JP2974637B2 - Automatic focusing device - Google Patents

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 plurality of distance measuring points used for a camera or the like.

[0002]

2. Description of the Related Art Conventionally, most automatic focusing systems of a single-lens reflex camera attempt to focus on a subject by repeating a cycle of "focus detection (sensor signal input, focus detection calculation), lens driving". Is what you do.
The lens drive amount in each cycle is based on the defocus amount at the time of performing focus detection in that cycle,
This is expected to eliminate the defocus amount at the time of focus detection at the end of lens driving.

Naturally, it takes a considerable amount of time for focus detection and lens drive. However, in the case of a stationary subject, the amount of defocus does not change unless the lens is driven. The defocus amount to be eliminated when the lens driving is completed is equal to the defocus amount at the time of focus detection, and correct focus adjustment is performed.

However, in the case of a moving subject, the defocus amount changes during focus detection and lens driving, and the defocus amount to be eliminated and the detected defocus amount may be significantly different. As a result, There is a problem that the subject is not focused after the lens driving is completed.

As an automatic focusing method for solving the above-mentioned problem, Japanese Patent Laid-Open Publication Nos.
Japanese Patent Application Laid-Open Nos. 139512 and 62-139511 and Japanese Patent Application No. 62-328233 are disclosed.

[0006] The gist of the method disclosed in the Japanese Patent Application No. Sho-A-58-28139 is that, in consideration of the detected defocus change in each cycle and the time interval of each cycle, a defocus change caused by the movement of the subject is predicted. This method is intended to correct the amount (hereinafter, referred to as “follow-up correction”), and from the viewpoint of focusing accuracy at the end of driving the lens, the above method is expected to improve the above problem.

However, when the following correction is actually performed, the following problem occurs.

That is, if the subject in the ranging field moves to another subject while the subject is being tracked in the tracking correction mode, the continuity of the change of the image plane position is lost. If the prediction is made based on the data of the new subject, an incorrect prediction is made, and as a result, the lens is driven to a completely different place.

As described above, when a subject within the range-finding field moves to another subject, erroneous prediction is made, and this is solved while performing prediction control using data of an old subject. There is a problem that there is no.

The operation of the device shown in the above-mentioned Japanese Patent Application will be described below with reference to the drawings.

FIG. 3 is a diagram for explaining the lens drive correction method disclosed in the above-mentioned Japanese Patent Application. The horizontal axis in the figure represents time t, and the vertical axis represents the image plane position x of the subject.

A curve x (t) represented by a solid line indicates an image plane position at time t of a subject approaching the camera in the optical axis direction when the taking lens is at infinity. L (t) represented by a broken line indicates the position of the photographing lens at time t, and focusing is achieved when x (t) and l (t) match. Then [t _i, t _i '] focus detection operation, [t _i' is, t _i + _1] is the lens driving operation. Further, in the conventional example shown in FIG. 1, it is assumed that the image plane position changes according to a quadratic function. That is, at time t ₃
At the current and past three image plane positions (t ₁ , x ₁ )
If (t ₂ , x ₂ ) (t ₃ , x ₃ ) is known, the above equation x
Based on (t) = at ² + bt + c, TL starts at time t _3.
Time t ₄ after (AF time lag + release time lag)
Image plane position x ₄ in those which can be predicted.

However, what can be actually detected by the camera is not the image plane position x ₁ , x ₂ , x ₃ but the defocus amount D
F ₁ , DF ₂ , DF ₃ and lens drive amounts DL ₁ , DL ₂ in terms of image plane movement amount. The time t ₄ is a value in the future, and is actually a value that changes with the change in the accumulation time of the accumulation type sensor depending on the luminance of the subject. Assume.

T ₄ −t ₃ = TL = TM ₂ + (release time lag) (1)

Under the above assumption, the lens driving amount DL ₃ calculated from the focus detection result at the time t ₃ is obtained as follows.

X (t) = at ² + bt + c (2) Assuming that (t ₁ , l ₁ ) in the figure is the origin, t ₁ = 0 x ₁ = DF ₁ (3) t ₂ = TM ₁ x ₂ = DF ₂ + DL ₁ (4) t ₃ = TM ₁ + TM ₂ × ₃ = DF ₃ + DL ₁ + DL ₂ (5) Substituting the equations (3), (4) and (5) into the equation (2), a ,
When b and c are obtained,

[0017]

[Outside 1] c = DF ₁ (8) Therefore, the lens driving amount DL _{3 in} terms of the image plane movement amount at the time t ₄ is DL ₃ = x ₄ −l ₃ = x ₄ −x ₃ + DF ₃ = a ｛(TM ₁ + TM ₂ + TL) ) ² − (TM ₁ + TM ₂ ) ² ＋ + b · TL + DF ₃ (9)

Next, a problem that occurs when an object in the distance measurement field moves to another object will be described with reference to FIG.

FIG. 4 shows the relationship between the time and the image plane position. The solid line indicates the image plane position of the first object, and the dashed line indicates the image plane position of the second object.

Here, at times t ₁ and t ₂ , focus detection is performed on the first object to drive the lens, and at time t ₃ , the second object is detected.
It is assumed that focus detection has been performed on the subject.

Then, on the camera side, based on the defocus amount and the lens driving amount obtained by the focus detection, the times t ₁ and t
₂ and t ₃ , image plane positions x ₁ , x ₂ and x ₃ ′ are calculated,
A quadratic function f (t) passing through (t ₁ , x ₁ ) (t ₂ , x ₂ ) (t ₃ , x ₃ ′) is calculated, and the image plane position x at time t ₄ is calculated by the f (t). Predict ₄ ″.

However, the image plane position of the first object at time t ₄ is x ₄ , the image plane position of the second object is x ₄ ′, and x ₄ ″ obtained by the prediction is The position is different from the image plane position.

[0023] This is because in order to predict the image plane position x ₄ of the first object _{(t 1, x 1) (} t 2, x 2) (t 3,
It is necessary to find a function that passes through x ₃ ), and to estimate the image plane position x ₄ ′ of the second object, (t ₁ , x ₁ ′)
It is necessary to find a function passing through (t ₂ , x ₂ ′) (t ₃ , x ₃ ′).

[0024] However, in the camera side because it can not be distinguished from the first object and the second object performs a prediction calculation with the defocus amount obtained by the focus detection time t _3. As a result, the prediction function is not an approximation function of the image plane position of the first subject, and is different from the approximation function of the second subject, and the predicted lens driving position is also incorrect. Would. This is because if the data used for the prediction includes data obtained by performing focus detection on an object other than the main object, the above-described incorrect prediction is performed. This is a problem that always occurs when the main subject is switched to the second subject during operation.

Techniques for solving such a problem are disclosed in Japanese Patent Application No. 62-328233 or Japanese Patent Application Laid-Open No. Sho 62-328233.
No. 139511 and Japanese Patent Application Laid-Open No. 62-139512. The gist of the invention is to immediately suspend the following mode immediately when conditions unsuitable for prediction, such as loss of continuity of image plane position change or low brightness of a subject.

[0026]

However, in the multi-point AF for detecting the focus state of a subject in each of different areas of the screen, a situation occurs in which a subject captured in a certain area is shifted to another area. However, in this case, although there is no need to stop the following mode, there is a disadvantage that the following mode is immediately stopped in the conventional method. Also, in this multi-point AF, if a subject different from the previous subject is captured in each area, it is necessary to immediately stop the tracking mode. Then, if the processing is performed, it is a problem whether proper processing can be performed.

[0027]

According to a first aspect of the present invention, there is provided a focus detection circuit for repeatedly detecting detection data corresponding to a focus state in a plurality of measurement areas, and a focus detection circuit for obtaining the detection data. A focusing mechanism driving circuit for driving a focusing mechanism based on the detected data, and an automatic focus adjustment device that repeatedly performs an autofocus operation, the detection data obtained by the latest detection operation performed for the autofocus operation. And a calculation circuit for predicting and calculating data for moving the focusing mechanism to a position corresponding to the image plane position of the image of the target object after a predetermined time based on the past detection data, and the calculation circuit calculated by the calculation circuit While performing focusing based on data, it is suitable for performing a prediction calculation among the plurality of measurement areas. A selection unit for selecting an area where an elephant is present is provided, and detection data from the area selected by the selection unit is set as the latest detection data used for the prediction calculation, and further based on a relationship with past detection data. When it is not possible to select an area where a target object suitable for the prediction calculation is present by the selection means, a setting means for setting a specific area at the center position of the screen among the areas as an area for an autofocus operation is provided. On the other hand, even if the target moves, it enables prediction calculation for that target, and when the target captured in each area is different from the previous target, it is captured in the center area of the screen The above-mentioned problem is solved by focusing on a target object.

According to a second aspect of the present invention, there is provided a focus detection circuit for repeatedly detecting detection data corresponding to a focus state in a plurality of measurement areas, and a focusing mechanism based on the detection data obtained by the focus detection circuit. A focusing mechanism driving circuit for driving, and an auto-focusing device that repeatedly performs an auto-focus operation, after a predetermined time based on detection data obtained by the latest detection operation performed for the auto-focus operation and past detection data. An arithmetic circuit for predicting and calculating data for moving the focusing mechanism to a position corresponding to the image plane position of the image of the object is provided, and focusing is performed based on the data calculated by the arithmetic circuit. Select the area where the target object suitable for performing the prediction calculation exists from the multiple measurement areas Selection means, the detection data from the area selected by the selection means is used as the latest detection data used for the prediction calculation, and the detection data is suitable for the prediction calculation by the selection means based on the relationship with the past detection data. When it is not possible to select the area where the object is present, a setting unit is provided for setting an area in which the detection data for the last autofocus operation among the areas is formed as an area for the next autofocus operation. Even if the target moves, the prediction calculation for the target is enabled, and when the target captured in each area is different from the previous target, the area in the last auto focus operation The above-mentioned problem is solved by focusing on the object captured by the camera.

[0029]

Next, the present invention will be described. First, as an embodiment of the present invention, a case will be described in which an automatic focus adjustment device having a focus detection system capable of measuring a distance between the center of a viewfinder and three points on the left and right thereof is employed.

FIGS. 9 and 10 are optical arrangement diagrams showing an embodiment of a focus detecting device capable of detecting the above three points.

FIG. 9 shows a perspective view, and FIG. 10 shows a longitudinal sectional shape.

In FIG. 9, reference numeral 42 denotes a perforated field mask, which has long sides in the horizontal direction, has rectangular openings arranged in parallel, and is arranged in the vicinity of a predetermined image forming plane of the objective lens. Reference numeral 43 denotes a filter that blocks light having a wavelength longer than that of near-infrared light, and reference numeral 50 denotes a split field lens, which is disposed slightly shifted from a predetermined imaging plane of the objective lens. The split field lens 50 includes lens portions 50c, 50d, and 50e having different optical functions as described later, and these portions are formed by changing one or both of the lens thickness and the radius of curvature of the lens surface. .
When each lens portion is formed separately, it can be made of a material having a different refractive index.

The lenses 51 and 53 form a re-imaging lens unit with a two-hole aperture 52 interposed therebetween, and the convex lens 51 converts incident light into a state close to parallel light (the optical function is described in Japanese Patent Publication No. Sho 62-335).
No. 64) and two convex lenses 5
The two-image forming lens 53 formed by joining 3a and 53b side by side forms two secondary images of the object image formed by the objective lens.
The above-described two-hole stop 52 has vertically long elliptical openings 52a and 52b arranged in the horizontal direction in the drawing.

Numeral 54 denotes a concave lens for correcting the curvature of field, which is disposed on a transparent plastic package 56 for accommodating a photoelectric conversion device 55. The split field lens 5
0, convex lens 51, concave lens 5 of the re-imaging lens unit
Reference numeral 4 denotes a spherical lens system which is shaped vertically and is rotationally symmetric.

The light beam passing through the apertures 42... 42 g of the perforated field mask 42 passes through the lens portions 50 c, 50 b and 50 e of the split field lens 50 as shown in FIG.
A secondary image of the object is formed on each of the photoelectric conversion devices.

In the secondary image, the relative position of the pair of two images changes depending on the focus state of the objective lens (photographing lens). Then, the secondary image is converted into an image signal by a photoelectric conversion device, and the focus state of each ranging point is detected from the image signal.

FIG. 5 is a circuit diagram showing an embodiment of a camera provided with an automatic focusing device according to the present invention.

In the figure, PRS is a camera control device.
For example, CPU (central processing unit), ROM, RA
This is a one-chip microcomputer having an M / A / D conversion function. The computer PRS performs a series of camera operations such as an automatic exposure control function, an automatic focus detection function, and film winding according to a camera sequence program stored in the ROM. For this purpose, PRS includes synchronous communication signals SO, SI, SCLK and communication selection signal CL.
The CM, CSDR, and CDDR are used to communicate with peripheral circuits and lenses in the camera body to control the operation of each circuit and lens.

SO is a data signal output from the computer PRS, SI is a data signal input to the computer PRS, and SCLK is a synchronous clock of the signals SO and SI.

LCM is a lens communication buffer circuit,
When the camera is in operation, power is supplied to the lens power supply terminal and a selection signal CL from the computer PRS is supplied.
When the CM is at a high potential level (hereinafter abbreviated as “H”), it serves as a communication buffer between the camera and the lens.

That is, the computer PRS sets CLCM to “H”, and synchronizes predetermined data with SO
Transmitted from the LCM, the buffer signals LCK and DC of SCLK and SO are transmitted via the camera / lens indirect point.
L is output to the lens. At the same time, the buffer signal of the signal DLC from the lens is output as SI, and the computer PRS inputs the SI as data from the lens in synchronization with SCLK.

SDR is a drive circuit of a focus detection line sensor device SNS composed of a CCD or the like.
Selected when SDR is 'H', SO, SI, SCL
It is controlled from the PRS using K.

The signal CK is a CCD driving clock φ1, φ
2 for generating the signal INTEND
Is a signal notifying the PRS that the accumulation operation has been completed.

The output signal OS of the SNS includes clocks φ1, φ
2 is a time-series image signal synchronized with 2, and after being amplified by an amplifier circuit in the SDR, is output to the computer PRS as AOS. The computer PRS inputs AOS from an analog input terminal, and after synchronizing with CK, performs A / D conversion by an internal A / D conversion function, and sequentially stores the AOS at a predetermined address in RAM.

SAGC, which is an output signal of the sensor device SNS, is an output of an AGC (Auto Gain Control) sensor in the sensor device SNS.
Used for image signal accumulation control in NS.

SPC is an exposure control photometric sensor for receiving light from a subject through a photographic lens, and its output SSPC is input to an analog input terminal of a computer PRS, and after A / D conversion, according to a predetermined program. Used for automatic exposure control (AE).

DDR is a switch detection and display circuit, which is selected when the signal CDDR is "H", and
It is controlled from the PRS using SI and SCLK. That is,
The display of the display member DSP of the camera is switched based on the data sent from the PRS, and the ON / OFF state of the switch SWS linked to various operation members of the camera is notified to the computer PRS by communication.

The switches SW1 and SW2 are linked to a release button (not shown).
SW1 is turned on by pressing down the stage, and SW2 is subsequently turned on by pressing down to the second stage. As will be described later, the computer PRS performs photometry and automatic focus adjustment operation when SW1 is turned on, and performs exposure control and film winding by using SW2 as a trigger. The SW2 is connected to the "interrupt input terminal" of the microcomputer PRS. Even when the program is executed when the SW1 is turned on, an interrupt is generated by turning on the SW2, and the process can immediately proceed to a predetermined interrupt program.

MTR1 is a motor for feeding the film, and MTR2 is a motor for mirror up / down and shutter spring charging. The control of forward rotation / reverse rotation is performed by respective drive circuits MDR1 and MDR2. PRS to MDR1, M
The signals M1F, M1R, M2F,
M2R is a signal for motor control.

MG1, MG2 are magnets for starting the movement of the first and second curtains of the shutter, respectively, are energized by signals SMG1, SMG2 and amplification transistors TR1, TR2, and the shutter is controlled by PRS.

The switch detection and display circuit DD
R, the motor drive circuits MDR1 and MDR2, and the shutter control are not directly related to the present invention, and a detailed description thereof will be omitted.

A signal DCL input to the in-lens control circuit LPRS in synchronization with LCK is transmitted from the camera to the lens FLN.
This is data of a command for S, and the operation of the lens for the command is predetermined.

The LPRS analyzes the instruction in accordance with a predetermined procedure, and performs operations of focus adjustment and aperture control, and output DLC.
Output various parameters (open F number, focal length, defocus amount vs. extension amount coefficient, etc.) of the lens.

The embodiment shows an example of a zoom lens. When a focus adjustment command is sent from a camera, a focus adjustment motor LMTR is sent to the signals LMF and LMF in accordance with the drive amount and direction sent at the same time. Driven by LMR,
The focus is adjusted by moving the optical system in the optical axis direction. The moving amount of the optical system is determined by the pulse signal SENC of the encoder circuit ENCF.
At F, the counter is counted by a counter in the LPRS, and when the predetermined movement is completed, the LPRS itself sets the signals LMF, LMR to 'L' to brake the motor LMTR.

Therefore, once the focus adjustment command is sent from the camera, the control device PRS in the camera does not need to be involved in driving the lens at all until the driving of the lens is completed.

When an aperture control command is sent from the camera, a well-known stepping motor DMTR for driving the aperture is driven in accordance with the number of aperture stages sent at the same time. Incidentally, since the stepping motor can be controlled to be open, an encoder for monitoring the operation is not required.

ENCZ is an encoder circuit attached to the zoom optical system, and the in-lens control circuit LPRS receives the signal SENCZ from the encoder circuit ENCZ to detect the zoom position. Lens parameters at each zoom position are stored in the in-lens control circuit LPRS,
When there is a request from the computer PRS on the camera side, a parameter corresponding to the current zoom position is sent to the camera. Note that three sets of photoelectric conversion devices are provided in the sensor device SNS for a pair of two images, respectively, and three points can be measured.

FIG. 6 shows the operation of the camera having the above configuration.
This will be described according to the following flowchart.

When a power switch (not shown) is turned on, power supply to the microcomputer PRS is started, and the computer PRS starts executing a sequence program stored in the ROM.

FIG. 6 is a flowchart showing the entire flow of the above program. When the execution of the program is started by the above operation, the state of the switch SW1 which is turned on by pressing the release button in the first stage is detected in step (002) through step (001).
When W1 is off, the process proceeds to step (003) to clear and initialize all control flags and variables set in the RAM in the computer PRS.

The above steps (002) and (003) are repeatedly executed until the switch SW1 is turned on or the power switch is turned off. When the switch SW1 is turned on, the steps (002) to (005) are performed.
Move to.

In step (005), a "photometry" subroutine for exposure control is executed. Computer PRS
Inputs the output SSPC of the photometric sensor SPC shown in FIG. 5 to an analog input terminal, performs A / D conversion, calculates the optimal shutter control value and aperture control value from the digital photometric value, and Store at a predetermined address. During the release operation, the shutter and the aperture are controlled based on these values.

Subsequently, in step (006), an "image signal input" subroutine is executed. Although the flow of this subroutine is shown in FIG. 7, the computer PRS inputs image signals of three sets of sensor arrays of the focus detection sensor device SNS. Details will be described later.

In the next step (007), the defocus amounts DEF of the three ranging points based on the respective image signals of the photographing lens are calculated based on the input three sets of image signals. The specific calculation method is described in Japanese Patent Application No.
The detailed description is omitted since it is disclosed in Japanese Patent Application Laid-Open No. 1-160824.

In step (008), a "prediction calculation" subroutine is executed. In the “prediction calculation” subroutine, the lens drive amount is corrected, and the details will be described later.

In the next step (009), the "lens drive" subroutine is executed, and the lens is driven based on the lens drive amount corrected in the previous step (008).
This "lens drive" subroutine is shown in FIG. After the lens driving is completed, step (00) is performed again.
Steps (005) to (009) are repeated until the switch SW1 is turned off or the second stroke SW2 of the release switch (not shown) is turned on. Is performed.

When the release button is further depressed and the switch SW2 is turned on, the interrupt function causes
Regardless of the step, immediately step (010)
Then, the release operation is started.

In step (011), it is determined whether or not lens driving is being executed.
The process proceeds to 2), a lens drive stop command is transmitted, the lens is stopped, and the process proceeds to step (013). If the lens is not driven, the process directly proceeds to step (013).

In step (013), the quick return mirror of the camera is mirrored up. This is executed by controlling the motor control signals M2F and M2R shown in FIG. In the next step (014), the aperture control value already stored in the photometry subroutine in the previous step (005) is sent as an SO signal to the in-lens control circuit LPRS via the circuit LCM to perform aperture control.

It is determined in step (013) or (014) whether or not the mirror up and aperture control have been completed.
The mirror-up can be confirmed by a detection switch (not shown) attached to the mirror, and the aperture control communicates whether the lens has been driven to a predetermined aperture value. Confirm with. If any of them is not completed, the process stands by at this step and continues to detect the state. When both control ends are confirmed, step (016) is performed.
Is moved to

In step (016), the previous step (0
The shutter is controlled at the shutter time already stored in the photometry subroutine of 05) to expose the film.

When the shutter control is completed, in the next step (017), a command is sent to the lens to open the aperture through the above-mentioned communication operation, and then the mirror is lowered in step (018). . Mirror down is similar to mirror up, and the motor control signals M2F and M2R
This is executed by controlling the motor MTR2 using.

In the next step (019), step (0)
Wait for mirror down and aperture opening to be completed as in 15). When both mirror down and aperture opening control are completed, the process proceeds to step (020).

In step (020), the motor control signals M1F and M1R shown in FIG. 5 are appropriately controlled to wind up one frame of the film.

The above is the entire sequence of the camera that has performed the prediction AF.

Next, the "image signal input" subroutine shown in FIG. 7 will be described.

The "image signal input" is an operation executed at the beginning of a new focus detection operation. When this subroutine is called, the process proceeds to the step (101) and then to the step (10).
In 2), the flags INA, INB, INC are reset. This flag determines whether or not the accumulation of each of the three sets of line sensors as each photoelectric conversion device for measuring the distance of three points has been completed. Therefore, the flag is first reset before the accumulation is started.

When the step (102) is completed, the process proceeds to a step (103). In this step (103), the start time of the focus detection operation is stored by storing the timer value TIMER of the self-running timer of the microcomputer PRS itself in the storage area TN on the RAM.

In the next step (104), the time interval TM ₁ in the lens drive amount correction equations (6), (7) and (9) is used.
, To update the contents of the memory _TM 1, _{TM 2} to memory the TM _2. Before executing step (104), the time intervals in the previous and previous focus detection operations are stored in TM ₁ and TM ₂ , and the items in which the previous focus detection operation was started are stored in TN _1. It is remembered.

Therefore, the execution of step (104) causes the TN
₁ -TN represents the time interval of the focus detecting operation to the current from the previous, which is input to the memory TM _2, TM ₁
Stores the previous and previous time intervals. And TN ₁
Stores the current focus detection start time TN for the next focus detection operation. That is, the last time interval before the memory TM ₁ at step (104), the last time interval to the TM ₂ is the TN ₁ focus detection start time of this time is always stored.

In the next step (105), the sensor device SNS is started to store an optical image. Specifically, the microcomputer PRS sends an “accumulation start command” to the sensor drive circuit SDR by communication, and in response to this, the drive circuit SDR changes the clear signal CLR of the photoelectric conversion element of the sensor device SNS to “L”. To start charge accumulation.

In step (106), the timer value of the self-running timer is stored in a variable TI, and the current time is stored.

In step (107), it is determined whether or not the accumulation of the first line sensor and the A / D conversion of the image signal have been completed. If the accumulation has been completed, the process proceeds to step (109). Move to step (108).

In step (108), the computer PR
The state of the S input INTEND terminal A is detected, and it is checked whether or not the accumulation is completed. The sensor drive circuit SDR sets the signal INTEND to “L” at the same time as the start of accumulation, monitors the AGC signal SAGC from the sensor device SNS, and
When C reaches a predetermined level, the signal INTEND is set to "H".
At the same time, the charge transfer signal SH is set to "H" for a predetermined time to transfer the charge of the photoelectric conversion element unit to the CCD unit.

In the step (108), the INTEND terminal A
Is "H", it means that the accumulation of the first line sensor has been completed, and the process proceeds to step (115), and if "L", it means that the accumulation has not been completed yet (step (10)).
Go to 9).

In step (109), it is determined whether the accumulation of the second line sensor and the A / D conversion of the image signal have been completed, and if completed, the process proceeds to step (111). Move to step (110).

In step (110), step (10)
Similarly to 8), if the INTEND terminal B is "H", the accumulation of the second line sensor is completed, and the process proceeds to step (116). If "L", the accumulation is not completed yet. Move to step (111).

In step (111), it is determined whether the accumulation of the third line sensor and the A / D conversion of the image signal have been completed, and if completed, the process proceeds to step (113).
If not, the process proceeds to step (112).

In step (112), step (10)
Similarly to 8), if the INTEND terminal C is "H", the third
The process proceeds to step (117) when the accumulation of the line sensor has been completed, and proceeds to step (113) if the accumulation is not completed if it is "L".

Steps (115), (116) and (11)
7) is a step which is executed when the accumulation of each line sensor is completed.
"1" is input to the flags of INB and INC. And parameters TEA, T representing the accumulation time of each line sensor.
The storage time TE at that time is input to EB and TEC.
When these steps are completed, step (12)
Go to 5).

In step (113), the time TI stored in step (106) is subtracted from the timer value TIMER of the self-propelled timer and stored in a variable TE. Therefore, the time from the start of the accumulation to the TE, that is, the so-called accumulation time, is stored in the TE. In the next step (114), TE
Is compared with the constant MAXINT. If TE is less than MAXINT, the process returns to step (107) and again waits for the end of accumulation. When TE becomes MAXINT or more, step (11)
The process moves to 8) to forcibly end the accumulation. The forced accumulation end is executed by sending an “accumulation end command” from the computer PRS to the circuit SDR.
, The charge transfer signal SH is set to “H” for a predetermined time, and the charge of the photoelectric conversion unit is transferred to the CCD.
To the department. The accumulation of the sensors ends in the flow up to step (118).

In step (119), it is determined whether or not the accumulation and A / D conversion of the first line sensor have been completed, and if completed, the process proceeds to step (121), and if not, the process proceeds to step (120). Move to.

In step (121), it is determined whether or not the accumulation and A / D conversion of the second line sensor have been completed. If the conversion has been completed, the process proceeds to step (123), and if not, the process proceeds to step (122). Move to.

In step (123), it is determined whether or not the accumulation and A / D conversion of the third line sensor have been completed. If the conversion has been completed, the process proceeds to step (125), and if not, the process proceeds to step (124). Move to.

Steps (120), (122) and (12)
4) is the accumulation time T of the first, second and third line sensors.
The current accumulation time TE is input to EA, TEB, and TEC, and the accumulation end flags INA, IN of each line sensor are input.
"1" is input to B and INC.

In step (125), the sensor device SNS
A / D conversion of the signal AOS, which is obtained by amplifying the image signal OS of each line sensor by the sensor drive circuit SDR after the completion of the accumulation, is stored in the RAM. More specifically, the SDR generates the clocks φ1 and φ2 for driving the CCD in synchronization with the clock CK from the PRS and supplies the clocks to the sensor position SNS. The CCD unit is driven by the φ1 and φ2 in the sensor device SNS. Are output in time series from the output OS as image signals. This signal is amplified by the amplifier inside the drive circuit SDR, and then AOS
Is input to the analog input terminal of the computer PRS. The computer PRS performs A / D conversion in synchronization with the clock CK outputted by itself, and sequentially stores the digital image signals after A / D conversion at predetermined addresses in the RAM.

In steps (126) to (128), it is determined whether or not the accumulation and A / D conversion of each line sensor have been completed. If the accumulation and A / D conversion of all the line sensors have been completed, the process proceeds to step (128). The process returns to (129), returns to this subroutine, and if not completed, returns to step (10).
The process proceeds to step 7), and the accumulation of the line sensor that has not been completed is continued.

FIG. 8 shows a flowchart of the "lens drive" subroutine.

When this subroutine is executed, two data "S" and "PTH" are input in step (202) by communicating with the lens. “S” is a “defocus amount vs. a coefficient of the focus adjustment lens protrusion amount” unique to the photographing lens. For example, in the case of a single lens of the whole protrusion type, S = 1 because the entire photographing lens is a focus adjustment lens.
In the case of a zoom lens as in the present application, each zoom position is detected by an encoder circuit ENCZ, and a control circuit LPR
At S, S is determined according to the zoom position. “PTH” is the amount of focus adjustment lens per pulse output from the encoder ENCF in conjunction with the movement of the focus adjustment lens LNS in the optical axis direction.

Therefore, the defocus amount D to be adjusted is
The value obtained by converting the amount of protrusion of the focusing lens by L, S, and PTH into the number of output pulses of the encoder, that is, the so-called lens drive amount FP, is given by the following equation.

FP = DL × S / PTH Step (203) executes the above equation as it is.

In step (204), step (20)
The FP obtained in 3) is sent to the lens, and the focusing lens (in the case of a whole single lens, the entire photographing lens)
Command to drive.

In the next step (205), it is communicated with the lens to detect whether or not the driving of the lens driving amount FP commanded in the step (205) has been completed, and when the driving has been completed, the flow proceeds to step (206). To return the "lens drive" subroutine. This lens drive completion detection is performed by the encoder EN by the counter in the control circuit LPRS as described above.
The pulse signal of the CF is counted, and is executed by detecting whether or not the count value coincides with the lens drive amount FP by the above-described communication.

Next, the flow of the "prediction calculation" subroutine will be described with reference to FIG. FIG. 1 shows the flow of the "prediction calculation" subroutine, in which it is determined whether or not prediction calculation is possible. If prediction is possible, the lens driving amount is calculated in consideration of the AF time lag and the release time lag.

In step (302), it is determined whether or not a counter COUNT for determining whether data necessary for prediction has been accumulated is counted up. In this embodiment, when distance measurement data and lens drive data are accumulated three or more times, that is, when COUNT> 2, prediction calculation can be performed, and further counting up is not required. BA step (3
Go to 04). If COUNT <3, COUNT is counted up in step (303), and then the process proceeds to step (304).

In step (304), data for the current prediction operation is updated. That is, since the prediction calculation is performed based on the equations (6), (7), (8), and (9), the data includes the previous and previous defocus amounts DF ₂ , DF ₁ , FIG. The lens drive amount DL ₁ , the current lens drive amount DL ₂ , the previous and previous and previous time intervals TM ₁ and TM ₂ , and the expected time lag TL are required. Thus the previous defocus amount in each step (304) in which focus detection is performed in the storage area DF _2, also stores the previous previous defocus amount region D
Fill in F _1, enter further lens driving force DL in the preceding image plane movement amount converted into the memory area DL _2, the lens drive amount DL ₁ before the previous image plane movement amount converted into the memory area DL _1, each The data in the storage area is updated to the data necessary for the current prediction operation.

At step (305), it is determined whether or not the AFP indicating the position of the used distance measuring point is "0". Here, when the AFP is “−1”, the left ranging point is used, when the AFP is “0”, the center ranging point is used, and when the AFP is “1”, the right ranging point is used. That is, in step (305), it is determined whether or not the center ranging point is being used. If the center ranging point is being used, step (306) is performed.
Otherwise, to step (307).

In step (307), step (30)
In the same manner as in 5), it is determined whether or not the left ranging point is used. If the left ranging point is used, the process proceeds to step (308), and the right ranging point is used. If so, the process proceeds to step (309).

Steps (306), (308), (30)
9) Enter the defocus amount obtained by the distance measuring time distance measuring point used this time in the storage area DF ₃ on RAM, to update the data. Here, in step (306), the defocus amount DFB based on the image signal of the sensor at the center ranging point, and in step (308), the defocus amount DFA based on the image signal of the sensor at the left ranging point, and step (309). Inputs a defocus amount DFC based on the image signal of the sensor at the right distance measuring point. When the above steps are completed, the process proceeds to step (310).

In step (310), it is determined whether or not data necessary for the prediction operation has been input to each of the storage areas. As described above, the prediction calculation requires the current, previous, and last two times of defocus amount and the last, last and last time of lens drive amount,
The condition is that three or more focus adjustment operations have been performed in the past. Therefore, each time the focus adjustment operation is performed in step (303), the counter COUNT is incremented by one, and the counter is made to count the number of times the focus adjustment operation has been performed. It is determined whether or not the above operation has been performed, and the operation is performed three times or more. If the prediction calculation is possible, the process proceeds to step (312), and if not, the process proceeds to step (319).

In step (312), it is determined whether or not the continuity of the image plane position is determined as to whether the defocus amount updated this time is suitable for prediction. If it is determined that there is continuity, the process proceeds to step (313). Otherwise, the process proceeds to step (314). Here, the method of determining the “continuity of the image plane position” will be described later.

In step (312), it is determined that there is no continuity of the image plane position. When the process proceeds to step (314), the distance measuring point used in the subroutine "change distance measuring point" is changed in this step. . A detailed description of this subroutine will be described later.

In step (315), after changing the distance measuring point,
It is determined whether or not prediction is possible by ANG, and if possible, the process proceeds to step (313), and if unpredictable (inappropriate data), the process proceeds to step (316).

In step (316), the COUNT for counting the number of times data has been accumulated is reset to temporarily stop the prediction control. And step (31)
In 7), the flag ANG of the prediction possibility determination is reset.

In step (318), the defocus amount DF of the center distance measuring point is added to the lens drive amount DL in terms of the image plane movement amount.
Enter B. In this case, once the prediction becomes unpredictable, the distance measuring point used when restarting the AF is set as the center distance measuring point. However, this need not be the center distance measuring point. For example, the distance measuring point selected first or the distance measuring point used last may be used.

In the first and second distance measurement, step (3)
19), and in step (319), the defocus amount D which has been updated this time to the lens drive amount DL in terms of the image plane movement amount.
To enter the F _3.

If it is determined in step (312) that prediction is possible and the process proceeds to step (313), the expected time lag TL is calculated in step (313). Storage area TM to ₂ as described above, and the time until the current focus detection operation is stored from the previous, under the assumption that a match also TM ₂ time required for focus adjustment of the time, Obtain the expected time lag TL = TM ₂ + TR. Here, TR is a release time lag.

In the next steps (320) and (321), each of the storage areas DF _{1 to} DF ₃ , DL ₁ , DL ₂ ,
Based on the data stored in TM ₁ and TM ₂ , A and B representing the terms a and b in the equations (6) and (7) are obtained, and the process proceeds to step (322).

In the step (322), the data of each storage means and the steps (313) and (320),
Based on the calculated value of (321), the calculated value of formula (9) is obtained, and this is used to obtain the lens drive amount DL in terms of the current image plane movement amount.

In the next step (323), the lens drive amount DL determined in steps (322), (318), and (319), the open F number FN of the taking lens, and a predetermined coefficient δ (0. 035mm) product FN · δ
And if DL <FN · δ, step (324)
Otherwise, return to step (325).

In step (324), the previous step (3)
23), it is determined that the lens driving amount DL is smaller than the image plane depth FN · δ, that is, it is not necessary to drive the lens,
The lens driving amount DL is set to 0, and the driving of the lens is prohibited.
Accordingly, unnecessary driving of the minute lens is not performed, and both the usability and the power consumption can be improved. In the present embodiment, FN is the open F number of the taking lens. However, there is no problem even if this is used as the taking aperture value, and δ is not limited to 0.035 mm. When this step is completed, the next step (32
In 5), this subroutine is returned.

Next, the flow of the "change distance measuring point" subroutine will be described with reference to FIG. FIG. 2 shows the flow of the "change ranging point" subroutine. Since it is determined that the defocus amount of the selected ranging point is not suitable for the prediction control, another distance measurement that can be predicted and controlled is performed. This is a subroutine for changing to points.

In step (402), it is determined by the AFP whether or not the currently used ranging point is the central ranging point. If the central ranging point is used, the process proceeds to step (40).
Go to 3), otherwise go to step (413).

In step (413), step (40)
In the same manner as in 2), it is determined whether or not the used ranging point is the left ranging point, and if the left ranging point is used,
The process proceeds to step (414), and if the right distance measuring point is used, the process proceeds to step (425).

Steps (403) to (412), (41)
4) to (423) and (425) to (434) indicate changes in the image plane position close to the previous image plane position conversion from the defocus amounts of the ranging points other than the currently used ranging point. This is for selecting a ranging point.

In step (403), the image plane moving speed V1 from the distance measurement two times before to the previous distance measurement is calculated. In the next step (404), the image plane moving speed V2 from the previous distance measurement to the current distance measurement is calculated using the defocus amount DFA of the left distance measurement point.

In step (405), step (40)
The absolute value VA of the difference between V1 and V2 calculated in 3) and (404) is calculated. This is the conventional image plane moving speed V1
And the continuity of the image plane moving speed V2 at the new left ranging point, that is, the continuity. The smaller the value of VA, the higher the continuity.

In step (406), the image plane moving speed V3 from the previous distance measurement to the current distance measurement is calculated using the defocus amount DFC of the right distance measurement point. Then, in step (407), VC representing the continuity when the right ranging point is used is calculated in the same manner as in step (405).

In the next step (408), VA and VC for evaluating the continuity of image plane position change are compared, and VA <V
If C, that is, the continuity at the left ranging point is higher, the process proceeds to step (411), and if not, the process proceeds to step (409).

[0130] At step (409), from the fact that towards the right side of the distance measuring point is higher continuity, enter the defocus amount DFC of the right distance-measuring point in the storage area DF ₃ on RAM. In step (410), "1" representing the right ranging point is input to the AFP representing the ranging point to be used.

[0131] At step (411), from the fact that towards the left distance measuring point is higher continuity, enter the defocus amount DFA of the left distance measuring point in the storage area DF ₃ on RAM. In step (412), "-1" representing the left ranging point is input to the AFP.

When the step (410) or (412) is completed, the routine goes to a step (435). Steps (414) to (423) and (425) to (43)
Similarly, 4) selects a ranging point having high continuity, which is close to the change in the image plane position from the previous two times to the previous time. The operation is the same as steps (403) to (412). Detailed description is omitted.

In step (435), it is determined whether or not the continuity of the image plane position is suitable for predictive control based on the defocus amount of the changed ranging point.
38), if not suitable, step (436)
Move to.

In step (436), since it is determined that the distance measurement point is not suitable for the prediction control even though the distance measurement point has been changed to the most suitable point, "1" is set to the flag ANG for temporarily stopping the prediction control. input. And step (43)
7) In order to return the used ranging point to the center ranging point,
"0" is input to FP. Then, when this step ends, the flow shifts to the step (438), and this subroutine is returned.

In the above-described prediction calculation and ranging point change subroutine, when the continuity of the image is not recognized in step (312) with the defocus data of the ranging point used first, the ranging point is changed. The defocus data at the ranging point having the highest continuity among the three ranging points is detected, and the presence or absence of continuity is determined again in step (435) based on this data. The prediction calculation based on the most continuous defocus data is (313)-
Execution is continued in the step (322). At this time, the value of AFP indicating the ranging point of the defocus data becomes a value corresponding to the ranging point of the data, and the subsequent focus detection is performed according to the defocus data from the changed ranging point. Then, the distance measuring point is changed. Step (435)
However, when the continuity is not recognized, ANG = 1 is set, the prediction process is temporarily stopped, and the lens is driven by the data of the center ranging point.

Next, the "determination of continuity of image plane position" subroutine will be described with reference to FIG.

In step (502), an operation of (DF ₂ + DL ₁ -DF ₁ ) / TM ₁ is performed based on the data in each storage area. This operation is a step of calculating the average value V1 of the image plane movement velocity between time t ₁ and t ₂ of FIG. Calculation in the next step (503) is a step of calculating an average value V2 of the image plane movement velocity between time t ₂ and t ₃ as well. Thereafter, the process proceeds to step (504).

In step (504), step (50)
2) The absolute value VA of the difference between the image plane moving speeds V1 and V2 obtained in (503) is calculated, and the process proceeds to step (505).

In step (505), step (50)
The VA obtained in 4) is compared with a preset number AX. When VA is larger than AX, it is determined that there is no continuity of the image plane position, and when VA is smaller than AX, it is determined that there is continuity.

The principle of judging presence / absence of continuity according to the above flow is based on the fact that if the same object is followed, the image plane moving speed at that time also changes continuously.
Therefore, the image plane moving speeds that are temporally adjacent to each other are calculated, and if this difference is small, it is considered that the image plane moving speed is continuously changing, and it is determined that the same subject is being measured. And perform a prediction calculation. On the other hand, when the change in the image plane moving speed is sufficiently large, it is considered that the image plane moving speed does not continuously change.

FIG. 12 is a viewfinder of a camera having three distance measuring points according to the present embodiment. The distance measuring areas a, b and c in FIG. 12 show three distance measuring areas, respectively.

In this embodiment, a distance measuring point suitable for predictive control is automatically selected from the three distance measuring points. Therefore, a camera that has a viewfinder display that can indicate to the photographer which ranging point is being used, displays the ranging point and informs the photographer of the subject, so that the subject matching the photographer's purpose can be obtained. The photographer can confirm whether or not the prediction control is being performed on the image.
If two or more ranging points are the same ranging data and the ranging points are used, all the ranging points of the same ranging data are displayed, so that the photographer can be further photographed. Can easily recognize which range is in focus.

In the above embodiment, the distance measuring point is selected based on the degree of continuity of the image plane position. Hereinafter, an example in which the contrast of the image signal at each ranging point is detected and a ranging point suitable for predictive control is selected from the contrast will be described. However, the system and main flow of the entire camera are the same as those in the above-described embodiment, and a description thereof will be omitted, and only the prediction calculation and the ranging point changing subroutine will be described.

FIG. 13 shows the flow of the "prediction calculation" subroutine for changing the distance measuring point by the above method.

Step (602) is a subroutine for calculating the contrast of the image signal at each distance measuring point.
The method of detecting the contrast is already known, and a detailed description thereof will be omitted in this embodiment.

In the step (603), it is determined whether or not a counter COUNT for determining whether or not data necessary for prediction has been accumulated is counted up. In this embodiment, when distance measurement data and lens drive data are accumulated three or more times, that is, when COUNT> 2, prediction calculation can be performed, and further counting up is not required. BA step (6
Go to 05). If COUNT <3, COUNT is counted up in step (604), and then the process proceeds to step (605).

In step (605), the data for the current prediction operation is updated. That is, since the prediction calculation is performed based on the equations (6), (7), (8), and (9), the data includes the previous and previous defocus amounts DF ₂ and DF ₁ in FIG. The lens drive amount DL ₁ , the current lens drive amount DL ₂ , the previous and previous and previous time intervals TM ₁ and TM ₂ , and the expected time lag TL are required. Thus the previous defocus amount in each step (605) in which focus detection is performed in the storage area DF _2,
The type a previous defocus amount in the storage area DF _1,
Furthermore the amount of lens driving DL of the previous image plane movement amount converted into the memory area DL _2, the lens drive amount D of the previous last image plane movement amount conversion
Enter the L ₁ in the storage area DL _1, and updates the data necessary data for each storage area in the current prediction calculation.

In the step (606), it is determined whether or not the AFP indicating the position of the distance measuring point used is "0". Here, when the AFP is “−1”, the left ranging point is used, when the AFP is “0”, the center ranging point is used, and when the AFP is “1”, the right ranging point is used. That is, in step (606), it is determined whether or not the center ranging point is being used. If the center ranging point is being used, step (608) is performed.
Otherwise, to step (607).

In step (607), step (60)
In the same manner as in 6), it is determined whether the left ranging point is used. If the left ranging point is used, the process proceeds to step (609), and the right ranging point is used. If so, the process proceeds to step (610).

Steps (608), (609), (61)
0) Enter the defocus amount obtained by the distance measurement in the distance measuring point used this time in the storage area DF ₃ on RAM, to update the data. Here, in step (608), the defocus amount DFB of the center ranging point, in step (609), the defocus amount DFA of the left ranging point, and in step (610), the defocus amount DFC of the right ranging point. You are typing.
When the above steps are completed, the process moves to step (611).

In the step (611), it is determined whether or not data necessary for the prediction operation has been input to each of the storage areas. As described above, the prediction calculation requires the current, previous, and last two times of defocus amount and the last, last and last time of lens drive amount,
The condition is that three or more focus adjustment operations have been performed in the past. Therefore, every time the focus adjustment operation is performed in step (604), the counter COUNT is incremented by one, and the counter is made to count the number of times the focus adjustment operation has been performed. It is determined whether or not the above operation has been performed, and the operation is performed three times or more. If the prediction calculation is possible, the process proceeds to step (612). If the prediction operation is not possible, the process proceeds to step (618).

In step (612), it is determined whether or not the contrast of the image signal at the distance measuring point used for prediction is sufficient to perform focus detection. If so, the process proceeds to step (613).

In step (613), a distance measuring point that can be measured is selected because the distance measuring point used this time cannot be measured. The description of the "change ranging point" subroutine will be described later.

In the step (614), after changing the distance measuring point, A
It is determined whether or not it is possible to predict by NG. If possible, the process proceeds to step (619). 615).

In step (615), COUNT for counting the number of times data has been accumulated is reset so that the prediction control is once performed. And step (61)
In 6), the flag ANG of the prediction possibility determination is reset.

In the step (617), the defocus amount DF of the center distance measuring point is added to the lens drive amount DL in terms of the image plane movement amount.
Enter B. In this case, once the prediction becomes unpredictable, the distance measuring point used when restarting the AF is set as the center distance measuring point. However, this need not be the center distance measuring point. For example, the distance measuring point selected first or the distance measuring point used last may be used.

In step (618), the defocus amount D which has been updated this time to the lens drive amount DL converted into the image plane movement amount.
To enter the F _3.

Then, step (617) or (6)
After the end of (18), the flow shifts to step (628).

In steps (619) and (620), similarly to steps (606) and (607), the distance measuring point used this time is determined by the AFP. If the center ranging point is selected, step (621) is performed.
The process proceeds to step (622) if the left ranging point is selected, and proceeds to step (623) if the right ranging point is selected.

In step (621), the contrast value CNTB of the center ranging point used this time is input to the storage area CNT on the RAM for storing the contrast value of the ranging point used for the previous ranging.

In steps (622) and (623), similarly to step (621), the contrast values CNTA and CNTC of the left or right distance measuring point are input. When step (621) or (622) or (623) is completed, the process proceeds to step (624). The contrast value of the ranging point used this time is stored in the CNT as the next data.

If it is determined in steps (612) and (614) that prediction is possible and the process proceeds to step (619), an expected time lag TL is calculated in step (624). Storage area TM to ₂ as described above, and the time until the current focus detection operation is stored from the previous, under the assumption that a match also TM ₂ time required for focus adjustment of the time, Time lag TL = TM ₂ + TR is determined.

[0163] The next step (625) and (626) each storage area _{DF 1 ~DF 3, DL 1,} DL 2, TM 1,
Based on the data stored in the TM ₂ (6), the process proceeds to (7) of a, A representing the section b, the step obtains the B (627).

In step (627), the data of each storage means, step (624) and step (625),
The calculated value of Expression (9) is obtained based on the calculated value of (626), and this is set as the lens drive amount DL in terms of the current image plane movement amount.

In the next step (628), the lens drive amount DL obtained in steps (627), (617), and (618), the open F-number FN of the photographing lens, and a predetermined coefficient δ (0. 035mm) product FN · δ
And if DL <FN · δ, step (629)
Otherwise, return to step (630).

Next, the flow of the "change ranging point" subroutine used in FIG. 13 will be described with reference to FIG. FIG. 14 shows the flow of the "change focus detection point" subroutine. Since the contrast of the focus detection point selected this time is low and it is determined that focus detection cannot be performed, other focus detection points capable of focus detection can be used. Is a subroutine for changing to

In step (702), it is determined by the AFP whether or not the currently used ranging point is the center ranging point. If the center ranging point is used, step (70) is performed.
Go to 4), otherwise go to step (703).

In step (703), step (70)
In the same manner as in 2), it is determined whether the currently used ranging point is the left ranging point. If the left ranging point is used, the process proceeds to step (717), and the right ranging point is determined. If the distance point has been used, the process proceeds to step (730).

Steps (704) to (716), (71)
7) to (729) and (730) to (742) respectively represent the contrast of the current ranging point other than the currently used ranging point and the previous contrast CNT of the previously used ranging point.
Are compared, and a distance measuring point having a contrast close to CNT is selected. This means that if the objects are the same, it is considered that the contrast of the image signal is also close, and in the predictive control, whether or not the objects are the same is determined by the contrast, and a distance measuring point is selected.

In step (704), a difference CN1 between the contrast value CNTA of the current left ranging point and the contrast value CNT of the previously used ranging point is calculated. In addition, CN
T is the contrast value used last time in step (62).
1) to (623). In step (705), similarly to step (704), a difference between the contrast CNTC of the current right distance measuring point and the CNT of the previously used distance measuring point, CN2, is calculated.

In the next step (706), CN1 and C
The absolute value of N2 is compared, and if | CN1 | <| CN2 |, the process proceeds to step (709); otherwise, the process proceeds to step (707). Here, CN1 and CN2 are the differences between the contrast of each ranging point for which the current distance measurement is performed and the contrast CNT of the previously used image signal. The smaller the absolute value of this value, the closer to the previously used image signal. That is, it is determined that the same subject is measured for distance. Therefore, if the same subject as the previous one enters the left ranging point, the process proceeds to step (709), and if the same subject enters the right ranging point, the process proceeds to step (707).

[0172] At step (707), the memory area DF ₃ on the RAM storing the defocus amount of time to be used for prediction calculation, and inputs the defocus amount DFC of the right distance-measuring point. In the next step (708), "1" indicating that the right ranging point is to be used is input to the AFP, and the flow advances to step (711).

In step (709), step (70)
Similarly to 7), the defocus amount DFA of the left ranging point is set to D.
Input to F _3. Then, in the next step (710), "-" indicating that the left ranging point is used for the AFP.
"1", and the routine goes to Step (711).

In step (711), it is determined whether or not the contrast of the changed distance measuring point is sufficient for performing focus detection. If it is sufficient, the process proceeds to step (743), and if not, the process proceeds to step (712) to change the ranging point.

In step (712), it is determined whether or not the changed ranging point is the left ranging point. If the changed ranging point is the left ranging point, the process proceeds to step (715), and if the changed ranging point is the right ranging point. If so, the process proceeds to step (713).

In step (713), "-1" is input to the AFP to change the distance measuring point to the left. Then, the defocus amount of the left distance measuring point in step (714) in DF _3, inputs the DFA.

In the step (715), "1" is inputted to the AFP to change the distance measuring point to the right. Then, the defocus amount of the right distance measuring point to DF ₃ step (716), and inputs the DFC.

After the step (714) or (716) is completed, the flow shifts to the step (743).

In steps (717) to (729) and (730) to (742), steps (704) to (742)
The ranging point is changed in the same manner as in (716), but the description is omitted here.

In step (743), it is determined whether or not the contrast of the finally selected distance measuring point is sufficient to perform focus detection. If sufficient, the process proceeds to step (746). If the contrast is insufficient, that is, the contrast is low, the flow proceeds to step (744).

In step (744), "1" is input to the flag ANG indicating that the focus cannot be detected, and it is detected that the focus cannot be detected. And in step (745)
To return the ranging point to the center, "0" is input to the AFP, and this subroutine in step (746) is returned.

In the above operation, when the contrast data of the distance measuring point used this time is low, the distance measuring point having a high probability is determined based on the contrast data of the other distance measuring points by using the distance measuring point (7).
04) to (710), if the contrast at this ranging point is high, a prediction calculation is performed based on the defocus signal at the ranging point indicating this contrast, and thereafter, the prediction calculation at the changed ranging point is performed. The prediction calculation lens is driven by the data.
If the contrast at the ranging point changed in steps (704) to (710) is low, the ranging point is further changed,
When the contrast at the re-changed ranging point is high, the prediction calculation is continued with the data at the re-changed ranging point. When the contrast at the re-changed ranging point is also low, the prediction process is temporarily stopped. The lens driving of the normal servo AF based on the data at the center ranging point is performed.

FIG. 15 is a diagram showing the flow of a "low contrast determination" subroutine for determining whether the contrast of the image signal in FIGS. 13 and 14 is at a level at which focus can be detected, that is, whether the contrast is low. It is.

In step (802), the flag CNN for judging whether the contrast of the distance measuring point to be used is low or not is reset.

In step (803), it is determined by the AFP whether or not the focus detection point to be used is at the center. If the focus detection point at the center is used, the process proceeds to step (805). Move to step (804).

In step (804), it is determined by the AFP whether or not the ranging point to be used is the right ranging point. If the left ranging point is used, step (807) is performed.
To step (8) if the right AF point is used.
09).

In step (805), the contrast CNTB at the center distance measuring point is compared with a predetermined number BX, and CNTB is compared.
If> BX, the process proceeds to step (811); otherwise, the process proceeds to step (806). Here, BX is the lower limit of the contrast at which the focus can be detected. If the contrast is higher than this value, the focus can be detected with sufficient accuracy.

At step (805), it is determined that the contrast of the center distance measuring point is low contrast. When the process proceeds to step (806), "1" is input to the flag CNN indicating the low contrast state at step (806). And
Move to step (811).

Steps (807), (808) and (809), (810) are also performed in steps (805), (80)
In the same manner as in 6), it is determined whether or not the contrast is between the left ranging point and the right ranging point. If the contrast is low, "1" is input to CNN, and the flow shifts to step (811).

In step (811), the CNN determines whether or not the camera is in the low contrast state. If the camera is in the low contrast state, the process proceeds to step (813). If not, the process proceeds to step (812). I do.

FIGS. 16, 17 and 18 are diagrams for explaining another embodiment of the prediction calculation and the ranging point changing subroutine. FIG. 16 shows the flow of the "prediction calculation" subroutine. Reference numeral 17 denotes the flow of the "change ranging point" subroutine, and FIG. 18 shows the flow of the "low brightness determination" subroutine.

The gist of the present embodiment is to change the distance measurement point when the distance of a low-luminance object that cannot be measured or is inappropriate for prediction is determined by the luminance determination of the object. Then, a ranging point where a subject having a luminance close to the subject luminance at the previous ranging point exists is selected. As a method of measuring and judging the luminance, the accumulation times TEA, TEB, and TEC of the line sensors at each ranging point are used.
This is because the shorter the accumulation time, the higher the brightness, and the TEA, TE
When the values of B and TEC are large, the subject has low brightness.

The flow shown in FIGS. 16, 17, and 18 is different from the flow shown in FIGS. 13, 14, and 15 in that the processing is performed using the accumulation time data instead of the contrast data. Since it is processed, a detailed description is omitted.

Next, as another example of the prediction calculation, a subroutine for explaining a prediction calculation subroutine for detecting a change in the image plane position of the subject at each ranging point and selecting a ranging point having a large change in the image plane position will be described. The prediction control itself is for causing a fast-moving subject to follow, and the fact that the photographer has selected this prediction mode is a subroutine performed on the assumption that the main subject is a fast-moving subject. In other words, this subroutine is based on the idea that the ranging point having a large change in the image plane position captures the correct subject. FIGS. 19 and 20 are explanatory diagrams of the above subroutine. Since the main flow and the entire camera system share the same flow as in the above-described embodiments, the description is omitted here.

In FIG. 19, step (1202)
It is determined whether or not a counter COUNT for determining whether data necessary for prediction has been accumulated is counted up. In the present embodiment, when distance measurement data and lens drive data are accumulated three or more times, that is, when COUNT> 2, prediction calculation can be performed, and further count-up is not required. If so, proceed to step (1204). Also, COUNT <3
If so, after counting up COUNT in step (1203), the process proceeds to step (1204).

In steps (1204) and (1205), the data for the current prediction calculation is updated.

That is, the predictive operations are (6), (7),
Since the calculation is performed based on equations (8) and (9), the data is the DF of the current defocus amount in FIG.
₃ , the previous and previous defocuses DF ₂ and DF ₁ , the previous lens drive amount DL ₁ , the current lens drive amount DL ₂ , the previous and previous time intervals TM ₁ and TM ₂ , and the expected time lag TL are required. . Therefore, in step (1204), every time the focus detection operation is performed, the previous lens drive amount DL converted into the image plane movement amount is stored in the storage area DL _{2 in the} RAM.
And the lens drive amount DL in terms of the previous and previous image plane movement amounts
Inputs ₂ in the storage area DL _1. And step (12)
05), the defocus amounts DFA, DFB, and DFC detected this time at the respective distance points are stored in the storage areas DFA3 and DFA3, respectively.
DFB3 and DFC3 are input, and the previously detected defocus amounts are input to DFA2, DFB2 and DFC2, and the previously detected defocus amounts are input to DFA1 and DFB.
1, input to DFC1, and updated to data necessary for the current prediction operation.

In the step (1206), it is determined whether or not data necessary for the prediction operation has been input to each of the storage areas. As described above, the prediction calculation requires the current, previous, previous and previous defocus amounts and the previous and previous and previous lens drive amounts, and is conditioned on the fact that three or more past focus adjustment operations have been performed. Therefore, in step (1203), every time the focus adjustment operation is performed, the counter COUN is set.
T is incremented by one, and the counter is made to count the number of times the focus adjustment operation is performed.
That is, it is determined whether or not the operation has been performed three or more times.
The process proceeds to step 7), or if not possible, to step (1209).

Step (1207) is a "ranging point selection" subroutine for performing predictive control and selecting ranging points, the details of which will be described later.

In the step (1208), it is determined whether or not the counter for counting the number of stored data has been reset. If the counter has been reset, the process proceeds to the step (1209).
Go to 19). This is because when the previous ranging point is determined to be inappropriate for the predictive control in the "ranging point selection" subroutine of step (1207), the counter COUNT is determined.
This is because T is reset and the prediction calculation is not performed.

In the step (1209), it is determined whether or not the data necessary for the prediction has been stored twice. If the data has been stored twice, the process proceeds to the step (1210).
Go to step 10), otherwise, go to step (12)
The process proceeds to 18), and the defocus amount DL of the center distance measuring point is input to the lens drive amount DL.

Steps (1210) to (1218)
A distance measuring point having the largest change in the image plane position from the two distance measurement data is detected. In step (1210),
The image plane moving speed VA2 at the left ranging point is calculated, and in the next step (1211), the image plane moving velocity V at the central ranging point is calculated.
B2, In a step (1212), the image plane moving speed VC2 of the right distance measuring point is calculated.

In step (1213), the image plane moving speed VA2 of the left ranging point and the image plane moving speed V of the central ranging point are calculated.
B2 is compared, and if | VA2 |> | VB2 |, the process proceeds to step (1215); otherwise, the process proceeds to step (1214). In step (1215),
Compare the image plane moving speed of the left ranging point and the right ranging point,
If VA2 |> | VC2 |, step (1216)
Otherwise, to step (1217).

In step (1214), the image plane moving speeds of the center ranging point and the right ranging point are compared, and | VB2 |> |
If VC2 |, the process proceeds to step (1218); otherwise, the process proceeds to step (1217).

The above steps (1210) to (1215)
Accordingly, if the image area moving speed VA2 of the left ranging point is the maximum, the process proceeds to step (1216), and if the image plane moving speed VB2 of the central ranging point is the maximum, the step (121) is performed.
The process proceeds to 8), and if the image plane moving speed VC2 of the right distance measuring point is the maximum, the process proceeds to step (1217).

Then, steps (1216) and (121)
7) In (1218), the defocus amount of the distance measuring point at which the image plane moving speed becomes the maximum is input to the lens drive amount DL, and the flow shifts to step (1223).

If it is determined in step (1208) that prediction is possible and the process proceeds to step (1219), the expected time lag TL is calculated in step (1219). Storage area TM to ₂ as described above, and the time until the current focus detection operation is stored from the previous, under the assumption that a match also TM ₂ time required for focus adjustment of the time, Time lag TL = TM ₂ + TR is determined.

Next steps (1220) and (1221)
In each storage _{area, DF 1 ~DF 3, DL 1} , DL 2, T
Based on the data stored in M ₁ and TM ₂ (6),
A and B representing the a and b terms of the equation (7) are obtained, and the flow proceeds to step (1222).

In the step (1222), the data of each storage means and the steps (1219) and (122)
The calculated value of equation (9) is calculated based on the calculated values of (0) and (1221), and this is used to determine the lens drive amount DL in terms of the current image plane movement amount.

In the next step (1223), steps (1223), (1216), (1217) and (121)
Lens drive amount DL obtained in 8) and shooting lens opening F
The number FN and the predetermined coefficient δ (0.03 in this embodiment)
The product FN · δ of 5 mm) is compared, and if DL <FN · δ, the flow shifts to step (1224); otherwise, the flow returns to step (1225).

FIG. 20 shows the flow of the "distance-measuring point selection" subroutine shown in FIG. 19. In this subroutine, a distance-measuring point having a large image plane movement amount and suitable for prediction is detected.

In step (1302), the image plane moving speed VA1 from the previous previous distance measurement to the previous distance measurement and the image plane moving speed from the previous distance measurement to the current distance measurement at the left distance measuring point are determined. VA2 is calculated, and the routine goes to the next step (1303).

In step (1303), step (13)
The change amount VDA of the image plane moving speed at the left ranging point is calculated based on the calculation result of 02), and the flow shifts to step (1304).

In step (1304), step (13)
02), the image plane moving speed VB1, at the center ranging point.
VB2 is calculated, and step (1305) is performed based on this value.
Calculates the image plane moving speed change amount VDB at the center ranging point.

Step (1306) is also performed at step (130).
Image plane moving speed VC at the right ranging point in the same manner as in 2)
1, VC2 is calculated. Then, based on this value, in the next step (1307), the change amount VDC of the image plane moving speed of the right distance measuring point is calculated.

In step (1308), step (13)
03) The image plane moving speed change amount V of the left ranging point obtained in step 03)
DA is compared with a predetermined number AX, and if VDA <AX, the process proceeds to step (1310); otherwise, the process proceeds to step (1309). Here, if the same subject is measured, the image plane moving speed also changes continuously. Therefore,
If the change amount of the image plane moving speed is equal to or less than AX, it is determined that the distance is continuously changing, that is, it is determined that the same subject is being measured. I have.

If it is determined in step (1308) that the distance of another object has been measured, step (1309) is performed so that the data of the left ranging point is not used for prediction.
, "-1" is input to VA2. When this step ends, the process moves to step (1310).

In steps (1310), (1311) and (1312), (1313), step (130)
8) and (1309), it is determined whether the data of the center ranging point and the right ranging point data can be used for predictive control, and a detailed description thereof will be omitted.

In the next step (1314), the image plane moving speed VA2 of the left ranging point is compared with the image plane moving speed VB2 of the central ranging point. If | VA2 |> | VB2 | Go to 1315), otherwise go to step (1316).

In step (1315), the image plane moving speeds VA2 and VC2 of the left and right distance measuring points are compared, and | VA
If 2 |> | VC2 |, the process proceeds to step (1317); otherwise, the process proceeds to step (1321).
In step (1316), VB2 is compared with VC2, and |
If VB2 |> | VC2 |, step (1324)
Otherwise, to step (1321).

In steps (1314) to (1316), a focus detection point suitable for predictive control and having the maximum image plane moving speed is selected. If the focus detection point is the left focus detection point, step (1317) is executed. ), To the step (1321) if it is the center ranging point, and to step (13) if it is the right ranging point.
Go to 24).

At step (1317), it is determined whether or not the selected left ranging point is suitable for prediction.
If = -1, it is determined in step (1308) that it is inappropriate for prediction, so the counter is reset in step (1318), and the flow advances to step (1328). If not, the process proceeds to step (1319).

In step (1319), "-1" is input to AFP representing the ranging point to be used to indicate that the left ranging point is to be used, and the flow advances to step (1320). In step (1320), data D used for prediction is
F ₁ , DF ₂ , and DF ₃ are updated with the data of the left ranging point.

In steps (1321) to (1325) and (1325) to (1327), step (131)
In the same manner as in 7) to (1320), the data is updated to the data of the center or right distance measuring point, and the flow shifts to step (1328) to return this subroutine. Here, steps (1321) to (1325) and (1325) to (1325)
The flow of (27) is the same as (1317) to (1320), and a detailed description will be omitted.

As described above, in this embodiment, it is possible to detect a moving subject and perform predictive control on the subject.

In the embodiments shown in FIGS. 19 and 20, in the first focus detection operation, the lens is driven by the defocus amount from the center distance measuring unit, and in the second laser drive, the image moving at the highest speed is measured. The lens is driven based on the defocus from the distance measuring unit that has moved, and the above-described predictive driving is performed after the third time. At the time of predictive driving, the above-described predictive calculation driving process is performed based on past and present data detected by a distance measuring unit that measures the image moving at the highest speed. At this time, when the moving speed of the previous image is greatly different from the moving speed of the previous image, the predictive driving is temporarily prohibited, and the predictive driving based on data for a subject different from the current subject is prohibited.

In all of the above embodiments, the distance measuring points are selected based on different criteria. However, it is clear that the present invention is effective even if these determining means are combined and used.

Further, in the above-described embodiment, once the ranging point is changed, until the prediction control at the ranging point becomes impossible,
If you do not change the AF point, but the photographer selects the initial AF point, or if you want to mainly use the center AF point, the AF point selected by the photographer or the center If predictive control is possible with the distance measuring point, the control may return to the distance measuring point.

[0229]

According to the first aspect, even if the target is moved to a different position on the screen, the prediction calculation for the target can be appropriately performed and the target captured in each focus detection area can be calculated. Even if the object is different from the previous object, the camera focuses on the object in the center area of the screen, so the photographer captures the object in the center of both sides and shoots while following the object Thus, it is possible to realize an autofocus operation suitable for photographing a moving object having a lot of chances of performing.

Further, according to the present invention, even if the target moves to a different position on the screen, the prediction calculation for the target can be appropriately performed, and each focus can be temporarily detected due to camera shake or the like. Even if the object captured in the area is different from the previous object, focus is performed on the symmetrical object in the area where the object captured in the last autofocus was captured, It is possible to realize the autofocus operation for the object up to that time.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a flow of a “prediction calculation” subroutine as a control flow in a focus adjustment device according to the present invention.

FIG. 2 is an explanatory diagram showing a flow of a “change ranging point” subroutine in FIG. 19;

FIG. 3 is an explanatory diagram showing the principle of lens driving based on prediction.

FIG. 4 is an explanatory diagram for explaining a problem of lens driving according to FIG. 3;

FIG. 5 is a circuit diagram showing an embodiment of a focus adjustment device according to the present invention.

FIG. 6 is an explanatory diagram showing a main flowchart for explaining the operation of the apparatus shown in FIG. 5;

FIG. 7 is an explanatory diagram showing a flowchart of an “image signal input” subroutine in FIG. 6;

FIG. 8 is an explanatory diagram showing a flowchart of a “lens drive” subroutine in FIG. 6;

FIG. 9 is a perspective view illustrating a structure of a focus detection device according to an embodiment of the present invention.

FIG. 10 is a sectional view of a focus detection point shown in FIG. 9;

FIG. 11 is an explanatory diagram showing a flowchart of a “determination of continuity of image plane position” subroutine in FIGS. 1 and 2;

FIG. 12 is an explanatory diagram showing a camera finder having the focus adjustment position of FIG.

FIG. 13 is an explanatory diagram showing a flowchart of another “prediction calculation” subroutine.

FIG. 14 is an explanatory diagram showing a flowchart of a “ranging point change” subroutine in FIG. 13;

FIG. 15 is an explanatory diagram showing a flowchart of a “low contrast determination” subroutine in FIGS. 13 and 14;

FIG. 16 is an explanatory diagram showing a flowchart of another “prediction calculation” subroutine.

FIG. 17 is an explanatory diagram showing a flowchart of a “ranging point change” subroutine in FIG. 16;

FIG. 18 is an explanatory diagram showing a flowchart of a “low luminance determination” subroutine in FIGS. 16 and 17;

FIG. 19 is an explanatory diagram showing a flowchart of another “prediction calculation” subroutine.

FIG. 20 is an explanatory diagram showing a flowchart of a “ranging point selection” subroutine in FIG. 19;

[Explanation of symbols]

 PRS Computer SNS Sensor device LPRS Control circuit

Continued on the front page (72) Inventor Terutake Kadohara 770 Shimonoge, Takatsu-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Tamagawa Office of Canon Inc. In-house (72) Inventor Yasuo Suda 770 Shimo-noge, Takatsu-ku, Kawasaki-shi, Kanagawa Prefecture Canon Inc. References JP-A-1-287512 (JP, A) JP-A-63-94213 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 7/28-7/40

Claims (2)

(57) [Claims] A focus detection circuit for repeatedly detecting detection data according to a focus state in a plurality of measurement areas; a focusing mechanism driving circuit for driving a focusing mechanism based on the detection data obtained by the focus detection circuit; An automatic focus adjustment device that repeatedly performs an autofocus operation, wherein an image of an image of an object after a predetermined time based on detection data obtained by the latest detection operation performed for the autofocus operation and past detection data An arithmetic circuit for predicting and calculating data for moving the focusing mechanism to a position corresponding to the surface position is provided, and focusing is performed based on the data calculated by the arithmetic circuit, and prediction is performed among the plurality of measurement areas. Selecting means for selecting an area where an object suitable for performing an operation is provided; The latest detection data using the detection data from the selected area in stages to the prediction operation further past detection data
Suitable for prediction calculation by the selection means based on the relationship with
An automatic focus adjustment device provided with setting means for setting a specific area at the center of the screen among the areas as an area for an autofocus operation when it is not possible to select an area where the target object exists. . 2. A focus detection circuit for repeatedly detecting detection data according to focus states in a plurality of measurement areas, and a focusing mechanism driving circuit for driving a focusing mechanism based on the detection data obtained by the focus detection circuit. An automatic focus adjustment device that repeatedly performs an autofocus operation, wherein an image of an image of an object after a predetermined time based on detection data obtained by the latest detection operation performed for the autofocus operation and past detection data An arithmetic circuit for predicting and calculating data for moving the focusing mechanism to a position corresponding to the surface position is provided, and focusing is performed based on the data calculated by the arithmetic circuit, and prediction is performed among the plurality of measurement areas. Selecting means for selecting an area where an object suitable for performing an operation is provided; The latest detection data using the detection data from the selected area in stages to the prediction operation further past detection data
Suitable for prediction calculation by the selection means based on the relationship with
Setting means for setting, as an area for the next autofocus operation, an area in which the detection data for the last autofocus operation is formed among the areas when the area in which the target object exists cannot be selected. An automatic focusing device characterized by the following.