JPWO2008146458A1 - Imaging device with autofocus function, imaging method, program, and integrated circuit - Google Patents

Abstract

In the imaging device (100), the optical path separator (2) separates the light from the subject collected by the optical system (1) into at least a first light flux and a second light flux. The first imaging unit (3) driven by the first driving unit (21) converts the first light flux into an electrical signal and outputs it as a first signal. The second imaging unit (5) driven by the second driving unit (9) converts the second light flux into an electrical signal and outputs it as a second signal. The first signal processing unit (4) performs signal processing of the first signal to generate a video signal for photographing. The second signal processing unit (6) performs signal processing of the second signal. The evaluation value generation unit (8) generates an evaluation value of the contrast of the second signal. The autofocus control unit (11) controls the optical path length changing unit, detects the maximum contrast evaluation value optical path length that is the optical path length of the second light flux at which the contrast evaluation value of the second signal is maximized, and sets the maximum The focus control of the optical system (1) is performed based on the contrast evaluation value optical path length. [Selection] Figure 1

Description

  The present invention relates to an imaging apparatus such as a video camera, an imaging method, a program, and an integrated circuit. Specifically, the present invention relates to an imaging device with an autofocus function, an imaging method, a program, and an integrated circuit that automatically focus.

Conventionally, in an imaging apparatus such as a video camera, a contrast maximum position detection method using wobbling is generally used as an autofocus method. The contrast maximum position detection method is as follows. A wobbling operation that moves the focus lens back and forth is performed. The contrast of the acquired video signal (the contrast of the video formed from the video signal) is compared. Then, the focus lens is sequentially moved in the direction in which the contrast of the video signal is maximized. Thus, a position where the contrast of the video signal is maximized (maximum contrast position) is detected, and the maximum contrast position is determined as the in-focus position.
For example, Japanese Patent Application Laid-Open No. 10-4517 describes a video camera including a focus adjustment device that uses a maximum contrast position detection method and is further reduced in size, weight, and cost. The video camera is a multi-plate type using a color separation prism that separates a light beam incident from an optical system into three colors of R, G, and B. This publication discloses that the color separation prism has a configuration that does not require an air gap, thereby realizing a reduction in size, weight, and cost. The focus adjustment device of the publication has a configuration in which the color separation prism does not require an air gap, thus solving the problem that the influence of the blue signal, the red signal, and the green signal on the focus adjustment operation occurs due to the mirror image relationship. is doing. In the same focus adjustment device, the same problem is solved by selecting a video signal that is not a mirror image and using it for focus adjustment.
Japanese Patent Laid-Open No. 10-4517

(Problems to be solved by the invention)
In a contrast maximum position detection method used in a conventional imaging apparatus such as a video camera, the contrast of the acquired video signal is compared every time a video signal is acquired by a wobbling operation. In this method, it is necessary to sequentially move the focus lens in the direction in which the contrast of the video signal is maximized. However, when the focus is completely out of focus, the contrast of the video signal hardly changes due to the wobbling operation. Therefore, there is a problem that the in-focus direction cannot be determined when the focus is completely out of focus.
Further, in the conventional contrast maximum position detection method, when the autofocus operation is activated in the focused state, the wobbling operation is performed at the focused position. In this case, a phenomenon occurs in which the main line system, that is, the video signal for shooting (hereinafter referred to as “video signal for shooting”) is focused (focused) or slightly blurred (out of focus). Has the problem.

In the conventional maximum contrast position detection method, contrast is detected using a video signal for photographing. Therefore, one field period of the video signal for photographing is required to detect the contrast once. For this reason, when the frame rate of the video signal for photographing is lowered, the absolute time required for detecting the contrast for autofocus control becomes longer. As a result, the autofocus response speed becomes slow. Therefore, particularly when shooting a moving subject or the like, there is a problem that it is difficult to obtain a good image.
Further, the conventional maximum contrast position detection method requires a high-speed wobbling operation. However, when an interchangeable lens or the like is used in the imaging apparatus, the focus lens operates slowly. Therefore, it is difficult to realize a high-speed wobbling operation, and there is a problem that the autofocus operation becomes extremely slow.

The present invention solves the above-mentioned conventional problems, and an object thereof is to enable reliable and quick optical system focus control.
(Means for solving the problem)
An image pickup apparatus according to a first aspect of the present invention condenses light from a subject and can control a focus, an optical path separation unit, a first image pickup unit, a second image pickup unit, and a first image pickup unit. Imaging device comprising: a signal processing unit; a second signal processing unit; an evaluation value generating unit; a first driving unit; a second driving unit; an optical path length changing unit; and an autofocus control unit. It is. The optical path separation unit separates light from the subject collected by the optical system into at least a first light flux and a second light flux. The first imaging unit converts the first light flux into an electrical signal and outputs it as a first signal. The second imaging unit converts the second light flux into an electrical signal and outputs it as a second signal. The first signal processing unit performs signal processing of the first signal to generate a video signal for photographing. The second signal processing unit performs signal processing of the second signal. The evaluation value generation unit generates an evaluation value of the contrast of the second signal. The first driving unit drives the first imaging unit. The second drive unit drives the second imaging unit. The optical path length changing unit changes the optical path length of the second light flux. The autofocus control unit controls the optical path length changing unit, detects the maximum contrast evaluation value optical path length that is the optical path length of the second light flux that maximizes the contrast evaluation value of the second signal, and determines the maximum contrast evaluation value. Focus control of the optical system is performed based on the optical path length.

In this imaging apparatus, the light from the subject collected by the optical system is separated into at least a first light beam and a second light beam by the optical path separation unit. The first light beam is used for shooting video signal processing, and the second light beam is used for autofocus (AF) signal processing that is completely independent of the shooting video signal processing. In this imaging apparatus, the autofocus control unit controls the optical path length changing unit so as to change the optical path length of the second light flux based on the contrast evaluation value, and performs focus control of the optical system. That is, the optical path length changing unit is controlled by the autofocus control unit, and the maximum contrast evaluation value optical path length that is the optical path length of the second light flux at which the contrast evaluation value of the second signal is maximized is detected. Based on the evaluation value optical path length, focus control of the optical system is performed.
As described above, since the imaging apparatus generates an autofocus video signal and detects the maximum contrast evaluation value optical path length using this signal, the adverse effect at the time of detection does not affect the imaging video signal.

In addition, since this imaging device performs focus control of the optical system after detecting the maximum contrast evaluation value optical path length by the optical path length changing unit of the imaging unit for autofocus, it can be reliably controlled even in a large blurred state. is there.
In addition, even if the autofocus operation is started in the in-focus state, the imaging apparatus does not affect the main line system, that is, the video signal for shooting, and uses the video signal for autofocus detection. Make the state searchable.
In addition, since this image pickup apparatus performs the focus adjustment of the optical system after detecting the optical path length of the maximum contrast evaluation value in the video signal for autofocus, for example, a high-speed lens operation such as a wobbling operation cannot be performed. Even in the case of using the autofocus function, the autofocus function can be reliably realized.

“Performing focus control of the optical system based on the maximum contrast evaluation value optical path length” includes, for example, the following. First, the detected maximum contrast evaluation value optical path length is compared with a reference position corresponding to the optical path length of the first light flux input to the first imaging unit (imaging imaging unit). The in-focus position (focus position) of the optical system is calculated from the difference between both optical path lengths. Then, for example, the focusing lens (group) is moved so that the optical system is in a focused state based on the calculated focusing position. Thereby, focus control of the optical system is performed.
An image pickup apparatus according to a second aspect of the present invention is the image pickup apparatus according to the first aspect, wherein the first driver has a frame rate corresponding to the first signal and an independently variable first frame rate. Acquiring the first imaging unit at a first frame rate, and the second driving unit acquires a second frame rate that is independently variable and is a frame rate for the second signal; The second driving unit is driven at a frame rate of 2.

In this imaging apparatus, since the frame rate for autofocus detection can be controlled independently, it is not affected by the frame rate of the video signal for photographing. Therefore, the response speed of autofocus can be improved, or the power consumption of the imaging apparatus can be reduced.
An imaging apparatus according to a third aspect of the present invention is the imaging apparatus according to the first aspect, further comprising a frame rate changing unit that changes a first frame rate, which is a frame rate for the first signal. Further, the autofocus control unit can set or change a second frame rate that is a frame rate for the second signal based on the first frame rate, and controls the focus of the optical system based on the second frame rate. I do. Here, being able to set or change the second frame rate based on the first frame rate includes setting or changing the second frame rate in accordance with the change of the first frame rate.

In this imaging apparatus, the autofocus detection frame rate can be automatically set or changed in accordance with the shooting frame rate.
An image pickup apparatus according to a fourth aspect of the present invention is the image pickup apparatus according to the first aspect, wherein the second image pickup unit has an image pickup device capable of reading an arbitrary position.
In this image pickup device, the number of read pixels of the image pickup device for autofocus detection can be suppressed and the frame rate of the image pickup device for autofocus detection can be increased, so that the response speed of autofocus can be increased. Have.
An image pickup apparatus according to a fifth aspect of the present invention is the image pickup apparatus according to the first aspect, wherein the autofocus control unit causes the second image pickup unit to move in the optical axis direction of the second light flux by the optical path length changing unit. The maximum contrast evaluation value optical path length is detected by moving back and forth and repeatedly detecting the direction in which the contrast evaluation value increases.

In this imaging apparatus, it is possible to shorten the time until the maximum contrast evaluation value is detected. In addition, since the optical path is adjusted after the optical path length with the maximum contrast is detected in the video signal for autofocus, high-speed lens operation such as wobbling operation cannot be performed. An excellent effect that it can be provided is obtained.
An image pickup apparatus according to a sixth aspect of the present invention is the image pickup apparatus according to the first aspect, wherein the autofocus control unit moves the second image pickup unit in the optical axis direction of the second light flux by the optical path length changing unit. The maximum contrast evaluation value optical path length is detected by sequentially moving and evaluating the contrast evaluation value when the optical path length of the second light flux is sequentially changed. Here, sequentially moving the second image pickup unit in the optical axis direction of the second light beam detects the evaluation value of the contrast sequentially while moving the second image pickup unit in a certain direction of the optical axis direction, The maximum evaluation value among the detected evaluation values in a certain range is set as the maximum contrast evaluation value.

In this imaging apparatus, although it takes time, the maximum contrast evaluation value can be detected more reliably.
An image pickup apparatus according to a seventh aspect of the present invention is the image pickup apparatus according to the third aspect, wherein the autofocus control unit lowers the second frame rate when the first frame rate is lowered.
This imaging apparatus can be controlled to suppress power consumption for autofocus detection.
According to an eighth aspect of the present invention, there is provided an imaging method for condensing light from a subject and controlling the focus, light from the subject condensed by the optical system at least a first light flux and a second light beam. An optical path separating unit that separates the first light beam into an electrical signal, a first imaging unit that outputs the first light beam as a first signal, a second light beam into an electrical signal, An imaging method used in an imaging apparatus comprising: a second imaging unit that outputs as a signal; and an optical path length changing unit that changes the optical path length of the second light beam, the first signal processing step, A signal processing step, an evaluation value generation step, a drive step, another drive step, a detection step, and an autofocus control step. In the first signal processing step, signal processing of the first signal is performed to generate a video signal for photographing. In the second signal processing step, signal processing of the second signal is performed. The evaluation value generation step generates an evaluation value of the contrast of the second signal. In the driving step, the first imaging unit is driven. Another driving step drives the second imaging unit. In the detecting step, the optical path length changing unit is controlled to detect a maximum contrast evaluation value optical path length that is an optical path length of the second light flux that maximizes the contrast evaluation value of the second signal. In the autofocus control step, focus control of the optical system is performed based on the maximum contrast evaluation value optical path length.

  According to a ninth aspect of the present invention, there is provided a program for collecting light from a subject, focusing an optical system capable of focus control, and at least first light flux and second light from the subject collected by the optical system. An optical path separating unit that separates into a light beam, a first imaging unit that converts the first light beam into an electrical signal and outputs it as a first signal, a second light beam that is converted into an electrical signal, and a second signal A program used for an imaging apparatus comprising: a second imaging unit that outputs a second optical path; and an optical path length changing unit that changes an optical path length of the second light beam, the first signal processing step, and a second signal A processing step, an evaluation value generation step, a driving step, another driving step, a detection step, and an autofocus control step are provided. In the first signal processing step, signal processing of the first signal is performed to generate a video signal for photographing. In the second signal processing step, signal processing of the second signal is performed. The evaluation value generation step generates an evaluation value of the contrast of the second signal. In the driving step, the first imaging unit is driven. Another driving step drives the second imaging unit. In the detection step, the optical path length changing unit is controlled to detect a maximum contrast evaluation value optical path length which is an optical path length of the second light flux at which the contrast evaluation value of the second signal is maximized. In the autofocus control step, focus control of the optical system is performed based on the maximum contrast evaluation value optical path length.

  An integrated circuit according to a tenth aspect of the present invention includes one or more first imaging units, a second imaging unit, a first signal processing unit, a second signal processing unit, an evaluation value generation unit, A first drive unit, a second drive unit, an optical path length changing unit, and an autofocus control unit are provided. The first imaging unit converts one or more lights out of the light separated from the output of the optical system into an electrical signal, and outputs it as a first signal. The second imaging unit converts light other than the one or more lights out of the plurality of lights into an electrical signal and outputs it as a second signal. The first signal processing unit performs signal processing of the first signal to generate a video signal for photographing. The second signal processing unit performs signal processing of the second signal. The evaluation value generation unit generates an evaluation value of the contrast of the second signal. The first driving unit generates a driving pulse for the first imaging unit. The second driving unit generates a driving pulse for the second imaging unit. The optical path length changing unit changes the optical path length of the second light flux. The autofocus control unit controls the optical path length changing unit, detects the maximum contrast evaluation value optical path length that is the optical path length of the second light flux that maximizes the contrast evaluation value of the second signal, and determines the maximum contrast evaluation value. Focus control of the optical system is performed based on the optical path length.

An integrated circuit according to an eleventh aspect of the present invention includes a first signal processing unit, a second signal processing unit, an evaluation value generating unit, a first driving unit, a second driving unit, and an optical path length change. And an autofocus control unit. The first signal processing unit receives one or more electric signals among the plurality of electric signals generated by converting the light separated into a plurality via the optical system in the plurality of imaging units and performs signal processing. To generate a video signal for shooting. The second signal processing unit receives a second signal other than the one or more electrical signals and performs signal processing. The evaluation value generation unit generates an evaluation value of the contrast of the second signal. The first driving unit generates a driving pulse for the first imaging unit. The second driving unit generates a driving pulse for the second imaging unit. The optical path length changing unit changes the optical path length of the second light flux. The autofocus control unit controls the optical path length changing unit, detects the maximum contrast evaluation value optical path length that is the optical path length of the second light flux that maximizes the contrast evaluation value of the second signal, and determines the maximum contrast evaluation value. Focus control of the optical system is performed based on the optical path length.
(The invention's effect)
As described above, the present invention provides an excellent effect that an adverse effect when detecting the optical path length with the maximum contrast cannot be applied to the video signal for photographing.

1 is a block diagram showing a configuration of an imaging apparatus with an autofocus function according to Embodiment 1 of the present invention. Schematic diagram for explaining an optical path separation unit according to Embodiment 1 of the present invention 1 is a block diagram showing a configuration of an AF evaluation value generation unit according to Embodiment 1 of the present invention. Schematic diagram for explaining a part of the operation of the AF evaluation value generation unit according to the first embodiment of the present invention. Schematic diagram for explaining a state of searching for an optical path length that maximizes the contrast evaluation value according to Embodiment 1 of the present invention. FIG. 3 is a block diagram illustrating a configuration of an imaging apparatus with an autofocus function according to a second embodiment of the present invention. The schematic diagram for demonstrating the mode of the output signal in a different frame rate by Embodiment 2 of this invention The schematic diagram for demonstrating the optical path separation part by the other form of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical system 2 Optical path separation part 3 The imaging part for imaging | photography (1st imaging part)
4 Signal processing unit for photographing (first signal processing unit)
5 AF imaging unit (second imaging unit)
6 Analog signal processor (second signal processor)
7 AD conversion 8 AF evaluation value generation unit (evaluation value generation unit)
9 AF drive section (second drive section)
10 AF optical path length changing section (optical path length changing section)
11 AF control unit (autofocus control unit)
12 Frame Rate Change Signal Processing Unit 13 Shooting Frame Rate Change Control Unit 14 Adaptive AF Control Unit (Autofocus Control Unit)
21. Shooting drive unit (first drive unit)
101 horizontal low-pass filter 102 first horizontal high-pass filter 103 second horizontal high-pass filter 104 vertical high-pass filters 105, 106, 107 accumulator 108 adder 109 selector

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
(Embodiment 1)
<1.1: Configuration of Imaging Device>
FIG. 1 is a block diagram showing a configuration of an imaging apparatus 100 with an autofocus function according to Embodiment 1 of the present invention.
In FIG. 1, an imaging apparatus 100 includes an optical system 1, an optical path separation unit 2, an imaging imaging unit 3 that constitutes a first imaging unit, and an imaging signal processing unit 4 that constitutes a first signal processing unit. And a photographing drive unit 21 constituting a first drive unit. The imaging apparatus 100 further includes an autofocus imaging unit 5 (hereinafter referred to as “AF imaging unit 5”) that constitutes the second imaging unit, and an analog signal processing unit 6 that constitutes the second signal processing unit. , An AD conversion unit 7, an autofocus evaluation value generation unit 8 (hereinafter referred to as “AF evaluation value generation unit 8”), and a drive unit 9 (hereinafter referred to as “autofocus imaging unit”) as a second drive unit. AF driving section 9 ”), autofocus optical path length changing section 10 (hereinafter referred to as“ AF optical path length changing section 10 ”), and autofocus control section 11 (hereinafter referred to as“ AF control section 11 ”). And).

The optical system 1 has a configuration capable of condensing light from a subject and adjusting a focal length of the light (light flux) from the subject, that is, a configuration capable of focus control. The optical system 1 outputs the collected light (light flux) from the subject to the optical path separation unit 2. The optical system 1 may be composed of a plurality of lenses. In the optical system 1, a focus control lens (which may be a lens unit including a plurality of lenses) that performs focus control is provided, and focus control is performed by moving the focus control lens. Good. Further, the optical system 1 may be configured by an interchangeable lens or the like.
The optical path separation unit 2 receives light (light beam) output from the optical system 1, and uses the light beam that has passed through the optical system 1 for autofocus detection (the first light beam for photographing and the second light beam). Hereinafter, the light beam may be separated into “light detection AF”. Then, the optical path separation unit 2 outputs the photographing light flux to the photographing imaging unit 3 and outputs the autofocus detection light flux to the AF imaging unit 5. Here, the optical path separation unit 2 converts the photographic light flux that has passed through the optical system 1 into a plurality of photographic light fluxes (for example, three light fluxes of R, B, and G, and R light flux). , B light beam, G1 light beam, and G2 light beam). In addition, the ratio of the AF detection light flux among the light fluxes input to the optical system 1 may be an arbitrary ratio (for example, 10%, 50%, etc.). For example, an optical prism (beam splitter) as shown in FIGS. 2 and 8 is preferably used as the optical path separation unit 2.

The imaging imaging unit 3 has an imaging element such as a CMOS or CCD, and receives the light beam output from the optical system 1 as an input. The photographing imaging unit 3 converts the light beam input from the optical system 1 into an electric signal by photoelectric conversion, and outputs the converted electric signal to the photographing signal processing unit 4.
The photographing signal processing unit 4 receives the output from the photographing imaging unit 3 as an input. The photographing signal processing unit 4 performs signal processing such as correlated double sampling processing, gain control processing, pedestal control processing, and gamma processing on the output signal of the photographing imaging unit 3 to obtain a photographing video signal.
The shooting drive unit 21 receives a frame rate signal for shooting. The imaging drive unit 21 outputs a drive pulse signal according to the frame rate signal. The photographing imaging unit 3 is driven by the output drive pulse signal.
The AF imaging unit 5 receives the light beam for autofocus detection output from the optical path separation unit 2 as an input. The AF imaging unit 5 converts the light beam for autofocus detection into an electrical signal and outputs it to the analog signal processing unit 6. The AF imaging unit 5 is connected to the AF optical path length changing unit 10. The AF imaging unit 5 is translated by the AF optical path length changing unit 10 on the optical axis of the autofocus detection light beam. The AF imaging unit 5 receives the drive pulse signal from the AF drive unit 9 and is driven by this drive pulse signal. The AF imaging unit 5 includes an image sensor that can read an arbitrary position. The electrical signal acquired in the entire area of the imaging device may be output to the analog signal processing unit 6, or the electrical signal acquired in a partial area of the imaging device is output to the analog signal processing unit 6. You may do it. Note that in which region of the image sensor the electrical signal that is the output of the AF imaging unit 5 is acquired is determined by the driving pulse signal from the AF driving unit 9.

The analog signal processing unit 6 receives the output from the AF imaging unit 5 as an input. The analog signal processing unit 6 performs correlated double sampling processing, gain control processing, pedestal control processing, and the like on the output from the AF imaging unit 5 and outputs the result to the AD conversion unit 7.
The AD conversion unit 7 converts the signal from the analog signal processing unit 6 into a digital signal and outputs it to the AF evaluation value generation unit 8.
The AF evaluation value generation unit 8 includes a selection signal output from the AF control unit 11, an evaluation region signal output from the AF drive unit 9, and an autofocus detection video signal (hereinafter referred to as an AF conversion unit 7). , “AF detection video signal”). The AF evaluation value generation unit 8 performs high-pass filter processing or the like on the video signal for autofocus detection based on an evaluation region signal and a selection signal, which will be described later, and extracts a high-frequency component of the signal to perform autofocus operation. An evaluation value (contrast evaluation value) is calculated. The AF evaluation value generation unit 8 outputs the calculated evaluation value to the AF control unit 11.

The AF driving unit 9 generates a driving pulse signal for driving the AF imaging unit 5.
The AF optical path length changing unit 10 translates the AF imaging unit 5 on the optical axis of the autofocus detection light beam using a small actuator or the like. As a result, the AF optical path length changing unit 10 changes the optical path length of the AF imaging unit 5. As the small actuator, a linear drive motor, a stepping motor, a piezoelectric ultrasonic linear actuator using a piezoelectric element, a slide mechanism, or the like can be used.
The AF control unit 11 controls the AF drive unit 9, the AF optical path length changing unit 10, and the like, and detects the optical path length that maximizes the evaluation value (contrast evaluation value) obtained from the AF evaluation value generation unit 8. To do. Thereby, the AF control unit 11 controls the focus position of the optical system 1.
FIG. 2 is a schematic diagram showing a more specific example of the optical path separation unit 2, the imaging unit 3 for shooting, the imaging unit 5 for AF, and the optical path length changing unit 10 for AF.

As shown in FIG. 2, the optical path separation unit 2 is configured using a color separation prism used in the four-plate imaging method. In the three-plate imaging method, the light is divided into R (red) light, G (green) light, and B (blue) light by a color separation prism. On the other hand, in the optical path separation unit 2 in the present embodiment, the G light after RGB spectroscopy is further divided by a half mirror as shown in FIG. 2 to create G1 (green 1) light and G2 (green 2) light. To do. Then, G2 (green 2) light is used as a light beam for autofocus detection. The remaining R (red) light, G1 (green 1) light, and B (blue) light are subjected to signal processing of a normal three-plate imaging method as a light flux for photographing. Further, an AF optical path length changing unit 10 using a small actuator is connected to an AF imaging unit 5 which is an imaging unit for G2 (green 2) light. The AF optical path length changing unit 10 enables the AF imaging unit 5 to move on the optical axis.
FIG. 3 is a block diagram illustrating an example of the configuration of the AF evaluation value generation unit 8.

  In FIG. 3, the AF evaluation value generation unit 8 includes a horizontal low-pass filter 101, two horizontal high-pass filters 102 and 103, a vertical high-pass filter 104, integration units 105 to 107, and an adder 108. And a selector 109. The low-pass filter 101 in the horizontal direction is a low-pass filter (hereinafter referred to as “horizontal LPF”) for the horizontal component of the video (two-dimensional video) formed by the video signal for autofocus detection. The two high-pass filters in the horizontal direction are high-pass filters (hereinafter referred to as “first horizontal HPF” and “second horizontal HPF”, respectively) for horizontal components of the video (two-dimensional video) formed by the video signal for autofocus detection. "). The high-pass filter in the vertical direction is a high-pass filter (hereinafter referred to as “vertical HPF”) for the vertical component of the video (two-dimensional video) formed by the video signal for autofocus detection. The horizontal LPF 101, the first horizontal HPF 102, the second horizontal HPF 103, the vertical HPF 104, and the accumulating units 105 to 107 constitute an arithmetic unit 111.

The horizontal LPF 101 receives an autofocus detection video signal (AF detection video signal) output from the AD converter 7 as an input. The horizontal LPF 101 is a low-pass filter for extracting a frequency band component necessary for generating a contrast evaluation value for the AF detection signal. The horizontal LPF 101 outputs the output signal to the first horizontal HPF 102, the second horizontal HPF 103, and the vertical HPF 104.
The first horizontal HPF 102 and the second horizontal HPF 103 have different frequency bands to pass. The first horizontal HPF 102 and the second horizontal HPF 103 are high-pass filters (for low frequency) that allow the first horizontal HPF 102 to pass a lower frequency band, and high-pass filters (high frequency) that allow the second horizontal HPF 103 to pass a higher frequency band. For).
Accumulators 105 to 107 accumulate the outputs of the high-pass filters 102 to 104 and output them to the adder 108 and the selector 109.

The calculation unit 111 includes a horizontal LPF 101, a first horizontal HPF 102, a second horizontal HPF 103, a vertical HPF 104, and integration units 105 to 107. An evaluation area signal is input from the AF drive unit 9 to the calculation unit 111. The evaluation area signal is used by the AF evaluation value generation unit 8 to select an area for evaluating autofocus (hereinafter referred to as an AF evaluation area). For example, when the AF detection video signal is taken from the center of the screen, the evaluation area signal is a pulse signal indicating the timing of the center of the screen. Note that this evaluation region signal may be input only to the integration units 105 to 107. In this case, the accumulators 105 to 107 accumulate the values in the AF evaluation area among the outputs of the high-pass filters 102 to 104 and output the accumulated values to the adder 108 and the selector 109.
The adder 108 adds the outputs of the integrating units 105 to 107 and outputs the addition result to the selector 109.

The selector 109 selects the outputs from the integrating units 105 to 107 and the adder 108 based on the selection signal. The selector 109 outputs the selected output signal to the AF control unit 11 as an evaluation value (contrast evaluation value). The selection signal is used to select a signal most suitable for the image to be captured. The selection signal will be described later.
The pass bands of the horizontal LPF 101, the first horizontal HPF 102, the second horizontal HPF 103, and the vertical HPF 104 are as follows, for example. When the video signal handled by the imaging apparatus 100 is an SDTV video signal, the horizontal LPF 101 is 0 to 2.0 MHz, the first horizontal HPF 102 is 300 kHz or more, the second horizontal HPF 103 is 1.2 MHz or more, and the vertical HPF 104 is 20 TV or more. Preferably there is. When the video signal handled by the imaging apparatus 100 is an HDTV video signal, the horizontal LPF 101 is 0 to 13.2 MHz, the first horizontal HPF 102 is 2.0 MHz or higher, the second horizontal HPF 103 is 6.6 MHz or higher, and the vertical HPF 104 is It is preferable that there are 45 TV lines or more.

<1.2: Operation of Imaging Device>
The operation of the image pickup apparatus with an autofocus function configured as described above will be described in detail with reference to FIGS.
The light beam that has passed through the optical system 1 is input to the optical path separation unit 2 shown in FIG. The light beam input from the optical system 1 by the optical path separation unit 2 is R (red) light for photographing, G1 (green 1) light, B (blue) light, and G2 (green) for autofocus detection. 2) Divided into luminous flux. The divided light fluxes are respectively converted into electrical signals by the three photographing imaging units 3 and one AF imaging unit 5.
The output of the imaging unit 3 is signal-processed by the imaging signal processing unit 4 in the same manner as in the normal three-plate imaging system. The processed signal is then output as a main line system, that is, a video signal for photographing.

On the other hand, the output of the AF imaging unit 5 is subjected to analog signal processing such as correlated double sampling, gain control, and pedestal control, as in normal signal processing. The analog signal processed output is then converted into a digital signal by the AD converter 7 and input to the AF evaluation value generator 8.
The AF evaluation value generation unit 8 evaluates the contrast of the video. Specifically, first, horizontal LPF processing is performed on an AF detection video signal input to the AF evaluation value generation unit 8. This is performed in order to suppress the noise component of the video signal for AF detection. Thereafter, a plurality of high-pass filter processes are performed on the AF detection signal that has been subjected to the horizontal LPF process. In the case of FIG. 3, the AF detection video signal input to the calculation unit 111 passes through the horizontal LPF 101. As described above, the calculation unit 111 receives the evaluation region signal from the AF drive unit 9 and calculates only the signal component in the AF evaluation region of the input AF detection video signal. In addition, in the calculation unit 111, the AF detection video signal is input to the first horizontal HPF 102, the second horizontal HPF 103, and the vertical HPF 104, respectively. The first horizontal HPF 102 extracts a high frequency component of a signal from a lower frequency in the horizontal direction. The second horizontal HPF 103 extracts a high frequency component of the video signal from a higher frequency in the horizontal direction. The vertical HPF 104 extracts a high-frequency component in the vertical direction. The signals after the high-pass processing in each of the high-pass filters 102 to 104 are integrated by the integrating units 105, 106, and 107 and output. Note that the evaluation region signal may be input only to the integration units 105 to 107. In this case, the integrating units 105 to 107 integrate the values in the AF evaluation area among the outputs of the high-pass filters 102 to 104, and output them to the adder 108 and the selector 109.

Outputs from the accumulating units 105, 106 and 107 are added by an adder 108. The added signal is input to the selector 109. That is, the outputs of the accumulators 105 to 107 and the output of the adder 108 that adds the outputs of these accumulators are input to the selector 109, and 4 of the selector 109 according to the selection signal from the AF controller 11. One of the two inputs is selected. The selected signal is output to the AF control unit 11 as a contrast evaluation value (contrast evaluation value).
The selection signal is used to select the most suitable signal depending on the image to be captured. For example, the evaluation value curves of the first horizontal HPF 102 (for low frequency) and the second horizontal HPF 103 (for high frequency) have characteristics as shown in FIG. As shown in FIG. 4, the first horizontal HPF 102 (for low frequency) draws a gentle mountain, and the second horizontal HPF 103 (for high frequency) draws a steep mountain in the vicinity of the focal point from a flat state. For example, in the case of a pattern such as a horizontal stripe pattern, there are almost no peaks in the evaluation value curve in both the first and second horizontal HPFs 102 and 103, and in the vertical HPF 104, a mountain is formed at the focal point. When detecting the optical path length of the maximum contrast evaluation value by repeatedly moving the AF imaging unit 5 back and forth to increase the contrast, for example, the following is performed. First, the output from the second horizontal HPF 103 (for high frequency) is selected, and when there is no change in the second horizontal HPF 103 (for high frequency), the output for AF is based on the output from the first horizontal HPF 102 (for low frequency). The imaging unit 5 is moved to near the in-focus position. Then, finally, it is conceivable to control such that the maximum contrast evaluation value optical path length is determined based on the output of the second horizontal HPF 103. Further, when there is no change in the evaluation values of the first and second horizontal HPFs 102 and 103, it can be controlled to select the output of the vertical HPF 104. Further, for example, first, control is performed roughly using the added values of the first and second horizontal HPFs 102 and 103 and the vertical HPF 104, and finally the control is performed based on the evaluation value of the second horizontal HPF 103 or the vertical HPF 104. May be performed. Note that the band, type, and selection method of these high-pass filters are various and not limited to these.

The AF control unit 11 monitors the contrast evaluation value output from the AF evaluation value generation unit 8, and the optical path length of the AF imaging unit 5 (input to the AF imaging unit 5 is performed by the AF optical path length changing unit 10. The optical path length of the luminous flux is changed sequentially. Thereby, the AF control unit 11 detects the optical path length of the AF imaging unit 5 that maximizes the contrast evaluation value. The AF optical path length changing unit 10 includes a linear drive motor, a stepping motor, a piezoelectric ultrasonic linear actuator using a piezoelectric element, and a slide mechanism along the optical axis. The AF optical path length changing unit 10 has a function of sliding the AF imaging unit 5 parallel to the optical axis (in the direction indicated by the bidirectional arrow D1 in FIG. 2), and is controlled by serial communication or the like, for example. The
In addition, the AF control unit 11 outputs a frame rate signal independent of the shooting frame rate signal that is the frame rate signal of the shooting imaging unit 3, that is, an AF frame rate signal, to the AF driving unit 9. The AF imaging unit 5 is driven by the output AF frame rate signal. Note that the frame rate of the AF imaging unit 5 according to the AF frame rate signal is changed by a frame rate changing unit (not shown) such as a menu or dial provided in the imaging apparatus 100. The AF control unit 11 sets the AF drive unit 9 so as to read out only the AF evaluation region (the region set for AF detection on the image sensor of the AF imaging unit 5). The AF driving unit 9 drives the AF imaging unit 5 and outputs an evaluation area signal to the AF evaluation value generation unit 8 and outputs an effective signal corresponding to the AF evaluation area as described above. Control. When the AF control unit 11 detects the optical path length of the AF imaging unit 5 that maximizes the contrast evaluation value, it is determined in advance corresponding to the detected optical path length and the optical path length of the imaging unit 3 for photographing. The difference from the reference value is calculated. The focus control of the optical system 1 is executed by detecting the focus position of the optical system 1 from the difference value.

That is, the AF optical path length changing unit 10 acquires the respective contrast evaluation values while sequentially changing the optical path length of the AF imaging unit 5, and detects the optical path length that maximizes the contrast evaluation value. The detected optical path length is compared with a reference position corresponding to the optical path length of the imaging unit 3 for photographing, the focus position of the optical system 1 is calculated from the difference, and the focus position control of the optical system 1 is performed. .
<1.2.1: Method of detecting optical path length that maximizes contrast evaluation value>
A method in which the AF control unit 11 acquires the respective contrast evaluation values while sequentially changing the optical path length of the AF imaging unit 5 and detects the optical path length that maximizes the contrast evaluation value will be described with reference to FIG. .
FIG. 5 is a schematic diagram for explaining an example of an operation for searching for an optical path length that maximizes the contrast evaluation value.

  In FIG. 5, the horizontal axis indicates the optical path length of the AF imaging unit 10, and the vertical axis indicates the contrast evaluation value calculated by the AF evaluation value generation unit 8. A thick arrow indicates a state of search for each time, and a thin curve indicates a contrast evaluation value curve. The case where a search from the search start position to the point where the contrast evaluation value is maximized is performed will be described with reference to this figure. The optical path length changing unit 10 for AF first changes the optical path length in either direction, and reads the contrast evaluation value acquired by the AF evaluation value generating unit. The contrast evaluation value at the current position is compared with the contrast evaluation value at the previous position. When the evaluation value decreases, the AF optical path length changing unit 10 reverses the direction in which the AF imaging unit 5 is moved. In the case of FIG. 5, the contrast evaluation value hardly changes when the optical path length is changed in the right direction (the direction in which the optical path length of the AF imaging unit increases) in the first time. Therefore, the optical path length is changed in the same direction for the second time. Since the contrast evaluation value has increased in the second change, the search is continued in the same direction. In all of the changes from the second time to the sixth time, the contrast evaluation value has increased, so it is determined that the maximum contrast point is further to the right. The contrast evaluation value has decreased due to the seventh change. That is, it is determined that the maximum point of the contrast evaluation value has been passed. In the eighth time, the direction of changing the optical path length of the AF imaging unit is reversed from the direction in the seventh time. At this time, it can be predicted that the position is in the vicinity of the maximum point (the point that becomes the maximum contrast evaluation value optical path length). Next, the same search is continued with a smaller amount of change. Finally, the point that decreases regardless of which direction is changed is detected as the maximum point (the point that becomes the maximum contrast evaluation value optical path length). When the first change direction is changed to the left direction in FIG. 5, the search position is at the extreme end (the limit at which the AF imaging unit 5 can be moved by the AF optical path length changing unit 10). Detecting that it has arrived. At this point, the search direction is reversed to the right, and the point where the contrast evaluation value finally becomes maximum can be reliably detected.

It should be noted here that the focus position of the optical system 1 is not controlled (changed) at all while the imaging apparatus 100 searches for a point where the contrast evaluation value is maximized using the AF optical path length changing unit 10. Therefore, the video signal for photographing is not affected at all.
Furthermore, when searching for an optical path length that maximizes the contrast evaluation value in the imaging apparatus 100, a wide range of search is possible because it does not affect the video signal for shooting at all. Therefore, the maximum point of the contrast evaluation value can be reliably detected even from a large blurred state.
As described above, in the imaging apparatus 100 according to the first embodiment, the focus control of the optical system 1 is performed by detecting the optical path length with the maximum contrast using the autofocus signal independent of the video signal for photographing. Therefore, the imaging apparatus 100 according to the first embodiment has an excellent effect that the adverse effect at the time of detection does not reach the imaging video signal.

As described above, the imaging apparatus 100 according to the first embodiment has no influence on the video signal for shooting even during the focus search operation. Therefore, the imaging apparatus 100 according to the first embodiment has an excellent effect that a wide range search is possible and the control can be surely performed even from a so-called large-blurred state.
Further, the AF imaging unit 5 of the imaging apparatus 100 includes an AF driving unit 9 different from the imaging driving unit 21. Therefore, the frame rate of the AF imaging unit 5 can be set independently of the frame rate of the imaging unit 3 for photographing. This has the following effects. For example, when the frame rate of the imaging unit 3 for shooting is lowered to 12P or less, if the frame rate of the AF imaging unit 5 is also lowered to 12P or less, the photographer feels that the autofocus responsiveness has deteriorated. Sometimes. In this case, the responsiveness of autofocus is improved by keeping only the frame rate of the AF imaging unit 5 at a constant height. On the other hand, when the frame rate of the photographing imaging unit 3 is increased to, for example, 60P or more, if the frame rate of the AF imaging unit 5 is also increased in the same manner, power may be consumed more than necessary. This is because, even if the frame rate of the AF imaging unit 5 is increased, the improvement of the autofocus response may be limited depending on the size, weight, type, and the like of the lens. In this case, wasteful power consumption can be prevented by suppressing only the frame rate of the AF imaging unit 5. The imaging apparatus 100 according to the first embodiment can independently change the frame rate of the AF imaging unit 5, thereby improving the autofocus response speed according to the situation or reducing power consumption. Further, the imaging apparatus 100 can easily increase the frame rate of the AF imaging unit 5 by using the AF imaging unit 5 having an imaging device capable of reading an arbitrary position so as to read out only a necessary region. The autofocus response time can be improved.

As described above, the imaging apparatus 100 according to the first embodiment has an excellent effect that the frame rate of the AF imaging unit 5 can be independently controlled, and is not affected by the frame rate of the imaging unit 3 for photographing. It is done. That is, in order to improve the autofocus response time, the frame rate of the AF imaging unit 5 may be increased separately from the frame rate of the imaging unit 3 for shooting. This represents a remarkable effect at the time of shooting at a low frame rate, particularly in the case of an imaging device in which the frame rate of a video signal for shooting is variable. When the frame rate of the imaging unit 3 for shooting is high, only the frame rate of the AF imaging unit 5 needs to be set low in order to prevent wasteful consumption of power consumption.
In the first embodiment, the optical path separation unit 2 has been described with the color separation prism used in the four-plate imaging method. If the photographing light beam and the AF light beam can be separated, it is not necessary to be a four-plate color separation prism, and the AF light beam does not have to be Gch.

In the first embodiment, the AF evaluation value generation unit 8 is an arithmetic operation including a horizontal LPF 101, a first horizontal HPF 102, a second horizontal HPF 103, a vertical HPF 104, accumulating units 105, 106, 107, an adder 108, and a selector 109. The example constituted by the unit 111 has been described. However, the AF evaluation value generation unit 8 may have any configuration (circuit) as long as the value for evaluating the contrast of the video can be detected. The AF evaluation value generation unit 8 may be configured by, for example, one type of horizontal HPF that can change the characteristics of the passband.
In the first embodiment described above, the method for detecting the position where the contrast evaluation value is maximized has been described as a method of greatly changing the optical path length from the beginning, but is not limited thereto. For example, the AF control unit 11 uses the AF optical path length changing unit 10 to sequentially move the AF imaging unit 5 in the optical axis direction, and the contrast evaluation value when the optical path length of the second light flux is sequentially changed. By evaluating, the optical path length that maximizes the contrast evaluation value may be detected. In this case, the contrast evaluation value is sequentially detected while moving the AF imaging unit 5 in a certain direction along the optical axis. The maximum evaluation value among the detected evaluation values in a certain range is set as the maximum contrast evaluation value. Detection in this way takes time, but makes it possible to obtain the maximum contrast evaluation value more reliably. Alternatively, the search method may be combined with conventional wobbling. In other words, the wobbling operation may be repeated, and a method of detecting a point at which the contrast evaluation value becomes maximum may be detected by a so-called hill-climbing algorithm, or a method of changing the optical path length using the golden section method or the like. Any method may be used as long as the optical path length that maximizes the contrast evaluation value can be detected.
(Embodiment 2)
<2.1: Configuration of imaging apparatus>
FIG. 6 is a block diagram showing a configuration of an imaging apparatus 200 with an autofocus function according to the second embodiment of the present invention. The imaging apparatus 200 differs from the imaging apparatus 100 according to the first embodiment in the following points. First, the imaging apparatus 200 according to the second embodiment includes an imaging frame rate change control unit 13 and a frame rate change signal processing unit 12 that constitute a frame rate change unit. In the imaging apparatus 200 of the second embodiment, the adaptive AF control unit 14 changes the frame rate of the auto AF imaging unit 5 according to the main line system, that is, the frame rate of the imaging imaging unit 3. In addition, the same code | symbol is attached | subjected about the component same as the imaging device 100 of the said Embodiment 1. FIG.

The imaging apparatus 200 includes an optical system 1, an optical path separation unit 2, a photographing imaging unit 3, a frame rate change signal processing unit 12, a photographing driving unit 21, and an autofocus imaging unit 5 (hereinafter referred to as AF). Imaging unit 5), analog signal processing unit 6, AD conversion unit 7, autofocus evaluation value generation unit 8 (hereinafter referred to as AF evaluation value generation unit 8), AF drive unit 9, and AF optical path length change Unit 10, adaptive AF control unit 14, and shooting frame rate change control unit 13.
The optical system 1 is configured by an interchangeable lens or the like, and has a configuration capable of controlling the focus position. The optical path separator 2 separates the light beam that has passed through the optical system 1 into a light beam for photographing and a light beam for autofocus detection. The imaging unit 3 has an imaging element such as a CMOS or CCD, and converts the imaging light flux into an electrical signal.
The frame rate change signal processing unit 12, like the imaging signal processing unit 4 of the imaging apparatus 100, performs correlated double sampling processing, gain control processing, pedestal control processing, gamma processing, and the like on the output of the imaging imaging unit 3. A signal processing unit for photographing that performs signal processing. The frame rate change signal processing unit 12 further performs signal processing corresponding to the frame rate change.

The shooting drive unit 21 receives the shooting frame rate signal from the shooting frame rate change control unit 13. The imaging drive unit 21 outputs a drive pulse signal according to the frame rate signal. The photographing imaging unit 3 is driven by the output drive pulse signal.
The AF imaging unit 5 converts the light beam for autofocus detection into an electrical signal. The analog signal processing unit 6 performs signal processing such as correlated double sampling processing, gain control processing, and pedestal control processing. The AD converter 7 converts the signal from the analog signal processor 6 into a digital signal.
The AF evaluation value generation unit 8 includes a selection signal output from the adaptive AF control unit 14, an evaluation region signal output from the AF drive unit 9, and an autofocus detection video signal output from the AD conversion unit 7. (Hereinafter referred to as “AF detection video signal”) as an input. The AF evaluation value generation unit 8 performs high-pass filter processing or the like on the video signal for autofocus detection based on the evaluation region signal and the selection signal to extract a high-frequency component of the signal, and evaluates the evaluation value of the autofocus operation (Evaluation value of contrast) is calculated. The AF evaluation value generation unit 8 outputs the result to the adaptive AF control unit 14.

The AF driving unit 9 generates a driving pulse for driving the AF imaging unit 5.
The AF optical path length changing unit 10 translates the AF imaging unit 5 on the optical axis of the autofocus detection light beam using a small actuator or the like. As a result, the AF optical path length changing unit 10 changes the optical path length of the AF imaging unit 5. The small actuator can be realized using a linear drive motor, a stepping motor, a piezoelectric ultrasonic linear actuator using a piezoelectric element, a slide mechanism, or the like.
The adaptive AF control unit 14 reads the frame rate of the photographing imaging unit 3 and controls the AF driving unit 9, the AF optical path length changing unit 10, and the like. The adaptive AF control unit 14 controls the focus position of the optical system 1 by detecting the optical path length that maximizes the evaluation value obtained from the AF evaluation value generation unit 8. The shooting frame rate change control unit 13 changes the frame rate of the shooting imaging unit 3.

The differences between the imaging apparatus 200 with the autofocus function configured as described above and the first embodiment are mainly in the following points. The frame rate of the video signal for shooting can be changed by the shooting frame rate change control unit 13 and the frame rate change signal processing unit 12. The AF control unit 14 can change the frame rate of the AF imaging unit 5 in accordance with a shooting frame rate signal (a signal for determining the frame rate of a shooting video signal). In other words, when the frame rate of the imaging unit 3 for shooting is very low, the power consumption for autofocus detection is reduced by reducing the frame rate of the AF imaging unit 5 to such an extent that a sense of incongruity does not occur in the autofocus response. It can control to suppress.
<2.2: Operation of Imaging Device>
Next, operations of the frame rate change signal processing unit 12, the shooting frame rate change control unit 13, and the adaptive AF control unit 14 will be described in detail. Other components are the same as those in the first embodiment, and thus the description thereof is omitted.

For example, consider the case where the imaging apparatus 200 can change the frame rate and the frame rate is 12p and 60p in the 720 / 60p (progressive) format. In the case of 12p, an effective video signal of 12 frames is output per second, and in the case of 60p, an effective video signal of 60 frames is output per second. In other words, 12p outputs a video signal acquired by accumulating charges in the imaging unit for 1/12 seconds, and 60p outputs a video signal acquired by accumulating charges in 1/60 seconds.
FIG. 7 is a schematic diagram for explaining a state of an output signal when the photographing imaging unit 3 operates at 12p and 60p.
When the frame rate of the image pickup unit 3 is 60p, the image pickup unit 3 outputs a video signal obtained by accumulating charges for 1/60 seconds as shown in FIG. 7A. When the frame rate of the imaging unit 3 for shooting is changed to 12p by a menu or a dial provided in the imaging apparatus 200, the shooting frame rate change control unit 13 reads the changed frame rate. The read frame rate signal is input to the photographing drive unit 21. The imaging drive unit 21 outputs drive pulses including timing pulses in accordance with the input frame rate signal. The imaging drive unit 21 drives the imaging imaging unit 3 with this drive pulse. As a result, as shown in FIG. 7B, the imaging unit 3 for photographing outputs a video signal obtained by accumulating charges for 1/12 seconds in a 1/60 second period every 1/12 seconds. The output signal is input to the frame rate change signal processing unit 12. The frame rate change signal processing unit 12 also performs processing such as gain adjustment, pedestal adjustment, and gamma correction on a 12p video signal. The frame rate change signal processing unit 12 writes a 12p effective video signal to a storage unit such as a memory to cope with the frame rate change, and a circuit (data reading unit) that reads the same data even when there is no video signal. Use. As a result, even when the shooting imaging unit 3 operates at 12p, the frame rate change signal processing unit 12 creates the same signal as when the shooting imaging unit 3 operates at 60p, and performs signal processing at a different frame rate. Is running.

A signal for determining the frame rate of the video signal for photographing is also input to the adaptive AF control unit 14. The adaptive AF control unit 14 sets the AF detection frame rate lower when the photographing imaging unit 3 operates at 12p than when it operates at 60p. The set frame rate signal is input to the AF drive unit 9 as the frame rate of the AF imaging unit 5. The AF imaging unit 5 is controlled according to the frame rate.
That is, an important effect different from that of the first embodiment is that, when the frame rate of the imaging unit 3 for shooting is low, automatically suppressing detection of autofocus at a higher frame rate than necessary. It is in. As a result, the power consumption of the entire imaging apparatus and the heat generated can be suppressed.
As described above, the imaging apparatus 200 according to the present embodiment automatically sets the autofocus frame rate to be low when the imaging unit 3 for imaging video signals for imaging is operating at a low frame rate. . Thereby, the outstanding effect which can suppress the power consumption of the whole imaging device is acquired, hold | maintaining a substantial autofocus response.

In the second embodiment described above, the frame rate change signal processing unit 12 generates a signal corresponding to the frame rate change by creating a signal similar to that in the 60p operation even during the 12p operation using a memory or the like. The case of realizing the processing has been described. However, the present invention is not limited to this, and other configurations such as changing the signal processing clock itself may be used.
In the second embodiment described above, the cases of 12p and 60p have been described, but the present invention is not limited to this. If the frame rate for shooting is variable, and if the frame rate of the video signal for shooting is low, control to automatically lower the frame rate of the video signal for autofocus is performed. Any frame rate may be used.
Further, in the above-described second embodiment, it has been described that the frame rate of the video signal for autofocus is set lower when the frame rate of the video signal for shooting is low. On the contrary, it is naturally possible to automatically set the frame rate of the video signal for autofocus to a high value in accordance with the frame rate of the video signal for shooting.

In addition, the imaging apparatus 200 according to the second embodiment may be used for the AF imaging unit 5 having an imaging element capable of reading an arbitrary position. In this case, if the control is performed so that the signal acquired by accumulating charges only in the necessary area of the image sensor is read, the frame rate of the video signal for autofocus can be increased more easily, and the autofocus response time is improved. be able to.
(Other embodiments)
In the first and second embodiments described above, a system using a four-plate image sensor as the optical path separation unit 2 is employed, but the number of image sensors is not limited to this. For example, as shown in FIG. 8, a five-plate image sensor may be used.
The optical path separation unit 2 in FIG. 8 further generates a G1 (green 1) light beam and a G2 (green 2) light beam by further dividing the G light beam after RGB spectroscopy by a half mirror as shown in FIG. All these luminous fluxes are converted into electric signals in the four photographing imaging sections 3 respectively. On the other hand, the G1 (green 1) light flux is further split before being input to the imaging unit 3 for photographing. The split light flux is input to another image sensor, that is, the AF imaging unit 5 and processed as an autofocus detection video signal.

In this optical path separation unit 2, R light, G1 light, G2 light, and B light can be respectively taken as video signals for photographing as in the conventional four-plate imaging method. As a result, it is possible to realize reliable and quick autofocus control, which is a unique effect of the present invention, while maintaining the performance of the video signal for photographing at the same level as before.
(Other)
The imaging device may be either HDTV compatible or SDTV compatible. In addition, an image pickup device (image pickup device of the image pickup unit 3 for shooting) for generating a video signal for shooting related to the video performance is compatible with HDTV, and a video signal for autofocus detection not related to the video performance is generated. The image pickup device (the image pickup device of the AF image pickup unit 5) may be adapted for SDTV. Thereby, it can be set as the imaging device which suppressed cost.

Also, the area used for autofocus evaluation, that is, the position and size of the AF evaluation area are arbitrary. The AF evaluation area may be an area obtained by adding a plurality of places or an area selected from a plurality of places. For example, the left area, the center area, and the right area of the screen may be detected separately, and the area where the subject exists may be selected. As a method for selecting the region where the subject exists, the region having the maximum AF evaluation value may be selected, or the user may perform a switch operation or face determination.
The above-described imaging apparatus may be partially integrated on a single chip using a semiconductor device such as an LSI.
Further, although it is referred to as LSI here, it may be referred to as 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's, and implementation using dedicated circuitry or general purpose processors 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.

Furthermore, 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.
(Effect of the embodiment of the present invention)
The imaging apparatus, imaging method, program, and integrated circuit according to all the embodiments of the present invention detect autofocus by detecting the optical path length with the maximum contrast from the video signal for autofocus when realizing the autofocus function. Since the control is performed, there is an effect that the video signal for photographing is not adversely affected at the time of detecting the optical path length.

The imaging apparatus, imaging method, program, and integrated circuit according to all the embodiments of the present invention, when realizing the autofocus function, detect the optical path length with the maximum contrast from the video signal for autofocus, Since the focus control of the system is performed, there is an effect that an autofocus function can be provided even for an imaging apparatus that cannot perform a high-speed lens operation such as a wobbling operation.
Further, according to the imaging apparatus, imaging method, program, and integrated circuit according to all embodiments of the present invention, when the autofocus function is realized, the video signal for shooting is completely affected during the focus search operation. Therefore, it is possible to search over a wide range and to control reliably even from a so-called large blurred state.
In addition, the imaging apparatus, imaging method, program, and integrated circuit according to the first embodiment of the present invention can control the frame rate of the video signal for autofocus detection independently when realizing the autofocus function. Response time can be improved by speeding up the frame rate of the video signal for autofocus regardless of the frame rate of the video signal for shooting. It has such an effect.

The imaging device, imaging method, program, and integrated circuit according to all embodiments of the present invention use an imaging device that can read an arbitrary position for an imaging unit for autofocus detection when realizing an autofocus function. As a result, the frame rate of the video signal for autofocus detection can be increased more easily, and the response speed of autofocus can be improved.
The imaging apparatus, imaging method, program, and integrated circuit according to the second embodiment of the present invention automatically autofocus when the imaging unit for imaging is operating at a low frame rate when the autofocus function is realized. Therefore, the power consumption of the entire image pickup apparatus can be suppressed while maintaining a substantial autofocus response.

  The present invention is useful because it can be applied to an imaging apparatus such as a video camera, an imaging method, a program, and an integrated circuit.

  The present invention relates to an imaging apparatus such as a video camera, an imaging method, a program, and an integrated circuit. Specifically, the present invention relates to an imaging device with an autofocus function, an imaging method, a program, and an integrated circuit that automatically focus.

Conventionally, in an imaging apparatus such as a video camera, a contrast maximum position detection method using wobbling is generally used as an autofocus method. The contrast maximum position detection method is as follows. A wobbling operation that moves the focus lens back and forth is performed. The contrast of the acquired video signal (the contrast of the video formed from the video signal) is compared. Then, the focus lens is sequentially moved in the direction in which the contrast of the video signal is maximized. Thus, a position where the contrast of the video signal is maximized (maximum contrast position) is detected, and the maximum contrast position is determined as the in-focus position.
For example, Japanese Patent Application Laid-Open No. 10-4517 describes a video camera including a focus adjustment device that uses a maximum contrast position detection method and is further reduced in size, weight, and cost. The video camera is a multi-plate type using a color separation prism that separates a light beam incident from an optical system into three colors of R, G, and B. This publication discloses that the color separation prism has a configuration that does not require an air gap, thereby realizing a reduction in size, weight, and cost. The focus adjustment device of the publication has a configuration in which the color separation prism does not require an air gap, thus solving the problem that the influence of the blue signal, the red signal, and the green signal on the focus adjustment operation occurs due to the mirror image relationship. is doing. In the same focus adjustment device, the same problem is solved by selecting a video signal that is not a mirror image and using it for focus adjustment.

Japanese Patent Laid-Open No. 10-4517

In a contrast maximum position detection method used in a conventional imaging apparatus such as a video camera, the contrast of the acquired video signal is compared every time a video signal is acquired by a wobbling operation. In this method, it is necessary to sequentially move the focus lens in the direction in which the contrast of the video signal is maximized. However, when the focus is completely out of focus, the contrast of the video signal hardly changes due to the wobbling operation. Therefore, there is a problem that the in-focus direction cannot be determined when the focus is completely out of focus.
Further, in the conventional contrast maximum position detection method, when the autofocus operation is activated in the focused state, the wobbling operation is performed at the focused position. In this case, a phenomenon occurs in which the main line system, that is, the video signal for shooting (hereinafter referred to as “video signal for shooting”) is focused (focused) or slightly blurred (out of focus). Has the problem.

In the conventional maximum contrast position detection method, contrast is detected using a video signal for photographing. Therefore, one field period of the video signal for photographing is required to detect the contrast once. For this reason, when the frame rate of the video signal for photographing is lowered, the absolute time required for detecting the contrast for autofocus control becomes longer. As a result, the autofocus response speed becomes slow. Therefore, particularly when shooting a moving subject or the like, there is a problem that it is difficult to obtain a good image.
Further, the conventional maximum contrast position detection method requires a high-speed wobbling operation. However, when an interchangeable lens or the like is used in the imaging apparatus, the focus lens operates slowly. Therefore, it is difficult to realize a high-speed wobbling operation, and there is a problem that the autofocus operation becomes extremely slow.

  The present invention solves the above-mentioned conventional problems, and an object thereof is to enable reliable and quick optical system focus control.

  An imaging apparatus according to a first aspect of the present invention condenses light from a subject and can control a focus, an optical path separation unit, a first imaging unit, a second imaging unit, and a first imaging unit. Imaging device comprising: a signal processing unit; a second signal processing unit; an evaluation value generating unit; a first driving unit; a second driving unit; an optical path length changing unit; and an autofocus control unit. It is. The optical path separation unit separates light from the subject collected by the optical system into at least a first light flux and a second light flux. The first imaging unit converts the first light flux into an electrical signal and outputs it as a first signal. The second imaging unit converts the second light flux into an electrical signal and outputs it as a second signal. The first signal processing unit performs signal processing of the first signal to generate a video signal for photographing. The second signal processing unit performs signal processing of the second signal. The evaluation value generation unit generates an evaluation value of the contrast of the second signal. The first driving unit drives the first imaging unit. The second drive unit drives the second imaging unit. The optical path length changing unit changes the optical path length of the second light flux. The autofocus control unit controls the optical path length changing unit, detects the maximum contrast evaluation value optical path length that is the optical path length of the second light flux that maximizes the contrast evaluation value of the second signal, and determines the maximum contrast evaluation value. Focus control of the optical system is performed based on the optical path length.

In this imaging apparatus, the light from the subject collected by the optical system is separated into at least a first light beam and a second light beam by the optical path separation unit. The first light beam is used for shooting video signal processing, and the second light beam is used for autofocus (AF) signal processing that is completely independent of the shooting video signal processing. In this imaging apparatus, the autofocus control unit controls the optical path length changing unit so as to change the optical path length of the second light flux based on the contrast evaluation value, and performs focus control of the optical system. That is, the optical path length changing unit is controlled by the autofocus control unit, and the maximum contrast evaluation value optical path length that is the optical path length of the second light flux at which the contrast evaluation value of the second signal is maximized is detected. Based on the evaluation value optical path length, focus control of the optical system is performed.
As described above, since the imaging apparatus generates an autofocus video signal and detects the maximum contrast evaluation value optical path length using this signal, the adverse effect at the time of detection does not affect the imaging video signal.

In addition, since this imaging device performs focus control of the optical system after detecting the maximum contrast evaluation value optical path length by the optical path length changing unit of the imaging unit for autofocus, it can be reliably controlled even in a large blurred state. is there.
In addition, even if the autofocus operation is started in the in-focus state, the imaging apparatus does not affect the main line system, that is, the video signal for shooting, and uses the video signal for autofocus detection. Make the state searchable.
In addition, since this image pickup apparatus performs the focus adjustment of the optical system after detecting the optical path length of the maximum contrast evaluation value in the video signal for autofocus, for example, a high-speed lens operation such as a wobbling operation cannot be performed. Even in the case of using the autofocus function, the autofocus function can be reliably realized.

“Performing focus control of the optical system based on the maximum contrast evaluation value optical path length” includes, for example, the following. First, the detected maximum contrast evaluation value optical path length is compared with a reference position corresponding to the optical path length of the first light flux input to the first imaging unit (imaging imaging unit). The in-focus position (focus position) of the optical system is calculated from the difference between both optical path lengths. Then, for example, the focusing lens (group) is moved so that the optical system is in a focused state based on the calculated focusing position. Thereby, focus control of the optical system is performed.
An image pickup apparatus according to a second aspect of the present invention is the image pickup apparatus according to the first aspect, wherein the first driver has a frame rate corresponding to the first signal and an independently variable first frame rate. Acquiring the first imaging unit at a first frame rate, and the second driving unit acquires a second frame rate that is independently variable and is a frame rate for the second signal; The second driving unit is driven at a frame rate of 2.

In this imaging apparatus, since the frame rate for autofocus detection can be controlled independently, it is not affected by the frame rate of the video signal for photographing. Therefore, the response speed of autofocus can be improved, or the power consumption of the imaging apparatus can be reduced.
An imaging apparatus according to a third aspect of the present invention is the imaging apparatus according to the first aspect, further comprising a frame rate changing unit that changes a first frame rate, which is a frame rate for the first signal. Further, the autofocus control unit can set or change a second frame rate that is a frame rate for the second signal based on the first frame rate, and controls the focus of the optical system based on the second frame rate. I do. Here, being able to set or change the second frame rate based on the first frame rate includes setting or changing the second frame rate in accordance with the change of the first frame rate.

In this imaging apparatus, the autofocus detection frame rate can be automatically set or changed in accordance with the shooting frame rate.
An image pickup apparatus according to a fourth aspect of the present invention is the image pickup apparatus according to the first aspect, wherein the second image pickup unit has an image pickup device capable of reading an arbitrary position.
In this image pickup device, the number of read pixels of the image pickup device for autofocus detection can be suppressed and the frame rate of the image pickup device for autofocus detection can be increased, so that the response speed of autofocus can be increased. Have.
An image pickup apparatus according to a fifth aspect of the present invention is the image pickup apparatus according to the first aspect, wherein the autofocus control unit causes the second image pickup unit to move in the optical axis direction of the second light flux by the optical path length changing unit. The maximum contrast evaluation value optical path length is detected by moving back and forth and repeatedly detecting the direction in which the contrast evaluation value increases.

In this imaging apparatus, it is possible to shorten the time until the maximum contrast evaluation value is detected. In addition, since the optical path is adjusted after the optical path length with the maximum contrast is detected in the video signal for autofocus, high-speed lens operation such as wobbling operation cannot be performed. An excellent effect that it can be provided is obtained.
An image pickup apparatus according to a sixth aspect of the present invention is the image pickup apparatus according to the first aspect, wherein the autofocus control unit moves the second image pickup unit in the optical axis direction of the second light flux by the optical path length changing unit. The maximum contrast evaluation value optical path length is detected by sequentially moving and evaluating the contrast evaluation value when the optical path length of the second light flux is sequentially changed. Here, sequentially moving the second image pickup unit in the optical axis direction of the second light beam detects the evaluation value of the contrast sequentially while moving the second image pickup unit in a certain direction of the optical axis direction, The maximum evaluation value among the detected evaluation values in a certain range is set as the maximum contrast evaluation value.

In this imaging apparatus, although time consuming, it is possible to detect the maximum contrast evaluation value more reliably.
An image pickup apparatus according to a seventh aspect of the present invention is the image pickup apparatus according to the third aspect, wherein the autofocus control unit lowers the second frame rate when the first frame rate is lowered.
This imaging apparatus can be controlled to suppress power consumption for autofocus detection.
According to an eighth aspect of the present invention, there is provided an imaging method for condensing light from a subject and controlling the focus, light from the subject condensed by the optical system at least a first light flux and a second light beam. An optical path separating unit that separates the first light beam into an electrical signal, a first imaging unit that outputs the first light beam as a first signal, a second light beam into an electrical signal, An imaging method used in an imaging apparatus comprising: a second imaging unit that outputs as a signal; and an optical path length changing unit that changes the optical path length of the second light beam, the first signal processing step, A signal processing step, an evaluation value generation step, a drive step, another drive step, a detection step, and an autofocus control step. In the first signal processing step, signal processing of the first signal is performed to generate a video signal for photographing. In the second signal processing step, signal processing of the second signal is performed. The evaluation value generation step generates an evaluation value of the contrast of the second signal. In the driving step, the first imaging unit is driven. Another driving step drives the second imaging unit. In the detecting step, the optical path length changing unit is controlled to detect a maximum contrast evaluation value optical path length that is an optical path length of the second light flux that maximizes the contrast evaluation value of the second signal. In the autofocus control step, focus control of the optical system is performed based on the maximum contrast evaluation value optical path length.

  According to a ninth aspect of the present invention, there is provided a program for collecting light from a subject, focusing an optical system capable of focus control, and at least first light flux and second light from the subject collected by the optical system. An optical path separating unit that separates into a light beam, a first imaging unit that converts the first light beam into an electrical signal and outputs it as a first signal, a second light beam that is converted into an electrical signal, and a second signal A program used for an imaging apparatus comprising: a second imaging unit that outputs a second optical path; and an optical path length changing unit that changes an optical path length of the second light beam, the first signal processing step, and a second signal A processing step, an evaluation value generation step, a driving step, another driving step, a detection step, and an autofocus control step are provided. In the first signal processing step, signal processing of the first signal is performed to generate a video signal for photographing. In the second signal processing step, signal processing of the second signal is performed. The evaluation value generation step generates an evaluation value of the contrast of the second signal. In the driving step, the first imaging unit is driven. Another driving step drives the second imaging unit. In the detection step, the optical path length changing unit is controlled to detect a maximum contrast evaluation value optical path length which is an optical path length of the second light flux at which the contrast evaluation value of the second signal is maximized. In the autofocus control step, focus control of the optical system is performed based on the maximum contrast evaluation value optical path length.

  An integrated circuit according to a tenth aspect of the present invention includes one or more first imaging units, a second imaging unit, a first signal processing unit, a second signal processing unit, an evaluation value generation unit, A first drive unit, a second drive unit, an optical path length changing unit, and an autofocus control unit are provided. The first imaging unit converts one or more lights out of the light separated from the output of the optical system into an electrical signal, and outputs it as a first signal. The second imaging unit converts light other than the one or more lights out of the plurality of lights into an electrical signal and outputs it as a second signal. The first signal processing unit performs signal processing of the first signal to generate a video signal for photographing. The second signal processing unit performs signal processing of the second signal. The evaluation value generation unit generates an evaluation value of the contrast of the second signal. The first driving unit generates a driving pulse for the first imaging unit. The second driving unit generates a driving pulse for the second imaging unit. The optical path length changing unit changes the optical path length of the second light flux. The autofocus control unit controls the optical path length changing unit, detects the maximum contrast evaluation value optical path length that is the optical path length of the second light flux that maximizes the contrast evaluation value of the second signal, and determines the maximum contrast evaluation value. Focus control of the optical system is performed based on the optical path length.

  An integrated circuit according to an eleventh aspect of the present invention includes a first signal processing unit, a second signal processing unit, an evaluation value generating unit, a first driving unit, a second driving unit, and an optical path length change. And an autofocus control unit. The first signal processing unit receives one or more electric signals among the plurality of electric signals generated by converting the light separated into a plurality via the optical system in the plurality of imaging units and performs signal processing. To generate a video signal for shooting. The second signal processing unit receives a second signal other than the one or more electrical signals and performs signal processing. The evaluation value generation unit generates an evaluation value of the contrast of the second signal. The first driving unit generates a driving pulse for the first imaging unit. The second driving unit generates a driving pulse for the second imaging unit. The optical path length changing unit changes the optical path length of the second light flux. The autofocus control unit controls the optical path length changing unit, detects the maximum contrast evaluation value optical path length that is the optical path length of the second light flux that maximizes the contrast evaluation value of the second signal, and determines the maximum contrast evaluation value. Focus control of the optical system is performed based on the optical path length.

  As described above, the present invention provides an excellent effect that an adverse effect when detecting the optical path length with the maximum contrast cannot be applied to the video signal for photographing.

1 is a block diagram showing a configuration of an imaging apparatus with an autofocus function according to Embodiment 1 of the present invention. Schematic diagram for explaining an optical path separation unit according to Embodiment 1 of the present invention 1 is a block diagram showing a configuration of an AF evaluation value generation unit according to Embodiment 1 of the present invention. Schematic diagram for explaining a part of the operation of the AF evaluation value generation unit according to the first embodiment of the present invention. Schematic diagram for explaining a state of searching for an optical path length that maximizes the contrast evaluation value according to Embodiment 1 of the present invention. FIG. 3 is a block diagram illustrating a configuration of an imaging apparatus with an autofocus function according to a second embodiment of the present invention. The schematic diagram for demonstrating the mode of the output signal in a different frame rate by Embodiment 2 of this invention The schematic diagram for demonstrating the optical path separation part by the other form of this invention

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
(Embodiment 1)
<1.1: Configuration of Imaging Device>
FIG. 1 is a block diagram showing a configuration of an imaging apparatus 100 with an autofocus function according to Embodiment 1 of the present invention.
In FIG. 1, an imaging apparatus 100 includes an optical system 1, an optical path separation unit 2, an imaging imaging unit 3 that constitutes a first imaging unit, and an imaging signal processing unit 4 that constitutes a first signal processing unit. And a photographing drive unit 21 constituting a first drive unit. The imaging apparatus 100 further includes an autofocus imaging unit 5 (hereinafter referred to as “AF imaging unit 5”) that constitutes the second imaging unit, and an analog signal processing unit 6 that constitutes the second signal processing unit. , An AD conversion unit 7, an autofocus evaluation value generation unit 8 (hereinafter referred to as “AF evaluation value generation unit 8”), and a drive unit 9 (hereinafter referred to as “autofocus imaging unit”) as a second drive unit. AF driving section 9 ”), autofocus optical path length changing section 10 (hereinafter referred to as“ AF optical path length changing section 10 ”), and autofocus control section 11 (hereinafter referred to as“ AF control section 11 ”). And).

The optical system 1 has a configuration capable of condensing light from a subject and adjusting a focal length of the light (light flux) from the subject, that is, a configuration capable of focus control. The optical system 1 outputs the collected light (light flux) from the subject to the optical path separation unit 2. The optical system 1 may be composed of a plurality of lenses. In the optical system 1, a focus control lens (which may be a lens unit including a plurality of lenses) that performs focus control is provided, and focus control is performed by moving the focus control lens. Good. Further, the optical system 1 may be configured by an interchangeable lens or the like.
The optical path separation unit 2 receives light (light beam) output from the optical system 1, and uses the light beam that has passed through the optical system 1 for autofocus detection (the first light beam for photographing and the second light beam). Hereinafter, the light beam may be separated into “light detection AF”. Then, the optical path separation unit 2 outputs the photographing light flux to the photographing imaging unit 3 and outputs the autofocus detection light flux to the AF imaging unit 5. Here, the optical path separation unit 2 converts the photographic light flux that has passed through the optical system 1 into a plurality of photographic light fluxes (for example, three light fluxes of R, B, and G, and R light flux). , B light beam, G1 light beam, and G2 light beam). In addition, the ratio of the AF detection light flux among the light fluxes input to the optical system 1 may be an arbitrary ratio (for example, 10%, 50%, etc.). For example, an optical prism (beam splitter) as shown in FIGS. 2 and 8 is preferably used as the optical path separation unit 2.

The imaging imaging unit 3 has an imaging element such as a CMOS or CCD, and receives the light beam output from the optical system 1 as an input. The photographing imaging unit 3 converts the light beam input from the optical system 1 into an electric signal by photoelectric conversion, and outputs the converted electric signal to the photographing signal processing unit 4.
The photographing signal processing unit 4 receives the output from the photographing imaging unit 3 as an input. The photographing signal processing unit 4 performs signal processing such as correlated double sampling processing, gain control processing, pedestal control processing, and gamma processing on the output signal of the photographing imaging unit 3 to obtain a photographing video signal.
The shooting drive unit 21 receives a frame rate signal for shooting. The imaging drive unit 21 outputs a drive pulse signal according to the frame rate signal. The photographing imaging unit 3 is driven by the output drive pulse signal.
The AF imaging unit 5 receives the light beam for autofocus detection output from the optical path separation unit 2 as an input. The AF imaging unit 5 converts the light beam for autofocus detection into an electrical signal and outputs it to the analog signal processing unit 6. The AF imaging unit 5 is connected to the AF optical path length changing unit 10. The AF imaging unit 5 is translated by the AF optical path length changing unit 10 on the optical axis of the autofocus detection light beam. The AF imaging unit 5 receives the drive pulse signal from the AF drive unit 9 and is driven by this drive pulse signal. The AF imaging unit 5 includes an image sensor that can read an arbitrary position. The electrical signal acquired in the entire area of the imaging device may be output to the analog signal processing unit 6, or the electrical signal acquired in a partial area of the imaging device is output to the analog signal processing unit 6. You may do it. Note that in which region of the image sensor the electrical signal that is the output of the AF imaging unit 5 is acquired is determined by the driving pulse signal from the AF driving unit 9.

The analog signal processing unit 6 receives the output from the AF imaging unit 5 as an input. The analog signal processing unit 6 performs correlated double sampling processing, gain control processing, pedestal control processing, and the like on the output from the AF imaging unit 5 and outputs the result to the AD conversion unit 7.
The AD conversion unit 7 converts the signal from the analog signal processing unit 6 into a digital signal and outputs it to the AF evaluation value generation unit 8.
The AF evaluation value generation unit 8 includes a selection signal output from the AF control unit 11, an evaluation region signal output from the AF drive unit 9, and an autofocus detection video signal (hereinafter referred to as an AF conversion unit 7). , “AF detection video signal”). The AF evaluation value generation unit 8 performs high-pass filter processing or the like on the video signal for autofocus detection based on an evaluation region signal and a selection signal, which will be described later, and extracts a high-frequency component of the signal to perform autofocus operation. An evaluation value (contrast evaluation value) is calculated. The AF evaluation value generation unit 8 outputs the calculated evaluation value to the AF control unit 11.

The AF driving unit 9 generates a driving pulse signal for driving the AF imaging unit 5.
The AF optical path length changing unit 10 translates the AF imaging unit 5 on the optical axis of the autofocus detection light beam using a small actuator or the like. As a result, the AF optical path length changing unit 10 changes the optical path length of the AF imaging unit 5. As the small actuator, a linear drive motor, a stepping motor, a piezoelectric ultrasonic linear actuator using a piezoelectric element, a slide mechanism, or the like can be used.
The AF control unit 11 controls the AF drive unit 9, the AF optical path length changing unit 10, and the like, and detects the optical path length that maximizes the evaluation value (contrast evaluation value) obtained from the AF evaluation value generation unit 8. To do. Thereby, the AF control unit 11 controls the focus position of the optical system 1.
FIG. 2 is a schematic diagram showing a more specific example of the optical path separation unit 2, the imaging unit 3 for shooting, the imaging unit 5 for AF, and the optical path length changing unit 10 for AF.

As shown in FIG. 2, the optical path separation unit 2 is configured using a color separation prism used in the four-plate imaging method. In the three-plate imaging method, the light is divided into R (red) light, G (green) light, and B (blue) light by a color separation prism. On the other hand, in the optical path separation unit 2 in the present embodiment, the G light after RGB spectroscopy is further divided by a half mirror as shown in FIG. 2 to create G1 (green 1) light and G2 (green 2) light. To do. Then, G2 (green 2) light is used as a light beam for autofocus detection. The remaining R (red) light, G1 (green 1) light, and B (blue) light are subjected to signal processing of a normal three-plate imaging method as a light flux for photographing. Further, an AF optical path length changing unit 10 using a small actuator is connected to an AF imaging unit 5 which is an imaging unit for G2 (green 2) light. The AF optical path length changing unit 10 enables the AF imaging unit 5 to move on the optical axis.
FIG. 3 is a block diagram illustrating an example of the configuration of the AF evaluation value generation unit 8.

  In FIG. 3, the AF evaluation value generation unit 8 includes a horizontal low-pass filter 101, two horizontal high-pass filters 102 and 103, a vertical high-pass filter 104, integration units 105 to 107, and an adder 108. And a selector 109. The low-pass filter 101 in the horizontal direction is a low-pass filter (hereinafter referred to as “horizontal LPF”) for the horizontal component of the video (two-dimensional video) formed by the video signal for autofocus detection. The two high-pass filters in the horizontal direction are high-pass filters (hereinafter referred to as “first horizontal HPF” and “second horizontal HPF”, respectively) for horizontal components of the video (two-dimensional video) formed by the video signal for autofocus detection. "). The high-pass filter in the vertical direction is a high-pass filter (hereinafter referred to as “vertical HPF”) for the vertical component of the video (two-dimensional video) formed by the video signal for autofocus detection. The horizontal LPF 101, the first horizontal HPF 102, the second horizontal HPF 103, the vertical HPF 104, and the accumulating units 105 to 107 constitute an arithmetic unit 111.

The horizontal LPF 101 receives an autofocus detection video signal (AF detection video signal) output from the AD converter 7 as an input. The horizontal LPF 101 is a low-pass filter for extracting a frequency band component necessary for generating a contrast evaluation value for the AF detection signal. The horizontal LPF 101 outputs the output signal to the first horizontal HPF 102, the second horizontal HPF 103, and the vertical HPF 104.
The first horizontal HPF 102 and the second horizontal HPF 103 have different frequency bands to pass. The first horizontal HPF 102 and the second horizontal HPF 103 are high-pass filters (for low frequency) that allow the first horizontal HPF 102 to pass a lower frequency band, and high-pass filters (high frequency) that allow the second horizontal HPF 103 to pass a higher frequency band. For).
Accumulators 105 to 107 accumulate the outputs of the high-pass filters 102 to 104 and output them to the adder 108 and the selector 109.

The calculation unit 111 includes a horizontal LPF 101, a first horizontal HPF 102, a second horizontal HPF 103, a vertical HPF 104, and integration units 105 to 107. An evaluation area signal is input from the AF drive unit 9 to the calculation unit 111. The evaluation area signal is used by the AF evaluation value generation unit 8 to select an area for evaluating autofocus (hereinafter referred to as an AF evaluation area). For example, when the AF detection video signal is taken from the center of the screen, the evaluation area signal is a pulse signal indicating the timing of the center of the screen. Note that this evaluation region signal may be input only to the integration units 105 to 107. In this case, the accumulators 105 to 107 accumulate the values in the AF evaluation area among the outputs of the high-pass filters 102 to 104 and output the accumulated values to the adder 108 and the selector 109.
The adder 108 adds the outputs of the integrating units 105 to 107 and outputs the addition result to the selector 109.

The selector 109 selects the outputs from the integrating units 105 to 107 and the adder 108 based on the selection signal. The selector 109 outputs the selected output signal to the AF control unit 11 as an evaluation value (contrast evaluation value). The selection signal is used to select a signal most suitable for the image to be captured. The selection signal will be described later.
The pass bands of the horizontal LPF 101, the first horizontal HPF 102, the second horizontal HPF 103, and the vertical HPF 104 are as follows, for example. When the video signal handled by the imaging apparatus 100 is an SDTV video signal, the horizontal LPF 101 is 0 to 2.0 MHz, the first horizontal HPF 102 is 300 kHz or more, the second horizontal HPF 103 is 1.2 MHz or more, and the vertical HPF 104 is 20 TV or more. Preferably there is. When the video signal handled by the imaging apparatus 100 is an HDTV video signal, the horizontal LPF 101 is 0 to 13.2 MHz, the first horizontal HPF 102 is 2.0 MHz or higher, the second horizontal HPF 103 is 6.6 MHz or higher, and the vertical HPF 104 is It is preferable that there are 45 TV lines or more.

<1.2: Operation of Imaging Device>
The operation of the image pickup apparatus with an autofocus function configured as described above will be described in detail with reference to FIGS.
The light beam that has passed through the optical system 1 is input to the optical path separation unit 2 shown in FIG. The light beam input from the optical system 1 by the optical path separation unit 2 is R (red) light for photographing, G1 (green 1) light, B (blue) light, and G2 (green) for autofocus detection. 2) Divided into luminous flux. The divided light fluxes are respectively converted into electrical signals by the three photographing imaging units 3 and one AF imaging unit 5.
The output of the imaging unit 3 is signal-processed by the imaging signal processing unit 4 in the same manner as in the normal three-plate imaging system. The processed signal is then output as a main line system, that is, a video signal for photographing.

On the other hand, the output of the AF imaging unit 5 is subjected to analog signal processing such as correlated double sampling, gain control, and pedestal control, as in normal signal processing. The analog signal processed output is then converted into a digital signal by the AD converter 7 and input to the AF evaluation value generator 8.
The AF evaluation value generation unit 8 evaluates the contrast of the video. Specifically, first, horizontal LPF processing is performed on an AF detection video signal input to the AF evaluation value generation unit 8. This is performed in order to suppress the noise component of the video signal for AF detection. Thereafter, a plurality of high-pass filter processes are performed on the AF detection signal that has been subjected to the horizontal LPF process. In the case of FIG. 3, the AF detection video signal input to the calculation unit 111 passes through the horizontal LPF 101. As described above, the calculation unit 111 receives the evaluation region signal from the AF drive unit 9 and calculates only the signal component in the AF evaluation region of the input AF detection video signal. In addition, in the calculation unit 111, the AF detection video signal is input to the first horizontal HPF 102, the second horizontal HPF 103, and the vertical HPF 104, respectively. The first horizontal HPF 102 extracts a high frequency component of a signal from a lower frequency in the horizontal direction. The second horizontal HPF 103 extracts a high frequency component of the video signal from a higher frequency in the horizontal direction. The vertical HPF 104 extracts a high-frequency component in the vertical direction. The signals after the high-pass processing in each of the high-pass filters 102 to 104 are integrated by the integrating units 105, 106, and 107 and output. Note that the evaluation region signal may be input only to the integration units 105 to 107. In this case, the integrating units 105 to 107 integrate the values in the AF evaluation area among the outputs of the high-pass filters 102 to 104, and output them to the adder 108 and the selector 109.

Outputs from the accumulating units 105, 106 and 107 are added by an adder 108. The added signal is input to the selector 109. That is, the outputs of the accumulators 105 to 107 and the output of the adder 108 that adds the outputs of these accumulators are input to the selector 109, and 4 of the selector 109 according to the selection signal from the AF controller 11. One of the two inputs is selected. The selected signal is output to the AF control unit 11 as a contrast evaluation value (contrast evaluation value).
The selection signal is used to select the most suitable signal depending on the image to be captured. For example, the evaluation value curves of the first horizontal HPF 102 (for low frequency) and the second horizontal HPF 103 (for high frequency) have characteristics as shown in FIG. As shown in FIG. 4, the first horizontal HPF 102 (for low frequency) draws a gentle mountain, and the second horizontal HPF 103 (for high frequency) draws a steep mountain in the vicinity of the focal point from a flat state. For example, in the case of a pattern such as a horizontal stripe pattern, there are almost no peaks in the evaluation value curve in both the first and second horizontal HPFs 102 and 103, and in the vertical HPF 104, a mountain is formed at the focal point. When detecting the optical path length of the maximum contrast evaluation value by repeatedly moving the AF imaging unit 5 back and forth to increase the contrast, for example, the following is performed. First, the output from the second horizontal HPF 103 (for high frequency) is selected, and when there is no change in the second horizontal HPF 103 (for high frequency), the output for AF is based on the output from the first horizontal HPF 102 (for low frequency). The imaging unit 5 is moved to near the in-focus position. Then, finally, it is conceivable to control such that the maximum contrast evaluation value optical path length is determined based on the output of the second horizontal HPF 103. Further, when there is no change in the evaluation values of the first and second horizontal HPFs 102 and 103, it can be controlled to select the output of the vertical HPF 104. Further, for example, first, control is performed roughly using the added values of the first and second horizontal HPFs 102 and 103 and the vertical HPF 104, and finally the control is performed based on the evaluation value of the second horizontal HPF 103 or the vertical HPF 104. May be performed. Note that the band, type, and selection method of these high-pass filters are various and not limited to these.

The AF control unit 11 monitors the contrast evaluation value output from the AF evaluation value generation unit 8, and the optical path length of the AF imaging unit 5 (input to the AF imaging unit 5 is performed by the AF optical path length changing unit 10. The optical path length of the luminous flux is changed sequentially. Thereby, the AF control unit 11 detects the optical path length of the AF imaging unit 5 that maximizes the contrast evaluation value. The AF optical path length changing unit 10 includes a linear drive motor, a stepping motor, a piezoelectric ultrasonic linear actuator using a piezoelectric element, and a slide mechanism along the optical axis. The AF optical path length changing unit 10 has a function of sliding the AF imaging unit 5 parallel to the optical axis (in the direction indicated by the bidirectional arrow D1 in FIG. 2), and is controlled by serial communication or the like, for example. The
In addition, the AF control unit 11 outputs a frame rate signal independent of the shooting frame rate signal that is the frame rate signal of the shooting imaging unit 3, that is, an AF frame rate signal, to the AF driving unit 9. The AF imaging unit 5 is driven by the output AF frame rate signal. Note that the frame rate of the AF imaging unit 5 according to the AF frame rate signal is changed by a frame rate changing unit (not shown) such as a menu or dial provided in the imaging apparatus 100. The AF control unit 11 sets the AF drive unit 9 so as to read out only the AF evaluation region (the region set for AF detection on the image sensor of the AF imaging unit 5). The AF driving unit 9 drives the AF imaging unit 5 and outputs an evaluation area signal to the AF evaluation value generation unit 8 and outputs an effective signal corresponding to the AF evaluation area as described above. Control. When the AF control unit 11 detects the optical path length of the AF imaging unit 5 that maximizes the contrast evaluation value, it is determined in advance corresponding to the detected optical path length and the optical path length of the imaging unit 3 for photographing. The difference from the reference value is calculated. The focus control of the optical system 1 is executed by detecting the focus position of the optical system 1 from the difference value.

That is, the AF optical path length changing unit 10 acquires the respective contrast evaluation values while sequentially changing the optical path length of the AF imaging unit 5, and detects the optical path length that maximizes the contrast evaluation value. The detected optical path length is compared with a reference position corresponding to the optical path length of the imaging unit 3 for photographing, the focus position of the optical system 1 is calculated from the difference, and the focus position control of the optical system 1 is performed. .
<1.2.1: Method of detecting optical path length that maximizes contrast evaluation value>
A method in which the AF control unit 11 acquires the respective contrast evaluation values while sequentially changing the optical path length of the AF imaging unit 5 and detects the optical path length that maximizes the contrast evaluation value will be described with reference to FIG. .
FIG. 5 is a schematic diagram for explaining an example of an operation for searching for an optical path length that maximizes the contrast evaluation value.

  In FIG. 5, the horizontal axis indicates the optical path length of the AF imaging unit 10, and the vertical axis indicates the contrast evaluation value calculated by the AF evaluation value generation unit 8. A thick arrow indicates a state of search for each time, and a thin curve indicates a contrast evaluation value curve. The case where a search from the search start position to the point where the contrast evaluation value is maximized is performed will be described with reference to this figure. The optical path length changing unit 10 for AF first changes the optical path length in either direction, and reads the contrast evaluation value acquired by the AF evaluation value generating unit. The contrast evaluation value at the current position is compared with the contrast evaluation value at the previous position. When the evaluation value decreases, the AF optical path length changing unit 10 reverses the direction in which the AF imaging unit 5 is moved. In the case of FIG. 5, the contrast evaluation value hardly changes when the optical path length is changed in the right direction (the direction in which the optical path length of the AF imaging unit increases) in the first time. Therefore, the optical path length is changed in the same direction for the second time. Since the contrast evaluation value has increased in the second change, the search is continued in the same direction. In all of the changes from the second time to the sixth time, the contrast evaluation value has increased, so it is determined that the maximum contrast point is further to the right. The contrast evaluation value has decreased due to the seventh change. That is, it is determined that the maximum point of the contrast evaluation value has been passed. In the eighth time, the direction of changing the optical path length of the AF imaging unit is reversed from the direction in the seventh time. At this time, it can be predicted that the position is in the vicinity of the maximum point (the point that becomes the maximum contrast evaluation value optical path length). Next, the same search is continued with a smaller amount of change. Finally, the point that decreases regardless of which direction is changed is detected as the maximum point (the point that becomes the maximum contrast evaluation value optical path length). When the first change direction is changed to the left direction in FIG. 5, the search position is at the extreme end (the limit at which the AF imaging unit 5 can be moved by the AF optical path length changing unit 10). Detecting that it has arrived. At this point, the search direction is reversed to the right, and the point where the contrast evaluation value finally becomes maximum can be reliably detected.

It should be noted here that the focus position of the optical system 1 is not controlled (changed) at all while the imaging apparatus 100 searches for a point where the contrast evaluation value is maximized using the AF optical path length changing unit 10. Therefore, the video signal for photographing is not affected at all.
Furthermore, when searching for an optical path length that maximizes the contrast evaluation value in the imaging apparatus 100, a wide range of search is possible because it does not affect the video signal for shooting at all. Therefore, the maximum point of the contrast evaluation value can be reliably detected even from a large blurred state.
As described above, in the imaging apparatus 100 according to the first embodiment, the focus control of the optical system 1 is performed by detecting the optical path length with the maximum contrast using the autofocus signal independent of the video signal for photographing. Therefore, the imaging apparatus 100 according to the first embodiment has an excellent effect that the adverse effect at the time of detection does not reach the imaging video signal.

As described above, the imaging apparatus 100 according to the first embodiment has no influence on the video signal for shooting even during the focus search operation. Therefore, the imaging apparatus 100 according to the first embodiment has an excellent effect that a wide range search is possible and the control can be surely performed even from a so-called large-blurred state.
Further, the AF imaging unit 5 of the imaging apparatus 100 includes an AF driving unit 9 different from the imaging driving unit 21. Therefore, the frame rate of the AF imaging unit 5 can be set independently of the frame rate of the imaging unit 3 for photographing. This has the following effects. For example, when the frame rate of the imaging unit 3 for shooting is lowered to 12P or less, if the frame rate of the AF imaging unit 5 is also lowered to 12P or less, the photographer feels that the autofocus responsiveness has deteriorated. Sometimes. In this case, the responsiveness of autofocus is improved by keeping only the frame rate of the AF imaging unit 5 at a constant height. On the other hand, when the frame rate of the photographing imaging unit 3 is increased to, for example, 60P or more, if the frame rate of the AF imaging unit 5 is also increased in the same manner, power may be consumed more than necessary. This is because, even if the frame rate of the AF imaging unit 5 is increased, the improvement of the autofocus response may be limited depending on the size, weight, type, and the like of the lens. In this case, wasteful power consumption can be prevented by suppressing only the frame rate of the AF imaging unit 5. The imaging apparatus 100 according to the first embodiment can independently change the frame rate of the AF imaging unit 5, thereby improving the autofocus response speed according to the situation or reducing power consumption. Further, the imaging apparatus 100 can easily increase the frame rate of the AF imaging unit 5 by using the AF imaging unit 5 having an imaging device capable of reading an arbitrary position so as to read out only a necessary region. The autofocus response time can be improved.

As described above, the imaging apparatus 100 according to the first embodiment has an excellent effect that the frame rate of the AF imaging unit 5 can be independently controlled, and is not affected by the frame rate of the imaging unit 3 for photographing. It is done. That is, in order to improve the autofocus response time, the frame rate of the AF imaging unit 5 may be increased separately from the frame rate of the imaging unit 3 for shooting. This represents a remarkable effect at the time of shooting at a low frame rate, particularly in the case of an imaging device in which the frame rate of a video signal for shooting is variable. When the frame rate of the imaging unit 3 for shooting is high, only the frame rate of the AF imaging unit 5 needs to be set low in order to prevent wasteful consumption of power consumption.
In the first embodiment, the optical path separation unit 2 has been described with the color separation prism used in the four-plate imaging method. If the photographing light beam and the AF light beam can be separated, it is not necessary to be a four-plate color separation prism, and the AF light beam does not have to be Gch.

In the first embodiment, the AF evaluation value generation unit 8 is an arithmetic operation including a horizontal LPF 101, a first horizontal HPF 102, a second horizontal HPF 103, a vertical HPF 104, accumulating units 105, 106, 107, an adder 108, and a selector 109. The example constituted by the unit 111 has been described. However, the AF evaluation value generation unit 8 may have any configuration (circuit) as long as the value for evaluating the contrast of the video can be detected. The AF evaluation value generation unit 8 may be configured by, for example, one type of horizontal HPF that can change the characteristics of the passband.
In the first embodiment described above, the method for detecting the position where the contrast evaluation value is maximized has been described as a method of greatly changing the optical path length from the beginning, but is not limited thereto. For example, the AF control unit 11 uses the AF optical path length changing unit 10 to sequentially move the AF imaging unit 5 in the optical axis direction, and the contrast evaluation value when the optical path length of the second light flux is sequentially changed. By evaluating, the optical path length that maximizes the contrast evaluation value may be detected. In this case, the contrast evaluation value is sequentially detected while moving the AF imaging unit 5 in a certain direction along the optical axis. The maximum evaluation value among the detected evaluation values in a certain range is set as the maximum contrast evaluation value. Detection in this way takes time, but makes it possible to obtain the maximum contrast evaluation value more reliably. Alternatively, the search method may be combined with conventional wobbling. In other words, the wobbling operation may be repeated, and a method of detecting a point at which the contrast evaluation value becomes maximum may be detected by a so-called hill-climbing algorithm, or a method of changing the optical path length using the golden section method or the like. Any method may be used as long as the optical path length that maximizes the contrast evaluation value can be detected.
(Embodiment 2)
<2.1: Configuration of imaging apparatus>
FIG. 6 is a block diagram showing a configuration of an imaging apparatus 200 with an autofocus function according to the second embodiment of the present invention. The imaging apparatus 200 differs from the imaging apparatus 100 according to the first embodiment in the following points. First, the imaging apparatus 200 according to the second embodiment includes an imaging frame rate change control unit 13 and a frame rate change signal processing unit 12 that constitute a frame rate change unit. In the imaging apparatus 200 according to the second embodiment, the adaptive AF control unit 14 changes the frame rate of the auto AF imaging unit 5 in accordance with the frame rate of the main line system, that is, the imaging imaging unit 3. In addition, the same code | symbol is attached | subjected about the component same as the imaging device 100 of the said Embodiment 1. FIG.

The imaging apparatus 200 includes an optical system 1, an optical path separation unit 2, a photographing imaging unit 3, a frame rate change signal processing unit 12, a photographing driving unit 21, and an autofocus imaging unit 5 (hereinafter referred to as AF). Imaging unit 5), analog signal processing unit 6, AD conversion unit 7, autofocus evaluation value generation unit 8 (hereinafter referred to as AF evaluation value generation unit 8), AF drive unit 9, and AF optical path length change Unit 10, adaptive AF control unit 14, and shooting frame rate change control unit 13.
The optical system 1 is configured by an interchangeable lens or the like, and has a configuration capable of controlling the focus position. The optical path separator 2 separates the light beam that has passed through the optical system 1 into a light beam for photographing and a light beam for autofocus detection. The imaging unit 3 has an imaging element such as a CMOS or CCD, and converts the imaging light flux into an electrical signal.
The frame rate change signal processing unit 12, like the imaging signal processing unit 4 of the imaging apparatus 100, performs correlated double sampling processing, gain control processing, pedestal control processing, gamma processing, and the like on the output of the imaging imaging unit 3. A signal processing unit for photographing that performs signal processing. The frame rate change signal processing unit 12 further performs signal processing corresponding to the frame rate change.

The shooting drive unit 21 receives the shooting frame rate signal from the shooting frame rate change control unit 13. The imaging drive unit 21 outputs a drive pulse signal according to the frame rate signal. The photographing imaging unit 3 is driven by the output drive pulse signal.
The AF imaging unit 5 converts the light beam for autofocus detection into an electrical signal. The analog signal processing unit 6 performs signal processing such as correlated double sampling processing, gain control processing, and pedestal control processing. The AD converter 7 converts the signal from the analog signal processor 6 into a digital signal.
The AF evaluation value generation unit 8 includes a selection signal output from the adaptive AF control unit 14, an evaluation region signal output from the AF drive unit 9, and an autofocus detection video signal output from the AD conversion unit 7. (Hereinafter referred to as “AF detection video signal”) as an input. The AF evaluation value generation unit 8 performs high-pass filter processing or the like on the video signal for autofocus detection based on the evaluation region signal and the selection signal to extract a high-frequency component of the signal, and evaluates the evaluation value of the autofocus operation (Evaluation value of contrast) is calculated. The AF evaluation value generation unit 8 outputs the result to the adaptive AF control unit 14.

The AF driving unit 9 generates a driving pulse for driving the AF imaging unit 5.
The AF optical path length changing unit 10 translates the AF imaging unit 5 on the optical axis of the autofocus detection light beam using a small actuator or the like. As a result, the AF optical path length changing unit 10 changes the optical path length of the AF imaging unit 5. The small actuator can be realized using a linear drive motor, a stepping motor, a piezoelectric ultrasonic linear actuator using a piezoelectric element, a slide mechanism, or the like.
The adaptive AF control unit 14 reads the frame rate of the photographing imaging unit 3 and controls the AF driving unit 9, the AF optical path length changing unit 10, and the like. The adaptive AF control unit 14 controls the focus position of the optical system 1 by detecting the optical path length that maximizes the evaluation value obtained from the AF evaluation value generation unit 8. The shooting frame rate change control unit 13 changes the frame rate of the shooting imaging unit 3.

The differences between the imaging apparatus 200 with the autofocus function configured as described above and the first embodiment are mainly in the following points. The frame rate of the video signal for shooting can be changed by the shooting frame rate change control unit 13 and the frame rate change signal processing unit 12. The AF control unit 14 can change the frame rate of the AF imaging unit 5 in accordance with a shooting frame rate signal (a signal for determining the frame rate of a shooting video signal). In other words, when the frame rate of the imaging unit 3 for shooting is very low, the power consumption for autofocus detection is reduced by reducing the frame rate of the AF imaging unit 5 to such an extent that a sense of incongruity does not occur in the autofocus response. It can control to suppress.
<2.2: Operation of Imaging Device>
Next, operations of the frame rate change signal processing unit 12, the shooting frame rate change control unit 13, and the adaptive AF control unit 14 will be described in detail. Other components are the same as those in the first embodiment, and thus the description thereof is omitted.

For example, consider the case where the imaging apparatus 200 can change the frame rate and the frame rate is 12p and 60p in the 720 / 60p (progressive) format. In the case of 12p, an effective video signal of 12 frames is output per second, and in the case of 60p, an effective video signal of 60 frames is output per second. In other words, 12p outputs a video signal acquired by accumulating charges in the imaging unit for 1/12 seconds, and 60p outputs a video signal acquired by accumulating charges in 1/60 seconds.
FIG. 7 is a schematic diagram for explaining a state of an output signal when the photographing imaging unit 3 operates at 12p and 60p.
When the frame rate of the image pickup unit 3 is 60p, the image pickup unit 3 outputs a video signal obtained by accumulating charges for 1/60 seconds as shown in FIG. 7A. When the frame rate of the imaging unit 3 for shooting is changed to 12p by a menu or a dial provided in the imaging apparatus 200, the shooting frame rate change control unit 13 reads the changed frame rate. The read frame rate signal is input to the photographing drive unit 21. The imaging drive unit 21 outputs drive pulses including timing pulses in accordance with the input frame rate signal. The imaging drive unit 21 drives the imaging imaging unit 3 with this drive pulse. As a result, as shown in FIG. 7B, the imaging unit 3 for photographing outputs a video signal obtained by accumulating charges for 1/12 seconds in a 1/60 second period every 1/12 seconds. The output signal is input to the frame rate change signal processing unit 12. The frame rate change signal processing unit 12 also performs processing such as gain adjustment, pedestal adjustment, and gamma correction on a 12p video signal. The frame rate change signal processing unit 12 writes a 12p effective video signal to a storage unit such as a memory to cope with the frame rate change, and a circuit (data reading unit) that reads the same data even when there is no video signal. Use. As a result, even when the shooting imaging unit 3 operates at 12p, the frame rate change signal processing unit 12 creates the same signal as when the shooting imaging unit 3 operates at 60p, and performs signal processing at a different frame rate. Is running.

A signal for determining the frame rate of the video signal for photographing is also input to the adaptive AF control unit 14. The adaptive AF control unit 14 sets the AF detection frame rate lower when the photographing imaging unit 3 operates at 12p than when it operates at 60p. The set frame rate signal is input to the AF drive unit 9 as the frame rate of the AF imaging unit 5. The AF imaging unit 5 is controlled according to the frame rate.
That is, an important effect different from that of the first embodiment is that, when the frame rate of the imaging unit 3 for shooting is low, automatically suppressing detection of autofocus at a higher frame rate than necessary. It is in. As a result, the power consumption of the entire imaging apparatus and the heat generated can be suppressed.
As described above, the imaging apparatus 200 according to the present embodiment automatically sets the autofocus frame rate to be low when the imaging unit 3 for imaging video signals for imaging is operating at a low frame rate. . Thereby, the outstanding effect which can suppress the power consumption of the whole imaging device is acquired, hold | maintaining a substantial autofocus response.

In the second embodiment described above, the frame rate change signal processing unit 12 generates a signal corresponding to the frame rate change by creating a signal similar to that in the 60p operation even during the 12p operation using a memory or the like. The case of realizing the processing has been described. However, the present invention is not limited to this, and other configurations such as changing the signal processing clock itself may be used.
In the second embodiment described above, the cases of 12p and 60p have been described, but the present invention is not limited to this. If the frame rate for shooting is variable, and if the frame rate of the video signal for shooting is low, control to automatically lower the frame rate of the video signal for autofocus is performed. Any frame rate may be used.
Further, in the above-described second embodiment, it has been described that the frame rate of the video signal for autofocus is set lower when the frame rate of the video signal for shooting is low. On the contrary, it is naturally possible to automatically set the frame rate of the video signal for autofocus to a high value in accordance with the frame rate of the video signal for shooting.

In addition, the imaging apparatus 200 according to the second embodiment may be used for the AF imaging unit 5 having an imaging element capable of reading an arbitrary position. In this case, if the control is performed so that the signal acquired by accumulating charges only in the necessary area of the image sensor is read, the frame rate of the video signal for autofocus can be increased more easily, and the autofocus response time is improved. be able to.
(Other embodiments)
In the first and second embodiments described above, a system using a four-plate image sensor as the optical path separation unit 2 is employed, but the number of image sensors is not limited to this. For example, as shown in FIG. 8, a five-plate image sensor may be used.
The optical path separation unit 2 in FIG. 8 further generates a G1 (green 1) light beam and a G2 (green 2) light beam by further dividing the G light beam after RGB spectroscopy by a half mirror as shown in FIG. All these luminous fluxes are converted into electric signals in the four photographing imaging sections 3 respectively. On the other hand, the G1 (green 1) light flux is further split before being input to the imaging unit 3 for photographing. The split light flux is input to another image sensor, that is, the AF imaging unit 5 and processed as an autofocus detection video signal.

In this optical path separation unit 2, R light, G1 light, G2 light, and B light can be respectively taken as video signals for photographing as in the conventional four-plate imaging method. As a result, it is possible to realize reliable and quick autofocus control, which is a unique effect of the present invention, while maintaining the performance of the video signal for photographing at the same level as before.
(Other)
The imaging device may be either HDTV compatible or SDTV compatible. In addition, an image pickup device (image pickup device of the image pickup unit 3 for shooting) for generating a video signal for shooting related to the video performance is compatible with HDTV, and a video signal for autofocus detection not related to the video performance is generated. The image pickup device (the image pickup device of the AF image pickup unit 5) may be adapted for SDTV. Thereby, it can be set as the imaging device which suppressed cost.

Also, the area used for autofocus evaluation, that is, the position and size of the AF evaluation area are arbitrary. The AF evaluation area may be an area obtained by adding a plurality of places or an area selected from a plurality of places. For example, the left area, the center area, and the right area of the screen may be detected separately, and the area where the subject exists may be selected. As a method for selecting the region where the subject exists, the region having the maximum AF evaluation value may be selected, or the user may perform a switch operation or face determination.
The above-described imaging apparatus may be partially integrated on a single chip using a semiconductor device such as an LSI.
Further, although it is referred to as LSI here, it may be referred to as 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's, and implementation using dedicated circuitry or general purpose processors 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.

Furthermore, 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.
(Effect of the embodiment of the present invention)
The imaging apparatus, imaging method, program, and integrated circuit according to all the embodiments of the present invention detect autofocus by detecting the optical path length with the maximum contrast from the video signal for autofocus when realizing the autofocus function. Since the control is performed, there is an effect that the video signal for photographing is not adversely affected at the time of detecting the optical path length.

The imaging apparatus, imaging method, program, and integrated circuit according to all the embodiments of the present invention, when realizing the autofocus function, detect the optical path length with the maximum contrast from the video signal for autofocus, Since the focus control of the system is performed, there is an effect that an autofocus function can be provided even for an imaging apparatus that cannot perform a high-speed lens operation such as a wobbling operation.
Further, according to the imaging apparatus, imaging method, program, and integrated circuit according to all embodiments of the present invention, when the autofocus function is realized, the video signal for shooting is completely affected during the focus search operation. Therefore, it is possible to search over a wide range and to control reliably even from a so-called large blurred state.
In addition, the imaging apparatus, imaging method, program, and integrated circuit according to the first embodiment of the present invention can control the frame rate of the video signal for autofocus detection independently when realizing the autofocus function. Response time can be improved by speeding up the frame rate of the video signal for autofocus regardless of the frame rate of the video signal for shooting. It has such an effect.

The imaging device, imaging method, program, and integrated circuit according to all embodiments of the present invention use an imaging device that can read an arbitrary position for an imaging unit for autofocus detection when realizing an autofocus function. As a result, the frame rate of the video signal for autofocus detection can be increased more easily, and the response speed of autofocus can be improved.
The imaging apparatus, imaging method, program, and integrated circuit according to the second embodiment of the present invention automatically autofocus when the imaging unit for imaging is operating at a low frame rate when the autofocus function is realized. Therefore, the power consumption of the entire image pickup apparatus can be suppressed while maintaining a substantial autofocus response.

  The present invention is useful because it can be applied to an imaging apparatus such as a video camera, an imaging method, a program, and an integrated circuit.

DESCRIPTION OF SYMBOLS 1 Optical system 2 Optical path separation part 3 The imaging part for imaging | photography (1st imaging part)
4 Signal processing unit for photographing (first signal processing unit)
5 AF imaging unit (second imaging unit)
6 Analog signal processor (second signal processor)
7 AD conversion 8 AF evaluation value generation unit (evaluation value generation unit)
9 AF drive section (second drive section)
10 AF optical path length changing section (optical path length changing section)
11 AF control unit (autofocus control unit)
12 Frame Rate Change Signal Processing Unit 13 Shooting Frame Rate Change Control Unit 14 Adaptive AF Control Unit (Autofocus Control Unit)
21. Shooting drive unit (first drive unit)
101 horizontal low-pass filter 102 first horizontal high-pass filter 103 second horizontal high-pass filter 104 vertical high-pass filters 105, 106, 107 accumulator 108 adder 109 selector

Claims (11)

An optical system that collects light from the subject and controls focus;
An optical path separation unit for separating light from the subject collected by the optical system into at least a first light beam and a second light beam;
A first imaging unit that converts the first light flux into an electrical signal and outputs the first signal;
A second imaging unit that converts the second light flux into an electrical signal and outputs the second signal as a second signal;
A first signal processing unit that performs signal processing of the first signal and generates a video signal for photographing;
A second signal processing unit for performing signal processing of the second signal;
An evaluation value generator for generating an evaluation value of the contrast of the second signal;
A first driving unit for driving the first imaging unit;
A second drive unit for driving the second imaging unit;
An optical path length changing unit for changing an optical path length of the second light flux;
The optical path length changing unit is controlled to detect a maximum contrast evaluation value optical path length which is an optical path length of the second light flux at which the contrast evaluation value of the second signal is maximized, and the maximum contrast evaluation value optical path An autofocus control unit for controlling the focus of the optical system based on the length;
Comprising
Imaging device. The first driving unit acquires a first variable frame rate that is an independent frame rate for the first signal, drives the first imaging unit at the first frame rate,
The second driving unit obtains a variable second frame rate which is a frame rate for the second signal and independently drives the second driving unit at the second frame rate;
The imaging device according to claim 1. A frame rate changing unit that changes a first frame rate that is a frame rate for the first signal;
The autofocus control unit can set or change a second frame rate that is a frame rate for the second signal based on the first frame rate, and the optical focus control unit can change the optical rate based on the second frame rate. System focus control,
The imaging device according to claim 1. The second imaging unit includes an image sensor that can read an arbitrary position.
The imaging device according to claim 1. The autofocus control unit detects the direction in which the contrast evaluation value increases by moving the second imaging unit back and forth in the optical axis direction of the second light flux by the optical path length changing unit. , To detect the maximum contrast evaluation value optical path length,
The imaging device according to claim 1. When the optical path length changing unit sequentially moves the second imaging unit in the optical axis direction of the second light beam and sequentially changes the optical path length of the second light beam by the optical path control unit. By detecting the contrast evaluation value, the maximum contrast evaluation value optical path length is detected.
The imaging device according to claim 1. The autofocus control unit lowers the second frame rate when the first frame rate is low;
The imaging device according to claim 3. An optical system that collects light from the subject and controls focus;
An optical path separation unit for separating light from the subject collected by the optical system into at least a first light beam and a second light beam;
A first imaging unit that converts the first light flux into an electrical signal and outputs the first signal;
A second imaging unit that converts the second light flux into an electrical signal and outputs the second signal as a second signal;
An optical path length changing unit for changing an optical path length of the second light flux;
An imaging method used for an imaging apparatus comprising:
A first signal processing step of performing signal processing of the first signal and generating a video signal for photographing;
A second signal processing step for performing signal processing of the second signal;
An evaluation value generating step for generating an evaluation value of the contrast of the second signal;
A driving step of driving the first imaging unit;
Another driving step of driving the second imaging unit;
A detection step of controlling the optical path length changing unit to detect a maximum contrast evaluation value optical path length that is an optical path length of the second light flux at which the contrast evaluation value of the second signal is maximized;
An autofocus control step for performing focus control of the optical system based on the maximum contrast evaluation value optical path length;
Comprising
Imaging method. An optical system that collects light from the subject and controls focus;
An optical path separation unit for separating light from the subject collected by the optical system into at least a first light beam and a second light beam;
A first imaging unit that converts the first light flux into an electrical signal and outputs the first signal;
A second imaging unit that converts the second light flux into an electrical signal and outputs the second signal as a second signal;
An optical path length changing unit for changing an optical path length of the second light flux;
A program used for an imaging apparatus comprising:
A first signal processing step of performing signal processing of the first signal and generating a video signal for photographing;
A second signal processing step for performing signal processing of the second signal;
An evaluation value generating step for generating an evaluation value of the contrast of the second signal;
A driving step of driving the first imaging unit;
Another driving step of driving the second imaging unit;
A detection step of controlling the optical path length changing unit to detect a maximum contrast evaluation value optical path length that is an optical path length of the second light flux at which the contrast evaluation value of the second signal is maximized;
An autofocus control step for performing focus control of the optical system based on the maximum contrast evaluation value optical path length;
Comprising
program. One or more first imaging units that convert one or more lights out of the light separated from the output of the optical system into an electrical signal and output it as a first signal;
A second imaging unit that converts light other than the one or more of the plurality of lights into an electrical signal and outputs the second signal as a second signal;
A first signal processing unit that performs signal processing of the first signal and generates a video signal for photographing;
A second signal processing unit for performing signal processing of the second signal;
An evaluation value generator for generating an evaluation value of the contrast of the second signal;
A first driving unit that generates a driving pulse of the first imaging unit;
A second driving unit for generating a driving pulse of the second imaging unit;
An optical path length changing unit for changing an optical path length of the second light flux;
The optical path length changing unit is controlled to detect a maximum contrast evaluation value optical path length which is an optical path length of the second light flux at which the contrast evaluation value of the second signal is maximized, and the maximum contrast evaluation value optical path An autofocus control unit for controlling the focus of the optical system based on the length;
Comprising
Integrated circuit. Among the plurality of electrical signals generated by converting the light separated into a plurality via the optical system in a plurality of imaging units, one or more electrical signals are received and signal processing is performed, and a video signal for photographing is obtained. A first signal processor to generate;
A second signal processing unit that receives a second signal other than the one or more electrical signals and performs signal processing;
An evaluation value generator for generating an evaluation value of the contrast of the second signal;
A first driving unit that generates a driving pulse of the first imaging unit;
A second driving unit for generating a driving pulse of the second imaging unit;
An optical path length changing unit for changing an optical path length of the second light flux;
The optical path length changing unit is controlled to detect a maximum contrast evaluation value optical path length which is an optical path length of the second light flux at which the contrast evaluation value of the second signal is maximized, and the maximum contrast evaluation value optical path An autofocus control unit for controlling the focus of the optical system based on the length;
Comprising
Integrated circuit.

Images