JP4579958B2 - Imaging device - Google Patents

Description

The present invention relates to an imaging equipment, in particular, relates an automatic focus adjustment means of the phase difference detection type, the imaging equipment is interchangeable lens SLR electronic camera having an automatic focusing device of the contrast detection type.

  2. Description of the Related Art Conventionally, a phase difference detection type is used as an automatic focus adjustment device of an interchangeable lens type single-lens reflex electronic camera. This automatic focus adjustment device performs a focus adjustment operation of a focus adjustment lens of a photographing lens by using a defocus detection mechanism for autofocus provided in a camera body and a motor in the lens or the camera.

  In addition, a contrast detection type automatic focus adjustment device that performs contrast detection using a high-frequency component of a signal from the image sensor, and a contrast detection type automatic focus adjustment device in addition to a phase difference detection type automatic focus adjustment device are used in combination. Things have been proposed.

  The phase difference detection type auto focus adjustment device can know the defocus direction and defocus amount by one focus detection, so it takes less time for auto focus adjustment and is important as an interchangeable lens single lens reflex electronic camera There is an advantage that a short release time lag is short (for example, Patent Document 1).

The contrast detection type automatic focus adjustment apparatus has an advantage of high focusing accuracy because focus detection can be performed using a signal from the image sensor itself.
JP 05-64056 A

  However, in the phase difference detection type automatic focus adjustment device, since the focus detection sensor is different from the image sensor, the focus detection sensor is focused due to manufacturing errors including an interchangeable lens, environmental changes, changes over time, and the like. There is a difference between the position and the focus position of the image sensor. In order to guarantee an in-focus accuracy that is important as an automatic focusing device for an interchangeable-lens single-lens reflex electronic camera, the camera becomes large and the cost becomes very high. Since the contrast detection type automatic focus adjustment device searches for the in-focus position while moving the focus adjustment lens and the like and repeating the focus detection cycle, the release time lag becomes longer.

  In the case of using a contrast detection type auto focus adjustment device in addition to the phase difference detection type auto focus adjustment device, the focus adjustment lens is quickly driven to the vicinity of the in-focus position by the phase difference detection type auto focus adjustment device. The contrast detection type auto-focusing device can correct errors due to manufacturing errors including interchangeable lenses, environmental changes, changes over time, etc. The number of frames that can be taken per second (hereinafter referred to as “the number of continuous shots”) cannot be increased.

An object of the present invention is to provide an imaging device capable of increasing the continuous shooting speed and increasing the number of continuous shootings while guaranteeing focusing accuracy from the second frame during continuous shooting, and an automatic focus adjusting device and a control method thereof. It is to provide.

In order to achieve the above-described object, an imaging apparatus according to claim 1 includes an imaging unit that captures a subject image, and a first focus adjustment unit that performs first focus adjustment based on a phase difference between the two images. And second focus adjustment means for performing second focus adjustment based on the contrast of the image, and the first focus adjustment by the first focus adjustment means in the first imaging at the time of continuous imaging. After that, the second focus adjustment by the second focus adjustment means is performed, the subject image is taken by the imaging means, and after the first focus adjustment by the first focus adjustment means in the second and subsequent imaging. And a control means for capturing a subject image in the imaging means without performing the second focus adjustment by the second focus adjustment means.

As described above in detail, according to the present invention, the second focus adjustment by the second focus adjustment means is not performed after the first focus adjustment by the first focus adjustment means in the second and subsequent imaging. In addition, since the imaging unit performs control to continuously capture the subject image, it is possible to increase the continuous shooting speed and increase the number of continuous shooting while guaranteeing the focusing accuracy from the second frame during continuous shooting.

  FIG. 1 is a block diagram showing a schematic configuration of an electronic camera including an automatic focus adjustment apparatus according to an embodiment of the present invention, and shows a case where the electronic camera is in a viewfinder observation state.

  The electronic camera shown in FIG. 1 is a single-lens reflex digital still camera with a replaceable lens that uses a large-size solid-state image sensor and picks up an image by primary imaging. The photographing lens used in the electronic camera is for an autofocus single-lens reflex camera using a silver salt photograph.

  In FIG. 1, the electronic camera includes a camera body 5 which will be described later, and a photographing lens 1 which is detachably attached to the camera body 5. FIG. 1 shows the case where the electronic camera is in the viewfinder observation state and the electronic camera is in the exposure state.

  The photographing lens 1 includes an imaging optical system 2 having a focus adjustment lens, a lens driving unit 3 that drives the focus adjustment lens to adjust the focal position of the imaging optical system 2, and a lens control that controls the lens driving unit 3. Means 4.

  The camera body 5 mainly has a half mirror at the center, a first mirror 6 that reflects part of the subject image by the imaging optical system 2 and transmits the rest as it is, and a first mirror on the lower surface. 6 is focused on the upper surface of the finder screen 7 and the finder screen 7 in which the Fresnel lens for condensing the focused subject image is formed on the upper surface. A pentaprism 8 that reflects the subject image, a finder 9 that observes the subject image reflected by the pentaprism 8 as a finder image, and a second mirror 10 that reflects the subject image transmitted through the first mirror 6 are provided. .

  In addition, the camera body 5 has a focal plane shutter 14 that blocks the imaging light beam behind the second mirror 10, and behind that, an individual such as a CCD or CMOS that forms the subject image from the photographing lens 2. It has an image sensor 15 and further has a release switch (not shown). The release switch has a first stroke position (first stroke switch SW1: ON) in the middle of the stroke and a second stroke position (second stroke switch SW2: ON) of the full stroke. The electronic camera performs a focusing operation in the first stroke, and performs a shutter operation in the second stroke.

  The first mirror 6, the second mirror 10, and the focal plane shutter 14 are deployed as shown in FIG. 1 when the electronic camera is in the viewfinder observation state, and when the electronic camera is in the exposure state. As shown in FIG. 2, the mirror is raised or retracted.

  Further, as shown in FIG. 1, the camera body 5 includes a phase difference detection type AF sensor 11 that detects a subject image that is transmitted through the first mirror 6 and reflected by the second mirror 10, and an AF sensor 11. A first focus adjustment unit 12 that calculates a focus shift from the output signal, and a camera control circuit 13 that receives the focus shift calculated by the first focus adjustment unit 12 and sends the focus shift to the lens control circuit 4. Have.

  The lens control circuit 4 drives the focus adjustment lens of the imaging optical system 2 by the lens driving unit 3 based on the focus shift calculated by the first focus adjustment unit 12 to focus the imaging optical system 2. Do.

  The phase difference detection type AF sensor 11 quickly performs a focusing operation based on the defocus direction and the defocus amount of the imaging optical system 2. The focusing accuracy includes a manufacturing error including the photographing lens 1. , Errors due to environmental changes, changes over time, etc. are included.

  Further, as shown in FIG. 2, the camera body 5 processes the output signal of the solid-state imaging device 15 that forms a subject image by the imaging optical system 2 to extract image contrast information, as well as white balance, γ processing, An image processing unit 16 that forms a captured image by performing color matrix processing or the like, a second focus adjustment unit 17 that calculates a focus shift based on image contrast information obtained from the image processing unit 16, and a first focus The storage unit 18 stores a difference between the focus adjustment result by the adjustment unit 12 and the focus adjustment result by the second focus adjustment unit 17.

  In addition to the above-described functions, the camera control circuit 13 receives the focus shift calculated by the second focus adjustment unit 17 and sends it to the lens control circuit 4. At this time, the lens control circuit 4 drives the focus adjustment lens of the image pickup optical system 2 by the lens drive unit 3 based on the focus shift calculated by the second focus adjustment unit 17, thereby moving the image pickup optical system 2. Focus.

  FIG. 3 is a flowchart showing an automatic focus adjustment process executed by the automatic focus adjustment device provided in the electronic camera of FIG.

  First, when the first stroke switch SW1 of the release switch is turned on and is in the first stroke position (YES in step S1), the camera control circuit 13 indicates “1” that the release switch is in the first stroke. After setting the flag 1ST to “1” (step S2), phase difference AF (automatic focus adjustment) is executed (step S3). In step S3, the first focus adjustment unit 12 calculates a focus shift amount from the output signal of the AF sensor 11, and the camera control circuit 13 uses the lens control unit 4 of the photographing lens 1 based on the calculated shift amount. The focus adjustment lens of the image pickup optical system 2 is moved via the lens, and the image pickup optical system 2 is focused on the in-focus position by the phase difference AF (step S3).

  Next, the camera control circuit 13 determines whether or not the flag 1ST is “1” (step S4). Initially, since the flag 1ST is set to “1”, it is determined whether or not the release switch continues to be at the first stroke position (step S5).

  If the result of determination in step S5 is that the release switch is not in the first stroke position (NO in step S5), the processing from step S1 is repeated, but if the release switch continues to be in the first stroke position (step S5). YES), the release switch determines whether or not the second stroke switch SW2 is turned on and is at the second stroke position (step S6).

  If the result of determination in step S6 is that the release switch is not in the second stroke position, the processing from step S5 is repeated, while if the release switch is in the second stroke position (YES in step S6), the camera control circuit 13 In order to start the photographing sequence, mirror up is performed to retract the first mirror 6, the second mirror 10, and the focal plane shutter 14 to the photographing position (position in FIG. 2) (step S7).

  Next, the camera control circuit 13 determines whether or not the flag 1ST is “1” (step S8). Initially, since the flag 1ST is set to “1”, contrast detection autofocus (TVAF) is executed (step S9). In the TVAF in step S9, the image processing means 16 reads out the image of the portion corresponding to the position where the signal of the AF sensor 11 is taken out from the solid-state image sensor 15 within the angle of view, extracts the image contrast information, and the second The focus adjusting unit 17 calculates a focus shift amount based on the image contrast information, and the camera control circuit 13 determines the focus of the imaging optical system 2 via the lens control unit 4 based on the calculated focus shift amount. The adjustment lens is moved, and the imaging optical system 2 is focused on a focus position by TVAF.

  When the TVAF in step S9 is completed and the imaging optical system 2 reaches the in-focus position with respect to the solid-state image sensor 15, the in-focus position (result of focus adjustment) by the phase difference AF and the in-focus position by the TVAF (focus adjustment). The difference between the results is stored in the storage means 18 (step S10).

  Next, the aperture (not shown) of the taking lens 1 is reduced to the set aperture value, the solid-state image sensor 15 is normally driven, and the exposure time is controlled by the electronic shutter (step S11). At this time, the image processing means 16 performs white balance, γ processing, color matrix processing, and the like to form a captured image.

  Further, the focal plane shutter 14 is closed to return to the blocking state, the diaphragm of the lens 1 is returned to the open position, and the first mirror 6 and the second mirror 10 are returned to the viewfinder observation state (step S12). ).

  Thereafter, the flag 1ST is reset to “0” (step S13), and the captured image formed in step 11 is stored in a nonvolatile memory or the like.

  In subsequent step S14, after the recording of the photographed image is completed, it is determined whether or not the release switch remains at the first stroke position (step S14), and the release switch exceeds the first stroke position and returns to the original position. When the process returns, the process ends. On the other hand, when the release switch continues to be at the first stroke position (YES in step S14), the processes after step S3 are repeated to perform continuous shooting.

  In the processing after step S3, in the case of continuous shooting (YES in step S14), the flag 1ST is reset to “0” (step S13). Therefore, after the phase difference AF is executed (step S3), the determination in step S4 is performed. Thus, the process proceeds to step S15, and the imaging optical system 2 is moved and AF correction is performed to correct the difference between the in-focus position by the phase difference AF stored in step S10 and the in-focus position by TVAF. As a result of the determination in step S8, steps S9 and S10 are skipped, and the exposure operation is performed in step S11 without performing TVAF.

  According to the processing of FIG. 3, the difference between the in-focus position by the phase difference AF and the in-focus position by the TVAF is stored. Since the focal position is corrected, it is possible to increase the number of continuous shot frames while guaranteeing the focusing accuracy from the second frame during continuous shooting.

  In the above embodiment, the AF correction is performed after the phase difference AF in the continuous shooting. However, when the phase difference AF is performed in the continuous shooting, it is preferable to drive the photographing lens including the correction amount. This is desirable because it reduces the total drive time.

It is a block diagram which shows schematic structure of an electronic camera provided with the automatic focus adjustment apparatus which concerns on embodiment of this invention, and shows the case where an electronic camera is in a finder observation state. It is a block diagram which shows schematic structure of an electronic camera provided with the automatic focus adjustment apparatus which concerns on embodiment of this invention, and shows an exposure state. It is a flowchart which shows the automatic focus adjustment process performed by the automatic focus adjustment apparatus provided in the electronic camera of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shooting lens 2 Shooting optical system 3 Lens drive means 4 Lens control circuit 5 Electronic camera main body 6 First mirror 10 Second mirror 11 Phase difference AF sensor 12 First focus adjustment means 13 Camera control circuit 14 Focal plane shutter 15 Solid-state imaging device 16 Image processing means 17 Second focus adjustment means 18 Storage means

Claims (2)

Imaging means for capturing a subject image;
First focus adjusting means for performing first focus adjustment based on the phase difference between the two images;
Second focus adjusting means for performing second focus adjustment based on the contrast of the image;
During continuous imaging, in the first imaging, the second focus adjustment by the second focus adjustment means is performed after the first focus adjustment by the first focus adjustment means, and the subject image is obtained by the imaging means. Image
In the second and subsequent imaging, after the first focus adjustment by the first focus adjustment means, the subject image is picked up by the imaging means without performing the second focus adjustment by the second focus adjustment means. And an imaging device. When the second focus adjustment is performed, the second focus adjustment unit performs the second focus adjustment after the first focus adjustment unit performs the first focus adjustment. The imaging apparatus according to claim 1.

Images