JP2000292678A - Automatic focus adjustment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate focusing for a moving subject, and to eliminate hunting of a photographing lens relating to a stationary subject. SOLUTION: Imaging positions of a pair of subject images are detected repeated by a focus detecting part 2, and information as to a focus adjustment condition of a photographing lens with respect to a subject is output in a time series by a moving body predicting part 1. Whether the subject is a moving body or a stationary body is determined by a moving body determining part 7 based on the time-serial output of the focus detecting part 2. A determination value for the moving body and a determination value for the stationary body are set respectively for focusing determination in response to a determined result therein. The output of the focus detecting part 2 is compared with the determination values by a focusing determining part 6 to determine whether the photographing lens is focused to the subject or not. When that the photographing lens is not focused with respect to the subject is determined by the determining part 6, a lens driving amount required for focusing the photographing lens is computed by a correlation operation part 5 to drive the photographing lens in response to the lens driving amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focusing device having a moving object predicting function for focusing a photographic lens on a moving subject.

[0002]

2. Description of the Related Art Conventionally, a moving object is detected by detecting the movement of the photographing lens in the optical axis direction of the object, predicting the image plane position of the object after a predetermined time, and driving the photographing lens to the predicted image plane position. Many cameras having a so-called moving object prediction function that focuses on a camera have been proposed.

For example, Japanese Patent Publication No. 7-97173 discloses a technique for detecting the movement of a subject and expanding the focusing threshold when it is determined that the subject is moving.

[0004] Here, the focusing threshold is an allowable defocus amount at which it is determined that the taking lens is in focus, and is a numerical value obtained from a so-called allowable circle of confusion. If the detected defocus amount is within the in-focus threshold, it is determined that the object is in focus. If the detected defocus amount is not less than the in-focus threshold, the driving of the photographing lens is not performed. It is determined that the subject is in focus, and the photographic lens is driven to the focused state according to the determination.

[0005]

Here, the problem of a conventional camera having a moving object predicting function will be described with reference to FIG.

[0006] The photographing conditions are assumed as follows. Focusing threshold: Since it is determined by the permissible circle of confusion (33 μm) × the FNo of the photographing lens, tentatively, 0.15 mm focal length of the photographing lens: 110 mm FIG. 12 starts the focus detection when the subject is at a position 20 m from the camera. After that, the so-called continuous A
This is for describing a state in which focus detection is continued at F (auto focus).

In FIG. 12A, it is assumed that when the subject 101 is at a position 20 m from the camera 102, the photographic lens is in focus under the above photographic conditions. Then, as shown in FIG.
Assuming that the photographing lens is at the same position as that in FIG. 12A when moving from 02 to 15 m, the detected defocus amount is about 0.2 mm. Similarly, as shown in FIG. 12C, when the subject 101 moves to a position 10 m from the camera 102 and the photographing lens is at the same position as that in FIG. The focus amount is about 0.6 mm.

Assuming that the camera 102 detects the movement of the subject and expands the focusing threshold four times, the focusing threshold becomes 0.6 mm.
Are all at the position of 10 m to 20 m, it is determined that all the objects are in focus. When the subject 101 is at 10 m, the subject is significantly out of focus (focusing on the position of 20 m and the subject 1
01 is out of focus). That is, when capturing a moving object, there is a problem that widening the focusing threshold is contrary to the concept of moving object prediction (the concept of focusing on the moving object).

Next, the case of a still subject will be considered.
The focus detection for predicting a moving object is a method for detecting the image movement of a subject by continuously detecting the focus and determining whether or not the subject is a moving object (continuous AF). We are performing a New AF.

In general, the AF has a certain repetitive variation in the defocus amount due to factors such as an error in detection and camera shake of a photographer. If the focus is continuously detected on the subject by the continuous AF in a case where the subject is completely still, the detection defocus amount may be larger than the focusing threshold due to variation, and it is determined that the subject is out of focus. An operation such as driving to the in-focus position occurs.

As a result, there is also a problem that fine driving of the photographing lens occurs repeatedly (so-called hunting) even though the subject is stationary.

That is, when photographing a still subject, narrowing the focusing threshold has a problem in terms of hunting.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and provides an automatic focusing apparatus which makes it easy to focus on a moving subject and does not cause hunting of a photographing lens for a stationary subject. With the goal.

[0014]

That is, the present invention is a focus detecting means for repeatedly detecting the image forming positions of a pair of subject images and outputting time-series information on the focus adjustment state of a photographic lens with respect to the subject; Based on the time-series output of the focus detection unit, the subject is determined whether the moving body moving in the optical axis direction of the photographing lens or a static body that is not moving, and according to the determination result, Moving body determining means for setting a moving body determination value for focus determination and a stationary body determination value larger than the moving body determination value, respectively set according to the output of the focus detection means and the state of the subject Focusing judgment means for comparing whether or not the photographing lens is in focus with respect to the object by comparing the photographing lens with the object. In focus When it is determined that no, calculating means for calculating the lens drive amount necessary for focusing the photographing Reference, in accordance with the calculated lens drive amount,
Lens driving means for driving the photographing lens.

The present invention also provides a focus detecting means for repeatedly detecting a defocus amount of a photographing lens, and a moving object determining means for determining whether or not a subject is moving based on a temporal change of the defocus amount. When the moving object determination unit determines that the subject is stationary, a predetermined value larger than that when the subject is determined to be moving is set, and the defocus amount and the set value are set. Focusing judgment means for comparing with a predetermined value to judge whether or not the photographing lens is in focus.

In the automatic focusing device of the present invention,
The focus detection means repeatedly detects the image formation positions of the pair of subject images, and outputs time-series information on the focus adjustment state of the photographing lens with respect to the subject. Then, based on the time-series output of the focus detection means, the moving body determination means determines whether the subject is a moving body moving in the optical axis direction of the photographing lens or a static body that is not moving. . In accordance with this determination result, a moving body determination value for focus determination and a static body determination value larger than the moving body determination value are set. The output of the focus detection means and a determination value respectively set according to the state of the subject are compared by focus determination means, and it is determined whether or not the shooting lens is focused on the subject. You. When the focus determining means determines that the photographing lens is not focused on the subject, the calculating means calculates a lens driving amount necessary for focusing the photographing lens. Then, the photographing lens is driven by the lens driving means in accordance with the calculated lens driving amount.

In the automatic focusing apparatus according to the present invention, the defocus amount of the photographing lens is repeatedly detected by the focus detection means, and based on the temporal change of the defocus amount, whether the subject is moving or not is determined. Is determined by the moving object determination means. When the moving object determining means determines that the subject is stationary, a predetermined value larger than when the subject is determined to be moving is set by the focus determining means, and The defocus amount is compared with the set predetermined value to determine whether the photographing lens is in focus.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the concept of an embodiment of an automatic focusing apparatus for a camera according to the present invention.

Referring to FIG. 1, an automatic focusing apparatus for a camera according to the present invention includes a moving object prediction control section 1 for controlling a moving object prediction.
A focus detection unit 2 that outputs a focus detection signal for detecting a focus state of the photographing lens; an image movement amount calculation unit 3 that calculates an image movement amount based on the focus detection signal; A defocus amount detection unit 4 for detecting a defocus amount of the subject based on the detection result; and a correlation operation unit 5 for performing a correlation operation for detecting the defocus amount based on the focus detection signal.
A focus judging unit 6 for judging whether or not the photographing lens is in focus, and a moving object judging unit 7 for judging whether the subject is moving based on the output of the image moving amount calculating unit 3. The focus determination unit 6 makes a focus determination based on the outputs of the defocus amount detection unit 4 and the moving object determination unit 7.

FIG. 2 shows an embodiment of the present invention, and is a block diagram showing in detail a control system of a camera system to which an automatic focusing device for a camera is applied.

As shown in FIG. 2, this camera system comprises a CPU 11, an interface IC 12, a power supply unit 13, a strobe unit 14, a mirror shutter unit 15, a winding unit 16, a lens unit 17, a finder It comprises a unit 18, a display unit 19, an AF unit 20, and the like.

The CPU 11 is composed of a microcomputer that controls the entire camera system and performs various calculations, and has functions of a moving object determining unit, a focusing determining unit, and a calculating unit. The CPU 11 is connected to an interface IC described later via a serial communication line 21.
12, LCDIC67, AFIC74, EEPROM7
5 to transmit and receive data.

The CPU 11 and an interface IC
Between the (IFIC) 12 and another communication line 22, another communication line 22 is provided for inputting various analog communications, inputting a signal after shaping the waveform of a photo interrupter, and the like. The analog signal is input to an A / D conversion input terminal of the CPU 11 and is converted into a digital signal. In addition, the CPU 11 has various calculation units, data storage units, and time measurement units (not shown).

The interface IC 12 is a Bi-CMOS IC in which digital and analog circuits are mixed.
Motor and magnet drive, photometry, battery check,
It is composed of an analog processing unit such as a backlight LED, a lighting circuit of an auxiliary light LED, a waveform shaping circuit of a photo interrupter, and a digital processing unit such as a switch (SW) for converting input serial communication data.

The interface IC 12 is connected to the CPU 11, the finder unit 18, the display unit 19, and the AF unit 20 via communication lines 21 and 22, and the mirror shutter unit 15 and the winding unit 16 via a motor driver 25. , A lens unit 17 are connected. Also, interface IC
12 further includes a power supply unit 13 and a strobe unit 1
4, an auxiliary light LED 26 and a key switch (SW) group (2) 27 are connected.

The power supply unit 13 supplies two systems of power. In this power supply unit 13,
One is a power supply used for a driver requiring power such as a motor or a magnet, and the voltage of the battery 31 is constantly supplied. The other is a small-signal power supply stabilized by the DC / DC converter 32.
It is controlled through the interface IC 12.

The strobe unit 14 includes a strobe charging circuit 36, a main capacitor 37, a strobe light emitting circuit 38, a strobe light emitting tube 39, and the like. When the strobe light needs to be emitted in a low luminance or backlight state, the strobe charging circuit 36 boosts the battery voltage and charges the main capacitor 37 through the interface IC 12 according to the control signal of the CPU 11.
At the same time, the divided charging voltage from the flash charging circuit 36 is input to the A / D conversion input terminal of the CPU 11. Thereby, the CPU 11 controls the charging voltage.

When the charging voltage reaches a predetermined level, a charging stop signal is transmitted from the CPU 11 to the flash charging circuit 36 via the interface IC 12, and the charging of the main capacitor 37 is stopped. CPU1
Reference numeral 1 denotes a light emission start of a flash light emission tube 39 via a flash light emission circuit 38 at a predetermined timing at the time of film exposure;
Control of emission stop is performed.

The mirror shutter unit 15 includes a mirror shutter motor 41, two shutter magnets 42 for controlling the traveling of the front curtain and the rear curtain, a front curtain traveling completion switch included in a sequence switch group 91, and the like. I have. The mirror shutter motor 41 is connected to the CPU 11
The interface is controlled via the interface IC 12 and the motor driver 25. The forward rotation of the main mirror causes the main mirror (not shown) to be raised and lowered, the aperture of the shooting aperture to be reduced, and the opening shutter to be charged, that is, the operation of closing the front curtain and opening the rear curtain. Is what you do.

The shutter magnet 42 is controlled by the CPU 11 via the interface IC 12. At the start of exposure, first, the mirror shutter motor 41 retracts the main mirror and narrows the shooting aperture immediately before the start. Next, the shutter curtain 42 is energized, and at the same time as the exposure to attract the magnet is started, the suction of the shutter magnet 42 of the front curtain is released, so that the front curtain is opened.

After the desired exposure time has elapsed from the input of the front curtain preceding completion switch of the sequence switch group 91, the suction of the shutter magnet 42 of the rear curtain is released,
The second curtain is closed. In this way, the subject light image is exposed to the film while the front curtain is opened and the rear curtain is closed.

Next, the mirror is lowered by the normal rotation of the mirror shutter motor 41, and the photographing aperture is opened. At the same time, the shutter is charged. The mirror shutter motor 41 reverses the film to rewind the film.

The winding unit 16 includes a winding motor 46, a film detection photo interrupter (PI) 47, and the like. The hoist motor 46 is connected to the CP via the interface IC 12 and the motor driver 25.
It is controlled by U11. The output of the film detection photo interrupter 47 is output from the interface IC1.
The waveform is shaped in step 2 and transmitted to the CPU 11 to generate a winding feedback pulse. The CPU 11 controls the winding amount of one frame of the film by counting the number of pulses.

The lens unit 17 includes the photographing lens 5
1, a zoom gear train 52, a zoom motor 53, an AF
Gear train 54, AF motor 55, AF photo interrupter (PI) 56, zoom encoder 57, aperture photo interrupter (PI) 58, and aperture magnet 59
And the like. This zoom motor 53, AF
The motor 55 is controlled by the CPU 11 via the interface IC 12 and the motor driver 25.

The rotation of the zoom motor 53 is reduced by the zoom gear train 52, whereby the zoom system of the photographing lens 51 is driven. The zoom encoder 57 is an encoder composed of six switches installed around a lens frame that supports the photographing lens 51. Six switch ON / OFF data are input to the CPU 11, and the absolute position of the zoom lens is Is detected.

The CPU 11 calculates the focal length from the absolute position of the zoom lens and stores the focal length in the focal length storage unit 84. The rotation of the AF motor 55 is decelerated by the AF gear train 54, whereby the focusing lens of the photographing lens 51 is driven.

On the other hand, from the middle of the AF gear train 54, the output of the AF photointerrupter 56 is taken out. The output of the AF photo interrupter 56 is
And is transmitted to the CPU 11 so that A
An F lens drive amount feedback pulse is generated. C
The PU 11 counts the number of pulses to obtain A
The driving amount of the F lens is controlled. The extension amount of the AF lens from the mechanical system stopper or the infinite reference position is determined by AF
The pulse amount of the photo interrupter 56 is stored in the lens extension amount storage unit 84 in the CPU 11.

The aperture magnet 59 is controlled by the CPU 11 via the interface IC 12, and at the same time as the mirror-up is started, a magnet to which a current is supplied is attracted. At the same time as the mirror-up operation of the mirror shutter motor 41 of the mirror shutter unit 15 described above, the aperture of the shooting diaphragm is mechanically started by a spring. Then, when the desired aperture value is reached, the aperture magnet 59
Is set by releasing the suction and stopping the narrowing-down operation. Aperture photo interrupter 5
The output of 8 is waveform-shaped by the interface IC 12 and transmitted to the CPU 11. As a result, a narrowing-down amount feedback pulse is generated. The CPU 11 controls the stop-down amount of the shooting stop by counting the number of pulses.

The finder unit 18 includes an LCD panel 61 in the finder, a backlight LED 62,
It is composed of a photometric 8-division photodiode element (photometric element) 63 and the like.

The LCD panel 61 in the finder is made of transmissive liquid crystal.
The display is controlled by the LCD IC 67 in accordance with the display content sent to. And the backlight LED 62
Lighting is controlled by the CPU 11 via the interface IC 12 to illuminate the LCD panel 61 in the finder. The photometric element 63 is controlled by the CPU 11 via the interface IC 12.

The photocurrent generated by the photometric element 63 is sent to the interface IC 12 for every eight elements, and is subjected to current / voltage conversion therein. Then, only the output of the element specified by the CPU 11 is
The signal is sent to the A / D input conversion terminal of the PU 11 and is converted into a digital signal to be used for photometric calculation.

The display unit 19 comprises an external LCD panel 66, an LCD IC 67, a key switch (SW) group (1) 68 and the like. The LCD panel 66 is made of a reflection type liquid crystal, and the display is controlled by the LCD IC 67 in accordance with the display content sent from the CPU 11 to the LCD IC 67.

The key switch group (1) 68 is mainly for setting the mode of the camera, and includes an AF mode selection switch, a camera exposure mode selection switch, a strobe mode selection switch, an AF / PF switch, a macro mode switch. Etc. are included. The state of each of these switches is read into the CPU 11 via the LCD IC 67, whereby the respective modes are set.

The AF unit 20 includes the condenser lens 7
1, the separator lens 72, and the photosensor array 7
3 is provided with an AFIC 74 and an EEPROM 75, etc., each having the same.

A part of the subject light image is
1. Divided into two images by the separator lens 72,
The light is received by two rows of photoelectric conversion elements on the FIC 74. A
The FIC 74 generates an analog output corresponding to the light intensity for each element. The analog output is sent to an A / D conversion input terminal of the CPU 11 and is converted into a digital signal.
Is stored in the element output storage unit 81 in the inside.

The EEPROM 75 in the AF unit 20 stores non-uniformity correction data of the output of the photoelectric conversion element described later,
Various adjustment data such as the interval between two images at the time of focusing are written at the time of shipment from the factory, for example, while the camera is operating, data that needs to be stored even when the power is turned off, such as the number of film frames, is written. Is to be included.

The CPU 11 includes an element output storage section 81, a correlation operation circuit 82, a lens extension storage section 83, a focal length storage section 84, and the like. This CPU 11
Calculates the image interval between two divided images or the movement amount of each image after a predetermined time by an internal correlation operation circuit 82 based on the stored element outputs. Further, the CPU 11
It controls the photoelectric conversion operation of C74.

The motor driver 25 includes the mirror shutter motor 41, the winding motor 46, and the zoom motor 5 described above.
3. A driver for controlling a large current of the AF motor 55 and the like.

The auxiliary light LED 26 is an LED for illuminating a subject at low luminance. This auxiliary light LED 26
Means that the AFIC 74 does not complete the photoelectric conversion within a predetermined time,
This is turned on when the image interval between the two images cannot be detected so that the AFIC 74 can photoelectrically convert the subject image by the illumination light.

The key switch (SW) group (2) 27
Is a group of switches for controlling the operation of the camera, the first stroke signal (1R) and the second stroke signal (2R) of the release switch, a switch for driving the zoom lens to the long focal length side, and a switch for driving the zoom lens to the short focal length side , And a switch for storing spot photometric values. The states of these switches are read into the CPU 11 via the interface IC 12, and control of the camera operation is performed.

The sequence switch (SW) group 91
Is for detecting the state of the camera. The sequence switch group 91 includes a switch for detecting a mirror raised position, a switch for detecting completion of shutter charging, a switch for detecting completion of running of a shutter front curtain, a power switch, a switch for detecting a strobe pop-up state, and the like. Also, the buzzer 92 sounds and displays when the AF is in focus, when the AF is out of focus, when the power is turned on, when a camera shake is warned, and the like.

Next, the correlation calculation of the subject image signal will be described in detail.

In the apparatus according to the first embodiment, two types of correlation calculations are performed. That is, similarly to the conventional focus detection device, one is a first subject image formed on the photosensor array 73L divided by the separator lens 72 and the other is a second subject image formed on the photosensor array 73R. The correlation calculation is performed between the subject images, and the defocus amount is obtained from the shift amount between the two images. On the other hand, when the correlation operation between the object image in the object image and the time t ₁ at a given time t ₀ is carried out, in which the moving amount of the object image is determined. The calculation for obtaining the defocus amount is well-known, and has no direct relation to the gist of the present invention, so that the description is omitted.

Here, with reference to FIG. 3, the correlation calculation for obtaining the movement of the subject image will be described.

The movement of the subject image is described in JP-A-5-93850.
It is determined by the method disclosed in Japanese Unexamined Patent Application Publication No. H10-26095.

In the following description, for the sake of convenience, the first subject image is referred to as image L, the first subject image signal is referred to as L (I), and the second subject image signal is referred to as L (I).
Is an image R, and a second object image signal is R (I). Here, I is an element number, and in this embodiment,
.., 64 in order from the left. That is, each element row has 64 elements.

Subject images L '(I) and R' at time t ₀
(I), the head positions SLM 'and SRM' of the correlation block indicating the best correlation obtained by the correlation operation between the two images, and the image shift ΔZ are temporarily stored in a storage area in the CPU 11.

Next, at time t ₁ , the subject image signal L
(I) and R (I) are detected. Then, first, for the signal of the image L, a correlation operation is performed between the subject image signal L ′ (I) at time t ₀ and the subject image signal L (I) at time t ₁ .

Hereinafter, referring to the flowchart of FIG.
The manner in which the correlation is obtained will be described. Here, the image L
Only the moving amount calculation method will be described.

Here, the variable SL is the subject image signal L (I)
Is a variable that stores the head number of the small block element row for which a correlation is detected from among them.

First, at step S1, the variable SL is set to SL.
STR-10 is substituted. This SLSTR is an element number for starting the correlation operation, and details thereof will be described later. The variable J is a variable for counting the number of correlations, and is determined in step S2
, The initial value 20 is substituted.

Next, in step S3, a variable F _MIN representing a correlation result is initialized to a predetermined value. Then, in step S4, the correlation output F is calculated based on the correlation equation of the following equation (1).
(S) is calculated.

[0064]

(Equation 1)

Next, in step S5, F (s)
And F_MINAre compared. Where F _MINIs from F (s)
If smaller, the process proceeds to step S6 and F_MINTo F (s)
Is substituted, and the SL at that time is stored in the SLM. this
In this case, the number of elements of the block to be correlated is 12.

In step S7, 1 is added to SL, and
One is subtracted from J. Then, in step S8, the value of J is determined, and the correlation equation F (s) is repeated until J becomes a negative number. In this case, the correlation was obtained by changing to ± 10 elements, but this correlation range is determined by the movement amount range to be detected.

Next, at step S9, F _M and F _P is determined as follows (2) and (3) below.

[0068]

(Equation 2)

That is, F _M and F _P represent the image at time t ₁ ± 1 with respect to the block position showing the minimum correlation output.
The correlation output when the element is shifted is calculated.

The reliability index Sk indicating the reliability of the correlation between the detected image intervals is obtained by the following equations (4) and (5) in step S10.

[0071] F when the _{M ≧ F P Sk = (F} P + F MIN) / (F M -F MIN) ... (4) F M <Sk = (F M + F MIN) when the F _P / (F _P - F _MIN ) (5) It is known that the smaller the value of Sk (the closer to 1), the higher the reliability, and the larger the value of Sk, the lower the reliability.

Then, in step S11, the value of Sk is determined. That is, when Sk ≦ β, it is determined that there is a correlation, and the movement amount is obtained. This judgment value β
Is a value larger than the determination value α when the image interval at time t ₀ is obtained (β becomes about 7). This is because the waveform often changes when the subject is moving, so that there is a high possibility that the correlation will deteriorate.

Next, at step S12, the image moving amount Δ
_XL is obtained from the following equations (6) and (7).

[0074] _{ΔX L = SLM-SLSTR + (} 1/2) when the _{F M ≧ F P ((F} M -F P) / (F M -F MIN)) ... (6) when the F _M <F _{P ΔX L = SLM-SLSTR + (} 1/2) ((F P -F M) / (F P -F MIN)) ... (7) Then, at step S13, after undetectable flag is cleared, the return I do.

Similarly, a correlation operation is performed on the image R, and a correlation block position SRM and a movement amount ΔX _R are obtained. Image L, and amount of movement [Delta] X _R and [Delta] X _L of the object image on the image R is calculated, image-to-image gap [Delta] Z ₂ at time t _1, the time t
It is obtained from the two image interval ΔZ ₁ at ₀ as follows. ΔZ ₂ = ΔZ ₁ + ΔX _R −ΔX _L (8) To further reduce the calculation error, the image L at time t ₁
Based on the signal of the image R and the signal of the image R, the correlation operation may be performed again, the interval between the two images may be obtained, and ΔZ ₂ may be calculated.
Further, the image movement amount ΔZ ₀₁ between times t ₀ and t ₁ is obtained by the following equation. ΔZ ₀₁ = | ΔX _R −ΔX _L | (9) As described above, the two image interval ΔZ ′ at the time t ₂ is predicted by the following equation. ΔZ ′ = ΔZ ₁ + ((t ₂ −t ₀ ) / (t ₁ −t ₀ )) (ΔX _R −ΔX _L ) (10) By driving the lens by an amount based on ΔZ ′, the time t _{In step 2} , the moving subject can be focused.

On the other hand, in step S11, Sk
If not, the process proceeds to step S14, and the undetectable flag is set.

Note that the object image movement amount ΔX _R or ΔX _L
Is too large, it is determined that focusing is impossible, and the image shift amount is not predicted. On the other hand, when the movement amount of the subject image is small and is regarded as a detection error, the movement amount is set to zero. This determination value is increased when the movement amount of the subject image is predicted to be larger than the movement amount of the subject according to the focal length, the subject distance, and the subject brightness.

[0078] Here, with reference to FIGS. 5 (a) and (b), the subject image signal L at time t ₀ when the subject is moving '(I), R' ( I), and time An example of the subject image signals L (I) and R (I) at t ₁ will be described.

As shown in the figure, SLM 'and SR
M ′ is the object images L ′ (I) and R ′ (I) as described above.
_Is the head number of the block element row (44 elements) that has the smallest F _MIN when detecting the amount of image shift of.

As described above with reference to FIG. 4, when the correlation between the subject image signals at time t ₀ and time t ₁ is calculated to calculate the image movement amounts of the images L and R, the reliability is improved. At 44
A block row composed of elements is divided into, for example, three to calculate an image movement amount.

In this case, as shown in FIG.
It is divided into third blocks, each having 20 elements. The start element number of each small block, the first block is SLM'1 (= SLM '), the second block _{SLM' 2 (= SLM '1} +12), the third block S
LM ′ ₃ (= SLM ′ ₁ +24).

That is, when calculating the image movement amount of each block, first, SLSTR = SL in FIG.
M _'1 as determined image movement amount of the first block, then,
SLSTR = SLM 'as ₂ obtains the image movement amount of the second block, finally, SLSTR = SLM' Request ₃ as the image moving amount of the third block.

The movement amount of the first to third blocks is obtained in the same manner for the image R, and the image movement amount ΔZ ₀₁ between the time t ₁ and the time t ₀ is obtained by the above equation (9).

Next, referring to the flowchart of FIG.
The operation of the entire camera to which an embodiment of the present invention is applied will be described.

When the main switch of the camera is turned on by the photographer, the power is reset by the CPU 11 and the operation is started.
Initialization of the O port, initialization of the RAM, and the like are performed.

Next, at step S22, the photometric element 6
The output of No. 3 is calculated by the photometric circuit in the interface IC 12, and the calculation of the shutter speed and the calculation of the aperture value, that is, the Apex calculation are performed. Then, step S
At 23, the output of the AFIC 74 is calculated as described above, and the AF calculation including the moving object prediction function is performed. The details of step S23 will be described later.

By the way, the release button of the camera according to the present embodiment is configured in two stages, in which photometry and AF are performed in a first stroke (hereinafter referred to as 1R) in a half-pressed state, and in a fully-pressed state. Exposure is performed in two strokes (hereinafter referred to as 2R).

In step S24, it is determined whether or not 1R is on. If 1R is off, the process returns to step S22. On the other hand, if 1R is on in step S24, the lens is driven by the lens drive amount calculated in step S23 in subsequent step S25. This lens drive is known, but will be described later because it is related to the gist of the present invention (operation of the focusing flag).

Then, in step S26, it is determined whether or not the lens is in focus. This is determined by a focusing flag described later. If it is determined that the camera is not in focus, the process returns to step S22. On the other hand, if it is determined in step S26 that the subject is in focus,
The process shifts to step S27 to determine whether or not 2R is turned on.

If it is determined in step S27 that 2R is off, the process returns to step S23. Step S
If 2R is on at 27, the process moves to step S28, and the aperture is driven to the value calculated at step S22. Subsequently, in step S29, a mirror (not shown) is raised.

Then, in step S30, control is performed so that a shutter (not shown) is opened at the shutter speed calculated in step S22. Next, when the shutter is opened for a predetermined time, in step S31,
The mirror (not shown) is brought down.

Thereafter, in step S32, the aperture is set to open, and in step S33, a shutter (not shown) is charged to an initial position. Further, in step S24,
One frame is wound up. Then, returning to step S22, the above operation is repeated.

Next, referring to the flowchart of FIG.
The operation of the AF subroutine executed in step S23 of the flowchart of FIG. 6 will be described in detail.

First, in step S41, AF to be described later is performed.
A detection subroutine is executed. This subroutine “AF detection” is a subroutine from the start of integration to the calculation of the defocus amount ΔZ, and includes a moving object prediction calculation.

Then, in step S42, whether or not detection is impossible is determined by a detection impossible flag. Here, if it is determined that detection is not possible, the process proceeds to step S43, where the focus flag is cleared, and the process returns. On the other hand, if it is determined that detection is possible, then, in step S44, whether or not the camera is in the continuous AF mode is determined based on the continuous AF flag.

If it is determined in step S44 that the current distance is not continuous AF, it is not necessary to determine whether or not the first distance measurement is to be performed, and the flow advances to step S46. However, if it is determined that the current mode is continuous AF, it is determined in step S45 whether or not the first distance measurement is to be performed using the first calculation completion flag.

If it is determined in step S45 that the distance measurement is the first distance measurement, the process proceeds to step S43. If it is determined that the distance measurement is the second distance measurement, step S43 is performed.
The flow shifts to 46, where the calculation of the defocus amount is executed.

In step S46, the above-mentioned step S
From the defocus amount calculated in 41, a defocus amount is calculated by a known method. Subsequently, in step S47,
The calculated defocus amount is compared with the focus determination value. This judgment value is a value obtained based on the permissible circle of confusion,
If it is within the determination value, it is already in focus.

Then, in step S48, it is determined whether or not the camera is in focus. That is, if it is determined that the defocus amount is within the allowable focus range, there is no need to drive the lens, so the flow shifts to step S49 to set the focus flag, and then returns.

On the other hand, if it is determined in step S48 that the in-focus range is not within the allowable focus range, the flow shifts to step S50, where the in-focus flag is cleared. Then, step S5
In step 1, after the amount of lens driving necessary for focusing is calculated, the process returns.

Next, the operation of the AF detection subroutine will be described in detail with reference to the flowcharts of FIGS.

First, in step S61, the integration operation is reset. Next, in step S62,
It waits until the integration of the AFIC 74 is completed. And
In step S63, data of all elements (pixels) is read for each pixel. The output of the AFIC 74 is an analog value, and is converted into a digital signal by an A / D converter (not shown) in the CPU 11 every time one pixel is read, and stored in a predetermined storage area.

In step S64, non-uniformity correction is performed on the obtained subject image signal. This is for correcting subtle variations in sensitivity between pixels, which occur in manufacturing, and uneven illuminance of the re-imaging optical system in the AF unit 20. Correction is performed so that the output of the other pixel is matched with the pixel with the lowest sensitivity among all the pixels. The correction coefficient is adjusted for each product and stored in the EEPROM 75.

Subsequently, in steps S65 to S72, various photographing modes are determined.

That is, in step S65, it is determined whether or not the moving object mode (mode for performing moving object prediction) is selected. In step S66, it is determined whether or not the self-timer photographing mode is selected. It is determined whether or not the shooting mode is shooting. Further, it is determined in step S68 whether or not the landscape photography mode has been selected. In step S69, it is determined whether or not the night landscape photography mode has been selected. In step S70, whether or not the portrait photography mode has been selected. Is determined. In step S71, it is determined whether or not the camera shake prevention mode has been selected. In step S72, it is determined whether or not the auxiliary light LED 26 has been turned on during the current integration operation.

These mainly determine the state of the key switch group (1) 68.

Only when it is determined that the moving object mode has been selected, all the other shooting modes have not been selected, and the auxiliary light has been turned off in the above eight types of determination items, step S73. Then, the continuous AF flag is set. If this flag is set, the moving object prediction AF is executed thereafter.

On the other hand, if the judgment result is other than that, the flow shifts to step S74 to clear the continuous AF flag, and further shifts to step S76 where the following moving object prediction AF is not performed.

The reason why the auxiliary light is determined in step S72 is that, when the auxiliary light LED 26 is turned on, the AF detection accuracy is lower than when the subject is dark because the subject is dark, and the error of the moving object prediction calculation is reduced. It is because it becomes large. Basically, it is not suitable for photographing a moving object in a dark situation because the shutter speed becomes slow.

In step S75, it is determined whether the first image shift calculation has been completed. This is determined by the first calculation completion flag that is set and cleared in steps S78 and S79 described below. This flag is a flag indicating whether or not the first image shift amount has been calculated, and the initial value is the value of step S21 in the flowchart of FIG.
Is cleared in advance.

If it is determined in step S75 that the first image shift calculation has not been completed, the process proceeds to step S76, where the image shift amount ΔZ ₁ is calculated by a known method.

[0112] Then, in the step S77, the whether the image shift amount [Delta] Z ₁ is can be calculated is judged. That is, the determination is made based on the information on the reliability when calculating the image shift amount ΔZ ₁ .

If it is determined in this step S77 that detection is impossible, the flow shifts to step S78 to clear the first calculation completion flag. Then, after the undetectable flag is set in step S79, the process returns.

On the other hand, if it is determined in step S77 that detection is possible, the flow shifts to step S80, where the first calculation completion flag is set, and the flow returns.

When it is determined that detection is impossible, the process shifts to lens scanning in a lens driving subroutine to search for a position of a lens that can be detected.

If it is determined in step S75 that the first image shift amount calculation has been completed, a second image shift amount calculation is performed. That is, in step S81,
First, the first calculation completion flag is cleared for the next time. Next, in step S82, the first and second integration levels are corrected to make the integration amounts substantially the same.

Then, in step S83, the same correlation calculation is performed as in the first time, and the image shift amount ΔZ ₂ is calculated.
Subsequently, in step S84, the above-described step S77 is performed.
As in the case of the first time, it is determined whether or not the image shift amount ΔZ ₂ has been calculated.

[0118] Here, if you're not operation of the image shift amount [Delta] Z ₂ proceeds to step S101, [Delta] Z ₁ is an operation already is an image shift amount [Delta] Z 'at time t _2. On the other hand, if the calculation has been performed, the process proceeds to step S85, where the correlation calculation of the image L of the first block described with reference to FIG. 5 is performed, and the moving amount of the image L of the first block is determined by the flowchart of FIG. Is calculated according to

Subsequently, in steps S86 and S87,
The correlation calculation of the images L of the second and third blocks is performed, and the movement amounts of the images L of the second and third blocks are calculated, respectively. Then, in step S88, it is determined whether the calculated moving amount of the image L of the three blocks is larger than a predetermined first determination value.

This first determination value is a relatively large value. Step S88 is performed when the subject deviates from the distance measurement area in the viewfinder and cannot be measured, or when the moving speed of the subject is too high. It is provided to detect a case where focusing cannot be performed even when a moving object is predicted. If the calculated amount of movement of the image L is larger than the predetermined first determination value, it is determined that the moving object cannot be predicted, and the process proceeds to step S99 described later.

Similarly, in steps S89 to S91 and S92, calculation of the moving amount of the image R and determination of the calculated moving amount are performed. If it is determined in step S92 that the calculated movement amount of the image R is larger than the predetermined first determination value, the process moves to step S99 because the moving object cannot be predicted.

Next, in step S93, a block having the highest correlation is selected based on the reliability indexes of the first to third blocks calculated as described above. That is, the block having the smallest reliability index Sk is selected.

Next, in step S94, an undetectable flag is determined in the selected correlation block. Here, if the selected block cannot be detected, the process proceeds to step SS99 to perform a detection impossible process.

On the other hand, if the block selected in step S94 can be detected, the process moves to step S95, and the image movement amount moved between the first and second integration based on the above equation (9). ΔZ ₀₁ is determined. Then, in step S96, it is determined whether the subject is moving.

Next, in step S97, the moving object flag output from step S96 is determined. Here, when it is determined that the subject is moving, the process proceeds to step S98, and a future image shift amount ΔZ ′ is predicted based on the above equation (10). After that, it returns.

On the other hand, if it is determined in step S97 that the subject is stationary, there is no need to predict a moving object, so the flow shifts to step S99, where ΔZ ′ is calculated in step S83. Image shift amount ΔZ ₂ . Then, the flow shifts to step S100, and returns after the undetectable flag is cleared.

FIG. 10 is a flowchart for explaining the lens driving subroutine of step S25 in the flowchart of FIG.

First, in step S111, whether or not detection is impossible is determined by a detection impossible flag. Here, if it is determined that detection is not possible, the process shifts to lens scan to search for a detectable state. On the other hand, if it is determined that detection is possible, it is next determined in step S112 whether or not continuous AF is performed.

If it is determined in step S112 that the current mode is not continuous AF, step S114 is performed.
Move to If it is determined that the current mode is continuous AF, the process proceeds to step S113 to determine whether or not the first distance measurement has been performed. If it is determined that the distance measurement is the first distance measurement, the process returns without driving the lens. On the other hand, if it is determined that the distance measurement is the second distance measurement, the process shifts to step S114 to perform initialization for driving the lens.

Next, in step S115, it is determined whether or not the camera is already in focus. This is based on the determination result of step S47 in the flowchart of FIG. 7, and if it is determined that the lens is in focus, the process returns because there is no need to drive the lens. If it is determined that the lens is out of focus, the following lens driving is performed based on the driving amount calculated in step S51 in the flowchart of FIG.

First, in step S116, it is determined whether or not the drive amount is larger than the drive amount determination value. Here, when it is determined that the distance is larger than the determination value, the distance measurement is performed again after driving by the predetermined drive amount.

For example, if the predetermined drive amount determination value is 150 pulses and the calculated drive amount is 250 pulses,
First, the lens driving subroutine is returned after driving a predetermined driving amount of 150 pulses, and the distance measurement is performed again.

In step S117, the drive amount is set to a predetermined drive amount. Then, after the in-focus flag is cleared in step S118, the process proceeds to step S124.

On the other hand, if it is determined in step S116 that the drive amount is smaller than the drive amount determination amount, step S1 is performed.
In 19, it is determined whether or not the current driving direction (whether the feeding direction or the feeding direction) is the same as the previous driving direction. The determination in step S119 is, in other words, a determination as to whether or not the backlash of the drive system gear is blocked.

If it is determined in step S119 that the current driving direction is the same as the previous driving direction, the process proceeds to step S120, and the driving amount calculated in step S51 in the flowchart of FIG. Is set.
Next, after the focusing flag is set in step S121, the process proceeds to step S124.

On the other hand, if it is determined in step S119 that the current driving direction is different from the previous driving direction, the flow shifts to step S122 to set the driving amount corresponding to the play amount stored in the EEPROM 75. You. And
After the in-focus flag is cleared in step S123,
Move to step S124.

That is, if there is any play in the gear, drive is performed to reduce the play and then the distance measurement is performed again. In the next distance measurement, the play is reduced, and focusing is performed through the route of step S120. Will do.

After these, in step S124, the current driving direction is stored in the driving direction flag. Then, in step S125, the above steps S117,
When driving is performed in the driving direction of step S124 by the driving amount set in S120 and S122, the process returns.

Next, the operation of the focus determination subroutine of FIG. 7 will be described in detail with reference to the flowchart of FIG.

First, the focusing threshold is read from the EEPROM 75 in step S131. In the following step S132, the defocus amount of the photographing lens calculated in step S46 in the flowchart of FIG.
Read into M.

Then, in step S133, the continuous AF flag is determined. If it is not continuous AF, the process proceeds to step S138. If it is continuous AF, step S138 is performed.
In 134, it is determined whether or not the photographing lens was in focus with the previous AF moving object. This means that
In the previous lens drive, it is determined which of the path of step S117, the path of step S120, and the path of step S122 in the flowchart of FIG. 10 has passed.

If the camera was out of focus last time (passed the path of step S117 or step S122), the flow shifts to step S138, but the camera was focused previously (step S138).
If the path has passed 120), the process moves to step S134. That is, only in the case of the previous focusing, the focusing threshold is expanded in step S137 described later. This is because the focusing threshold is enlarged only in the vicinity of the in-focus state, so that the focusing threshold is prevented from being significantly out of focus due to the enlargement.

Then, in step S135, it is determined whether or not the luminance of the subject is equal to or higher than a predetermined luminance. Here, when the brightness is equal to or lower than the predetermined brightness, the process proceeds to step S138. This is because, in the case of low luminance, the focus threshold is not expanded in step S137 because the focus detection accuracy is reduced.

At step S136, it is determined whether or not the subject is moving. This is determined based on the result of the moving object determination subroutine in step S96 in the flowchart of FIG. If it is determined that the subject is stationary, the process proceeds to step S138. If it is determined that the subject is moving, the process proceeds to step S137 to expand the focusing threshold. This is obtained by multiplying the focusing threshold in step S131 by a predetermined number.

Then, in step S38, the in-focus threshold is compared with the detected defocus amount. If the detected defocus amount is larger, the flow shifts to step S139 to clear the focus flag and return. On the other hand, if the detected defocus amount is smaller, the process shifts to step S140 to set the focus flag and then returns.

In step S137, the focus threshold is enlarged when the subject is determined to be a stationary subject, but the focus threshold is reduced when the subject is determined to be a moving subject. You may. Also, when it is determined that the subject is a moving subject, the focusing threshold is reduced,
In addition, the focus threshold may be enlarged when it is determined that the subject is a stationary subject.

As described above, by forming the in-focus determination subroutine, in the case of a moving subject, the in-focus threshold remains the same, so that the in-focus determination is not performed without driving the photographing lens. Focus on the moving subject. On the other hand, in the case of a still subject at the previous focusing, the focusing threshold is enlarged, so that even in the continuous AF, the hunting of the photographing lens is eliminated.

Although the embodiments of the present invention have been described above, it goes without saying that modifications can be made without departing from the spirit of the present invention.

For example, Japanese Patent Laid-Open No. 5-938 discloses a moving object detection method.
Although the technique disclosed in Japanese Patent Publication No. 50 is used, the present invention is not limited to this, and any technique capable of detecting a moving object may be used.

[0150]

As described above, according to the present invention, it is possible to provide an automatic focusing apparatus which can easily focus on a moving subject and does not cause hunting of the photographing lens for a stationary subject. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing the concept of an embodiment of an automatic focusing apparatus for a camera according to the present invention.

FIG. 2 illustrates an embodiment of the present invention, and is a block configuration diagram illustrating in detail a control system of a camera system to which an automatic focusing apparatus for a camera is applied.

FIG. 3 is a diagram illustrating a correlation operation for obtaining the movement of a subject image.

FIG. 4 is a view for explaining a state of obtaining a correlation.
5 is a flowchart for explaining the operation of the movement amount calculation of FIG.

FIG. 5 shows subject image signals L ′ (I) and R ′ (I) at time t ₀ and subject image signals L (I) and R (I) at time t ₁ for a moving subject. It is a figure explaining the example of.

FIG. 6 is a flowchart illustrating an operation of the entire camera to which the embodiment of the present invention is applied;

7 is a flowchart describing in detail an operation of an AF subroutine executed in step S23 of the flowchart in FIG. 6;

FIG. 8 is a flowchart illustrating the operation of a subroutine for AF detection in detail.

FIG. 9 is a flowchart illustrating an operation of a subroutine for AF detection in detail.

FIG. 10 is a step S2 in the flowchart of FIG. 6;
5 is a flowchart illustrating a lens driving subroutine of No. 5;

FIG. 11 is a flowchart illustrating in detail the operation of a focus determination subroutine in FIG. 7;

FIG. 12 starts focus detection when a subject is at a position 20 m from a camera, and thereafter, a so-called continuous A
It is a figure explaining the state where focus detection is continued by F.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 moving object prediction control unit, 2 focus detection unit, 3 image movement amount calculation unit, 4 defocus amount detection unit, 5 correlation operation unit, 6 focus determination unit, 7 moving object determination unit, 11 CPU, 12 interface IC, 13 power supply Unit, 14 strobe unit, 15 mirror shutter unit, 16 winding unit, 17 lens unit, 18 finder unit, 19 display unit, 20 AF unit, 21 serial communication line, 22 communication line, 25 motor driver, 26 auxiliary light LED, 27 Key switch (SW) group (2), 31 battery, 32 DC / DC converter, 36 strobe charging circuit, 37 main capacitor, 38 strobe light emitting circuit, 39 strobe light emitting tube, 41 mirror shutter motor, 42 shutter magnet, 46 winding motor , 7 Film detection photo interrupter (PI), 51 shooting lens, 52 zoom gear train, 53 zoom motor, 54 AF gear train, 55 AF motor, 56 AF photo interrupter (PI), 57 zoom encoder, 58 aperture photo interrupter (PI), 59 aperture magnet, 61 LCD panel in viewfinder, 62 backlight LED, 63 eight-segment photodiode element for photometry (photometric element), 66 external LCD panel, 67 LCD IC, 68 key switch (SW) group (1), 71 condenser lens , 72 separator lens, 73 photo sensor array, 74 AFIC, 75 EEPROM, 81 element output storage unit, 82 correlation operation circuit, 83 lens extension storage unit, 84 focal length storage unit, 91 sequence switch (SW) group, 92 Buzzer.

Claims (3)

[Claims] A focus detection unit for repeatedly detecting an image formation position of a pair of subject images and outputting time-series information on a focus adjustment state of a photographing lens with respect to the subject, based on a time-series output of the focus detection unit; And determining whether the subject is a moving body that is moving in the optical axis direction of the photographing lens or a static body that is not moving, and, based on the determination result, a moving body determination for focus determination. A moving object determining unit that sets a value and a static body determining value that is larger than the moving object determining value, and compares the output of the focus detecting unit with the determining value that is set according to the state of the subject. Focus determination means for determining whether or not the photographing lens is focused on the subject, and the focus determination means determines that the photographing lens is not focused on the subject. When taking the above An operation means for calculating a lens drive amount necessary for focusing the lens, and a lens drive means for driving the photographing lens according to the calculated lens drive amount. Focus adjustment device. 2. A focus detecting means for repeatedly detecting a defocus amount of a photographing lens; a moving body determining means for determining whether a subject is moving based on a temporal change of the defocus amount; When it is determined by the determination means that the subject is stationary, a predetermined value larger than when the subject is determined to be moving is set, and the defocus amount and the set predetermined value are set. And an in-focus judging means for judging whether or not the photographing lens is in focus by comparing 3. The image forming apparatus according to claim 2, further comprising: a driving unit that drives the photographing lens; and a second focus determining unit that determines whether the photographing lens has reached a focused state by the driving unit. 2. The automatic focus adjustment device according to claim 1, wherein when the focus determination unit determines that the photographing lens is out of focus, the control by the control unit is prohibited.