JP2009128610A - Camera and automatic focusing device for camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly precisely attain a moving body estimation control to be focused on a moving subject. <P>SOLUTION: The camera includes: a focusing lens 102 configured in a photographic lens and used for focusing; and a quick return mirror for guiding light transmitted through the photographic lens to a finder. The camera exerts the moving body estimation control for focusing on a moving subject. In this camera, if a determination is made that the speed of the movement of an image plane corresponding to the movement of the subject is greater than a predetermined value, an AF/AECPU151 for exerting drive control for the focusing lens 102 in parallel with a mirror-down operation during a consecutive operation exerts drive control for the focusing lens 102 carrying out the mirror-down operation. This prevents continuity of an amount of defocus from losing due to the lens drive, resulting in degradation in moving body estimation accuracy. Thus, the highly precise moving body estimation control can be performed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a camera and an automatic focusing apparatus for the camera, and more particularly to a camera and an automatic focusing apparatus for the camera capable of moving object prediction control for focusing on a moving subject.

  There are many techniques related to moving object prediction that perform focus detection and lens driving so that a moving subject is focused.

  For example, as disclosed in Patent Document 1, there is known a method of switching a diaphragm driving, mirror-up driving, and lens driving sequence depending on the battery capacity.

  When the sequence of aperture drive, mirror up drive, and lens drive is switched depending on the battery capacity as in Patent Document 1 above, when lens capacity is small compared to when battery capacity is large, lens driving and other driving are executed simultaneously. Since the release time lag becomes longer, the continuous shooting interval becomes longer in the continuous shooting mode.

One way to solve this problem is to reduce the release time lag by performing lens drive during continuous shooting so that the normal lens drive time can be shortened. .
JP 2004-170633 A

  However, in the method of driving the lens while the mirror is down, if the lens surface is driven while the mirror is down when the image plane moving speed is slow or the speed changes from the high speed to the low speed, the lens drive causes an effect. There is a problem in that the continuity of the focus amount is lost and a side effect occurs that the moving object prediction accuracy deteriorates.

  The present invention has been made in view of the above points, and in a camera that performs moving object prediction control for focusing on a moving subject, a camera capable of performing moving object prediction control with higher accuracy than before, and an automatic focus of the camera An object is to provide an adjusting device.

One aspect of the camera of the present invention includes a focusing lens for adjusting the focus and a quick return mirror that guides light transmitted through the imaging lens to a finder, and is focused on a moving subject. In a camera that performs moving object prediction control,
Lens control means for controlling the driving of the focusing lens in parallel with the mirror-down operation during continuous shooting;
Image plane movement speed determination means for determining whether the image plane movement speed due to movement of the subject is greater than a predetermined value;
Comprising
The lens control unit performs drive control of the focus adjustment lens during a mirror down operation when a determination result of the image plane moving speed determination unit is larger than the predetermined value.
It is characterized by that.

Also, one aspect of the automatic focusing apparatus for a camera according to the present invention is an automatic focusing apparatus for a camera that performs moving object prediction control for focusing on a moving subject.
In the continuous shooting operation, in parallel to the mirror return operation of the quick return mirror that guides the transmitted light of the camera's photographic lens to the viewfinder, it controls the drive of the focus adjustment lens that is configured in the photographic lens and performs focus adjustment. Lens control means;
Image plane movement speed determination means for determining whether the image plane movement speed due to movement of the subject is greater than a predetermined value;
Comprising
The lens control unit performs drive control of the focus adjustment lens during a mirror down operation when a determination result of the image plane moving speed determination unit is larger than the predetermined value.
It is characterized by that.

  ADVANTAGE OF THE INVENTION According to this invention, in the camera which performs the moving body prediction control which focuses the to-be-moved subject, the camera which can perform a moving body prediction control with higher precision than before, and the automatic focus adjustment apparatus of a camera can be provided.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic view of a single-lens reflex camera as a camera according to an embodiment of the present invention equipped with an automatic focus adjustment apparatus according to an embodiment of the present invention.

  This camera includes a camera body 100 and an interchangeable lens unit 101 that can be attached to and detached from the camera body 100. Note that the configuration shown in FIG. 1 and the following description of the embodiment assume a digital still camera, but the present invention is naturally applicable to a silver salt camera as well.

  The interchangeable lens unit 101 includes a focus adjustment lens 102 and a zoom lens 103. The focus adjustment lens 102 is driven in the optical axis direction to adjust the focus state of the interchangeable lens unit 101. The zoom lens 103 is driven in the optical axis direction to change the focal length of the interchangeable lens unit 101.

  On the other hand, the camera body 100 includes a main mirror 104, a sub mirror 105, a focus detection optical system 106, a focus detection sensor (hereinafter referred to as AF sensor) 107, a focal plane shutter 108, an image sensor 109, a screen mat 110, and a viewfinder optical system 111. And an eyepiece 112.

  The main mirror 104 is composed of a half mirror, which partially transmits and partially reflects the light flux from the subject. Further, the main mirror 104 is configured to be rotatable in a direction indicated by an arrow in the drawing so that all light fluxes go to an imaging surface constituted by the imaging element 109 at the time of exposure.

  Except at the time of exposure, the light beam from the subject transmitted through the main mirror 104 is reflected by the sub mirror 105 and guided to the focus detection optical system 106. The focus detection optical system 106 includes a lens for focus detection and the like, and guides the light beam reflected by the sub mirror 105 to the AF sensor 107. The detailed configuration of the focus detection optical system 106 will be described in detail later.

  The AF sensor 107 is, for example, a sensor composed of a photodiode array. The AF sensor 107 is configured to be able to detect a plurality of focus points. That is, the AF sensor 107 has a plurality of photodiode arrays corresponding to a plurality of focus detection areas. The detailed configuration of the AF sensor 107 will also be described in detail later.

  As described above, at the time of exposure, the main mirror 104 is retracted from the optical axis of the interchangeable lens unit 101, so that the light flux from the subject is incident in the imaging surface direction. At this time, the focal plane shutter 108 is driven and controlled to give an appropriate amount of light to the imaging surface. In the case of a digital still camera, a CCD, a CMOS sensor, or the like is used for the image sensor 109 that constitutes the imaging surface. When the camera is a silver salt camera, a silver salt film is used instead of the image sensor 109. When the above-described focal plane shutter 108 is opened, the light flux from the subject is incident on the imaging surface formed by the imaging element 109.

  Further, at times other than the exposure time, the light beam from the subject reflected by the main mirror 104 is incident in the finder direction, and an image is formed by the screen mat 110. This image enters the eyepiece 112 through the finder optical system 111. The photographer can know the photographing range and the focus state of the subject by looking into the eyepiece 112.

  FIG. 2 is a schematic diagram of a focus detection area displayed in the viewfinder. When the photographer looks into the eyepiece 112, focus detection area marks 113 corresponding to the plurality of focus detection areas of the AF sensor 107 are displayed in the viewfinder. Note that the example of FIG. 2 shows an example of multi-AF having 11 distance measuring areas.

  Next, the configurations of the focus detection optical system 106 and the AF sensor 107 will be described in detail with reference to FIGS.

  As shown in FIG. 3A, the focus detection optical system 106 includes a field mask 120, a condenser lens 121, a total reflection mirror 122, an infrared cut filter 123, a separator diaphragm mask 124, and a separator lens 125. In the drawing, each lens group in the interchangeable lens unit 101, for example, a virtual lens obtained by synthesizing the focus adjustment lens 102 and the zoom lens 103 is illustrated as a photographing lens 126.

  The field mask 120 narrows down the light beam obtained through the sub mirror 105. In order to transmit the light fluxes (dotted lines in the drawing) of the plurality of focus detection areas guided from the sub mirror 105, the field mask 120 has an opening 127 as shown in the front view of FIG.

  The condenser lens 121 is for condensing the light that has passed through the field mask 120. The condenser lens 121 is arranged corresponding to the position of the opening 127 of the field mask 120.

  The total reflection mirror 122 reflects the light beam and guides it in the direction of the separator diaphragm mask 124 via the infrared cut filter 123.

  The infrared cut filter 123 is a filter for cutting an infrared light component harmful to focus detection.

  The separator diaphragm mask 124 is for narrowing the incident light flux. This separator diaphragm mask 124 has four openings 124a, 124b, 124c, as shown in the front view of FIG. 3C, in order to divide the light beam obtained through the condenser lens 121 into four light beams. 124d.

  The separator lens 125 re-images the light beam obtained through the separator diaphragm mask 124 on the AF sensor 107. The separator lens 125 includes four separator lenses 125a, 125b, 125c, and 125d as shown in the front view of FIG.

  The AF sensor 107 described above has four photodiode array sections 128a, 128b, and 128c as shown in the front view of FIG. 3E, which is a photoelectric conversion element array that obtains a light intensity signal corresponding to the light intensity distribution of the received light flux. , 128d. Among these, the photodiode array units 128a and 128b are arranged in a direction corresponding to the horizontal direction of the shooting screen, and the other two photodiode array units 128c and 128d are arranged in a direction corresponding to the vertical direction of the shooting screen. It is arranged and has a so-called cross sensor type configuration capable of detecting a subject pattern in the horizontal and vertical directions within one distance measuring area.

  In the focus detection optical system 106 configured in this way, focus detection that passes through different areas 126a and 126b and areas 126c and 126d on the exit pupil plane of the photographing lens 126 as shown in the front view of FIG. Light beams are received by the photodiode array units 128a, 128b and 128c, 128d, respectively, and converted into electrical signals indicating the light intensity distribution pattern of the image. Using this light intensity signal, focus detection is performed by a TTL phase difference method which is one method of focus detection.

  Note that reference numeral 129 in FIG. 3A indicates a primary imaging plane at a distance equivalent to the imaging element 109 constituting the imaging plane.

The electrical configuration of the camera as described above will be described with reference to FIG.
First, a configuration related to the interchangeable lens unit 101 will be described.
A zoom driving rotary ring 130 and a manual focus (MF) rotary ring 131 that are ring-shaped so as to surround the periphery of the interchangeable lens unit 101 are disposed. The photographer can change the focal length of the interchangeable lens unit 101 by driving the zoom lens 103 in the optical axis direction by rotating the zoom driving rotary ring 130 about the optical axis of the interchangeable lens unit 101. .

  When the MF rotating ring 131 is rotated about the optical axis of the interchangeable lens unit 101, the focus adjustment lens 102 is driven in the optical axis direction in conjunction therewith. Thereby, the focus of the interchangeable lens part 101 can be adjusted manually. The MF rotating ring 131 is used when the photographer selects the manual focus mode by operating a changeover switch (not shown) that switches between the autofocus mode and the manual focus mode.

  The interior of the interchangeable lens unit 101 includes a lens CPU (hereinafter referred to as lens drive control, aperture drive control, communication control, etc.) for controlling the focus adjustment lens 102, the zoom lens 103, the diaphragm 132, and the interchangeable lens unit 101. (Referred to as LCPU) 133. The LCPU 133 is connected to a zoom position detection circuit 134, a diaphragm drive circuit 135, a lens drive circuit 136, a lens position detection circuit 137, and a communication circuit 138.

  The position of the zoom lens 103 driven by the zoom driving rotary ring 130 is detected by a zoom position detection circuit 134. The LCPU 133 obtains focal length information of the interchangeable lens unit 101 based on the position of the zoom lens 103 detected by the zoom position detection circuit 134.

  The aperture 132 includes an opening for adjusting the amount of light incident in the direction of the camera body 100. The LCPU 133 changes the size of the opening of the diaphragm 132 by controlling the diaphragm driving circuit 135 so that an appropriate amount of light enters the camera body 100 direction.

  In the autofocus mode, the LCPU 133 controls the lens driving circuit 136 to drive the focus adjustment lens 102. The position of the focus adjustment lens 102 driven by the lens driving circuit 136 is detected by a lens position detection circuit 137. The lens position detection circuit 137 includes, for example, a photo interrupter (PI) circuit that detects the rotation amount of the drive motor included in the lens drive circuit 136 by converting it into the number of pulses. In this photo interrupter circuit, the absolute position from the focus adjustment lens 102 is represented by the number of pulses from a certain reference position. The LCPU 133 obtains the focus state information of the interchangeable lens unit 101 based on the lens position detected by the lens position detection circuit 137.

  Further, the LCPU 133 communicates information such as the aperture driving amount and the defocus amount of the interchangeable lens unit 101 with the CPU and AF / AECPU of the camera body, which will be described in detail later, via the communication circuit 138. For this reason, the communication connection terminal of the communication circuit 138 is provided outside the interchangeable lens unit 101.

Next, a configuration related to the camera body 100 will be described.
The interior of the camera body 100 is configured to include a body CPU 139 that controls the entire camera. The main body CPU 139 temporarily stores a communication line 140 for communicating with the LCPU 133 via the communication circuit 138, a flash ROM (FROM) 141 in which programs of the main body CPU 139 are stored, and various information of the main body CPU 139. A RAM 142, an image sensor control circuit 143 that controls the image sensor 109 to obtain image data, a strobe control circuit 144 that controls a strobe (not shown), a mirror control circuit 145 that controls up / down of the main mirror 104, and a focal plane shutter 108. A shutter control circuit 146 for controlling, an image processing circuit 147 for image processing of image data obtained by the image sensor control circuit 143, a display circuit 148 for displaying captured images and various types of shooting information on a display unit (not shown), a photographer Various operations operated by Operation switch detecting circuit 149 that the switch is connected, the power supply circuit 150 for supplying power to the camera, and AF / AECPU151 is connected.

  Here, the operation switch detection circuit 149 includes a changeover switch (not shown) that switches the shooting mode of the camera, a release switch that operates by operating a release button, and the like. The release switch in the present embodiment is a general two-stage switch. That is, when the release button is half-pressed, the first release switch 152 (hereinafter referred to as 1R switch) is turned on to perform focus detection and photometry, and the focus adjustment lens 102 is driven to be in focus. Further, when the release button is fully pressed, the second release switch 153 (hereinafter referred to as a 2R switch) is turned on, and the main mirror 104 and the focal plane shutter 108 are driven to perform exposure.

  Further, the power supply circuit 150 performs smoothing or boosting of the voltage of the battery 154 loaded.

  The AF / AECPU 151 performs automatic focus adjustment (AF) control and photometry (AE) control of the camera. The AF / AECPU 151 includes a communication line 155 for communicating with the AF / AECPU 151 via the communication circuit 138 of the interchangeable lens unit 101, a communication line 156 for communicating with the AF / AECPU 151 and the main body CPU 139, and AF. A flash ROM (FROM) 157 storing a program of the / AECPU 151, a RAM 158 for temporarily storing various information of the AF / AECPU 151, a photometry circuit 159, a focus detection circuit 160, and an auxiliary light circuit 161 are connected.

  Here, the photometric circuit 159 is a circuit for obtaining subject luminance information by controlling a photometric element (not shown) that measures the subject luminance. The focus detection circuit 160 is a circuit for performing focus detection calculation based on information obtained by controlling the AF sensor 107 and obtaining focus detection information. Further, the auxiliary light circuit 161 is a circuit for projecting light onto a subject by a light emitting element such as an LED when performing focus detection again when the subject has low brightness and focus detection by the focus detection circuit 160 is impossible. It is.

  In the single-lens reflex camera equipped with the automatic focus adjustment apparatus according to the present embodiment, it is possible to switch between the single AF mode and the continuous AF mode by an AF mode switching switch (not shown) included in the operation switch detection circuit 149. It has become. Here, the single AF mode is an AF mode in which the focus is locked once an in-focus state is detected, and the continuous AF mode is an object that moves by continuously performing focus detection and lens driving. This is an AF mode for performing so-called moving object prediction AF.

  The operation in the continuous AF mode will be described with reference to the flowcharts of FIGS. 5 to 8 and the explanatory diagrams of FIGS.

  FIG. 5 is a flowchart for explaining an example of the 1R sequence operation in the continuous AF mode of the single-lens reflex camera in the present embodiment.

  That is, first, when the operation switch detection circuit 149 detects that the 1R switch 152 is turned on, the main body CPU 139 starts an internal timer (not shown) for measuring a distance measurement interval or the like ( Step S101). However, this timer may be a timer inside the AF / AECPU 151.

  Thereafter, the AF / AECPU 151 reads the count value of the timer and stores it in the RAM 158 (step S102).

  Next, the AF / AECPU 151 causes the AF sensor 107 to start the accumulation operation via the focus detection circuit 160, and performs control so as to end the accumulation operation when the accumulation level reaches a predetermined level (step S103).

  When the accumulation operation of the AF sensor 107 is completed, the AF / AECPU 151 passes the photoelectric conversion signal (hereinafter referred to as sensor data) detected by the accumulation operation in S103 via the focus detection circuit 160 to the focus detection circuit 160. The digital signal is converted into a digital signal by the A / D conversion circuit and stored in the RAM 158, and correction for canceling an offset component due to the influence of fixed pattern noise, dark current, etc., predetermined filter calculation, etc. are performed (step S104). .

  Further, the AF / AECPU 151 communicates with the LCPU 133 via the communication circuit 138 simultaneously with the processing of the above steps S103 and S104, and the number of pulses indicating the current position of the focus adjustment lens 102 detected by the lens position detection circuit 137. Is stored in the RAM 158 (step S105).

  After that, the AF / AECPU 151 performs known correlation calculation and interpolation calculation using the sensor data subjected to various corrections in the above step S104, and the two image interval values of each of the 11 ranging areas as shown in FIG. And the defocus amount is calculated from the two image intervals of the distance measurement area determined to be reliable by the predetermined reliability determination based on the calculation result. If the focus detection point selection mode of the camera is the spot AF mode, the defocus amount of the designated distance measurement area is selected, and if it is the multi AF mode, one is selected by a predetermined selection method such as closest selection. A defocus amount in the distance measurement area is selected (step S106).

  Here, it is determined whether or not the designated ranging area in the spot AF mode or the ranging area in the multi AF mode is reliable and the defocus amount is obtained (step S107).

  If it is determined that the specified distance measurement area in the spot AF mode or all the distance measurement areas in the multi-AF mode are not reliable, the focus detection disabled display by the lens scan or the display circuit 148 is performed. AFNG processing is performed (step S108), and the process returns to step S102.

  On the other hand, in the above step S107, it is determined that there is reliability in either the designated ranging area in the spot AF mode or the ranging area in the multi AF mode and the defocus amount is obtained. In this case, the defocus amount obtained in step S106 is associated with the timer count value acquired in step S102 and stored in the RAM 158 as time series data (step S109).

  Then, the AF / AECPU 151 transmits the defocus amount obtained in step S106 to the LCPU 133 via the communication circuit 138 (step S110). Thus, the LCPU 133 obtains the target pulse number based on the received defocus amount and the current position of the focus adjustment lens 102, and controls the lens driving circuit 136 to start lens driving.

  After that, the main body CPU 139 confirms the state of the 2R switch 153 by the operation switch detection circuit 149 (step S111). If it is on, the process proceeds to step S135, and if it is off, the process proceeds to step S112.

  That is, when determining that the 2R switch 153 is in the OFF state, the main body CPU 139 confirms the state of the 1R switch 152 by the operation switch detection circuit 149 (step S112). If it is in the off state, the process proceeds to a shooting standby sequence and waits for the next camera operation by the user.

  That is, when it is determined in step S112 that the 1R switch 152 is in the on state, the AF / AECPU 151 reads the count value of the timer and stores it in the RAM 158 as in the process of step S102 (step S113). ).

  Next, similarly to the processing in step S103, the AF / AECPU 151 causes the AF sensor 107 to start the accumulation operation via the focus detection circuit 160, and terminates the accumulation operation when the accumulation level reaches a predetermined level. Control is performed (step S114).

  Then, when the accumulation operation of the AF sensor 107 is completed, the AF / AECPU 151 uses the focus detection circuit 160 to transmit the sensor data detected by the accumulation operation in S113 via the focus detection circuit 160, similarly to the processing in step S104. The digital signal is converted into a digital signal by the A / D conversion circuit and stored in the RAM 158, and correction for canceling the offset component due to the influence of fixed pattern noise, dark current, etc., predetermined filter calculation, and the like are performed (step S115). .

  The AF / AECPU 151 communicates with the LCPU 133 via the communication circuit 138 at the same time as the processing of step S113 and step S114, as in the processing of step S115, and adjusts the focus detected by the lens position detection circuit 137. The number of pulses indicating the current position of the lens 102 is acquired and stored in the RAM 158 (step S116).

  Thereafter, the AF / AECPU 151 obtains the defocus amount of each distance measurement area from the sensor data, and selects the defocus amount of the distance measurement area according to the distance measurement point selection mode of the camera (step S106). S117).

  Here, it is determined whether or not the data of the ranging area selected in step S117 is reliable (step S118).

  If it is determined that the data of the selected distance measurement area is not reliable, the distance measurement area selection mode of the camera is the multi-AF mode, and the distance measurement is reliable outside the selected distance measurement area. It is determined whether there is an area (step S119).

  Here, when it is determined that there is a reliable ranging area in the multi AF mode, the selected ranging area other than the selected ranging area is reselected by a predetermined selection method. After making the selection (step S120), the process returns to step S111 and the above process is repeated.

  On the other hand, if it is determined in step S119 that the data in the distance measurement area other than the selected distance measurement area is not reliable, the lens scanning or the focus detection disabled display by the display circuit 148 is performed. AFNG processing is performed (step S121), and the process returns to step S102.

  On the other hand, if it is determined in step S118 that there is reliability in the designated ranging area in the spot AF mode or any ranging area in the multi-AF mode and the defocus amount is obtained. Similarly to the processing in step S109, the defocus amount obtained in step S117 is associated with the timer count value acquired in step S113 and stored in the RAM 158 as time series data (step S122).

  Thereafter, it is determined whether or not the lens drive target position temporarily stored in the RAM 158 in the previous step S134 is valid data (step S123). If it is determined that the lens drive target position is invalid data, the process proceeds to step S125. .

  On the other hand, when it is determined that the lens drive target position in the previous distance measurement is valid data, the correction is performed (step S124).

  The system control in the camera according to the present embodiment is performed by adjusting the lens driving target position corresponding to the defocus amount at the time of the accumulation operation of the AF sensor 107 in step S114 (focus adjustment at which the subject position at the time of the accumulation operation is in focus). The position of the lens 102) is obtained as the number of pulses by the lens communication in step S133, and is temporarily stored in the RAM 158 in step S134.

  However, the target number of pulses obtained here is a value obtained by adding the number of pulses corresponding to the defocus amount transmitted from the AF / AECPU 151 to the number of pulses at the position of the focus adjustment lens 102 at the time of lens communication. Since it is transmitted from the LCPU 133, when the focus adjustment lens 102 is driven between the accumulation operation in step S114 and the lens communication in step S133, an error corresponding to the lens position change during this period is included in the target pulse number. It will be defeated. Since this target pulse number is used for a moving object prediction calculation described later, an error component included in this value affects the moving object prediction accuracy, and thus correction is necessary.

Hereinafter, the lens drive target position correction will be described with reference to FIG. FIG. 9 schematically shows the relationship between the focusing lens position and the actual lens position in an arbitrary period in the 1R sequence, the number of target pulses at each accumulation operation time point, and the like. In the figure, the solid line indicates the change in the target pulse number (focusing lens position) corresponding to the movement of the subject, and the alternate long and short dash line indicates the change in the pulse number corresponding to the actual movement of the lens position. In addition, PP _n is a correct lens drive target position at the n-th distance measurement, PR _n is a lens drive target position at the n-th distance measurement actually transmitted from the lens, PM _n is a lens position at the n-th distance measurement, PT _n is a lens position at the time of defocus amount transmission, PH _n is a lens drive target position at the n-th distance measurement after correction, D _n is a lens drive amount corresponding to the defocus amount detected at the n-th distance measurement, _En lens target position error at n-th distance measurement, M _n is the lens drive amount between n-th ranging ~n + 1 th ranging, TD _n defocus amount detection timing at the n-th distance measurement, TT _n lens The defocus amount transmission timing at the n-th distance measurement and TDT _n represents the defocus amount transmission delay time at the n-th distance measurement.

That is, the correct target pulse number at time TD _n during the n-th ranging accumulation operation is indicated by PP _n . The defocus amount detected by the n-th distance measurement is transmitted from the AF / AECPU 151 to the LCPU 133 at the time TT _n , and the LCPU 133 converts the received defocus amount into the pulse number D _n at this time. by adding the number of pulses PT _n, it calculates a target number of pulses PR _n, and transmits to the AF / AECPU151.

At this time, the AF / AECPU 151 recognizes that the target pulse number at time TD _n is PR _n as shown in the figure, and this value is the defocus amount transmission delay time from time TD _n to TT _n. It would contain the actual lens movement amount error of E _n min at TDT _n. Therefore, in step S124, the time TD _{n + 1} acquired by the lens communication during the accumulation operation in the (n + 1) th distance measurement (step S116) executed immediately after transmission of the defocus amount detected in the nth distance measurement. The difference M _n between the pulse number PM _{n + 1} at time TD _n and the pulse number PM _n at time TD _n acquired in the lens communication (step S116) during accumulation operation at the n-th distance measurement is obtained at time TD _n . by subtracting the error of the target number of pulses PR _n, performs lens target position correction.

In other words, the corrected target pulse number PH _n depends on the driving direction of the lens.
(1) When driving the lens in the feeding direction
_{PH n = PR n - | PM} n -PM n + 1 | = PR n -M n
(2) When the lens is being driven in the feeding direction
_{PH n = PR n + | PM} n -PM n + 1 | = PR n + M n
Next, the association is stored in the RAM158 with the timer count value obtained in step S113 the target number of pulses PH _n as an official target pulse number corrected.

In the above example, the pulse number PM _{n + 1} at time TD _{n + 1} immediately after the defocus amount transmission is used to calculate the correction value M _n . However, the LCPU 133 uses the target pulse number PR in lens communication at the time of defocus amount transmission. _{If the} control method is such that not only _n but also the number of pulses PT _n at the time TT _n at this time can be transmitted to the AF / AECPU 151 and PT _n is used instead of PM _{n + 1} when calculating the correction value M _n , Further, the correction accuracy can be improved.

Also, since not happen when the error component E _n of the target number of pulses PR _n obtained at the defocus amount transmission lens drive is stopped, this case does not perform the lens target position correction, the defocus amount stored in the RAM158 the target number of pulses PR _n obtained at the time of transmission as an official target pulse number.

  After performing the lens drive target position correction in step S124 as described above, or when it is determined in step S123 that the lens drive target position in the previous distance measurement is invalid data, the AF / AECPU 151 is then used. Performs continuity determination using the defocus amount detected by the previous distance measurement and the defocus amount detected by the current distance measurement (step S125).

  The continuity here refers to a state in which the selected distance measurement area continues to capture the same subject. First, it is confirmed whether or not the defocus amount detected in the previous distance measurement is within a predetermined range, for example, ± 0.2 mm or less. If it is not within the set range, the continuity determination itself is not performed. This is because when the defocus amount is large, it is considered that the moving subject is not sufficiently followed, and it is meaningless to determine the continuity in such a state.

  If the defocus amount is within the predetermined range, continuity is determined. Prior to the determination, either low speed or high speed is used as the continuity determination value depending on the moving speed of the image plane of the currently tracked subject. Judge whether to do.

For selection of the continuity judgment value, the relative pulse number that is the difference between the latest target pulse number and the target pulse number of one point in the past is used as a substitute value for the image plane moving speed, and this is compared with a predetermined value and Make a selection as follows.
Relative pulse count (= | Latest pulse count−Past pulse count |) <Predetermined value → Selection of judgment value for low speed
Relative pulse number (= | latest pulse number−past pulse number |) ≧ predetermined value → high speed judgment value selection However, in actuality, even if the image plane moving speed is the same, the relative pulse number for each interchangeable lens unit 101 is since different, the following by using a value obtained by multiplying a predetermined fixed coefficient K _c (the number of pulses in a range which can be regarded as focus) focus threshold number of pulses are stored as internal data for each lens as described above a predetermined value Make a selection as follows.
Relative pulse count <In-focus threshold pulse count × _Kc → Select low speed judgment value
Relative pulse count ≧ focus threshold pulse count × K _c → high speed judgment value selection For example, if relative pulse count = 100 pulses, focus threshold pulse count = 10 pulses, K _c = 20,
100 <10 × 20 = 200
Therefore, in this case, the low speed determination value is selected.

The determination of continuity is performed as follows using the determination value selected as described above.
| Previous defocus amount-Current defocus amount | <Low (high) speed judgment value → Continuous
｜ Previous defocus amount−Current defocus amount | ≧ Low (high) speed judgment value → Discontinuous For example, the previous defocus amount = −0.1 mm, the current defocus amount = 0.15 mm, and the low speed judgment value are selected. Assuming that the value is 0.2 mm,
| −0.1−0.15 | = 0.25 ≧ 0.2
Therefore, the determination result is discontinuous.

  As described above, the reason for switching the continuity determination value according to the subject's image plane moving speed is that it is fixed regardless of the image plane moving speed and is set to be easy to detect discontinuities on the low speed side. Since there is a large change in the focus amount, it may be determined that it is discontinuous due to a misjudgment, and if it is set easily to prevent misjudgment on the high speed side, the defocus amount change during low-speed subject tracking This is because there is a possibility that discontinuity cannot be detected.

  Therefore, in the above, for simplicity of explanation, the continuity determination value is switched in two stages for low speed and high speed, but the determination level is further subdivided or correlated with the image plane moving speed. Needless to say, the determination accuracy can be improved by obtaining the determination value using a predetermined calculation formula.

  Then, it is determined whether or not the result of the continuity determination in step S125 is discontinuous (step S126).

  Here, when it is determined that the continuity determination result is discontinuous, it is further determined whether or not the continuity determination result is continuous and discontinuous for a predetermined number of times (or after it is first determined to be discontinuous). It is determined whether or not it is discontinuous for a predetermined time or more (step S127).

  And when it is determined that the discontinuity determination result of discontinuity is not continuous more than a predetermined number of times (or when it is determined that the duration of discontinuity after the first determination of discontinuity is less than a predetermined time) In step S128, the current lens drive target position is set as invalid data (step S128), and the process returns to step S111 without performing lens drive.

  On the other hand, when it is determined that the continuity determination result is continuous and discontinuous for a predetermined number of times (or when it is determined that the discontinuity is continuous for a predetermined time after the first determination is made) Clears time series data such as the previous defocus amount and target pulse position stored in the RAM 158 as time series data in association with the timer count value acquired in step S113 (step S129).

  Thereafter, it is determined whether or not the camera ranging area selection mode is the multi-AF mode (step S130).

  If it is determined that the multi-AF mode is selected, the defocus amount of the distance measurement area selected in the current distance measurement is invalid data, and a distance measurement area other than the selected area is selected as a closest selection. Reselection is performed by the method, and the defocus amount in the reselection area is set as valid data for driving the lens (step S131).

  On the other hand, when it is determined that the spot AF mode is selected, the defocus amount detected by the current distance measurement is used as effective data for driving the lens (step S132).

  After performing such step S131 or step S132, or when it is determined in step S126 that it is not discontinuous, the AF / AECPU 151 then obtains the LCPU 133 via the communication circuit 138 in step S117. The valid data in the defocus amount is transmitted (step S133). As a result, the LCPU 133 obtains the target pulse number based on the received defocus amount and the current position of the focus adjustment lens 102, controls the lens driving circuit 136 to start lens driving, and sends the AF / AECPU 151 to the AF / AECPU 151. The calculated target pulse number is transmitted.

  The AF / AECPU 151 temporarily stores the acquired target pulse number in the RAM 158 (step S134), returns to step S111, and repeats the above processing.

  Thus, if it is determined in step S111 that the 2R switch 153 is in the on state, the AF / AECPU 151 communicates with the LCPU 133 via the communication circuit 138 and adjusts the focus detected by the lens position detection circuit 137. The number of pulses indicating the current position of the lens 102 is acquired and stored in the RAM 158 (step S135).

  Then, the same lens drive target position correction as in step S124 is executed (step S136), and the process proceeds to the 2R sequence operation.

  FIG. 6 is a flowchart for explaining an example of the 2R sequence operation in the continuous AF mode of the camera according to the present embodiment.

  That is, in the 2R sequence operation, the AF / AECPU 151 first performs moving object prediction based on the timer count value stored in the RAM 158 and the target pulse number associated with the timer count value, and the target pulse number at the time of exposure. Is obtained (step S141). Details of the moving object prediction will be described later.

  Next, the AF / AECPU 151 performs moving object prediction lens drive control using the target number of pulses obtained in step S141 (step S142). Details of this moving object prediction lens drive control will be described later.

  On the other hand, the main body CPU 139 performs mirror-up drive control by the mirror control circuit 145, and in parallel with this mirror-up drive, the AF / AECPU 151 instructs the LCPU 133 via the communication circuit 138 to perform aperture drive (step S143). ). As a result, the LCPU 133 controls the driving of the diaphragm 132 by the diaphragm driving circuit 135.

  Then, the main body CPU 139 performs drive control of the focal plane shutter 108 by the shutter control circuit 146 based on the photometric calculation result transmitted from the AF / AECPU 151, and controls the image sensor 109 by the image sensor control circuit 143 to control the image sensor 109. The image processing circuit 147 performs predetermined image processing on the image data of the subject image exposed to the image, and then stores the image data in the external storage means such as the RAM 142 or the compact flash (registered trademark) and the display circuit 148 performs TFT processing. The captured image is displayed on a display unit such as a monitor (step S144).

  After that, the main body CPU 139 determines whether or not the shooting mode of the camera is the continuous shooting mode (step S145).

  Here, when it is determined that the continuous shooting mode is set, the operation switch detection circuit 149 further detects whether or not the 2R switch 153 is in an OFF state (step S146).

  If it is detected that the 2R switch 153 is in the ON state, the AF / AECPU 151 transmits an aperture opening signal to the LCPU 133 via the communication circuit 138 (step S147). Thereby, the LCPU 133 controls the aperture driving circuit 135 to drive the aperture 132 to open.

  Thereafter, the AF / AECPU 151 checks whether or not it is determined in the determination in the moving object prediction process in step S141 or step S157 that it is necessary to drive the focus adjustment lens 102 during mirror-down driving ( Step S148).

  If it is determined that it is necessary to drive the focus adjustment lens 102, the AF / AECPU 151 obtains the LCPU 133 via the communication circuit 138 in the moving object prediction process in step S141 or step S157. The target pulse number is transmitted (step S149). Accordingly, the LCPU 133 controls the lens driving circuit 136 to drive the focus adjustment lens 102.

  Then, the AF / AECPU 151 waits for the lens driving end process to be executed during the lens driving period obtained in the moving object prediction process in step S141 or step S157 (step S150).

  Thereafter, a lens drive stop signal is transmitted to the LCPU 133 via the communication circuit 138 (step S151). As a result, the LCPU 133 controls the lens driving circuit 136 to stop driving the focus adjustment lens 102 and then transmits the stop position pulse number to the AF / AECPU 151.

  In parallel with the lens drive control in steps S147 to S150, the main body CPU 139 controls the mirror control circuit 145 to perform mirror down drive (step S152).

  Then, after the processing of step S151 and step S152, or when it is determined in step S148 that it is determined that driving of the focus adjustment lens 102 is unnecessary, the AF / AECPU 151 next performs the above-described 1R. The count value of the timer operating from the sequence is read and stored in the RAM 158 (step S153).

  Thereafter, a distance measurement operation similar to that in steps S103 to S106 or steps S114 to S117 described above is performed to detect the defocus amount (step S154).

  Then, it is determined whether or not the measurement data at the distance measurement in step S153 is reliable (step S155).

  If it is determined that the distance measurement data is reliable and the defocus amount is obtained, the defocus amount obtained in step S154 is associated with the timer count value obtained in step S153. The time series data is stored in the RAM 158 (step S156).

  After that, or when it is determined in step S155 that there is no reliability and the defocus amount is not obtained, the moving object prediction process similar to that in step S141 is performed (step S157).

  Then, the moving object prediction lens drive similar to that in step S142 is performed (step S158).

  Thereafter, mirror-up driving and diaphragm driving similar to those in step S143 are performed (step S159).

  Then, the same imaging process as in step S144 is performed (step S160), and the process returns to step S146.

  On the other hand, when the main body CPU 139 determines that the single-shot mode is selected in step S145 or when it is determined that the 2R switch 153 is in the OFF state in step S146, Further, it is determined whether or not the operation switch detection circuit 149 detects that the 1R switch 152 is in the OFF state (step S161).

  If it is determined that the ON state is detected, the 1R sequence described above is re-executed. On the other hand, when it is determined that the off state is detected, the process proceeds to the shooting standby sequence and waits for the next camera operation by the user.

  FIG. 7 is a flowchart for explaining an example of the moving object prediction processing operation executed by the AF / AECPU 151 in step S141 and step S157.

  That is, first, continuity determination similar to that in step S125 is performed (step S171). In the 1R sequence, immediately after 2R is turned on, the decision value switching level, the decision value, and the like can be set individually in the continuous shooting sequence so that optimum processing can be performed for each sequence.

  Then, it is determined whether or not the result of the continuity determination in step S171 is discontinuous (step S172).

  Here, when it is determined that the continuity determination result is discontinuous, it is further determined whether or not the continuity determination result is continuous and discontinuous for a predetermined number of times (or after it is first determined to be discontinuous). It is determined whether or not it is discontinuous for a predetermined time or more (step S173).

  Here, when it is determined that the continuity determination result is continuous and discontinuous for a predetermined number of times (or when it is determined that the discontinuity is discontinuous for a predetermined time since the first determination was made), The time series data such as the previous defocus amount and the target pulse number stored in the RAM 158 as time series data in association with the timer count value operating from the 1R sequence described above is cleared (step S174).

  Thereafter, it is determined whether or not the camera ranging area selection mode is the multi-AF mode (step S175).

  If it is determined that the multi-AF mode is selected, the defocus amount of the distance measurement area selected in the current distance measurement is invalid data, and a distance measurement area other than the selected area is selected as a closest selection. Reselection is performed by the method, and the defocus amount in the reselected area is set as valid data for driving the lens (step S176).

  On the other hand, when it is determined that the spot AF mode is selected, the defocus amount detected by the current distance measurement is used as valid data for driving the lens (step S177).

  After such step S176 or step S177 is executed, or when it is determined in step S172 that it is not discontinuous, the defocus amount detected by the current distance measurement by the LCPU 133 via the communication circuit 138 is next. Send. Accordingly, the LCPU 133 obtains the target pulse number based on the received defocus amount and the current position of the focus adjustment lens 102, and transmits the target pulse number to the AF / AECPU 151. The AF / AECPU 151 associates the received target pulse number with the timer count value operating from the 1R sequence described above and stores it in the RAM 158 as time series data (step S178).

  On the other hand, when it is determined in step S173 that the continuity determination result of discontinuity is not continuous for a predetermined number of times (or when the discontinuity duration after the first determination is discontinuous is less than the predetermined time) If it is determined, it is further determined whether or not the image plane moving speed of the tracked subject is high (step S179). For the determination of the image plane moving speed, the result in the continuity determination in step S171 may be used, or a determination criterion may be provided separately.

  If it is determined that the image plane moving speed of the tracked subject is high, the defocus amount measured this time is set as invalid data (step S180).

  If it is determined that the image plane moving speed is not high, the current position of the focus adjustment lens 102 acquired in step S151 is set as the target pulse number (step S181).

  After the defocus amount measured this time in step S180 is set as invalid data, or after the time series data is stored in the RAM 158 in step S178, the timer count operating from the 1R sequence described above is used. From the valid data in the target number of pulses stored in the RAM 158 as time-series data in association with the values, data up to about the past five points is extracted as moving object prediction data based on the latest data (step S182).

  Then, it is determined whether or not there is only one valid data in the valid data extraction in step S182 (step S183).

  If it is determined that there is only one valid data, the target pulse number acquired in step S178 is set as the target pulse number for driving the moving object prediction lens (step S184). However, if the effective data is not distance measurement data due to inability to measure distance, discontinuity, or the like, the current position of the focus adjustment lens 102 acquired in step S151 is set as the target pulse number.

On the other hand, when it is determined that there are two or more valid data, the moving object determination is performed using the latest data of the moving object prediction data extracted in step S182 and the one point past data (step S185). . In this moving object determination, similarly to the continuity determination in step S171, the relative pulse number, which is the difference between the latest target pulse number and the target pulse number one point in the past, is used as a substitute value for the image plane moving speed. a determination as follows by comparing the value obtained by multiplying a predetermined fixed coefficient K _m (the number of pulses in a range which can be regarded as focus) focus threshold number of pulses are stored as internal data for each lens.
Relative number of pulses <number of in-focus threshold pulses x K _m → stationary subject (hereinafter referred to as still body)
Relative pulse count ≧ Focus threshold pulse count × K _m → Moving subject (hereinafter referred to as moving object)
For example, if the relative pulse number = 100 pulses, the focusing threshold pulse number = 10 pulses, and K _m = 3,
100 ≧ 10 × 3 = 30
Therefore, in this case, it is determined as a moving object.

  Here, as a result of the moving body determination in step S185, it is determined whether or not it is determined as a stationary body (step S186). If it is determined that the object is still, the process proceeds to S184, and the target pulse number acquired in step S178 is set as the target pulse number when the moving object prediction lens is driven.

  On the other hand, if it is determined that it is determined as a moving object, the timer count value at the time of the oldest data ranging in the moving object prediction data extracted in step S182 is used as a reference for each data ranging. The relative time (relative count value) is calculated (step S187).

  Thereafter, the current count value of the timer operating from the 1R sequence is acquired (step S188).

  Then, the main body CPU 139 controls the shutter control circuit 146 to calculate the time lag from the time of the latest data ranging in the moving object prediction data extracted in step S182 (step S189). . This time lag is considered by dividing into the following five times as shown in FIG. 10 and adding each time.

(1) Time T _d from the time of the latest data ranging until the timer count acquisition in step S188
This is calculated by taking the difference between the latest data distance measurement time stored in the RAM 158 and the count value at the time of the timer count acquisition in S188.

(2) Driving time T _ld of the focus adjustment lens 102
This is obtained by reading the driving time stored in the ROM 157 in advance.

(3) Stop processing time T _s of the focus adjustment lens 102
This is from when the AF / AECPU 151 instructs the LCPU 133 to stop the lens until the LCPU 133 confirms the stop of the focus adjustment lens 102 from the output state of the lens position detection circuit 137 and transmits the lens stop information to the AF / AECPU 151. It's time. This time greatly varies depending on the lens driving condition due to the influence of the inertia of the focus adjustment lens 102. Therefore, this time is measured every time the lens is driven, and the target pulse of the moving object prediction calculation result in step S190 is stored in the table area as shown in FIG. The measurement time is stored according to the number of drive pulses up to the number. First, this time is used as a predetermined fixed value or a time lag calculated as the set time at the previous shooting to perform a temporary moving object prediction calculation to obtain a temporary driving pulse number. The stop processing time is obtained with reference to this table data. However, if the table data is not yet stored when referring to the table immediately after the camera is turned on, the fixed table data as shown in FIG. 11B stored in advance in the ROM 157 is referred to.

  As described above, by using the measured value of the lens stop time for the time lag calculation, the accuracy of the moving object prediction calculation can be improved.

(4) Time T _m from mirror start to exposure start
This is obtained by reading the value measured in the previous frame shooting and stored in the RAM 158. When there is no actual measurement data, a predetermined time stored in advance in the ROM 157 is read and obtained.

(5) offset time _{T o}
This is obtained by reading out operations not included in the above, sequence transition processing time, etc. stored in advance in the ROM 157.

Based on the above five data, the time lag T _t1 is calculated as follows.
T _t1 = T _d + T _ld + T _s + T _m + T _o
If the time lag is found in this way, then a predetermined prediction formula is selected according to the number of moving object prediction data extracted in step S182, relative change, etc., and the selected formula is found in step S189. The predicted pulse number is obtained by substituting the time lag (step S190).

  As for the selection of the prediction calculation formula, for example, when the number of data for moving object prediction is 4 or more and monotonously changes, a quadratic formula is selected, and even if the number of data is 3 or less or 4 or more, the data If there is a predetermined variation or more in the amount of change, a linear expression is selected.

  Also, at this time, it is determined whether or not the moving object prediction result is finally used, and the sign of the defocus amount detected in the current distance measurement and the previous distance measurement is reversed or the current focus adjustment is performed. When the driving direction from the number of pulses of the lens 102 to the predicted number of pulses obtained by the moving object prediction calculation is opposite to the sign of the defocus amount detected by the current distance measurement, the use of the prediction calculation result is prohibited.

  Thereafter, as a result of the prediction result use permission determination in step S190, it is determined whether or not the use of the prediction result is permitted (step S191). If it is determined that the use of the prediction result is prohibited, the process proceeds to S184, and the target pulse number acquired in step S178 is set as the target pulse number for driving the moving object prediction lens.

  On the other hand, when it is determined that the use of the prediction result is permitted, the number of drive target pulses at the time of drive control of the focus adjustment lens 102 in steps S149 to S151 performed during the mirror down in step S152 is obtained ( Step S192).

FIG. 12 shows an outline of a sequence at the time of continuous shooting in the continuous AF mode, and FIG. 13 shows a change in the number of focusing pulses of the focusing lens 102 with respect to a moving object. In these figures, TR is the time from the start of distance measurement to exposure, TM is the time from exposure to the start of distance measurement, TC is the continuous shooting interval time, and PT _n is the defocus amount detected by the distance measurement at the nth frame. target number of pulses based on, PE _n predicted number of pulses of object movement presumption calculation result of n-th frame, PM _n is the target number of pulses n-th frame of the mirror-down in the lens driving, T _n is n th frame in the ranging timing, TE _n indicates the exposure timing of the _n- th frame, DR _n indicates the relative number of pulses of the (n−1) -th frame and the n-th frame, and DM _n indicates the number of lens drive pulses during the mirror-down of the _n- th frame.

  During continuous shooting in continuous AF mode, if the lens drive can follow the movement of the moving object, it will be in focus at the exposure timing, but if the moving object is moving at a high speed and the image plane movement is large, If the lens is stopped during down, the defocus amount at the time of distance measurement becomes large, so that the detection accuracy is deteriorated and tracking by driving the moving object prediction lens becomes difficult.

  Therefore, the amount of focus pulse change (image plane movement) from the exposure to the start of distance measurement is simply predicted between consecutive shots to determine the target pulse number for the next frame, and the lens is moved while the mirror is down. By driving, distance measurement accuracy and moving object follow-up are improved.

The target pulse number PM _{n + 1} in the next frame is used for the predicted pulse number PE _n of the moving object prediction calculation result in step S190, the continuous shooting interval time TC, the time TM from exposure to the start of distance measurement, and the moving object determination in step S185. Using the relative pulse number DR _n (corresponding to the amount of change in the number of focusing pulses during the continuous shooting interval), the following is obtained.
PM _{n + 1} = PE _n + DM _{n + 1} = PE _n + DR _n × (TM / TC) × K
K in the above equation is a coefficient set according to the lens driving direction.
(1) When driving in infinite direction: K = K _i
(2) When driving in the close direction: K = K _n
K _i <K _n
For example, K _i = 0.9 and K _n = 1.1 are set. The reason why such a setting is made is that when the moving body is moving at a constant speed, the moving speed decreases when the moving surface moves in an infinite direction and increases when the moving object approaches the closest direction.

  As described above, when the drive target pulse number is set or calculated in step S181, step S184, or step S192, the focus adjustment in steps S149 to S151 performed during mirror down in step S152. The execution permission determination of the drive control of the lens 102 is performed (step S193).

  That is, the above drive control is effective for a high-speed subject, and when it is executed for a low-speed subject, a sign change of the detected defocus amount occurs due to a change in the subject speed or a variation in the stop accuracy of the lens. The accuracy may be degraded. Therefore, it is determined whether the subject is a low-speed subject (low image plane moving speed) by the following two determinations, and execution in the next frame is prohibited.

(1) when the relative number of pulses DR _n used in the moving object determination in step S185 is smaller than a value obtained by multiplying a predetermined fixed coefficient K _md the number of focus threshold pulse
DR _n <focus threshold pulse number × K _md
(2) When the defocus amount detected by the current distance measurement is smaller than a predetermined value When the above moving object prediction process is completed, the process returns to the 2R sequence, and the moving object prediction lens driving process in step S142 or step S158 is performed. Will be carried out.

  FIG. 8 is a flowchart for explaining an example of the moving object prediction lens drive control executed by the AF / AECPU 151 in step S142 and step S158.

  That is, first, it is determined whether or not drive control of the focus adjustment lens 102 is possible or permitted using the moving object prediction calculation result in the moving object prediction process of step S141 or step S157 (step S201). .

  If the number of moving object prediction data is insufficient, the moving object determination result is still body, and the moving object prediction permission determination result is neither prohibited, the moving object prediction calculation in step S190 is performed by the LCPU 133 via the communication circuit 138. The number of predicted pulses obtained by the above is transmitted (step S202). Accordingly, the LCPU 133 controls the lens driving circuit 136 accordingly to drive the focus adjustment lens 102.

Here, in the present embodiment, when the focus adjustment lens position does not reach the drive target position and the lens drive does not stop within the lens drive period, a predetermined extension period is set as shown in FIG. ing. Therefore, the AF / AECPU 151 calculates the predicted number of pulses used when the driving control of the focus adjustment lens 102 is not completed within the initial lens driving period and the lens driving period is extended (step S203). Calculation here, performs motion prediction calculation similar calculation in the step S190, the lens driving extended period of time T _e in addition to the time lag T _t1,
T _t1 = T _d + T _ld + T _s + T _m + T _o + T _e
The operation is performed as follows.

  Then, the lens driving period stored in advance in the ROM 157 is read out, and the process waits for the elapse of this time from the start of lens driving in step S202 (step S204). That is, as shown in FIG. 15, even if the position of the focus adjustment lens 102 reaches the target position and the driving is finished during the lens driving period, the process waits until the time set in the lens driving period elapses.

  Thereafter, it is determined whether or not the release priority mode of the camera is on (step S205). If it is determined that the camera is on, the process proceeds to step S214 described later.

  On the other hand, when it is determined that the release priority mode is off, the LCPU 133 is instructed to transmit the lens driving status via the communication circuit 138 (step S206). As a result, the LCPU 133 determines the driving state (driving / stopping) of the focus adjustment lens 102 from the output state of the lens position detection circuit 137 and transmits the determination result to the AF / AECPU 151.

  The AF / AECPU 151 determines whether or not the driving of the focus adjustment lens 102 is stopped based on the data acquired in step S206 (step S207). If it is determined that the focus adjustment lens 102 is stopped, the process proceeds to step S214 described later. .

  On the other hand, when it is determined that the focus adjustment lens 102 is being driven, the predicted number of pulses obtained by the moving object prediction calculation in step S203 is transmitted to the LCPU 133 via the communication circuit 138 (step S208). ). Accordingly, the LCPU 133 controls the lens driving circuit 136 accordingly to drive the focus adjustment lens 102.

Further, the AF / AECPU 151 calculates the predicted number of pulses used when the driving control of the focus adjustment lens 102 is not completed and the lens driving period is further extended (step S209). Calculation here, performs motion prediction calculation similar calculation in the step S190, plus the time to multiplied by the extension number N _e to the lens drive extension period of time T _e the time lag T _t1,
T _t1 = T _d + T _ld + T _s + T _m + T _o + T _e × N _e
The operation is performed as follows. By doing so, it is possible to improve the followability to a subject that requires a large lens driving amount without degrading the moving object prediction calculation accuracy.

  Then, the lens drive extension period stored in advance in the ROM 157 is read out, and the process waits for the elapse of this time from the start of lens drive in step S208 (step S210). In other words, during the lens drive extension period, even if the focus adjustment lens 102 reaches the target position and the drive ends, the process waits until the time set in the lens drive extension period elapses.

  Thereafter, as in step S206, the driving state of the focus adjustment lens 102 is acquired (step S211).

  Then, the maximum number of lens drive extensions stored in advance in the ROM 157 is read out, and it is determined whether or not the current number of extensions has reached the maximum number (step S212), and if it is determined that the maximum number has been reached. It progresses to step S214 mentioned later.

  On the other hand, if it is determined that the current number of extensions has not yet reached the maximum number, it is determined from the data acquired in step S211 whether or not the driving of the focus adjustment lens 102 is stopped (step S21). S213) When it is determined that the focus adjustment lens 102 is being driven, the process returns to step S208.

  On the other hand, when it is determined that the driving of the focus adjustment lens 102 is stopped, or when it is determined in step S205 that the release priority mode of the camera is on, or in step S207. If it is determined in step S212 that the driving of the focus adjustment lens 102 has been stopped, or if it is determined in step S212 that the current number of extensions has reached the maximum number, the operation starts from the 1R sequence described above. The current count value of the timer being acquired is acquired (step S214).

  Then, a lens drive stop signal is transmitted to the LCPU 133 via the communication circuit 138 (step S215). As a result, the LCPU 133 controls the lens driving circuit 136 to stop driving the focus adjustment lens 102 and then transmits the stop position pulse number to the AF / AECPU 151.

  When this stop position pulse number is received, the AF / AECPU 151 acquires the current count value of the timer operating from the 1R sequence described above (step S216).

  Then, it is determined whether or not the release priority mode of the camera is on (step S217). If it is determined that the camera is off, the process returns to the 2R sequence and the mirror up in step S143 or step S159 is performed. -Aperture drive processing will be performed.

  On the other hand, when it is determined that the release priority mode of the camera is on, the timer count value acquired in step S214 and the timer acquired in step S216 are used for calculating the time lag used for moving object prediction calculation. After the difference from the count value is stored as the stop processing time of the focus adjustment lens 102 in the area referred to by the number of drive pulses for driving the moving object prediction lens in the table shown in FIG. 11A in the RAM 158 (step S218). ) Return to the 2R sequence.

  In this step S218, when storing the stop processing time of the focusing lens 102 in the RAM 158, if valid data is already stored in the reference area, the already stored data and the data to be newly stored are stored. The average value of is stored as the latest data. This storage method is performed in order to weight the latest driving conditions while suppressing the influence of variations in lens driving time.

  By doing so, errors in the stop processing time can be suppressed. In addition to the above, if a posture sensor and a temperature sensor are provided, a table for each condition such as the posture and temperature of the camera is set in the ROM 157 and the RAM 158, and the stop processing time is predicted by referring to the table as well. Further, errors can be suppressed.

  On the other hand, if it is determined in step S201 that the number of moving object prediction data is insufficient, the moving object determination result is still body, and the moving object prediction permission determination result is prohibited, the above processing is performed by the LCPU 133 via the communication circuit 138. A target pulse number corresponding to the defocus amount set in step S184 is transmitted (step S219). Accordingly, the LCPU 133 controls the lens driving circuit 136 accordingly to drive the focus adjustment lens 102.

  Then, the AF / AECPU 151 reads the lens driving period stored in advance in the ROM 157 as in step S204, and waits for this time to elapse from the start of lens driving in step S219 (step S220).

  Thereafter, it is determined whether or not the release priority mode of the camera is on (step S221). If it is determined that the camera is on, the process proceeds to step S214.

  On the other hand, when it is determined that the release priority mode is off, the transmission of the lens driving status is instructed to the LCPU 133 via the communication circuit 138 as in step S205 (step S222). As a result, the LCPU 133 determines the driving state (driving / stopping) of the focus adjustment lens 102 from the output state of the lens position detection circuit 137 and transmits the determination result to the AF / AECPU 151.

  Then, the AF / AECPU 151 determines whether or not the driving of the focus adjustment lens 102 is stopped based on the data acquired in step S222 (step S223). If it is determined that the driving is still in progress, step S222 is performed. Return to.

On the other hand, when it is determined that the driving of the focus adjustment lens 102 is stopped, the process proceeds to step S214.
The processing after step S214 is as described above.

  As described above, according to the present embodiment, the drive target position of the focus adjustment lens 102 returned as a return value when the detected defocus amount is transmitted to the LCPU 133 is near the time when the defocus amount is transmitted to the LCPU 133. Correction is performed using the current focus adjustment lens position acquired from the LCPU 133, and moving object prediction control is performed using the corrected drive target position. If the focus adjustment lens 102 is driven while the distance measurement operation is continuously performed while the release button is half-pressed, the focus adjustment lens 102 is in the interval between the distance measurement time and the transmission of the defocus amount to the LCPU 133. Since the position changes, the lens drive target position acquired as the return value of the defocus amount transmission contains an error for this lens position change, and the moving object prediction accuracy deteriorates due to this error. According to the embodiment, since the moving object prediction control is performed using the corrected drive target position, the moving object prediction accuracy is not deteriorated, and the highly accurate moving object prediction control can be performed.

  Further, according to the present embodiment, the continuity determination value for determining whether or not the same subject can be tracked is switched according to the image plane moving speed due to the subject movement. When tracking a fast subject, there is no risk of determining that there is no continuity even though the same subject is actually being measured, and highly accurate moving object prediction control can be performed. It becomes possible.

  Furthermore, according to the present embodiment, the stop processing time of the focus adjustment lens 102 is measured and stored, the stop processing time is predicted based on the stored data, and the moving object prediction is performed using the prediction result. Predictive time lag related to control is used to perform moving object predictive control, so even if the stop processing time until the lens stops due to the amount of lens drive varies, highly accurate moving object predictive control can be performed. It becomes.

  In addition, according to the present embodiment, during the predetermined initial lens driving period, the focus adjustment lens 102 is driven and controlled at the drive target position of the focus adjustment lens 102 calculated by the moving object prediction calculation before the focus adjustment lens 102 is driven. If the lens drive does not stop within the initial lens drive period, a predetermined extension period is set and added to the time lag related to the moving object prediction calculation. Drive control of the adjustment lens 102 is performed. Therefore, the period during which the lens is driven is set as a fixed time, and until the fixed time elapses, even if the lens drive is completed, the aperture drive and mirror up drive are not started, so that highly accurate moving object prediction control can be performed. It becomes possible. In addition, by shortening the fixed time, the release time lag is short when the lens drive is short, and when the drive does not end within the fixed time, an extended period is set and the re-motion object prediction calculation is performed. This makes it possible to perform highly accurate moving object prediction control.

  Furthermore, if the image plane moving speed is slow or changes from high speed to low speed, if the lens is driven during the mirror down operation, the defocus amount continuity will be lost due to the effect of this lens driving, and moving object prediction accuracy will be lost. However, according to the present embodiment, the drive control of the focus adjustment lens 102 during the mirror down operation is performed only when the image plane moving speed due to the movement of the subject is high. Such side effects do not occur, and highly accurate moving object prediction control can be performed.

  As mentioned above, although this invention was demonstrated based on one Embodiment, this invention is not limited to one Embodiment mentioned above, Of course, a various deformation | transformation and application are possible within the range of the summary of this invention. It is.

FIG. 1 is a schematic view of a single-lens reflex camera as a camera according to an embodiment of the present invention equipped with an automatic focus adjustment apparatus according to an embodiment of the present invention. FIG. 2 is a schematic diagram of a focus detection area displayed in the viewfinder. 3A is a diagram showing a configuration of a focus detection optical system, FIG. 3B is a front view of a field mask, and FIG. 3C is a front view of a separator aperture mask, 3D is a front view of the separator lens, FIG. 3E is a front view of the AF sensor, and FIG. 3F is a virtual view in which the lens groups in the interchangeable lens unit are combined. It is a front view of the imaging lens which is a lens. FIG. 4 is a block diagram showing an electrical configuration of the camera of FIG. FIG. 5 is a flowchart for explaining an example of the 1R sequence operation in the continuous AF mode of the camera of FIG. FIG. 6 is a flowchart for explaining an example of the 2R sequence operation in the continuous AF mode of the camera of FIG. FIG. 7 is a flowchart illustrating an example of the moving object prediction processing operation in FIG. FIG. 8 is a flowchart for explaining an example of the moving object prediction lens drive control in FIG. FIG. 9 is a schematic diagram showing the relationship between the focusing lens position and the actual lens position in an arbitrary period in the 1R sequence. FIG. 10 is a schematic diagram illustrating an example of a 2R sequence. FIG. 11 is a diagram illustrating an example of a table for referring to the stop processing time of the focus adjustment lens. In particular, FIG. 11A illustrates a RAM table that is updated with actual measurement values for each lens driving, and FIG. Indicates a ROM table set in advance for reference when there is no RAM table data. FIG. 12 is a schematic diagram illustrating an example of a continuous shooting sequence. FIG. 13 is a conceptual diagram illustrating an example of a method for calculating the lens driving amount during mirror down. FIG. 14 is a schematic diagram illustrating an example of a continuous shooting sequence when the lens driving period is extended without stopping the lens within the lens driving period. FIG. 15 is a schematic diagram showing an example of a continuous shooting sequence when the lens is stopped within the lens driving period.

Explanation of symbols

    DESCRIPTION OF SYMBOLS 100 ... Camera body 101 ... Interchangeable lens part 102 ... Focus adjustment lens 103 ... Zoom lens 104 ... Main mirror 105 ... Sub mirror 106 ... Focus detection optical system 107 ... Focus detection sensor (AF sensor) 108 ... Focal plane shutter 109 ... Image sensor 110 ... Screen mat 111 ... Viewfinder optical system 112 ... Eyepiece lens 113 ... Focus detection area mark 120 ... Field mask 121 ... Condenser lens 122 ... Total reflection mirror 123 ... Infrared cut filter, 124: Separator diaphragm mask, 124a to 124d, 127 ... opening, 125, 125a to 125d ... separator lens, 126 ... photographing lens, 126a to 126d ... area, 128a to 128d ... photodiode 129: Primary imaging plane, 130: Rotating ring for zoom drive, 131: Rotating ring for manual focus (rotating ring for MF), 133: Lens CPU (LCPU), 134: Zoom position detection circuit, 135: Aperture Drive circuit, 136 ... Lens drive circuit, 137 ... Lens position detection circuit, 138 ... Communication circuit, 139 ... Main body CPU, 140,155,156 ... Communication line, 141,157 ... Flash ROM (FROM), 142,158 ... RAM 143 ... Image sensor control circuit, 144 ... Strobe control circuit, 145 ... Mirror control circuit, 146 ... Shutter control circuit, 147 ... Image processing circuit, 148 ... Display circuit, 149 ... Operation switch detection circuit, 150 ... Power supply circuit, 151 ... AF / AECPU, 152 ... First release switch (1R switch), 153 ... second release switch (2R switch), 154 ... battery, 159 ... photometry circuit, 160 ... focus detection circuit, 161 ... auxiliary light circuit.

Claims (10)

In a camera that is configured in a photographic lens, has a focus adjustment lens for performing focus adjustment, and a quick return mirror that guides the transmitted light of the photographic lens to a finder, and performs moving object prediction control for focusing on a moving subject.
Lens control means for controlling the driving of the focusing lens in parallel with the mirror-down operation during continuous shooting;
Image plane movement speed determination means for determining whether the image plane movement speed due to movement of the subject is greater than a predetermined value;
Comprising
The lens control unit performs drive control of the focus adjustment lens during a mirror down operation when a determination result of the image plane moving speed determination unit is larger than the predetermined value.
A camera characterized by that. A driving amount calculating means for calculating a target driving amount in driving control of the focus adjustment lens during the mirror down operation;
The driving amount calculation means calculates a target driving amount by multiplying a driving amount of the focus adjustment lens required for focusing during the continuous shooting interval by a predetermined coefficient, and a driving direction of the focus adjustment lens. The predetermined coefficient is switched according to
The camera according to claim 1.   3. The camera according to claim 2, wherein the driving amount calculation means makes a coefficient when the driving direction of the focusing lens is an infinite direction smaller than a coefficient when driving in the closest direction. . Further comprising defocus amount detection means for detecting the defocus amount of the subject relating to the focus adjustment lens,
The photographic lens has a storage means for storing a focus threshold that is a focus adjustment lens position range that can be regarded as in-focus,
The determination by the image plane movement speed determination means is based on the in-focus threshold stored in the storage means and the movement amount of the focus adjustment lens within the defocus amount detection interval time by the defocus amount detection means. Based on the
The camera according to claim 1. Further comprising defocus amount detection means for detecting the defocus amount of the subject relating to the focus adjustment lens,
The determination by the image plane moving speed determination means is performed based on the latest defocus amount by the defocus amount detection means.
The camera according to claim 1. In an automatic focus adjustment device of a camera that performs moving object prediction control for focusing on a moving subject,
In the continuous shooting operation, in parallel to the mirror return operation of the quick return mirror that guides the transmitted light of the camera's photographic lens to the viewfinder, it controls the drive of the focus adjustment lens that is configured in the photographic lens and performs focus adjustment. Lens control means;
Image plane movement speed determination means for determining whether the image plane movement speed due to movement of the subject is greater than a predetermined value;
Comprising
The lens control unit performs drive control of the focus adjustment lens during a mirror down operation when a determination result of the image plane moving speed determination unit is larger than the predetermined value.
An automatic focusing device for a camera. A driving amount calculating means for calculating a target driving amount in driving control of the focus adjustment lens during the mirror down operation;
The driving amount calculation means calculates a target driving amount by multiplying a driving amount of the focus adjustment lens required for focusing during the continuous shooting interval by a predetermined coefficient, and a driving direction of the focus adjustment lens. The predetermined coefficient is switched according to
The automatic focusing apparatus for a camera according to claim 6.   8. The camera according to claim 7, wherein the driving amount calculating means makes a coefficient when the driving direction of the focusing lens is an infinite direction smaller than a coefficient when driving in the closest direction. Automatic focusing device. Further comprising defocus amount detection means for detecting the defocus amount of the subject relating to the focus adjustment lens,
The determination by the image plane moving speed determination means is performed within the defocus amount detection interval time by the focus threshold, which is the focus adjustment lens position range that can be regarded as in-focus, stored in the photographing lens, and the defocus amount detection means. Based on the amount of movement of the focusing lens at
The automatic focusing apparatus for a camera according to claim 6. Further comprising defocus amount detection means for detecting the defocus amount of the subject relating to the focus adjustment lens,
The determination by the image plane moving speed determination means is performed based on the latest defocus amount by the defocus amount detection means.
The automatic focusing apparatus for a camera according to claim 6.

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