JP2014145880A - Focus adjustment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable suppression of a large blur picture caused by a wrong correction of a predicting amount of a correction in a photographing sequence.SOLUTION: The focus adjustment device has: first subject image position prediction means for predicting a subject image position after predetermined time has elapsed on the basis of a plurality of subject image detection results by a first photoelectric conversion element row; second subject image position prediction means for predicting a subject image position after predetermined time has elapsed on the basis of a plurality of subject image detection results by a second photoelectric conversion element row arranged in a direction different from the first photoelectric conversion element row; and means for adding or reducing a predicting amount of a correction to be calculated by the first subject image position prediction means in accordance with a detection distance of a subject in a drive mode in which operation time (a release time lag) until a photograph is actually shot since a release button is depressed resides for a period of time longer than normally.

Description

  The present invention relates to a focus adjustment device used for a camera or the like, and more particularly to a focus adjustment device having a moving object prediction mode function (AI-SERVO) of a subject.

  Conventionally, in a focus detection device of a camera, a subject image signal passing through a photographing lens is accumulated in an AF sensor, and a defocus amount is detected (focus detection) based on the subject image signal accumulated in the AF sensor. Detection devices are known. In the focus adjustment device, there is a control method for driving the photographing lens in conjunction with the movement of the moving subject in order to keep the moving subject in focus. When the moving subject is kept in focus, the focus detection is performed for each frame of continuous shooting, and the amount of predicted future subject movement position is added to the focus detection result to move the photographic lens. As shown in FIG. 4, the future subject movement position is predicted by obtaining an amount (correction amount) by which the subject moves in the future time from the start of the mirror up operation after the end of focus detection to the exposure to the image sensor.

  Many focus adjustment apparatuses having various means as means for obtaining the correction amount have been proposed in the past.

  For example, in Patent Document 1, the image plane position obtained from the image formation position acquired from the image formation position detection means provided in the photographic lens and the defocus amount detected by the defocus amount detection means and the image plane position Storage means for storing a plurality of detection times in the past, and image plane position prediction means for predicting future changes in the image plane position from changes in the image plane positions and detection times in the past a plurality of times. Disclosed is a means for predicting an image plane position at the time of exposure based on a predicted stop driving time acquired from a stop driving time predicting means provided in the photographing lens.

  Further, Patent Document 2 is a camera that includes a distance measuring device having a distance measuring optical system different from a photographing optical system having a photographing lens, and that adjusts the focus of the image capturing optical system based on a distance measurement result of the distance measuring device. A storage means for storing time lag information determined according to the shooting state; and a prediction calculation means for predicting and calculating the amount of movement of the subject based on a plurality of distance measurement results detected by the distance measuring device, The prediction calculation means calculates a release time lag corresponding to the shooting state based on the time lag information stored in the storage means, and predicts and calculates a subject distance at the time of exposure based on the release time lag. It is disclosed.

JP2008-233888 JP 2003-222790 A

  By the way, there is a shooting mode (silent shooting mode) that enables quiet shooting by performing mirror up and mirror down more gently than usual. In order to perform mirror-up and mirror-down quietly, as shown in FIG. 5, it is possible to lengthen the time required for mirror-up and mirror-down as compared with the normal shooting in FIG. The longer the time required for mirror up and mirror down, the longer the viewfinder disappearance time. If the finder disappearance time becomes long, there is a high possibility that the subject is lost or cannot be tracked during the viewfinder disappearance time in the moving object photographing mode in which the subject is photographed while chasing the subject.

  In addition, when the continuous shooting speed (frame speed) of the camera during continuous shooting is slow, the amount of movement of the subject in one shooting frame increases in the same way as when the viewfinder disappearance time is long. There is a high possibility of not being cut.

  If the subject is lost and cannot be tracked, the focus detection amount is not properly calculated, and the accuracy of the subject movement amount predicted using the focus detection result is also low.

  Further, as shown in FIG. 5, there is a camera that takes time until the mirror actually starts to rise even if the mirror up operation is started by the mechanical configuration. Thus, in a camera that takes a long time to mirror up and takes time until the mirror starts to rise, the time (release time lag) for predicting the amount of movement of the future subject moving from the focus detection to the start of exposure is long. Become. As the release time lag becomes longer, it becomes difficult to predict how the subject will move during that time, and the accuracy with which the predicted amount of movement of the subject is determined becomes lower. In that case, the probability of focusing decreases.

  As described above, the probability of focusing is reduced due to the fact that the finder disappearance time, the frame speed, and the release time lag are long, and it is easy to obtain a large blurred photo. It is not preferable to provide the user with a large blurred photo because the prediction is significantly different.

  In the case of the apparatus disclosed in Patent Document 1, if the future time to be predicted becomes longer, it is difficult to predict how the subject moves during that time, and if the accuracy of the predicted amount of movement of the subject becomes low, the probability of focusing will be increased. Decrease and increase the number of large blurred photos. Also, in Patent Document 2, the probability of focusing decreases for the same reason, and large blurred photographs increase.

  Accordingly, the object of the present invention is to suppress the large-blurred photo by performing focus detection for all the element arrays when the finder disappearance time is long and the frame speed is slow, and to predict when the release time lag is long An object of the present invention is to provide an apparatus that suppresses a large-blurred photograph by making a prediction for adjusting the correction amount.

  In order to achieve the above object, the present invention provides first subject image position prediction means for predicting a subject image position after a predetermined time based on a plurality of subject image detection results by the first photoelectric conversion element array; A second subject image position for predicting a subject image position after a predetermined time based on a plurality of subject image detection results by the second photoelectric conversion element row arranged in a direction different from the first photoelectric conversion element row. In the drive mode in which the operation time (release time lag) between the prediction unit and the actual shooting after the release button is pressed is longer than normal, the first subject image prediction is performed according to the subject detection distance. A focus adjustment apparatus comprising means for adjusting a prediction correction amount calculated by the means.

  According to the present invention, it is possible to suppress large-blurred photographs that occur due to erroneous correction of the predicted correction amount in the shooting sequence.

It is a block diagram which shows the concept of the focus adjustment apparatus of Claim 1 of this invention. It is a block diagram which shows the structure of the single-lens reflex camera which is embodiment of this invention. It is the figure which showed the focus detection principle of the phase difference method. Normal shooting sequence Silent shooting sequence It is the flowchart which showed the prediction correction amount calculation method concerning Example 1 of this invention. It is the figure which showed the frequency | count of focus detection in the focus detectable time when the accumulation | storage instruction | indication to an AF sensor was limited. It is the figure which showed a mode that the to-be-photographed object moved within the finder per unit time. It is the figure which showed the frequency | count of focus detection in the focus detection possible time at the time of the accumulation | storage instruction | indication to all the AF sensors.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows the components of the focus adjustment operation according to the embodiment of the present invention.

  In FIG. 1, this focus adjusting apparatus includes a signal storage means (101) for storing a subject signal in an AF sensor comprising a pair of photoelectric conversion element arrays, and a focus detection means (for detecting a defocus amount from the subject signal). 102), a prediction calculation means (103) for predicting a future amount of movement of the subject from a plurality of past focus detection results obtained by the focus detection means, and the focus detection result obtained by the focus detection means A focus adjustment unit (104) for determining the driving amount of the photographing lens in consideration of the future movement amount of the subject obtained by the prediction calculation unit and adjusting the focus of the photographing lens is configured.

[Example 1]
Next, a first embodiment of the present invention will be described.

  FIG. 2 is a block diagram illustrating a configuration of a single-lens reflex camera that is Embodiment 1 of the present invention.

  Reference numeral 201 denotes a photographing lens. Reference numeral 203 denotes an AF (autofocus) driving means. The AF driving unit 203 is configured by, for example, a DC motor or an ultrasonic motor, and focuses by changing the focus lens position of the photographing lens 201 under the control of the microcomputer 223.

  Reference numeral 204 denotes an aperture. Reference numeral 205 denotes an aperture driving unit. A diaphragm driving unit 205 drives the diaphragm 204. The amount to be driven is calculated by the microcomputer 223, and the optical aperture value is changed.

  Reference numeral 206 denotes a main mirror for switching the light beam incident from the photographing lens 201 between the viewfinder side and the image sensor side. The main mirror 206 is always arranged so as to reflect the light beam to the finder unit. However, when shooting is performed, the main mirror 206 jumps upward so as to guide the light beam to the image pickup device 215 and is retracted from the light beam. . The main mirror 206 is a half mirror so that the central part can transmit part of the light, and transmits a part of the light beam to the pair of AF sensors 231a and 231b for focus detection. .

  Reference numeral 207 denotes a sub-mirror for reflecting a light beam transmitted from the main mirror 206 and guiding it to a pair of AF sensors (disposed in the focus detection unit 212) for focus detection. Reference numeral 208 denotes a pentaprism that forms a finder. In addition, the finder is composed of a focus plate 209, an eyepiece 210, and the like.

  Reference numeral 212 denotes a focus detection means. In a state where the main mirror is lowered, the light beam transmitted through the central portion of the main mirror 206 and reflected by the sub-mirror 207 reaches a pair of AF sensors for performing photoelectric conversion disposed inside the focus detection unit 212. . The defocus amount indicating the focus adjustment state of the photographing lens with respect to the subject is obtained by calculating the outputs of the pair of AF sensors. The microcomputer 223 evaluates the calculation result and instructs the AF driving unit 203 to drive the focus lens.

  Reference numeral 213 denotes a focal plane shutter. Reference numeral 214 denotes shutter driving means that drives the focal plane shutter 213. The opening time of the shutter is controlled by the microcomputer 223.

  Reference numeral 215 denotes an image sensor. A CCD, CMOS sensor, or the like is used as the image sensor 215, and the subject image formed by the photographing lens 201 is converted into an electrical signal. Reference numeral 216 denotes a clamp circuit. Reference numeral 217 denotes an AGC circuit. The clamp circuit 216 and the AGC circuit 217 perform basic analog signal processing before A / D conversion, and the microcomputer 223 changes the clamp level and the AGC reference level.

  Reference numeral 218 denotes an A / D converter. The A / D converter 218 converts the analog output signal of the image sensor 215 into a digital signal. A video signal processing circuit 219 is realized by a logic device such as a gate array. Reference numeral 220 denotes a memory controller. Reference numeral 221 denotes a memory. Reference numeral 222 denotes a buffer memory.

  The video signal processing circuit 219 performs filter processing, color conversion processing, and gamma processing on the digitized image data, and also performs compression processing such as JPEG, and outputs the result to the memory controller 220.

  The video signal processing circuit 219 can output information such as exposure information and white balance of the signal from the image sensor 215 to the microcomputer 223 as necessary. Based on the information, the microcomputer 223 instructs white balance and gain adjustment. In the case of the continuous shooting operation, the shooting data is temporarily stored in the buffer memory 222 as an unprocessed image, the unprocessed image data is read through the memory controller 220, and image processing and compression processing are performed by the video signal processing circuit 219. Perform continuous shooting. The number of continuous shots depends on the size of the buffer memory 222.

  In the memory controller 220, unprocessed digital image data input from the video signal processing circuit 219 is stored in the buffer memory 222, and processed digital image data is stored in the memory 221. Conversely, the image data is output from the buffer memory 222 or the memory 221 to the video signal processing circuit unit 219. The memory 221 may be removable. Reference numeral 223 denotes a microcomputer. Reference numeral 224 denotes an operation member.

  The operation member 224 transmits the state to the microcomputer 223, and the microcomputer 223 controls each part according to the change of the operation member.

  In addition, the operation member 224 has a ONESHOT mode suitable for photographing a stationary subject, an AI-SERVO mode suitable for photographing a subject whose photographing distance constantly changes, and switches from ONESHOT to AI-SERVO depending on the state of the subject. A switching operation to the AI-FOCUS mode in which the camera automatically switches can be performed.

  Reference numeral 225 denotes a switch 1 (hereinafter referred to as SW1).

  Reference numeral 226 denotes a switch 2 (hereinafter referred to as SW2). The switches SW1 and SW2 are switches that are turned on / off by operating the release button, and are each one of the input switches of the operation member 224. When only the switch SW1 is on, the release button is half-pressed. In this state, the autofocus operation is performed and the photometry operation is performed.

  When the switches SW1 and SW2 are both on, the release button is fully pressed, and the release button for recording an image is on. Shooting is performed in this state. Further, a continuous shooting operation is performed while the switches SW1 and SW2 are kept on.

  In addition, switches such as an ISO setting button, an image size setting button, an image quality setting button, and an information display button are connected to the operation member 224, and the switch state is detected.

  Reference numeral 227 denotes a power supply unit. The power supply unit 227 supplies power necessary for each IC and drive system.

  FIG. 3 shows a schematic configuration of the focus detection means 212. 2 that are the same as those in FIG. 2 are assigned the same reference numerals as in FIG. In FIG. 3, each component is shown expanded on the optical axis of the photographic lens 201. However, in FIG. 3, the main mirror 206 and the sub mirror 207 are omitted.

  The focus detection unit 212 includes a field lens 303, a diaphragm 304 having a pair of openings, a pair of secondary imaging lenses 305, and AF sensors 306a and 306b including a pair of photoelectric conversion element arrays. Has been.

  A light beam emitted from one point on the optical axis 301 a passes through the photographing lens 301 and then forms an image on the image sensor 302, and a pair of AFs through the field lens 303, the diaphragm 304, and the secondary imaging lens 305. Images are formed on the sensors 306a and 306b at a predetermined interval.

  The field lens 303 is arranged so that the pupil 301 b of the photographing lens 301 and the entrance pupil of the pair of secondary imaging lenses 305, that is, the vicinity of the diaphragm 304, correspond to the pair of openings of the diaphragm 305. The pupil 301b of the photographic lens 301 is divided in the vertical direction in the figure.

  In such a configuration, for example, when the photographic lens 301 is extended to the left in the figure and a light beam forms an image to the left of the image sensor 302, the pair of images on the pair of AF sensors 306a and 306b is displaced in the direction of the arrow. . By detecting the relative shift amount of the pair of images with the AF sensors 306a and 306b, it is possible to detect the focus of the photographing lens 301 and further drive the focus adjustment of the photographing lens 301. When the photographing lens 301 is extended to the right in the figure, the pair of images on the pair of AF sensors 306a and 306b are displaced in the direction opposite to the arrow direction in the figure.

  The focus detection unit 212 as described above is used to detect the focus of the photographic lens 301 and cause the photographic lens to accurately follow the subject.

  Next, the focus adjustment operation of the first embodiment of the present invention will be described.

  As shown in FIG. 5, there is a camera with a mechanical configuration that takes time until the mirror actually starts to rise even when the mirror up operation is started in the silent photographing mode. In a camera having a mechanical configuration in which the drive of the main mirror 206 and the focal plane shutter 213 is controlled using a single motor, charging time is required for the motor that performs the mirror up in order to slow the mirror up. Since the charging time is required, it takes time until the mirror actually starts to rise even if the mirror up operation is started. In the camera having the above-described mechanical configuration, in order to achieve the first embodiment, the invention described in claim 1 is based on the detection distance of the subject in the drive mode in which the release time lag is longer than usual. The large-blurred photograph is suppressed by performing the prediction calculated by the subject image prediction means.

  FIG. 6 is a flowchart for obtaining a prediction amount by the first subject image prediction means in accordance with the detection distance of the subject.

  In step # 101, it is determined whether or not the subject detection distance is longer than a threshold value. If it is determined in step # 101 that it is longer than the threshold value, the process proceeds to step # 102 to predict using a plurality of past subject detection results for a long time. When the subject detection distance is long, the subject captured by the AF sensor is small, and the subject detection often fluctuates due to the fact that the photographer's skill and objects other than the subject captured by the AF sensor can be seen. Then, in the drive mode where the release time lag is longer than usual, the predicted amount often deviates greatly.

  Thus, by using the subject detection results of a plurality of past times for a long time, the prediction amount is slowed down and the calculation of a large amount of prediction amount is suppressed. On the other hand, if it is determined in step # 101 that the subject detection distance is shorter than the threshold value, the process proceeds to step # 103 to predict using a plurality of past subject detection results. When the subject detection distance is short, the subject detection amount per unit time increases. Therefore, in order to follow the subject with high accuracy, the prediction amount is calculated with sensitivity using a short prediction.

  The predicted amount obtained in step # 102 and step # 103 is added to the subject detection result, and the lens is driven in step # 104 to accurately follow the subject.

  As described above, according to the first embodiment, in the drive mode in which the release time lag is longer than usual, the focus adjustment with high accuracy can be performed by changing the length of the subject detection results of the past plural times according to the subject detection distance. Is possible.

[Example 2]
Embodiment 2 of the present invention will be described below.

  The second embodiment has the same camera configuration as that of the first embodiment. The focus detection circuit 210 is used to detect the focus of the photographing lens 201, and the focus detection result is added to the future subject movement amount obtained by the prediction calculation. The driving amount of the taking lens is determined, and the focus of the taking lens is adjusted.

  In the present invention, in the drive mode in which the photographing speed is low, the accumulation operation in the first photoelectric conversion element array is made to be an object for all the element arrays so that the subject can be accurately followed.

  In general, AI-SERVO defines a time during which focus detection can be performed per frame. The focus detection is performed multiple times within the specified time, and the amount of movement of the subject moving in the optical axis direction is predicted to the release time lag using the focus detection results of the multiple times, and the lens is accurately followed to the subject. Let Since the time during which focus can be detected per frame is limited, the accumulation instruction to the AF sensor is narrowed down within a predetermined time by narrowing down the AF sensors that issue the accumulation instruction rather than being issued to all AF sensors. Focus detection can be performed multiple times (FIG. 7). However, when the frame speed is slow, the amount of movement of the subject in the viewfinder at the first and second frames as shown in FIG. 8 is larger than when the frame speed is fast. If the amount of movement of the subject in the viewfinder is large, the possibility of the subject moving to an AF sensor that has not been instructed to accumulate increases, and the subject is often lost. If the subject is lost, the focus detection result used for prediction includes erroneous detection, the accuracy of prediction is lost, and a large blurred photo is easily obtained.

  Therefore, in the present invention, the number of times of focus detection is less than the number of times of focus detection by limiting the accumulation instruction to the AF sensor and increasing the number of times of focus detection within a predetermined time in which focus detection can be performed around one frame as shown in FIG. Thus, by giving an accumulation instruction to all AF sensors, the possibility of losing the subject is reduced, and prediction is made with fewer false detections.

  As described above, according to the second embodiment, in the drive mode in which the photographing speed is low, the accumulating operation in the first photoelectric conversion element array is made to follow all the objects with high accuracy, thereby achieving accurate focus adjustment. Is possible.

[Example 3]
Embodiment 3 of the present invention will be described below.
The third embodiment has the same camera configuration as that of the first and second embodiments. The focus detection of the photographing lens 201 is performed using the focus detection circuit 210, and the amount of movement of the future subject obtained by the prediction calculation as the focus detection result. In consideration of the above, the driving amount of the taking lens is determined, and the focus of the taking lens is adjusted.

  In the present invention, in the drive mode in which the finder disappearance time is long, the accumulating operation in the first photoelectric conversion element array is made to target all the element arrays so that the subject can be accurately followed.

  The viewfinder disappearance time represents the time taken from mirror up to mirror down. In the silent shooting mode, it takes more time from mirror up to mirror down than in the normal shooting mode. Therefore, the finder disappearance time becomes longer.

If the viewfinder disappears for a long time, it is difficult to know in which direction the subject has moved during that time, and it is difficult for the photographer to follow the subject. By doing so, the movement amount of the subject in the first frame and the second frame is increased as in the second embodiment, and if the accumulation instruction to the AF sensor is limited, the camera is likely to lose sight of the subject. If the subject is lost, the focus detection result used for prediction includes erroneous detection, the accuracy of prediction is lost, and a large blurred photo is easily obtained.
In the present invention, as shown in FIG. 9, in the time in which focus detection can be performed around one frame, it is possible to reduce the number of focus detections and reduce the number of focus detections, rather than limiting the accumulation instruction to the AF sensor to increase the number of focus detections. By causing the accumulation instruction to be made, the possibility of losing sight of the subject is reduced, and prediction is made with fewer false detections.

  As described above, according to the third embodiment, in the drive mode in which the finder disappearance time is long, the accumulating operation in the first photoelectric conversion element array is made to follow all of the elements with high accuracy, thereby accurately adjusting the focus. Is possible.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

DESCRIPTION OF SYMBOLS 101 Signal storage means 102 Focus detection means 103 Prediction calculation means 104 Focus adjustment means 201 Shooting lens 203 AF drive part 204 Diaphragm 205 Diaphragm drive part 206 Main mirror 207 Sub mirror 208 Penta prism 209 Focus plate 210 Eyepiece 212 Focus detection means 213 Shutter 214 Shutter Driving means 215 Image pickup element 216 Clamping means 217 AGC means 218 A / D converter 219 Video signal processing means 220 Memory controller 221 Memory 222 Buffer memory 223 Microcomputer 224 Operation member 225 Switch 1
226 Switch 2
227 Power supply unit 301 Shooting lens 302 Imaging element 303 Field lens 304 Aperture stop 305 Secondary imaging lens 306 AF sensor

Claims (7)

Signal accumulation means for accumulating the subject signal in the AF sensor, focus detection means for detecting a defocus amount from the subject signal, prediction calculation means for predicting a future subject movement amount from a plurality of past focus detection results, In a focus adjustment device having a focus adjustment unit that adjusts the focus of the taking lens from the defocus amount, in a shooting mode that takes time from when the main mirror is raised to when it actually starts to rise, according to the detection distance of the subject A focus adjustment apparatus comprising: means for adjusting a prediction correction amount calculated by the first subject image prediction means.   Signal accumulation means for accumulating the subject signal in the AF sensor, focus detection means for detecting a defocus amount from the subject signal, prediction calculation means for predicting a future subject movement amount from a plurality of past focus detection results, In a focus adjustment device having a focus adjustment means for adjusting the focus of the taking lens from the defocus amount, the subject signal is accumulated in the AF sensor in a shooting mode in which it takes time from when the main mirror is raised to when it actually starts to rise. A focusing apparatus characterized in that the accumulation operation is performed on all element arrays by the signal accumulation means.   Signal accumulation means for accumulating the subject signal in the AF sensor, focus detection means for detecting a defocus amount from the subject signal, prediction calculation means for predicting a future subject movement amount from a plurality of past focus detection results, In a focus adjustment apparatus having a focus adjustment unit that adjusts the focus of the photographic lens from the defocus amount, a plurality of past focus detection results in a shooting mode that takes time from when the main mirror is raised to when it actually starts to rise A focus adjusting apparatus comprising: a means for prohibiting a prediction calculation means for predicting a future movement amount of the subject.   2. The focus adjustment apparatus according to claim 1, wherein the shooting mode is a drive mode in which an operation time (release time lag) between when the release button is pressed and when actual shooting is performed is longer than normal. .   4. The focus adjustment device according to claim 2, wherein the photographing mode is a drive mode in which a finder disappearance time from mirror up to mirror down is longer than normal.   The focus adjustment apparatus according to claim 2 or 3, wherein the shooting mode is a drive mode with a low shooting speed (frame speed). 4. The focus adjustment apparatus according to claim 1, wherein the photographing mode is a mode for quietly photographing a moving subject (silent mode). 5.