RU2574325C2 - Image capturing device - Google Patents

Abstract

FIELD: physics, photography.

SUBSTANCE: image capturing device includes first autofocusing means, which obtain first focusing information using a phase-difference system, and second autofocusing means, which obtain second focusing information using a contrast system. The device is capable of switching to correction mode for the first focusing information. The device comprises: display control means, which control display means which display a photographed view in real time, and control means which control a focusing lens in correction mode such that it is focused using the second focusing information or the first focusing information corrected by a correction value for the first focusing information. The correction value is calculated in accordance with the difference between the first and second focusing information. The control means enables to the display control means to resume display of a view in real time on the display means after entering into focused state using the second focusing information. Real-time display of the view is interrupted in correction mode.

EFFECT: confirmation of focusing accuracy when calculating a correction value, through which focusing information obtained by phase-difference means is corrected using a contrast system.

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Description

FIELD OF THE INVENTION

The present invention relates to an image pickup apparatus that has a function for correcting focus information of an autofocus means where a phase difference system is applied, for example, to a single lens reflex camera.

State of the art

Currently, there are cases when, when using a single-lens reflex camera, which focuses using phase-difference AF, the focus position changes as the lens or camera body is used, and the focusing accuracy decreases compared to what it was soon after the camera was purchased.

In relation to the lens, there may be a case where the stopping position of the lens, which translates into the exact focus position, is shifted due to inaccuracy during operation.

With respect to the camera body, a case is possible when the AF sensor determines a position that differs from the exact focusing position as the focusing position, since the angle of the mirror changes when the mirror moves and thus the direction of the light incident on the AF sensor changes.

In the above cases, the user has no choice but to take the camera to the repairman and ask him to reconfigure the focus position to restore the focus position to its original state.

In order to solve the above problem, in PTL 1, for example, a function is disclosed by which the focus position obtained using phase difference AF can be automatically corrected using a contrast system.

List of cited sources

Patent source

PTL 1: Japanese Patent Publication No. 2000-292684

Disclosure of invention

Technical problem

However, according to PTL 1, it is not possible to confirm the focusing accuracy obtained after the user adjusts the focusing position obtained using phase difference AF.

Object of the invention

An object of the present invention is to provide an image pickup device whose focus accuracy obtained after the user adjusts the focus state can be confirmed by the user by calculating a correction value by which the focus information obtained by the AF system of the phase difference system is corrected using a contrast system.

The solution of the problem

To solve the above problem, the image pickup apparatus according to the present invention is an image pickup apparatus that includes first autofocus means that receives first focus information using a phase difference system, and second autofocus means that receives second focus information using a contrast system, the device image capture is able to switch to correction mode for the first focus information, the shooting device and image including a display control means that controls a display means that is capable of displaying a real-time view on which the photographed image is displayed, and a control means that drives the focusing lens and controls it in the correction mode, so that the focusing the lens enters the focused state using the second focus information or the corrected first focus information, which is the first focus information which has been corrected by the correction value for the first focus information, wherein the correction value is calculated in accordance with the difference between the first focus information and the second focus information, the control means allows the display control means to restart displaying the view in real time on the display means, and displaying the view in real time is interrupted in correction mode.

Advantages of the Invention

According to the present invention, the focus accuracy obtained after the user adjusts the focus state can be confirmed by the user by calculating the correction value by which the focus information obtained by the AF system of the phase difference system is corrected using the contrast system.

Brief Description of the Drawings

FIG. 1 is a flowchart showing an AF calibration operation according to the present invention.

FIG. 2 illustrates a screen for entering the AF calibration mode.

FIG. 3 illustrates a screen displaying a real-time view for confirming a focus state.

FIG. 4 is a flowchart showing another AF calibration operation.

FIG. 5 is a flowchart showing an operation of changing a correction value according to the present invention.

FIG. 6 illustrates a screen displaying a real-time view for changing a correction value.

FIG. 7 is a cross-sectional view of a principle structure when mirrors are facing down.

FIG. 8 is a sectional view of a basic structure when the mirrors are facing up.

FIG. 9 is a flowchart showing another AF calibration operation.

The implementation of the invention

An embodiment of the present invention is described below.

Option exercise

As an image pickup apparatus according to the present invention, a digital single lens reflex camera with interchangeable lens will be described.

In FIG. 7 and FIG. 8 is a schematic sectional view of the structure of a digital single lens reflex camera according to an embodiment.

The optical image pickup system 10 housed in the lens 1 includes one or more lens units and is capable of changing the focal length or focus position by moving all or some of the lens units.

The lens drive means 11 is a drive means that moves all or some of the lens units included in the optical image pickup system 10 to adjust the focus state.

The lens state detection means 12 is a detection means that detects a focal length, that is, a zoom position and a focus position, of the optical image pickup system 10.

In addition, the lens control means 13 is a control means that controls the entire lens 1, including the lens memory means 14 made in the form of a ROM or the like.

The connector 15 is a connector that is provided for the lens 1 and the camera body 2, and when the lens 1 and the camera body 2 are connected to each other, various types of information are transmitted through the connector 15 and power is supplied.

The main mirror 20 is formed by a half-mirror and is able to rotate in accordance with the operating state of the camera. When observing an object through an optical viewfinder, the main mirror 20 is tilted on the optical path of photographing and deflects the light flux from the lens 1, directing the light flux into the optical system of the viewfinder, which will be described below (Fig. 7). In the case of photographing or displaying the view in real time, the main mirror 20 leaves the optical path of photographing, allowing the light flux from the lens 1 to be directed to the image sensor 24, which will be described below (Fig. 8).

The auxiliary mirror 21 rotates in conjunction with the main mirror 20. When the main mirror 20 is tilted along the optical path of photography, the auxiliary mirror 21 deflects the light flux passed through the main mirror 20, directing the light flux to the AF sensor 22, which will be described later (FIG. 7). In the case of photographing or displaying the view in real time, the auxiliary mirror 21 leaves the optical path of photographing, turning together with the main mirror 20 (Fig. 8).

The AF sensor 22 includes a secondary imaging lens, an array sensor including a plurality of CCDs or CMOS sensors, etc. The AF sensor 22 is able to detect a focus point using a well-known phase difference system.

The shutter 23 is used to control the incidence of light from the lens 1 onto the image sensor 24, which will be described below. The shutter 23 is usually in the closed state (Fig. 7) and goes into the open state during photographing and displaying the view in real time (Fig. 8).

The image sensor 24 includes a CMOS image sensor and a peripheral circuit of a CMOS image sensor.

The focusing screen 30 is located on the primary imaging area for the lens 1. The focusing screen 30 has a Fresnel lens (condenser lens) on the falling side, and an object image (image in the viewfinder) is formed on the display side of the focusing screen 30. Pentaprism 31 is used to change the optical path of the viewfinder and converts the image of the object formed on the display surface of the focusing screen 30 into a direct image.

The eyepiece 32 is configured so that its optical power adjusts to the user's vision while the user is looking through the viewfinder. Here, an optical system including a focusing screen 30, a penta prism 31, and an eyepiece 32 is called an optical viewfinder system.

AE sensor 33 is formed by photodiodes that correspond to multi-segment zones in the image pickup zone and measures the brightness of the image of an object formed on the display surface of the focusing screen 30.

The camera control means 40 controls the camera body 2, as well as the entire camera including the lens 1. The microcomputer, for example, is used as the camera control means 40. The AF sensor 22 and the camera control means 40 constitute the first autofocus means (focal point detection means), which receives the first focus information through a phase difference system.

The digital control means 41 performs various image data control operations, and the memory controller, for example, is used as the digital control means 41. The digital control means 41 may include contrast system AF means (focal point detection means) that detects the contrast of the image photographed by the image sensor 24 and determines the position of the focused focus (hereinafter referred to as the focus position) using the contrast estimation value. The digital control means 41 forms a second autofocus means (focal point detection means) that receives second focus information using a contrast system.

The camera memory 42 stores the settings used for various control operations, adjustment data, etc., and flash memory is used as the camera memory 42.

The liquid crystal monitor 43 displays an image of a photographed object or various types of photographing information. The liquid crystal monitor 43 is a display means that displays a real-time view to confirm the focus state when switching to the AF calibration mode (focus information correction mode).

Although not shown in FIG. 7 and FIG. 8, the liquid crystal monitor 43 is provided with a “set” button and a “cancel” button. By pressing the “install” button displayed on the liquid crystal monitor 43, operations such as determination or selection can be performed. On the other hand, when you press the cancel button displayed on the LCD monitor 43, you can perform operations such as returning to a previous state or exiting a particular mode.

Digital control means 41 includes calculation means that calculates a correction value based on a difference between two outputs, one of which is obtained using a contrast system, and the other of which is used by camera control means 40 using a phase difference system based on the output of the AF sensor 22. The difference calculated by the calculator is stored in the camera memory 42 as a correction value.

A camera according to this embodiment may transition to an AF calibration mode in which the camera calculates stores the above correction value.

Next, a function for performing phase difference AF correction (hereinafter referred to as AF calibration) will be described.

A method of moving the lens to the focus position obtained after correcting the focus position obtained by the phase difference detection system

In FIG. 1 is a flowchart showing an AF calibration operation according to an embodiment.

Before the sequence of operations begins, an operation is first required to determine the object. After determining the subject, AF calibration begins. The initial screen at this time is shown in FIG. 2.

AF calibration starts at the user's command. When the camera is in the above AF calibration mode, the user presses the “start” button 205 shown in FIG. 2 to start the AF calibration. FIG. 2 illustrates a mode name display frame 201 where an AF micro adjustment is displayed, which is an alternative name for an AF calibration mode, a lens name 202, a calibration 203, a correction value index 204, and a cancel button 206.

In step S101, focusing on the subject is performed using a contrast detection system (alternative name for the contrast system).

In step S102, the camera control means 40 transmits a signal to the lens control means 13 to move the focusing lens to a predetermined position using the lens drive means 11.

In step S103, an image contrast signal received from the image sensor 24 is detected by the digital control means 41.

In step S104, a slight movement of the focusing lens in step S102 and contrast detection in step S103 are repeated until a predetermined number of N repetitions is reached.

In step S105, the digital control means 41 determines the focus position at which the image signal having the highest contrast from N contrast detection results is obtained as the focus position, and transmits the signal to the camera control means 40. The camera control means 40 receives position information at this time from the lens state detecting means 12 using the lens control means 13 and generates focus position information. As a result, a high value of the contrast assessment, which satisfies certain conditions, is converted to a focus position, which is considered as the focus position.

In step S106, the camera control means 40 instructs the AF sensor 22 to detect a focal point using a phase difference AF and generates focus position information by adding a value to the focus position information from the lens state detection means 12, the value being obtained by converting the result detected at that time, t .e. the magnitude of the shift of the focal point (the amount of defocus), the amount of movement of the focusing lens in the direction of focus.

In step S107, the camera control means 40 instructs the digital control means 41 to calculate a focus position correction value that is equal to the difference between the focus position information determined by the digital control 41 as the focus position and the focus position information obtained from the detection results of the AF sensor 22.

In step S108, the focus position correction value calculated by the digital control means 41 is stored in the camera memory means 42.

In step S109, the focus position information generated in step S106 is corrected by the focus position correction value stored in the camera memory 42.

In step S110, the camera control means 40 transmits a signal to the lens control means 13 for moving the focusing lens to the focus position corrected in step S109 using the lens drive means 11. At this stage, the focal point shift amount (defocus amount) obtained using phase difference AF is calculated, the focal point shift amount (defocus amount) is corrected by the focus position correction value stored in the camera memory 42, and the focusing lens moves in accordance with the adjusted value . Each of the calculation, correction and movement is carried out at least twice. When these operations are performed two or more times, it is possible to eliminate the shift from the target position due to inaccuracy of the drive part (gear, electric motor or other component) of the focusing lens.

In step S111, the real-time view display interrupted due to the transition to the AF calibration mode starts again, so that the real-time view image is displayed on the liquid crystal monitor 43. Since the focus lens moves in accordance with the focus position correction value, and the movement the focusing lens is carried out at least twice in step S110, a real-time view with a high degree of focusing can be displayed.

A screen showing a real-time view at this time is shown in FIG. 3. When the index 204 indicates the position +10 in the example shown in FIG. 3, the correction value displayed on the screen is +10. Here, the user can confirm the correction value and the focus accuracy corresponding to the correction value by observing the real-time view displayed on the liquid crystal monitor 43. FIG. 3 illustrates a confirmation button 207 that is displayed on the screen when the screen displays a real-time view, and when the user presses the confirmation button 207, the correction value is fixed.

This completes the AF calibration.

A method for moving a lens to a focus position obtained using a contrast detection system

In step S110, the focusing lens moves to a position obtained by correcting the focus position obtained using phase difference AF. In this regard, the focusing lens can be moved to the focus position obtained using the contrast detection system. The AF calibration sequence in this case is shown in FIG. 4. The flowchart shown in FIG. 4 follows the flowchart of FIG. one.

The focus position obtained using the contrast detection system in step S305 is stored in advance in the camera or RAM memory 42 and is extracted in step S309 in FIG. four.

In step S310, the camera control means 40 transmits a signal to the lens control means 13 for moving the focusing lens to the focus position extracted in step S309 using the lens drive means 11.

Here, the method was described in step S310, where the lens moves to the focus position obtained using the contrast detection system. In this regard, since the AF calibration is performed to correct the phase difference AF, the method in step S110 is preferable when the lens moves to the focus position obtained by performing the correction of the phase difference AF. The fact is that although the lens moves to the focus position obtained using the contrast detection system, the real-time view is displayed while the degree of focusing is slightly reduced compared with the case of the above example due to inaccuracy of the drive part (gear, motor or other component ) the lens. However, a decrease in the degree of focusing can be allowed, since the real-time view display is visually recognized through a small rear monitor or a movable monitor, which is usually connected to the camera.

A method of obtaining a focus position using a phase difference detection system after approaching a lens to a focus position obtained using a contrast detection system

At step 106 shown in FIG. 1, focus position information is obtained using a phase difference system after detecting the contrast and before moving the lens. Here, focus position information can be obtained using the phase difference system after the lens is moved to approach the focus position in accordance with the focus position information obtained using the contrast detection system in step S105. The AF calibration sequence in this case is shown in FIG. 4. The flowchart of FIG. 9 follows the flowchart of FIG. one.

The lens is driven to approximate the focus position obtained using the contrast detection system in step S905 in accordance with the focus position information (step S920). Then, in step S906, focus position information is generated using a phase difference system.

According to the flowchart shown in FIG. 9, focus position detection using a phase difference system can be performed with high accuracy. The fact is that the image obtained at this time is less blurry than the image obtained at the time when the movement of the lens ends to detect contrast. Thus, a plurality of calculations of the focal point shift amount (defocus amount) using phase difference AF and a lot of focal point shift amount adjustments (defocus amount) made in step S110 of the flowchart in FIG. 1, become unnecessary. Of course, the calculation and correction can be performed several times, which is illustrated in the sequence of operations in FIG. one.

In this case, after receiving the focus position information using the phase difference system in step S920, the focus position information generated in step S906 is corrected in step S909 by the focus position correction value stored in the camera memory 42. This step is carried out similarly to step S109 in FIG. one.

In step S910, in the same manner as in step S110, the camera control means 40 transmits a signal to the lens control means 13 to move the focusing lens to the focus position corrected in step S909 using the lens drive means 11.

User correction value change

Next, a case will be described when the user changes the correction value after performing the AF calibration. In FIG. 5 is a flowchart showing that the correction value can be changed by the user.

At step S501, the sequence of steps of the AF calibration operation shown in FIG. 1 or FIG. 4. In this case, a screen that displays the real-time view in step S111 or step S311 is shown in FIG. 6.

In step S502, the user can change the correction value. The user changes the correction value in the forward or backward direction by pressing the correction value (forward) button 208 or the correction value (back) button 209, which is displayed on the screen shown in FIG. 6. In the case where a change is not required, the user confirms the correction value by pressing the confirmation button 207. At this time, the user can change the correction value by confirming the image of the object displayed as the real-time view, since the real-time view display starts again at step S111 in FIG. one.

At step S503, a determination is made whether the correction value has changed at step S502. In the case where the correction value has changed, the flow proceeds to step S504. In the case where the correction value has not changed, the flow proceeds to step S505.

In step S504, the camera control means 40 transmits a signal to the lens control means 13 in accordance with the amount of the correction value change for moving the focusing lens using the lens drive means 11. In step S505, the correction value is stored in the camera memory 42.

In the above embodiment, the following effects can be obtained.

The user can confirm the accuracy of focusing using phase difference AF after calibrating the AF by moving the lens to the focus position obtained by correcting the focus position obtained using phase difference AF and then displaying the image at that time.

In addition, since the user can change the correction value, confirming the focusing accuracy, the user can correct the phase difference AF as desired.

Although a means that includes an AF sensor 22 and a camera control means 40 is described as a first autofocus means using a phase difference system, the present invention is not limited to this. A phase difference AF device using a phase difference image pickup system in which focal point detection pixels are located in a focal point detection area on an image pickup surface of the image sensor 24 can also be used as the first AF tool.

The present invention is not limited to the above-described embodiment, and allows various changes or modifications without departing from the spirit or scope of the present invention. Thus, in order to bring the scope of the present invention to the public, the claims are presented below.

This application claims priority based on Japanese Patent Application No. 2011-067813, filed March 25, 2011, which is hereby incorporated by reference in its entirety.

List of Reference Items

22 AF sensor

24 image sensor

40 camera control

41 digital controls

43 lcd monitor

207 confirmation button

208 button for changing the correction value (forward)

209 button for changing the correction value (back).

Claims (13)

1. An image pickup apparatus that includes first AF means receiving the first focus information using a phase difference system and second autofocus means receiving the second focus information using the contrast system, the image pickup apparatus being able to enter correction mode for the first focus information moreover, the image pickup device comprises:
display control means that controls a display means capable of displaying a real-time view on which the photographed image is displayed; and
control means that drives the focusing lens and controls it in the correction mode so that the focusing lens enters the focused state using the second focus information or the corrected first focus information, which is the first focus information adjusted by the correction value for the first focus information moreover, the correction value is calculated in accordance with the difference between the first focusing information and the second focusing information, wherein the control means is configured to allow the display control means to start displaying the real-time view again on the display means after entering the focused state using the second focus information, wherein the real-time view display is interrupted in the correction mode. 2. The image pickup apparatus according to claim 1,
in which the first focus information is obtained by converting the amount of defocus to the focus position, and
second focusing information is obtained by converting the value of the contrast estimate to the focus position. 3. The image pickup apparatus according to claim 1 or 2, wherein the display means displays a correction value on a screen displaying a real-time view. 4. The image pickup apparatus according to claim 1, wherein the display means displays a confirmation button by which the correction value is confirmed on the screen displaying the view in real time. 5. The image pickup apparatus according to claim 1, further comprising means for changing the correction value to change the correction value. 6. The image pickup apparatus according to claim 5, wherein the display means displays a correction value changing button by which the correction value is changed on a screen displaying a real-time view. 7. The focus correction device used in the image pickup apparatus according to claim 1 and capable of switching to the correction mode, the device comprising:
first focal point detection means configured to detect a focus state using the first focus information corresponding to a phase difference system;
second focal point detection means configured to detect a focus state using second focus information corresponding to a contrast system;
display control means configured to control a display means capable of displaying a real-time view on which the image is displayed; and
control means configured to control the focus state in the correction mode so that the focus state goes into the focused state using the second focus information, wherein the control means is adapted to adjust the first focus information by the detection result of the first focal point detection means and the second means detecting a focal point during a focused state period,
wherein the control means is configured to interrupt the real-time view display in the correction mode, and the control means is configured to allow the display control means to start displaying the real-time view on the display means again after entering the focused state using the second focus information. 8. The focus correction device according to claim 7, wherein the first focus information is obtained by converting the defocus amount to the focus position. 9. The focus correction device according to claim 7, wherein the second focus information is obtained by converting the value of the contrast estimate into a focus position. 10. The focus correction device according to claim 7, wherein the display means is configured to display the correction value on a screen displaying the view in real time, and the correction value is information for correcting the first focus information. 11. The focus correction device according to claim 7, wherein the display means is configured to display a confirmation button by which the correction value is confirmed on the screen displaying the view in real time, and the correction value is information for correcting the first focus information. 12. The focus correction device according to claim 11, further comprising means for changing the correction value, configured to change the correction value. 13. The focus correction device according to claim 7, wherein the display means is configured to display a button for changing a correction value by which the correction value is changed on the screen displaying the view in real time, and the correction value is information for correcting the first focus information.

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