JP2002250858A - Automatic focusing device and automatic focusing camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform highly accurate focusing to a moving object to be focused on in servo AF(automatic focusing) mode. SOLUTION: In the servo AF mode, a lens driving quantity computed from a defocusing quantity is compared with a predetermined specific lens driving quantity corresponding to a focusing range and when the computed lens driving quantity is larger than the defocusing quantity, the lens is driven according to the lens driving quantity; when the computed lens driving quantity becomes less than the specific driving quantity, the computed lens driving quantity is decreased at a specific rate and the lens is driven with the decreased lens driving quantity (#208 to #210).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an automatic focus adjustment device and an automatic focus adjustment camera capable of setting a servo AF mode in which a defocus amount is detected even after focusing and a lens drive is repeated based on the result. .

[0002]

2. Description of the Related Art Conventionally, in an automatic focusing apparatus for a camera, a light beam from a subject passing through different exit pupil regions of a photographing lens is formed on a pair of line sensors, and the subject image is obtained by photoelectric conversion. An automatic focus adjustment method for detecting a defocus amount of a subject and driving a photographing lens based on the defocus amount by calculating an image shift amount, which is a relative positional displacement amount of the pair of image signals, is widely known. Have been.

Many of them have a servo control function for driving and following a photographing lens even for a moving subject. Specifically, the amount of defocus is continuously detected, and the amount of lens driving is updated. Furthermore, the change of the image plane position obtained from the detected defocus amount and the driving amount of the photographing lens in a plurality of times in the past is regarded as a predetermined function depending on the time, and the function is obtained by a statistical method, so that the predictive driving of the photographing lens is performed. It is carried out.

Due to the structure of a single-lens reflex camera with a movable mirror,
If the mirror is not down, the defocus amount cannot be detected. On the other hand, exposure cannot be performed unless the mirror is raised. That is, there is a release time lag of a certain amount or more from the last focus detection to the start of exposure.

In the predictive drive, the lens drive in which the moving object predictive correction amount is added to the defocus amount at the time of the last focus detection is completed before the exposure, so that a release time lag from the last focus detection to the start of the exposure. Focusing can be performed in anticipation of the movement of the subject in between. This method is already known, has been disclosed by the present applicant in Japanese Patent Application Laid-Open No. H11-197185, and has been widely practiced.

[0006]

The servo control is performed as described above. However, the detection of the defocus amount has a considerable amount of error that cannot be ignored. Does not always make the defocus amount constant. Although there are various causes of the error, there are electric noise of the photoelectric conversion element and phase-in-phase-out generated due to a decrease in output sensitivity in a region adjacent to a pixel constituting the line sensor.

In order to suppress this, the depth of field is calculated from the permissible circle of confusion, and the lens drive amount corresponding to the amount of blur that cannot be seen practically as a photograph (lens drive amount within the depth of field). Is set as an in-focus range (in-focus range). During servo control, driving of a minute photographing lens is prohibited in a range (a drive inhibition range) narrower than the in-focus range, and unnecessary lenses are Driving is suppressed.

However, if the moving body moving near the in-focus state is servo-controlled according to the defocus amount including such an error, the photographing lens is driven by an amount corresponding to the defocus amount. Even so, the taking lens may go too far. Although there are various causes, there is a non-linear relationship between the amount of defocus and the corresponding amount of driving the photographing lens, and it is impossible to obtain the correct true lens driving amount theoretically, This was due to the stopping accuracy of the taking lens, such as a communication delay between the motors.

(Object of the Invention) A first object of the present invention is to provide an automatic focus adjusting apparatus capable of performing a highly accurate focus adjustment on a moving focus target in a servo AF mode. Things.

A second object of the present invention is to provide an automatic focusing camera capable of performing a highly accurate focusing on a moving subject in a servo AF mode.

[0011]

In order to achieve the first object, the invention according to the first aspect is characterized in that the difference between the image forming position of the lens and the image plane position of the lens for which the focus adjustment operation is to be performed. A defocus amount detecting means for detecting the defocus amount, and a lens driving means for driving the lens for focus adjustment based on the lens driving amount calculated from the defocus amount, and Servo AF that repeats the defocus amount detection and lens driving based on the result after that
In the automatic focus adjustment device capable of setting a mode, in the servo AF mode, a lens driving amount calculated from the defocus amount is compared with a predetermined lens driving amount corresponding to a focusing range, While the lens driving amount calculated from the defocus amount is larger, the lens is driven based on the lens driving amount, and the lens driving amount calculated from the defocus amount is equal to or less than the predetermined lens driving amount. Accordingly, the lens drive amount calculated from the defocus amount is set to a lens drive amount reduced at a predetermined rate, and the lens drive control is performed to drive the lens based on the lens drive amount reduced at the predetermined rate. An automatic focusing device having means is provided.

[0012] Similarly, in order to achieve the first object,
According to a second aspect of the present invention, there is provided a defocus amount detecting means for detecting a defocus amount which is a difference between an image forming position of a lens and an image plane position of the lens where a focus adjustment operation is to be performed. A lens driving means for driving the lens for focus adjustment based on the calculated lens driving amount, and a servo AF mode for repeating the defocus amount detection and lens driving based on the result even after focusing. In the settable automatic focusing device, in the servo AF mode, if the current position is not located within a predetermined lens driving amount corresponding to a focusing range from the image forming position of the lens, a defocus is performed. The lens driving is performed based on the lens driving amount calculated from the focus amount, and the current position is determined in advance at a predetermined position corresponding to the focusing range from the imaging position of the lens. The lens drive amount calculated from the defocus amount is set to a lens drive amount that is reduced by a predetermined ratio, and the lens control unit that drives the lens based on the lens drive amount. An adjusting device.

Further, in order to achieve the second object,
According to a fourth aspect of the present invention, there is provided a defocus amount detecting means for detecting a defocus amount which is a difference between an image forming position of a photographing lens and an image plane position of the photographing lens to be subjected to a focus adjustment operation, and the defocus amount. A lens driving unit for driving the lens for focus adjustment based on the lens driving amount calculated from the amount, and a servo AF for repeating the detection of the defocus amount and the lens driving based on the result even after focusing. In the automatic focus adjustment camera capable of setting a mode, in the servo AF mode, a lens driving amount calculated from the defocus amount is compared with a predetermined lens driving amount corresponding to a focusing range, While the lens drive amount calculated from the defocus amount is larger, the driving of the photographing lens is performed based on the lens drive amount, and the drive is performed based on the defocus amount. The lens driving amount calculated from the defocus amount is reduced by a predetermined ratio when the output lens driving amount is equal to or less than the predetermined lens driving amount, and the lens driving amount is reduced by the predetermined ratio. The present invention is directed to an automatic focusing camera having lens drive control means for driving the taking lens based on the amount.

Further, in order to achieve the second object,
The invention according to claim 5, wherein a defocus amount detecting means for detecting a defocus amount which is a difference between an image forming position of a photographing lens and an image plane position of the photographing lens at which a focus adjustment operation is to be performed; A lens driving means for driving the photographing lens for focus adjustment based on a lens driving amount calculated from the amount, and a servo for repeating the detection of the defocus amount and the lens driving based on the result even after focusing. A
In the automatic focusing camera capable of setting the F mode, in the servo AF mode, the current position is not located within a predetermined lens drive amount corresponding to a focusing range from the imaging position of the photographing lens. In this case, the lens drive is performed based on the lens drive amount calculated from the defocus amount, and the current position is within a predetermined lens drive amount corresponding to a focusing range from the imaging position of the photographing lens. In this case, the lens drive amount calculated from the defocus amount is reduced by a predetermined ratio to a lens drive amount, and the camera is an automatic focusing camera having lens control means for driving the lens based on the lens drive amount. .

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments.

FIG. 1 is a block diagram showing a configuration of an interchangeable lens type single-lens reflex camera which is an example of an optical apparatus according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a lens MPU (micro-processing unit) for performing all calculations and controls relating to the photographing lens, 2 denotes a lens driving unit for driving the photographing lens, 3 denotes a lens position detecting unit, and 4 denotes a lens position detecting unit. The extended position detecting unit 5 is an optical information table for storing optical information necessary for automatic focus adjustment.

A photographing lens is constituted by the MPU 1 to the optical information table 5, an aperture driving unit for driving an aperture (not shown), and the like. The photographing lens has a mount indicated by a solid line in the center of FIG. Through the camera.

Reference numeral 6 denotes a camera MPU (micro processing unit) which performs all calculations and controls related to the camera body.
It is connected to the lens MPU1 via the signal line of the mount, and can acquire the lens position, drive the lens, and acquire the unique optical information for each interchangeable lens with respect to the lens MPU1.

7 is a defocus amount detection unit, 8 is a shutter drive unit, 9 is a film feed unit, 10
Is a dial unit for making various camera settings (shutter speed, aperture value, shooting mode, etc.). SW1 is a switch that is turned on by the first stroke operation (half press) of the release button, and SW2 is a switch that is turned on by the second stroke operation (full press) of the release button.

Various photographing modes can be set by operating the dial unit 10. In the present embodiment, a servo AF mode (servo AF mode) for performing servo control suitable for photographing a moving subject using the dial unit 10 is described. AF mode in which focus detection and lens driving based on the result are repeatedly performed even after focusing is set, and servo control in the camera MPU 6 in this case is set as follows.
This will be described with reference to the flowchart of FIG.

First, in step # 101, the switch SW
When 1 is turned on, the camera MPU 6 proceeds to step # 102
Then, the automatic focus adjustment in the servo AF mode is executed. Details of the automatic focus adjustment will be described later.
Then, in the next step # 103, it is determined whether or not the switch SW1 is continuously turned on even after the automatic focus adjustment. If not, the process exits from this routine and waits until the switch SW1 is turned on again.

On the other hand, if it is determined in step # 103 that the switch SW1 is turned on, step # 1 is executed.
In step S04, it is determined whether the switch SW2 is turned on. If the switch SW2 is not turned on, the process returns to step # 102. If the switch SW2 is turned on, the process proceeds to step # 105 to perform a known release operation. Then, the process returns to step # 102.

Next, the details of the automatic focusing operation in the servo AF mode executed in step # 102 will be described with reference to the flowchart of FIG.

When the automatic focus adjustment operation is called in step # 201, the camera MPU 6 advances the operation to step # 202, and obtains the current extension position of the photographing lens from the lens position detection unit 3. This is camera M
This is performed by communicating from the PU 6 to the lens MPU 1.

The defocus amount (difference between the image forming position of the photographing lens and the image plane position of the photographing lens for performing the photographing operation) required for the automatic focus adjustment passes through two different areas sandwiching the optical axis of the photographing lens. It is calculated from the image shift amount (prediction amount) between two images formed from the subject light flux. Specifically, the luminous flux of these two images passes through a main mirror which is a half mirror, is reflected by a sub-mirror behind the mirror, and is guided to a defocus amount detection unit 7 by a focus detection optical system (not shown). It is calculated as follows.

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 the next step # 203. Then, in the next step # 204, optical information such as sensitivity, best focus correction value, and defocus amount per pulse necessary for automatic focusing is obtained from the taking lens. This is performed by communicating from the camera MPU6 to the lens MPU1. More specifically, the distance ring of the photographing lens is electrically divided at regular intervals, and is connected to the feed-out position detecting unit 4. The lens MPU 1 acquires the current feed-out position from the feed-out position detecting unit 4, and outputs the current feed-out position. The information necessary for the automatic focus adjustment is transmitted to the camera MPU 6 by referring to the optical information table 5 which is a table corresponding to.

In the following step # 205, the amount of image shift is calculated by performing a correlation operation, and the defocus amount is obtained. The defocus amount and the actual lens drive amount have a non-linear relationship, and are generally approximated by a function corresponding to the defocus amount. Also, the amount handled in the actual payout is
It is not the length but the number of defocus pulses that is the drive waveform to the taking lens. Therefore, camera MPU6
Calculates the defocus amount calculated on the basis of the optical information obtained from the lens MPU1 in the above step # 205, in the next step # 206, the number of defocus pulses,
That is, it is converted into a lens drive amount. Also this step #
In step 206, a change in the image plane position of the photographing lens is predicted, and the lens drive amount is corrected in anticipation of the movement of the subject during the release time lag so that the photographing lens comes to the subject predicted image plane position during photographing. Do. As described above, this method has already been disclosed by the present applicant (Japanese Unexamined Patent Application Publication No.
No. 197185), further detailed description will be omitted.

When the lens drive amount necessary for focusing is obtained as described above, the camera MPU 6 performs the operation in step # 20.
Then, the image plane position obtained by adding the lens position obtained in step # 202 to the lens driving amount is stored in an internal memory. A plurality of past image plane positions are stored in the memory.If this image plane position monotonously increases or decreases, the subject is regarded as moving, and conversely, if not, Indicates that the image plane position is vibrating and the subject is stationary.

Next, the routine proceeds to step # 208, where it is determined whether or not the lens drive amount is within the focusing range. More specifically, the number of defocus pulses calculated in step # 206 (the number of pulses for driving the lens from the current position of the photographing lens acquired in step # 202 to the ideal in-focus position) is predetermined. Comparing the number of pulses corresponding to the focusing range (the lens driving amount within the depth of field), and if the number of defocusing pulses is larger, it is determined that the lens driving amount is outside the focusing range. Proceeding to # 211, the lens driving unit 2 is driven to drive the lens, and thereafter, the process proceeds to step # 212 and returns to the main routine. Since the mode is the servo AF mode, the switch SW1 is on and the switch SW2 is off. Meanwhile, the same operation is repeated.

The focusing range is determined in advance by the open aperture value of the mounted photographing lens.
The lens drive amount corresponding to 35 μm if 2.0 or less, 50 μm if F2.8 or less, and 80 μm if F2.8 or less, that is, the pulse number is preset.

On the other hand, if it is determined that the lens drive amount is within the focusing range, that is, if the number of defocus pulses calculated in step # 206 is equal to or less than the number of pulses corresponding to the focusing range. If determined, step # 2
08, the process proceeds to a step # 209. In this case, it is determined whether or not the current lens driving amount is within a driving prohibition range for prohibiting the driving of the minute photographing lens, that is, the number of defocus pulses is a pulse corresponding to the driving prohibition range. It is determined whether the number is equal to or less than the number. If the driving lens is within the driving prohibition range, the lens is not driven because the photographing lens is at an almost ideal position, and the process immediately proceeds to step # 212 to return to the main routine, where the servo A
Since the mode is the F mode, the same operation is repeated while the switch SW1 is on and the switch SW2 is off.

If it is out of the drive prohibition range, step #
The process proceeds from step 210 to step # 210, in which the current lens drive amount, that is, the number of defocus pulses, is halved, and the process proceeds to step # 211 described above, where the lens drive unit 2 is driven to drive the lens. Then, the process proceeds to step # 212 and returns to the main routine. Since the mode is the servo AF mode, the same operation is repeated while the switch SW1 is on and the switch SW2 is off.

Accordingly, the same operation (# 210 → # 211) is performed until it is determined in step # 209 that the lens drive amount at that time is within the drive prohibition range. In other words, the photographing lens is repeatedly driven based on a lens driving amount that is half of the lens driving amount obtained from the defocus amount detected each time, and is driven to the ideal in-focus position.

According to the above-described embodiment, the number of defocus pulses corresponding to the lens driving amount calculated from the defocus amount is smaller than the number of pulses corresponding to the focusing range, and the number of defocus pulses is smaller than the number of pulses corresponding to the driving inhibition range. Is large, the lens driving amount (the number of defocus pulses) is reduced by half to drive the lens. In other words, the number of defocus pulses is reduced by half until the driving is within the driving prohibition range, and the ideal driving is performed. Since the control for driving the photographing lens to the focal point is performed, it is possible to perform a more accurate focus adjustment for the moving object as compared with the conventional case where the lens is driven to a desired position at a stretch.

(Modification) In the above embodiment, the focus range is determined in advance by the open aperture value of the mounted photographing lens. However, the present invention is not limited to this. Since the depth of field varies depending on the aperture value, the focusing range may be determined according to the depth of field. Also, since the depth of field changes depending on the focal length and shooting distance of the shooting lens other than the aperture,
You may set according to them.

Therefore, in step # 210 in FIG. 3, the lens drive amount (the number of defocus pulses) is reduced by half, but the lens drive amount is reduced according to the aperture value, focal length, and shooting distance of the taking lens. You may do it.

[0038]

As described above, according to the first or second aspect of the present invention, in the servo AF mode, the automatic focus which can perform the focus adjustment with high accuracy for the moving focus target. An adjusting device can be provided.

According to the fourth or fifth aspect of the present invention, it is possible to provide an automatic focusing camera capable of performing a highly accurate focusing on a moving subject in the servo AF mode.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a single-lens reflex camera according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an operation of a main part of the single-lens reflex camera according to one embodiment of the present invention.

FIG. 3 is a flowchart showing an automatic focusing operation performed in step # 102 of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lens MPU 2 Lens drive unit 3 Lens position detection unit 4 Extension position detection unit 5 Optical information table 6 Camera MPU 7 Defocus amount detection unit

Claims (9)

[Claims] 1. A defocus amount detecting means for detecting a defocus amount which is a difference between an image forming position of a lens and an image plane position of the lens on which a focus adjustment operation is to be performed, and a lens calculated from the defocus amount. Lens driving means for driving the lens for focus adjustment based on the driving amount, and an automatic AF capable of setting a servo AF mode for repeating the detection of the defocus amount and lens driving based on the result even after focusing. In the focus adjustment device, in the servo AF mode, a lens driving amount calculated from the defocus amount is compared with a predetermined lens driving amount determined in advance corresponding to a focusing range, and the lens driving amount calculated from the defocus amount is calculated. While the lens drive amount is larger, the lens is driven based on the lens drive amount, and the lens drive amount calculated from the defocus amount is smaller. The lens driving amount calculated from the defocus amount is set to a lens driving amount reduced by a predetermined ratio by being equal to or less than the predetermined lens driving amount, and the lens driving amount is reduced based on the lens driving amount reduced by the predetermined ratio. An automatic focus adjustment device having lens drive control means for driving the lens. 2. A defocus amount detecting means for detecting a defocus amount which is a difference between an image forming position of a lens and an image plane position of the lens on which a focus adjustment operation is to be performed, and a lens calculated from the defocus amount. Lens driving means for driving the lens for focus adjustment based on the driving amount, and an automatic AF capable of setting a servo AF mode for repeating the detection of the defocus amount and lens driving based on the result even after focusing. In the focus adjustment device, in the servo AF mode, if the current position is not within a predetermined lens driving amount corresponding to a focusing range from the imaging position of the lens, the current position is calculated from the defocus amount. The lens is driven based on the amount of lens driving performed, and the current position is determined by a predetermined lens corresponding to a focusing range from the imaging position of the lens. When located rotation amount in the the lens drive amount to reduce the lens drive amount calculated from the defocus amount in a predetermined ratio,
An automatic focusing device comprising a lens control means for driving a lens based on the lens driving amount. 3. The lens driving amount reduced by the predetermined ratio is a lens driving amount obtained by halving the lens driving amount calculated from the defocus amount. Automatic focus adjustment device. 4. A defocus amount detecting means for detecting a defocus amount, which is a difference between an image forming position of a photographing lens and an image plane position of the photographing lens at which a focus adjustment operation is to be performed, and is calculated from the defocus amount. Lens driving means for driving the lens for focus adjustment based on the lens driving amount to be set, and a servo AF mode that repeats the detection of the defocus amount and the lens driving based on the result even after focusing can be set. In the automatic focusing camera, in the servo AF mode, a lens driving amount calculated from the defocus amount is compared with a predetermined lens driving amount corresponding to a focusing range, and the defocus amount is calculated. While the calculated lens driving amount is larger, the photographing lens is driven based on the lens driving amount,
When the lens driving amount calculated from the defocus amount is equal to or less than the predetermined lens driving amount, the lens driving amount calculated from the defocus amount is reduced by a predetermined ratio to a lens driving amount. An automatic focusing camera, comprising: lens drive control means for driving the photographing lens based on a lens drive amount reduced in proportion. 5. A defocus amount detecting means for detecting a defocus amount which is a difference between an image forming position of a photographic lens and an image plane position of the photographic lens to be subjected to a focus adjustment operation, wherein the defocus amount is calculated from the defocus amount. Lens driving means for driving the photographing lens for focus adjustment based on a lens driving amount to be set, and setting a servo AF mode for repeating the detection of the defocus amount and the lens driving based on the result even after focusing. In a possible auto-focusing camera, in the servo AF mode, if the current position is not located within a predetermined lens drive amount corresponding to a focusing range from the imaging position of the taking lens, The lens is driven based on the lens drive amount calculated from the focus amount, and the current position is set in advance from the image forming position of the photographing lens to the in-focus range. If the lens driving amount is within the predetermined lens driving amount, the lens driving amount calculated from the defocus amount is reduced by a predetermined ratio to a lens driving amount, and a lens control unit that drives the lens based on the lens driving amount An automatic focusing camera comprising: 6. The lens driving amount reduced by the predetermined ratio is a lens driving amount obtained by halving the lens driving amount calculated from the defocus amount. Automatic focusing camera. 7. The automatic focusing camera according to claim 4, wherein the focusing range is determined in advance by an open aperture value of the photographing lens. 8. The automatic focusing camera according to claim 4, wherein the focusing range is determined according to a depth of field. 9. The apparatus according to claim 4, wherein the focus range is determined according to a selected aperture value, a focal length of the photographing lens, and a depth of field that varies depending on a photographing distance.
Or the automatic focusing camera according to 5.