JP4689023B2 - Auto focus device and camera - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in an automatic focus adjustment apparatus and a camera having a defocus amount detection means for detecting a defocus amount.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an automatic focusing device of a camera, a pair of image signals obtained by photoelectrically converting a subject image by combining light beams from a subject passing through different exit pupil regions of a photographing lens onto a pair of line sensors. 2. Description of the Related Art There is widely known an automatic focus adjustment method for detecting a defocus amount of a subject by obtaining an image shift amount that is a relative position displacement amount by correlation calculation, and driving a photographing lens based on the detected defocus amount.
[0003]
Many of them also have a servo control (predictive control) function that drives and follows the photographing lens even in a moving subject.
[0004]
Specifically, as shown in FIG. 7, the defocus amount is continuously detected even during continuous shooting, and the lens drive amount is updated. Furthermore, the change of the image plane position obtained from the past multiple detection defocus amounts and the driving amount of the photographing lens is regarded as a predetermined function according to time, and the function is obtained by a statistical method to predict the driving of the photographing lens. It is carried out. That is, assuming that the exposure operation is performed at the point A in FIG. 7, the exposure from the last focus detection is completed by completing the lens drive by adding the moving object prediction correction amount to the defocus amount at the next focus detection before the next exposure. The subject can be focused in anticipation of the movement of the subject during the release time lag until the start of.
[0005]
This method is already known, and is disclosed in Japanese Patent Application Laid-Open No. 11-197185 by the applicant of the present invention.
[0006]
In a mirror movable single-lens reflex camera, in order to reliably perform this servo control during continuous shooting, it is necessary to perform mirror down after the exposure operation and detect the defocus amount after a predetermined time. This is because of the configuration of a single-lens reflex camera, the defocus amount cannot be detected unless the mirror is completely down. Similarly, to detect the defocus amount, even during continuous shooting, Mirror up for starting the exposure operation cannot be performed. Therefore, in the conventional single-lens reflex camera, the defocus amount is detected once while the mirror is down, and at the same time as the lens driving considering the predicted correction amount is started, the release operation is also started to start the mirror up. Then, after completion of mirror up, exposure and mirror down are generally performed.
[0007]
[Problems to be solved by the invention]
Servo control is performed in this way, but in many cameras capable of high-speed continuous shooting, it is general that the continuous shooting speed can be changed by switching a mode switch. This is because even if high-speed continuous shooting is possible, the number of film shots is limited, and lower-speed continuous shooting may be preferable depending on the shooting situation. However, for example, in a camera that can set the shooting speed such as 9 fps (frames per second), 6 fps, and 3 fps, if only one defocus amount is detected while the mirror is down as in the conventional case, low-speed continuous shooting at 3 fps As shown in FIG. 8, since the change in the image plane position of the subject used for predictive driving extends with respect to time, the followability to a moving subject whose motion changes suddenly is higher than that at the time of high-speed shooting shown in FIG. There was a problem of deterioration.
[0008]
In addition, the film is generally fed by a motor, but many cameras that can only shoot at low speed due to the capacity of the installed motor and the capacity of the battery require a long time to feed when the battery is depleted. . In this case, there is a problem that even if the shooting speed cannot be set, the continuous shooting ability changes greatly, and as a result, the followability to the subject deteriorates.
[0009]
(Object of invention)
A first object of the present invention is to provide an automatic focus adjustment device and a camera capable of always detecting an optimum defocus amount regardless of the defocus amount detectable time during continuous shooting. .
[0014]
[Means for Solving the Problems]
In order to achieve the first object, the invention according to claim 1 detects a defocus amount which is a difference between an imaging position of the photographic lens and a planned image plane position of the photographic lens on which the photographing operation is to be performed. A setting means for setting the number of times of focus detection according to the set continuous shooting speed in the automatic focus adjustment apparatus that drives the photographing lens based on the defocus amount; An automatic focus adjustment device having control means for controlling the detection of the defocus amount and the driving of the photographing lens to perform the focus detection times set by the setting means during photographing during the continuous photographing, To do.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on illustrated embodiments.
[0026]
FIG. 1 is a block diagram showing a configuration of an interchangeable lens single-lens reflex camera as an example of an optical apparatus according to the first and the embodiments of the present invention.
[0027]
In FIG. 1, 1 is a lens MPU (microprocessing unit) that performs all calculations and control related to the photographic lens, 2 is a lens drive unit for driving the photographic lens, 3 is a lens position detection unit, and 4 is a feeding position detection. A unit 5 is an optical information table for storing optical information necessary for automatic focus adjustment. In an actual photographing lens, an aperture drive unit for driving the aperture is necessary, but the description is omitted because it is not relevant in the present embodiment. The photographing lens is constituted by the MPU 1 to the optical information table 5.
[0028]
The taking lens is connected to the camera body via a mount indicated by a dotted line in the center of FIG. Reference numeral 6 denotes a camera MPU (microprocessing unit) that performs all calculations and controls related to the camera body, and is connected to the lens MPU1 through a signal line of the mount, and obtains the lens position and drives and exchanges the lens with respect to the lens MPU1. It is possible to acquire unique optical information for each lens.
[0029]
7 is a defocus amount detection unit, 8 is a shutter drive unit, 9 is a film feeding unit, and 10 is a dial unit for performing various camera settings, continuous shooting speed, shutter speed, aperture value, shooting mode, and the like. is there. In the present embodiment, the continuous shooting speed can be set in three stages of 9 fps, 6 fps, and 3 fps. SW1 is a switch that is turned on by a first stroke operation (half press) of the release button, and SW2 is a switch that is turned on by a second stroke operation (full press) of the release button.
[0030]
(First embodiment)
Various shooting modes can be set by operating the dial unit 10, but in the first embodiment, the servo control suitable for continuous shooting of a moving subject according to the present invention is set. Servo control will be described.
[0031]
When the switch SW1 is turned on, automatic focus adjustment is performed, and when the switch SW2 is turned on, a release operation is also performed, and continuous shooting starts. The operation during continuous shooting will be described with reference to the flowchart of FIG. FIG. 4 is a diagram showing the state of predictive control during high-speed continuous shooting, and FIG. 5 is a diagram showing the state of predictive control during low-speed continuous shooting.
[0032]
At the time of continuous shooting, first, the process proceeds from step # 101 to step # 102, where the number of focus detection (defocus amount detection) is set. This is set according to the defocus amount detectable time. As described above, the defocus amount cannot be detected during a release operation such as mirror up, exposure, and mirror down. The release operation time required for these is obtained by measuring the time actually taken in the previous release operation. The defocus amount detectable time can be obtained by subtracting the release operation time from the continuous shooting interval that is the reciprocal of the currently set continuous shooting speed.
[0033]
For example, when the current continuous shooting speed is 9 fps, if the continuous shooting interval is about 111 ms and the release operation time is 46 ms, the defocus amount detectable time is about 65 ms. As a matter of course, since the continuous shooting interval is extended when the continuous shooting speed is reduced, the defocus amount detectable time is also extended. Conversely, when the shutter speed is extended even at the same continuous shooting speed, the release operation time is extended, and therefore the defocus amount detectable time is shortened. In addition, the film feeding mode is generally switched depending on the battery consumption state and the continuous shooting speed, and the release operation time is not always constant. Therefore, for the sake of simplicity, for example, it is assumed that the defocus amount detectable time at 9 fps is 60 ms, 100 ms at 6 fps, and 180 ms at 3 fps. The number of focus detections is set according to the defocus amount detectable time.
[0034]
Specifically, the time required for one focus detection is regarded as 50 ms, and the number of focus detections is determined within a range not exceeding the defocus amount detectable time. In other words, in the previous example, “1 time” is set for 9 fps, “2 times” for 6 fps, and “3 times” for 3 fps.
[0035]
After setting the number of focus detections as described above, the process proceeds to step # 103 and proceeds to automatic focus adjustment described later. Thereafter, the process proceeds to step # 104, and it is determined whether or not the switch SW2 is still turned on. If it is turned on, the mirror is raised in the next step # 105, and then the exposure is continued in step # 106. After performing a series of release operations such as mirror down at # 107 and so on, the process returns to step # 102 to continue continuous shooting. On the other hand, if the switch SW2 is turned off in step # 104, the process proceeds to step # 108, and continuous shooting is interrupted.
[0036]
Details of the automatic focus adjustment executed in step # 103 will be described below with reference to the flowchart of FIG.
[0037]
First, the process proceeds from step # 201 to step # 202, where the lens position is acquired from the lens position detection unit 3. This is performed by communicating from the camera MPU 6 to the lens MPU 1.
[0038]
The amount of defocus required for automatic focus adjustment (the difference between the imaging lens imaging position and the imaging lens image plane position on which the imaging operation is to be performed) is the subject luminous flux that passes through two different regions across the optical axis of the imaging lens. Is calculated from the image shift amount (prediction amount) of the two images formed from Specifically, the light beams of these two images pass through a main mirror that is a half mirror, are reflected by a sub mirror behind the main mirror, and are guided to a defocus amount detection unit 7 by a focus detection optical system (not shown). The defocus amount detection unit 7 has a photoelectric conversion element, and the camera MPU 6 reads out the signals of these two images in step # 203.
[0039]
In the next step # 204, optical information such as sensitivity necessary for automatic focus adjustment, a best focus correction value, and a defocus amount per pulse is acquired from the lens. This is done by communicating from the camera MPU6 to the lens MPU1. Specifically, the distance ring of the photographing lens is electrically divided at equal intervals and connected to the feeding position detection unit 4. The lens MPU 1 acquires the current extension position from the extension position detection unit 4 and transmits information necessary for automatic focus adjustment to the camera MPU 6 by referring to the optical information table 5 which is a table corresponding to the extension position.
[0040]
In the subsequent step # 205, an image shift amount is calculated by performing a correlation operation, and a defocus amount D is obtained. The defocus amount and the actual lens driving amount are in a non-linear relationship, and are generally approximated by a function corresponding to the defocus amount. In addition, the amount handled in the actual payout is not the length but the focus pulse number P that is the drive waveform to the photographing lens.
[0041]
Since the camera MPU 6 has acquired the optical information necessary for the conversion to the number of focus pulses in step # 204, the camera MPU 6 calculates the defocus amount D in step # 205, and in step # 206, the lens drive is performed. The amount P is converted. The lens drive amount necessary for focusing is obtained in this way, but in the next step # 207, the focus pulse number of the moving object prediction amount is corrected. This is because the lens position acquired in step # 201 is used as the origin, and the change in the image plane position obtained from the past defocus amount and the photographing lens drive amount is regarded as a predetermined function according to time. Is obtained by a statistical method, and correction is performed by obtaining a lens driving amount in anticipation of the movement of the subject during the release time lag from the last focus detection to the start of exposure. As described above, since this method is disclosed in Japanese Patent Application Laid-Open No. 11-197185 by the present applicant, further detailed explanation is omitted.
[0042]
In the next step # 208, the lens is driven, and in the following step # 209, it is determined whether or not the switch SW1 is turned on. If it is turned off, the process proceeds to step # 212, and the automatic focus adjustment is stopped. On the other hand, if it is turned on, the process proceeds to step # 210, and it is determined whether or not the number of focus detections of the defocus amount up to this time has reached the number of focus detections set in step # 102 of FIG. If the set number of focus detections has been reached, the process proceeds to step # 212, and automatic focus adjustment ends. If not, the process proceeds to step # 211 to determine whether refocus detection is possible.
[0043]
Specifically, as shown in FIG. 6, during continuous shooting, the defocus amount detection time may suddenly increase due to a decrease in subject brightness or the like (FIG. 5 shows a case where there is no decrease in subject brightness or the like). In such a case, in order to keep the continuous shooting speed constant, the refocus detection is not possible even if the set number of focus detections is not satisfied, and the process proceeds from step # 211 to step # 212, and the automatic focus adjustment is terminated. To do. On the other hand, if it is determined that redetection is possible, the process returns to step # 201 to continue the automatic focus adjustment.
[0044]
According to the first embodiment, during continuous shooting, as shown in FIGS. 4 and 5, the defocus amount detection count is changed according to the continuous shooting speed, so that the set continuous shooting speed is obtained. Regardless, it is possible to detect the defocus amount sufficient to predict the movement of the moving subject and to drive and follow the photographing lens.
[0045]
In addition, when the defocus detection time becomes long due to a decrease in subject brightness or the like, the automatic focus adjustment is terminated without satisfying the focus detection count, so that the continuous shooting speed can be kept constant. Thereby, sufficient performance of servo control can be exhibited.
[0046]
(Second Embodiment)
The second embodiment of the present invention has substantially the same configuration as that of the first embodiment, and even in a camera in which the film feeding time is extended due to battery consumption and the continuous shooting ability is changed. In this configuration, sufficient performance of servo control can be exhibited.
[0047]
Similar to the first embodiment, FIG. 1 is a block diagram showing a configuration of an interchangeable lens single-lens reflex camera according to the second embodiment of the present invention. However, the camera according to the second embodiment can only perform low-speed shooting and cannot set the shooting speed from the viewpoint of the capacity of the mounted motor and the capacity of the battery (continuous shooting in the dial unit 10). Speed cannot be set). The continuous shooting flow in FIG. 2 and the automatic focus adjustment flow in FIG. 3 are the same as those in the first embodiment.
[0048]
This is different from the first embodiment in the setting of the number of focus detections in step # 102 of FIG. Specifically, when the battery is exhausted, it takes much time to feed the film. Therefore, in the second embodiment, the time from the completion of the mirror down to the completion of the film feeding is counted, and this is set as the defocus amount detectable time. The number of focus detections is set according to the defocus amount detectable time. Specifically, the time required for one focus detection is regarded as 50 ms, and the number of focus detections is determined within a range not exceeding the defocus amount detectable time. For example, when the defocus detectable time is changed from 140 ms to 160 ms due to battery exhaustion, the number of focus detections is changed from 2 times to 3 times.
[0049]
According to the second embodiment, during continuous shooting, by changing the defocus amount detection count according to the continuous shooting capability, the movement of the moving subject is predicted regardless of the state of battery consumption, and shooting is performed. Defocus amount detection sufficient to drive and follow the lens can be performed. Thereby, sufficient performance of servo control can be exhibited.
[0050]
(Modification)
In the present embodiment, a single-lens reflex camera has been described. However, the present invention can also be applied to cameras such as video cameras and electronic still cameras, and other optical devices.
[0052]
【The invention's effect】
As described above, it is possible to provide an automatic focus adjustment apparatus or camera that can always detect the optimum defocus amount regardless of the defocus amount detectable time during continuous shooting.
[Brief description of the drawings]
FIG. 1 is a block diagram of a camera according to first and second embodiments of the present invention.
FIG. 2 is a flowchart showing an operation of continuous shooting according to the first and second embodiments of the present invention.
FIG. 3 is a flowchart showing an automatic focus adjustment operation according to the first and second embodiments of the present invention.
FIG. 4 is a diagram showing a high-speed continuous shooting operation according to the first embodiment of the present invention.
FIG. 5 is a diagram showing a low-speed continuous shooting operation according to the first embodiment of the present invention.
FIG. 6 shows defocus amount detection when there is a possibility that the defocus amount detection detectable time may be exceeded without satisfying the defocus amount detection count according to the first and second embodiments of the present invention; It is a figure which shows the example which interrupts.
FIG. 7 predicts an image plane position of a photographing lens to be photographed when photographing a moving subject according to the first and second embodiments of the present invention and the conventional example, and photographs the subject. It is a figure which shows the example which drives a photographic lens so that a photographic lens may come to a to-be-photographed object image plane position sometimes.
FIG. 8 is a diagram illustrating an operation of conventional low-speed continuous shooting.
[Explanation of symbols]
1 Lens MPU
2 Lens drive unit 3 Lens position detection unit 4 Feeding position detection unit 5 Optical information table 6 Camera MPU
7 Defocus amount detection unit 8 Shutter drive unit 9 Film feed unit 10 Dial unit

Claims (5)

Defocus amount detection means for detecting a defocus amount that is a difference between an imaging position of the photographic lens and a planned image plane position of the photographic lens that is to perform a photographing operation, and the photographic lens is based on the defocus amount In the automatic focusing device that drives
Setting means for setting the number of focus detections according to the set continuous shooting speed;
During continuous shooting, and characterized by having between shooting of the continuous shooting, the driving of detection and the taking lens of the defocus amount, and control means for controlling to perform focus detection number set by said setting means Automatic focusing device to do.   The defocus amount detection number setting means detects the defocus amount when the defocus amount detection detectable time is longer than a predetermined time, compared to when the defocus amount detection is shorter than the predetermined time. 2. The automatic focusing apparatus according to claim 1, wherein the number of times is increased.   The defocus amount detection is interrupted if there is a possibility that the defocus amount detection detectable time may be exceeded even if the defocus amount detection count set by the setting means is not reached. Item 3. The automatic focusing apparatus according to Item 1 or 2.   When photographing a moving subject, the image plane position of the photographing lens to be photographed is predicted, and the photographing lens is driven so that the photographing lens comes to the subject predicted image plane position at the time of photographing. The automatic focusing apparatus according to any one of claims 1 to 3.   A camera comprising the automatic focus adjustment device according to claim 1.

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