value, the maximum value of each contrast value, and other feature points (feature points that determine the position-contrast value characteristics on the optical axis) are stored in the ROM of the imaging apparatus 100, etc. You may make it memorize | store in a memory | storage device (not shown). By doing in this way, each image pick-up part is influenced by the light amount loss difference by the light separation part (prism) 3, the solid difference of the image pick-up element, the presence of the color filter that is the difference between the image pick-up element for luminance and the color image pick-up element, and the like. Variations in acquired contrast values can be absorbed.

Note that the first offset value and the second offset value are obtained as the maximum values of the respective contrast values (the contrast value at point A, the contrast value at point B, and the contrast value at point C in FIG. 3) when the imaging apparatus 100 is used. You may do it.
The corrected first color contrast value and the corrected second color contrast value, which are contrast values obtained by adding (setting) the first offset value and the second offset value obtained as described above, are the focus lens. This is input to the drive amount calculation unit 63.
The focus lens drive amount calculation unit 63 then moves and moves the focus lens 2 on the optical axis based on the luminance contrast value, the corrected first color contrast value, and the corrected second color contrast value ( Driving amount) is determined.
(1.2.2: How to determine the direction and amount of movement of the focus lens)
Next, a method for determining the movement direction and the movement amount (drive amount) of the focus lens 2 on the optical axis in the focus lens drive amount calculation unit 63 will be described.

FIG. 7 illustrates the relationship between the position on the optical axis in a so-called front focus state in which the focus position is in the front in the optical axis direction and the contrast value acquired by each imaging unit in the imaging apparatus 100. That is, the relationship between the position on the optical axis in the state of FIG. 5 and the contrast value acquired by each imaging unit is shown. 7A shows the relationship between the position on the optical axis and the contrast value for the second color signal acquisition imaging unit 42, and FIG. 7B shows the luminance signal acquisition imaging unit 40. FIG. 7C shows the relationship between the position on the optical axis and the contrast value for the first color signal acquisition imaging unit 41. FIG. is there.
FIG. 8 shows the relationship between the position on the optical axis in the so-called rear focus state and the contrast value acquired by each imaging unit, where the focus position is rearward in the optical axis direction in the imaging apparatus 100. That is, the relationship between the position on the optical axis in the state of FIG. 6 and the contrast value acquired by each imaging unit is shown. 8A shows the relationship between the position on the optical axis and the contrast value for the second color signal acquisition imaging unit 42, and FIG. 8B shows the luminance signal acquisition imaging unit 40. 8C shows the relationship between the position on the optical axis and the contrast value, and FIG. 8C shows the relationship between the position on the optical axis and the contrast value for the first color signal acquisition imaging unit 41. is there.

≪In the case of the front pin state≫
First, the case of the front pin state in FIG. 7 will be described.
In this case, as shown in FIG. 7A, the imaging surface of the imaging device of the imaging unit 42 for acquiring the second color signal is located at the position “−α” on the optical axis. The contrast value (second color contrast value) acquired by the acquisition imaging unit 42 is a value corresponding to the point C (this value is expressed as “C”). The corrected second color contrast value is C + (second offset value).
Further, as shown in FIG. 7B, the imaging surface of the imaging element of the luminance signal acquisition imaging unit 40 is located at the position “0” on the optical axis. The acquired contrast value (luminance contrast value) is a value corresponding to point A (this value will be expressed as “A”).
It is.

Further, as shown in FIG. 7C, the image pickup surface of the image pickup element of the first color signal acquisition image pickup unit 41 is located at the position “+ β” on the optical axis. The contrast value (first color contrast value) acquired by the imaging unit 41 is a value corresponding to the point B (this value is expressed as “B”). The corrected first color contrast value is B + (first offset value).
in this case,
C + (second offset value)>A> B + (first offset value) (Formula 1)
Therefore, it can be seen that the focal position (focusing point) of the imaging apparatus 100 exists near the second color signal acquisition imaging unit 42. Then, since the second color signal acquisition imaging unit 42 is known in advance that the position on the optical axis is ahead of the luminance signal acquisition imaging unit 40, as shown in FIG. It can be seen that it is only necessary to move in the (+) direction (positive direction).

That is, if it is known that the relationship of (Expression 1) is established, the moving direction of the focus lens 2 can be determined. This determination process is executed by the focus lens driving amount calculation unit 63.
When the focus lens 2 is moved in the movement direction determined by the focus lens drive amount calculation unit, the value (output) of the contrast value (luminance contrast value) by the luminance signal acquisition imaging unit 40 increases, and FIG. The curve indicating the characteristics of the contrast value (curve) moves to the right in FIG.
Here, the focus lens drive amount determination unit 6 monitors the value (output) of the contrast value C (or the corrected second color contrast value) of the second color signal acquisition imaging unit 42 to acquire the luminance signal. It can be confirmed that the contrast value C of the second color signal acquisition imaging unit 42 reaches the maximum value and further decreases before the contrast value A (output) of the imaging unit 40 reaches the maximum. .

  At this point, the in-focus position (in-focus) in the second color signal acquisition imaging unit 42 has been confirmed. In the imaging apparatus 100, it is known in advance that the luminance signal acquisition imaging unit 40 and the second color signal acquisition imaging unit 42 are arranged with a predetermined optical optical path length shifted. Therefore, in the imaging apparatus 100, how much the focus lens 2 is driven from the in-focus position in the second color signal acquisition imaging unit 42 to focus on the imaging surface of the imaging element of the luminance signal acquisition imaging unit 40. Therefore, it is possible to easily calculate, and it is possible to immediately drive to the optimum focus position. In the imaging apparatus 100, the second offset value is added to the contrast value (luminance contrast value) by the luminance signal acquisition imaging unit 40 and the contrast value C of the in-focus position in the second color signal acquisition imaging unit 42. By comparing the values, it is possible to determine whether or not the imaging surface of the imaging element of the luminance signal acquisition imaging unit 40 is correctly focused.

Furthermore, in the imaging apparatus 100, the value obtained by adding the first offset value to the contrast value (first color contrast value) B of the in-focus position of the imaging surface of the imaging device of the first color signal acquisition imaging unit and the luminance contrast. By adding a process of comparing the value, it is possible to determine whether or not the imaging surface of the imaging element of the luminance signal acquisition imaging unit 40 is in focus more accurately.
≪For rear pin state≫
Next, the case of the rear pin state in FIG. 8 will be described.
In this case, as shown in FIG. 8A, the imaging surface of the imaging element of the imaging unit 42 for acquiring the second color signal is located at the position “−α” on the optical axis. The contrast value (second color contrast value) acquired by the acquisition imaging unit 42 is a value corresponding to the point C (this value is expressed as “C”). The corrected second color contrast value is C + (second offset value).

Further, as shown in FIG. 8B, the imaging surface of the imaging element of the luminance signal acquisition imaging unit 40 is located at the position “0” on the optical axis. The acquired contrast value (brightness contrast value) is a value corresponding to point A (this value will be expressed as “A”).
Further, as shown in FIG. 8C, the image pickup surface of the image pickup element of the first color signal acquisition image pickup unit 41 is located at the position “+ β” on the optical axis. The contrast value (first color contrast value) acquired by the imaging unit 41 is a value corresponding to the point B (this value is expressed as “B”). The corrected first color contrast value is B + (first offset value).

in this case,
C + (second offset value) <A <B + (first offset value) (Formula 2)
Therefore, it can be seen that the focal position (focusing point) of the imaging apparatus 100 exists near the first color signal acquisition imaging unit 41. Since the first color signal acquisition imaging unit 41 knows in advance that the position on the optical axis is behind the luminance signal acquisition imaging unit 40, as shown in FIG. It can be seen that the movement in the (−) direction (negative direction) is sufficient.
That is, if it is known that the relationship of (Expression 2) is established, the moving direction of the focus lens 2 can be determined. This determination process is executed by the focus lens driving amount calculation unit 63.
When the focus lens 2 is moved in the movement direction determined by the focus lens drive amount calculation unit, the value (output) of the contrast value (luminance contrast value) by the luminance signal acquisition imaging unit 40 increases, and FIG. The curve indicating the characteristics of the contrast value (curve) moves to the left in FIG.

Here, the focus lens drive amount determination unit 6 monitors the value (output) of the contrast value B of the first color signal acquisition imaging unit 41 (or the corrected first color contrast value), thereby acquiring the luminance signal. It can be confirmed that the contrast value B of the first color signal acquisition imaging unit 41 reaches the maximum value and further decreases before the contrast value A (output) of the imaging unit 40 reaches the maximum. .
At this point, the in-focus position (in-focus point) in the first color signal acquisition imaging unit 41 has been confirmed. In the imaging apparatus 100, it is known in advance that the luminance signal acquisition imaging unit 40 and the first color signal acquisition imaging unit 41 are arranged with a predetermined optical optical path length shifted. Therefore, in the imaging apparatus 100, how much the focus lens 2 is driven from the in-focus position in the first color signal acquisition imaging unit 41 to focus on the imaging surface of the imaging element of the luminance signal acquisition imaging unit 40. Therefore, it is possible to easily calculate, and it is possible to immediately drive to the optimum focus position. In the imaging apparatus 100, the first offset value is added to the contrast value (luminance contrast value) obtained by the luminance signal acquisition imaging unit 40 and the contrast value B of the in-focus position in the first color signal acquisition imaging unit 41. By comparing the values, it is possible to determine whether or not the imaging surface of the imaging element of the luminance signal acquisition imaging unit 40 is correctly focused.

Furthermore, in the imaging apparatus 100, the value obtained by adding the second offset value to the contrast value (contrast value for second color) C of the focusing position of the imaging surface of the imaging element of the imaging unit for obtaining the second color signal and the contrast for luminance. By adding a process of comparing the value, it is possible to determine whether or not the imaging surface of the imaging element of the luminance signal acquisition imaging unit 40 is in focus more accurately.
In the imaging apparatus 100, if the moving direction (driving direction) of the focus lens 2 is detected, it can be determined to which direction the focus lens 2 is moved, so that the contrast peak is once passed as in the conventional video AF method. Thus, it is unnecessary to reverse the focus lens after confirming that the contrast value decreases.
As described above, the focus lens drive amount determination unit 6 determines whether the relationship of (Equation 1) or (Equation 2) is satisfied. 2 can be accurately determined, and the imaging apparatus 100 can realize a high-speed and high-precision autofocus function.

(1.2.3: Lab conversion)
In the imaging device 100, the luminance signal acquired by the luminance signal acquisition imaging unit 40, the first color signal acquired by the first color signal acquisition imaging unit 41, and the second color signal acquisition imaging unit 42 are acquired. The second color signal is input to the Lab converter 8.
The Lab converter 8 generates an L component signal in the Lab color space from the luminance signal acquired by the luminance signal acquisition imaging unit 40. In the imaging apparatus 100, when realizing the autofocus function, focus control is performed so that the imaging surface of the imaging element of the luminance signal acquisition imaging unit 40 is in focus. That is, the luminance signal acquired by the luminance signal acquisition imaging unit 40 is a focused and accurate luminance signal. Further, since no color filter is provided on the imaging surface of the imaging element of the luminance signal acquisition imaging unit 40, the L component signal acquired by the Lab conversion unit is a highly accurate signal (high contrast, high S / N ratio signal).

  Further, the Lab conversion unit 8 generates an a component signal and a b component signal in the Lab color space from the first color signal and the second color signal. Here, since the a component signal and the b component are signals having only color information, high visual accuracy is not required. Since the imaging apparatus 100 performs focus control so as to focus on the imaging surface of the imaging device of the luminance signal acquisition imaging unit 40, the first color signal acquisition imaging unit 41 and the second color signal acquisition imaging unit 42 The imaging surface of the imaging element exists at a position different from the focal point. Therefore, the color signals acquired by the first color signal acquisition imaging unit 41 and the second color signal acquisition imaging unit 42 are not in focus. In addition, since color filters are installed on the imaging surfaces of the imaging elements of the first color signal acquisition imaging unit 41 and the second color signal acquisition imaging unit 42, there is a light loss, so that the acquired color signal The amount of deterioration has occurred. However, since the sensitivity to human color information is considerably lower than that of luminance information, it is possible to synthesize a color image (video) at a level where there is no problem even if a color signal that is not completely in focus is used. is there. Alternatively, the first color signal output from the first color signal acquisition imaging unit 41 and the second color signal output from the second color signal acquisition imaging unit 42 are combined, and then the a component signal and the b component signal are combined. May be converted to

The L component signal, the a component signal, and the b component signal generated by the Lab conversion unit 8 are input to the captured image data generation unit 9. The captured image data generation unit 9 generates captured image data from the L component signal, the a component signal, and the b component signal. The captured image data generated by the captured image data generation unit 9 is generated by combining the high-accuracy L component signal and the a component signal and the b component signal, which are color signals that are slightly less accurate, as described above. Therefore, the composite image is sufficiently accurate.
<1.3: Arrangement of image pickup element of each image pickup unit in image pickup apparatus>
In order to accurately detect the moving direction (drive direction) of the focus lens 2 in the imaging apparatus 100, the imaging element of the first color signal acquisition imaging unit 41, the imaging element of the second color signal acquisition imaging unit, and It is necessary to arrange the optical distances of the imaging elements of the imaging unit for obtaining the luminance signal in an optimal relationship.

This will be described by taking a video camera optical system as an example.
In an optical system of a video camera, the F number is generally set to a relatively bright value. The optical system of the video camera is designed with an F number of F = 1.8 on the wide angle side and F = 2.8 on the telephoto side.
Assuming that the pixel size of the image sensor used in the video optical system (the length of one side of the image sensor, that is, the pixel pitch) is 5 [μm], the allowable minimum circle of confusion δ is 10 [μm]. ].
Next, as the contrast value detection capability, the blur amount of the subject (the diameter of the circle of confusion) can be set to 100 [μm].
The definition of the depth of field 1Fδ is as follows.

Wide angle side: 1Fδ = 1.8 × 10 = 18 [μm]
Telephoto side: 1Fδ = 2.8 × 10 = 28 [μm]
The blur amount of 100 [μm] that can be detected by contrast is 10 times δ = 10 [μm].
Wide angle side: 18 × 10 = 180 [μm] = 10 Fδ
Telephoto side: 28 × 10 = 280 [μm] = 10Fδ
It becomes.
However, in the imaging device 100, the color signals acquired by the first color signal acquisition imaging unit 41 and the second color signal acquisition imaging unit 42 are also used as color information of the captured image data. For this reason, if the imaging elements of the first color signal acquisition imaging unit 41 and the second color signal acquisition imaging unit 42 are arranged at a distance of 10Fδ from the imaging element of the luminance signal acquisition imaging unit 40, Lab synthesis is performed. Only image data with blurred colors can be acquired.

Therefore, if the allowable blur amount causing no problem in image formation (generation of captured image data) is set to be twice the allowable circle of confusion,
(Bokeh amount) = 10 × 2 = 20 [μm] = 2Fδ
It becomes.
Accordingly, the image pickup elements of the first color signal acquisition image pickup unit and the second color signal acquisition image pickup unit have an optical distance of about 20 [μm] = 2Fδ before and after the optical signal of the luminance signal acquisition image pickup unit 40 (light It is only necessary to displace them in the axial direction.
≪About detection limit of focus lens movement direction≫
Next, the detection limit of the focus lens moving direction will be described with reference to FIGS.

9 and 10 illustrate the above description.
FIG. 9 shows the case where the focus lens 2 is set at a position where the contrast peak comes to the imaging surface of the imaging device of the luminance signal acquisition imaging unit 40 (the imaging surface of the imaging device of the luminance signal acquisition imaging unit 40 is in focus). Case). FIG. 9A shows the relationship between the position on the optical axis and the contrast value for the corrected second color, and FIG. 9B shows the relationship between the position on the optical axis and the contrast value for luminance. FIG. 9C shows the relationship between the position on the optical axis and the contrast value for the corrected first color.
FIG. 10 shows a state where the focal point of the imaging apparatus 100 is deviated from the position (position on the optical axis) of the imaging surface of the imaging element of the luminance signal acquisition imaging unit 40. FIG. 10A shows the relationship between the position on the optical axis and the corrected second color contrast value, and FIG. 10B shows the relationship between the position on the optical axis and the contrast value for luminance. FIG. 10C shows the relationship between the position on the optical axis and the contrast value for the corrected first color.

In FIG. 10, the contrast value (corrected second color contrast value) by the second color signal acquisition imaging unit 42 and the contrast value (luminance contrast value) by the luminance signal acquisition imaging unit 40 are the detection limit values of the contrast value. (Contrast value when the position on the optical axis in FIG. 9 is ± 10 Fδ) or less, and it is not possible to determine the moving direction of the focus lens with these alone.
However, the contrast value (corrected first color contrast value) by the first color signal acquisition imaging unit is larger than the detection limit value of the contrast value.
Therefore, it can be detected that the contrast peak is shifted in the right direction in FIG. 10, and the direction in which the focus lens 2 should be driven (moved) can be determined in the imaging apparatus 100.

That is, the detection limit amount in the focus lens moving direction in the imaging apparatus 100 is
10Fδ + 2Fδ = 12Fδ
It becomes. That is, if the focal point from the imaging surface of the imaging device of the luminance signal acquisition imaging unit 40 is equal to or less than the deviation amount corresponding to 12Fδ on the optical axis, the focus lens moving direction can be determined in the imaging device 100. it can.
Therefore, if the contrast detection capability of the imaging apparatus 100 is high, 10Fδ in the above case can be set to a larger value, and the range in which the focus lens moving direction can be determined in the imaging apparatus 100 is widened.
Next, it is calculated how far the focal length can detect (determine) the focus lens movement direction in the entire focus range.

For example, the focal length of the photographic lens used is f5 mm / F2.8 (focal length is 5 [mm] when the F number is 2.8) to f50 mm / F2.8 (focal length is when the F number is 2.8). 50 [mm]), and when the closest possible photographing distance is 100 [mm], from the infinity at f5 mm (wide angle) to the closest defocus amount (from the in-focus point to the point where the light spreads from the allowable minimum circle of confusion) The distance) is about 0.3 [mm].
Since the F number is 2.8, when δ (the diameter of the allowable minimum circle of confusion) is set to 10 [μm], when converted to Fδ,
0.3 [mm] / (2.8 × 10) [μm] = 1.1 Fδ
Similarly, at f50 mm (telephoto), the defocus amount from infinity to the closest distance is about 50 [mm]. When converted to Fδ,
50 [mm] / (2.8 × 10) [μm] = 179Fδ
Back-calculating the focal length that can correspond to 12Fδ,
12 × (2.8 × 10) = 3.36 [mm]
∴f = 16.7 [mm]
It becomes.

Therefore, in the imaging apparatus 100, it is possible to immediately detect (determine) the focus lens movement direction at a focal length of 16.7 [mm] from the wide angle, and a quick focusing operation can be performed.
In addition, when both the digital camera and the digital video camera are supplied with camera power, the zoom is usually set to the wide angle side. In the imaging apparatus 100 that satisfies the above conditions, it is possible to immediately detect (determine) the focus lens movement direction from the above result, and to move the focus lens 2 near the in-focus position. That is, in the imaging apparatus 100, since the focus lens 2 is already in the vicinity of the in-focus point on the telephoto side, it is rare that a blur amount of 179Fδ is generated as in the above calculation, and the focus is immediately on the telephoto side. The probability that the lens moving direction can be detected (determined) is very high.

As described above, the imaging apparatus 100 can realize a high-precision and high-speed autofocus function without blurring an acquired image (video).
[Other Embodiments]
In the above-described embodiment, the imaging device of the luminance signal acquisition imaging unit 40, the imaging device of the first color signal acquisition imaging unit 41, and the imaging device of the first color signal acquisition imaging unit 41 are imaging devices having the same specifications ( That is, the description is based on the assumption that the number of pixels, the size, etc. are the same.) However, the present invention is not limited to this. For example, the number of pixels is determined by the number of pixels of the image sensor of the imaging unit 40 for acquiring luminance signals. You may make it use an image pick-up element with few numbers as an image pick-up element of the image pick-up part 41 for the 1st color signal acquisition, and the image pick-up element 41 for the 1st color signal acquisition. As described above, since the sensitivity on the human visual characteristic with respect to the color information is lower than that of the luminance information, an image (video) that does not cause any problem even if the specifications of the image sensor of the color signal acquisition imaging unit are reduced in this way. ) Can be acquired in the imaging apparatus. Thereby, there is an effect that the cost of the imaging apparatus can be reduced.

Further, the pixel size of the image sensor of the color signal acquisition imaging unit is larger than the pixel size of the image sensor of the luminance signal acquisition image capturing unit 40 (or the pixel of the image sensor of the luminance signal acquisition image capturing unit 40 The color signal may be acquired by a plurality of pixels having the same size as the above. Thereby, although the resolution of the color signal is lowered, the light loss in the color filter can be compensated, and the shortage of the charge amount at the time of detecting the contrast can be compensated.
In the imaging device described in the above embodiment, each block may be individually made into one chip by a semiconductor device such as an LSI, or may be made into one chip so as to include a part or the whole.
Note that the name used here is LSI, but it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

Further, the method of circuit integration is not limited to LSI, and implementation with a dedicated circuit or a general-purpose processor is also possible. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.
Further, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. Biotechnology can be applied as a possibility.
Moreover, each process of the said embodiment may be implement | achieved by hardware, and may be implement | achieved by software. Further, it may be realized by mixed processing of software and hardware.

  The specific configuration of the present invention is not limited to the above-described embodiment, and various changes and modifications can be made without departing from the scope of the invention.

  The imaging apparatus, focus control method, program, and integrated circuit according to the present invention can provide a high-precision and high-speed autofocus function. For this reason, the imaging apparatus, focus control method, program, and integrated circuit according to the present invention not only shorten the release time lag of a compact digital camera that uses a conventional autofocus function, but also speed up matching in a digital video camera. Enables singing.

1 is a schematic configuration diagram of an imaging apparatus 100 according to a first embodiment of the present invention. The imaging lens system LEN, the light separation unit 3, the luminance signal acquisition imaging unit 40, the first color signal acquisition imaging unit 41, and the second color signal acquisition of the imaging apparatus 100 according to the first embodiment of the present invention. Imaging unit 42 and schematic configuration diagram The figure which shows the relationship between the contrast value acquired from each imaging part of the imaging device 100 which concerns on 1st Embodiment of this invention, and the position on an optical axis. The figure which shows the positional relationship on the optical axis of each imaging part and the focus lens 2 in the focus state of the imaging device 100 which concerns on 1st Embodiment of this invention. The figure which shows the positional relationship on the optical axis of each imaging part and focus lens 2 in the front pin state of the imaging device 100 which concerns on 1st Embodiment of this invention. The figure which shows the positional relationship on the optical axis of each imaging part and focus lens 2 in the back pin state of the imaging device 100 which concerns on 1st Embodiment of this invention. The figure which shows the relationship between the contrast value acquired from each imaging part in the front pin state of the imaging device 100 which concerns on 1st Embodiment of this invention, and the position on an optical axis. The figure which shows the relationship between the contrast value acquired from each imaging part in the back pin state of the imaging device 100 which concerns on 1st Embodiment of this invention, and the position on an optical axis. The figure for demonstrating the detection limit of the contrast value of the imaging device 100 which concerns on 1st Embodiment of this invention. The figure for demonstrating the detection limit of the contrast value of the imaging device 100 which concerns on 1st Embodiment of this invention.

Claims (14)

A condenser lens that collects light from the subject;
A focus lens for adjusting the focus position of the light collected by the condenser lens;
A light separation unit that separates light that has passed through the focus lens into at least three paths;
A first color imaging device disposed at a position where the distance from the condenser lens is the first optical path length, and the light separated by the light separation unit is obtained as a first color signal by photoelectric conversion; A first color signal acquisition imaging unit;
For luminance signal acquisition, having a luminance imaging device disposed at a position where the distance from the condenser lens is the second optical path length, and acquiring light separated by the light separation unit as a luminance signal by photoelectric conversion An imaging unit;
A second color imaging device disposed at a position where the distance from the condenser lens is the third optical path length, and the light separated by the light separation unit is obtained as a second color signal by photoelectric conversion; A second color signal acquisition imaging unit;
A first color contrast value corresponding to a contrast value of light incident on the first color image sensor is obtained from the first color signal acquired by the first color signal acquisition imaging unit, and the luminance signal is acquired. A brightness contrast value corresponding to a contrast value of light incident on the brightness image sensor is obtained from the brightness signal acquired by the image capturing section, and the second color signal acquired by the second color signal acquiring image capturing section is obtained. A second color contrast value corresponding to a contrast value of light incident on the second color image sensor is obtained from a color signal, and the first color contrast value, the luminance contrast value, and the second color light contrast are obtained. A focus control unit that adjusts the position of the focus lens based on a value;
An imaging apparatus comprising: The focus control unit adjusts a position of the focus lens so that the luminance contrast value becomes a peak value;
The imaging device according to claim 1. The first color signal acquisition imaging unit includes a first color filter installed on the imaging element surface of the first color imaging element,
The second color signal acquisition imaging unit includes a second color filter installed on the imaging element surface of the second color imaging element,
The luminance signal acquisition imaging unit includes the luminance signal imaging element in which a color filter is not installed on the imaging element surface.
The imaging device according to claim 1 or 2. In the first color image sensor, the luminance image sensor, and the second color image sensor, the first optical path length is LC1, the second optical path length is LY, and the third optical path length is set. Is LC2,
LC1 <LY <LC2
Or LC2 <LY <LC1
Are arranged at positions that satisfy the relationship of
The imaging device according to claim 1. The luminance imaging device has a first number of pixels,
In the first color image sensor, the number of pixels is a second number equal to or less than the first number,
In the second color image sensor, the number of pixels is a third number equal to or less than the first number.
The imaging device according to claim 1. The focus control unit
A first color contrast detection unit for detecting the first color contrast value;
A luminance contrast detection unit for detecting the luminance contrast value;
A second color contrast detection unit for detecting the second color contrast value;
A focus lens drive amount determination unit that determines a drive amount for driving the focus lens and a drive direction of the focus lens based on the contrast value for the first color, the contrast value for luminance, and the contrast value for the second color light; ,
A focus lens driving unit that drives the focus lens in the driving direction based on the driving amount;
Having
The imaging device according to claim 1. The focus lens driving amount determination unit includes a corrected first color contrast value obtained by adding a first offset value to the first color contrast value, and a corrected first color value obtained by adding a second offset value to the second color contrast value. Determining a drive amount for driving the focus lens and a drive direction of the focus lens based on the contrast value for two colors and the contrast value for luminance;
The imaging device according to claim 6. In the case where the condenser lens collects light from the same subject,
The first offset value and the first contrast value so that the maximum value of the corrected first color contrast value, the maximum value of the corrected second color contrast value, and the luminance contrast value are substantially the same value. 2 Offset value is set,
The imaging device according to claim 7. The first color signal, the second color signal, and the luminance signal are subjected to Lab conversion, so that the a component signal and the b component signal from the first color signal and the second color signal are converted into the luminance signal. Lab component for generating L component signals from
An image data generation unit that generates captured image data from the L component signal, the a component signal, and the b component signal;
Further comprising
The imaging device according to claim 1. The first-color image sensor and the second-color image sensor are arranged at positions within 1 to 4Fδ in the front and rear directions in the optical axis direction with respect to the optical distance from the condenser lens of the luminance image sensor.
The imaging device according to claim 1. A condenser lens that collects light from the subject;
A focus lens for adjusting the focus position of the light collected by the condenser lens;
A light separation unit that separates light that has passed through the focus lens into at least three paths;
A first color imaging device disposed at a position where the distance from the condenser lens is the first optical path length, and the light separated by the light separation unit is obtained as a first color signal by photoelectric conversion; A first color signal acquisition imaging unit;
For luminance signal acquisition, having a luminance imaging device disposed at a position where the distance from the condenser lens is the second optical path length, and acquiring light separated by the light separation unit as a luminance signal by photoelectric conversion An imaging unit;
A second color imaging device disposed at a position where the distance from the condenser lens is the third optical path length, and the light separated by the light separation unit is obtained as a second color signal by photoelectric conversion; A focus control method used in an imaging device including an imaging unit for acquiring a second color signal,
Obtaining a first color contrast value corresponding to a contrast value of light incident on the first color image sensor from the first color signal acquired by the first color signal acquisition imaging unit;
Obtaining a luminance contrast value corresponding to a contrast value of light incident on the luminance imaging element from the luminance signal acquired by the luminance signal acquisition imaging unit;
Obtaining a second color contrast value corresponding to a contrast value of light incident on the second color image sensor from the second color signal acquired by the second color signal acquisition imaging unit;
Adjusting the position of the focus lens based on the first color contrast value, the luminance contrast value, and the second color light contrast value;
Focus control method. A condenser lens that collects light from the subject;
A focus lens for adjusting the focus position of the light collected by the condenser lens;
A light separation unit that separates light that has passed through the focus lens into at least three paths;
A first color imaging device disposed at a position where the distance from the condenser lens is the first optical path length, and the light separated by the light separation unit is obtained as a first color signal by photoelectric conversion; A first color signal acquisition imaging unit;
For luminance signal acquisition, having a luminance imaging device disposed at a position where the distance from the condenser lens is the second optical path length, and acquiring light separated by the light separation unit as a luminance signal by photoelectric conversion An imaging unit;
A second color imaging device disposed at a position where the distance from the condenser lens is the third optical path length, and the light separated by the light separation unit is obtained as a second color signal by photoelectric conversion; A second color signal acquisition imaging unit, and a program used for an imaging apparatus comprising:
Obtaining a first color contrast value corresponding to a contrast value of light incident on the first color image sensor from the first color signal acquired by the first color signal acquisition imaging unit;
Obtaining a luminance contrast value corresponding to a contrast value of light incident on the luminance imaging element from the luminance signal acquired by the luminance signal acquisition imaging unit;
Obtaining a second color contrast value corresponding to a contrast value of light incident on the second color image sensor from the second color signal acquired by the second color signal acquisition imaging unit;
Adjusting the position of the focus lens based on the first color contrast value, the luminance contrast value, and the second color light contrast value;
A program that causes a computer to execute a focus control method. A condenser lens that collects light from the subject;
A focus lens for adjusting the focus position of the light collected by the condenser lens;
An integrated circuit used in an imaging apparatus comprising: a light separation unit that separates light that has passed through the focus lens into at least three paths;
A first color imaging device disposed at a position where the distance from the condenser lens is the first optical path length, and the light separated by the light separation unit is obtained as a first color signal by photoelectric conversion; A first color signal acquisition imaging unit;
For luminance signal acquisition, having a luminance imaging device disposed at a position where the distance from the condenser lens is the second optical path length, and acquiring light separated by the light separation unit as a luminance signal by photoelectric conversion An imaging unit;
A second color imaging device disposed at a position where the distance from the condenser lens is the third optical path length, and the light separated by the light separation unit is obtained as a second color signal by photoelectric conversion; A second color signal acquisition imaging unit;
A first color contrast value corresponding to a contrast value of light incident on the first color image sensor is obtained from the first color signal acquired by the first color signal acquisition imaging unit, and the luminance signal is acquired. A brightness contrast value corresponding to a contrast value of light incident on the brightness image sensor is obtained from the brightness signal acquired by the image capturing section, and the second color signal acquired by the second color signal acquiring image capturing section is obtained. A second color contrast value corresponding to a contrast value of light incident on the second color image sensor is obtained from a color signal, and the first color contrast value, the luminance contrast value, and the second color light contrast are obtained. A focus control unit that adjusts the position of the focus lens based on a value;
An integrated circuit comprising: A condenser lens that collects light from the subject;
A focus lens for adjusting the focus position of the light collected by the condenser lens;
A light separation unit that separates light that has passed through the focus lens into at least three paths;
A first color imaging device disposed at a position where the distance from the condenser lens is the first optical path length, and the light separated by the light separation unit is obtained as a first color signal by photoelectric conversion; A first color signal acquisition imaging unit;
For luminance signal acquisition, having a luminance imaging device disposed at a position where the distance from the condenser lens is the second optical path length, and acquiring light separated by the light separation unit as a luminance signal by photoelectric conversion An imaging unit;
A second color imaging device disposed at a position where the distance from the condenser lens is the third optical path length, and the light separated by the light separation unit is obtained as a second color signal by photoelectric conversion; An integrated circuit comprising a second color signal acquisition imaging unit,
A first color contrast value corresponding to a contrast value of light incident on the first color image sensor is obtained from the first color signal acquired by the first color signal acquisition imaging unit, and the luminance signal is acquired. A brightness contrast value corresponding to a contrast value of light incident on the brightness image sensor is obtained from the brightness signal acquired by the image capturing section, and the second color signal acquired by the second color signal acquiring image capturing section is obtained. A second color contrast value corresponding to a contrast value of light incident on the second color image sensor is obtained from a color signal, and the first color contrast value, the luminance contrast value, and the second color light contrast are obtained. A focus control unit for adjusting the position of the focus lens based on the value;
An integrated circuit comprising:

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