JP3140500B2 - Focus detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus detecting device for optical equipment, and more particularly, to a focus detecting device capable of detecting a focus with higher accuracy even when an object has low contrast.

[0002]

2. Description of the Related Art The distance to a subject or the amount of defocus by a photographic lens is photoelectrically determined, and a focus indication for displaying in-focus or out-of-focus or an auto-focus for automatically adjusting the photographic lens. Optical devices such as cameras having a focus function are known. In a focus detection device used in such an optical device, a distance measurement process may be continuously performed in order to reliably determine in-focus and out-of-focus.

However, especially in the case of a focus detection device of the phase difference type, when a subject has a low contrast, a distance measurement error may occur even if the same condition is measured for the same subject. Therefore, even when the lens is once in focus, the lens is determined to be out of focus due to a distance measurement error or the like, and the lens is driven or the in-focus display flickers (blinks). There is.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent inconvenience caused by a measurement error in a focus detection device, particularly at a low contrast.

[0005]

SUMMARY OF THE INVENTION In order to achieve this object, the present invention provides a defocus amount measuring means for measuring a defocus amount for a specific subject, and a method for determining whether the specific subject has a low contrast when the defocus amount is measured. When the contrast determining means determines that the contrast is not low, the defocus amount is selected, and when the contrast determining means determines that the contrast is low, the defocus amount at that time is temporarily determined. The defocus amount is re-measured by re-operating the defocus measuring means in memory and the defocus amount is compared with the memorized defocus amount and the defocus amount re-measured this time, and the smaller one is selected as the defocus amount. And a focus amount selecting unit.

According to this configuration, when the specific subject has low contrast, at least two measurements of the defocus amount are performed.
This is executed twice, and the smaller defocus amount is selected from the two defocus amounts obtained immediately before, so that malfunctions due to measurement errors are reduced.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on illustrated embodiments. FIG. 1 is a block diagram showing a main configuration of an automatic focusing (AF) single-lens reflex camera to which the present invention is applied. This A
The F single-lens reflex camera includes a camera body 11 and a photographing lens 51 detachable from the camera body 11. Most of the luminous flux incident on the camera body 11 from the photographing lens 51 is reflected by the main mirror 13 toward the pentaprism 15 constituting the finder optical system, and a part of the reflected light is received by the light receiving element of the photometric IC 17. (Not shown). On the other hand, a part of the subject light beam incident on the half mirror section 14 of the main mirror 13 passes therethrough, is reflected downward by the sub mirror 19, and
The light enters the CD sensor unit 21.

The photometric IC 17 has a light receiving element for receiving the light beam of the subject, and this light receiving element logarithmically compresses an electric signal generated in accordance with the amount of received light, and a peripheral control circuit 23.
A / D conversion is performed by the main CPU 35 via the. Main C
The PU 35 performs a predetermined exposure calculation based on the photometric signal and the film sensitivity information, and calculates an appropriate shutter speed and aperture value for exposure. Then, based on the shutter speed and the aperture value, an exposure mechanism (shutter mechanism)
The exposure is performed by driving the aperture 25 and the aperture mechanism 27. Further, at the time of release, the peripheral control circuit 23 drives the mirror motor 31 via the motor drive circuit 29 to perform up / down processing of the main mirror 13, and after the exposure is completed, drives the winding motor 33 to release the film. Wind up.

The distance measuring CCD sensor unit 21 is a so-called phase difference type distance measuring sensor.
A split optical system that splits the subject light beam into two parts, and a CCD line sensor that receives and integrates the two split subject light beams (photoelectric conversion and accumulation of the charges). Then, the distance-measuring CCD sensor unit 21 outputs the integration data integrated by the CCD line sensor to the main CPU 35 as control means. The CCD sensor unit 21 for distance measurement is driven and controlled by the main CPU 35 and the peripheral control circuit 23. The CCD sensor unit 21 has a monitor element, and the peripheral control circuit 2
Reference numeral 3 detects the brightness of the subject via the monitor element, and changes the integration time according to the detection result.

The main CPU 35 calculates a defocus amount by a predetermined operation (predictor operation) based on the integrated data output from the distance-measuring CCD sensor unit 21, and based on the defocus amount, the AF motor 39.
Direction and number of rotations (number of pulses of encoder 41)
Is calculated. Then, the main CPU 35 determines the AF motor drive circuit 37 based on the rotation direction and the number of pulses.
The AF motor 39 is driven via the. Further main CP
U35 is the encoder 4 according to the rotation of the AF motor 39.
The pulse output by 1 is detected and counted, and when the count value reaches the number of pulses, the AF motor 39 is stopped. At the time of this drive, the main CPU 35 normally uses a DC
Before driving and before stopping, the AF motor 39 can be controlled at a constant speed based on the interval between output pulses of the encoder 41. The rotation of the AF motor 39 is controlled by the camera body 1.
The light is transmitted to the photographing lens 51 through a connection between the joint 47 provided on the mount portion 1 and the joint 57 provided on the mount portion of the photographing lens 51.

The main CPU 35 includes a ROM 35a storing a program, a RAM 35b,
5c and a counter 35d are built in, and an E ² PROM 43 as a memory means is connected. In this E ² PROM 43,
In addition to the various constants specific to the camera body 11,
Various functions and constants required for the F operation are stored in the memory.

Further, the main CPU 35 has a photometric switch SW which is turned on by pressing a release button (not shown) halfway.
S and a release switch SWR that is turned on by full pressing, an auto focus switch SWAF, and a main switch SWM that turns on / off the power to the main CPU 35 and peripheral devices are connected. The main CPU 35 displays the set AF, exposure, shooting mode, etc., shutter speed, aperture value, etc. on the display device 45. The display devices 45 are usually provided at two positions on the outer surface of the camera body 11 and in the viewfinder.

The main CPU 35 functions not only as control means for controlling the entire camera system but also as focus determination means and moving object determination means.
The sensor unit 21 and the peripheral control circuit 23 constitute a distance measuring means, and the AF motor 39 and the like constitute a lens driving means.

On the other hand, the photographing lens 51 is provided with a focus adjusting mechanism 55 for driving the focusing lens group 53 in the optical axis direction, and a mount portion of the photographing lens 51. A lens side joint 57 that transmits the rotation of the lens 39 to the focus adjustment mechanism 55 and a lens CPU 61 that calculates various data of the photographing lens 51 are provided. The lens CPU 61 includes electric contacts 59, 4
9 and is connected to the peripheral control circuit 23 via the peripheral control circuit 23 to execute predetermined data communication with the main CPU 35 via the peripheral control circuit 23. Lens CP
Data transmitted from the U61 to the peripheral control circuit 23 include the open aperture value Av, the maximum aperture value Av, the focal length,
K value information and the like. The K value information is
The image plane formed by the taking lens is set to a unit distance (for example, 1
mm) This is data on the number of pulses of the encoder 41 (the number of rotations of the AF motor 39) necessary for the movement.

Next, the AF operation of this embodiment will be described with further reference to FIGS. 2-7. This single-lens reflex camera starts AF processing when the photometric switch SWS is turned on. In the AF process, first, the CCD sensor unit 21 for distance measurement starts integration. After the integration is completed, the main CPU 35
Inputs the integral data, calculates the defocus amount and the number of drive pulses based on the data, and drives the AF motor 39 based on the number of drive pulses. Further, in this embodiment, when the subject does not move, an AF single mode in which AF can be locked once the subject is focused, and a focus priority mode in which release is required unless the subject is focused are provided.

The operation up to the moving object tracking AF process will be described with reference to FIGS. FIGS. 2 and 3 are graphs showing the relationship between the position of the subject image plane based on the position of the focusing lens 53 and the position of the film equivalent plane (focus position).

When the photometric switch SWS is turned on and the AF process starts, the lens is driven (the AF motor 39 is driven) based on the driving amount (the number of driving pulses) obtained by the first integration and calculation. In this embodiment, when the photometry switch SWS is turned on and the result of the first integration and calculation results in that the defocus amount (or the number of drive pulses) is larger than a certain amount, the integration and calculation are repeated even during the lens driving. When the defocus amount becomes smaller than the fixed value during the repetition, the subsequent integration and calculation are stopped, and the lens is driven based on the number of drive pulses obtained by the immediately preceding (latest) integration and calculation.
Hereinafter, the integration and calculation processing is also referred to as distance measurement processing.

When the first lens drive is completed, integration and calculation are executed again to check whether or not focusing has been achieved. If the subject is in focus, it is considered that the subject has not moved, but there is a possibility that the subject is moving. Therefore, the distance measurement process is performed again after waiting for a predetermined time. If an interruption due to the turning on of the release switch SWR occurs while waiting for the predetermined time, the release processing is performed, and if the interruption does not occur, the distance measuring processing and the lens driving processing are repeated while the photometric switch SWS is on.

In the continuation processing of the distance measurement and the lens drive, if the subject is not focused once in a plurality of times (three times in this embodiment), the subject is moving (moving object).
And enters the moving object prediction AF mode. Note that the distance measurement and the lens driving process are continued while the photometry switch SWS is on, and then the moving object prediction AF process is started when the in-focus state continues three times after focusing once. You may.

"Moving object prediction AF mode" Next, the moving object prediction AF mode of the present embodiment will be outlined. 4 and 5 are graphs showing an example of the operation in the moving object prediction AF mode processing. When the number C of defocus pulses is obtained by the calculation C based on the result of the integration I when it is determined that the moving object is a subject, the lens driving M is performed based on the number DP of defocus pulses.

When the lens driving M is completed, the integration I _{1 is} again performed.
The performed, defocus moving speed of the pulse number DP ₁ and the subject image from the time T ₁ Tokyo from the midpoint of the previous integration I to the current midpoint of integral I ₁ (object tracing speed) S ₁ at that time The calculated in the calculation C _1. Then, in order to make the subject image plane coincide with the film plane in a short time, the subject following speed S ₁ Of (in this embodiment 2-fold) predetermined times during the velocity at time T ₁ of the performs constant speed control (speed lens drive) M _1. After the double-speed lens drive M ₁ is completed, the subject tracking speed S _{1 is} maintained during the integration I _2.
In performing constant speed control (lens driver) M _2. The constant speed control is a control for driving the AF motor 39 at a constant speed.

When the integration I ₂ is completed, the lens driving M ₂ is stopped, and the calculation C ₂ is performed. In the calculation C ₂ , the subject following speed S ₂ is calculated based on the current number of defocus pulses DP ₂ , the calculated number of movement pulses MP ₁ of the subject, and the time T ₂ between the integrations I ₁ and I ₂ . Then, the time t ₂ minutes required for the calculation C _2, performing double speed lens drive M ₃ at double speed of the object following speed S _2. When the double-speed lens drive M ₃ is completed, the integral I ₃ is started, and the integral I ₃ is started.
₃ during do follow-up lens drive M ₄ by the object following speed S _2.

Further, the focusing lens 53 may be excessively moved by driving the double-speed lens. For example, in FIG. 4, the number of defocus pulses DP ₃ has passed by double speed lens drive M ₃ . This advance amount (the number of defocusing pulses D
If P ₃ ) is equal to or less than the predetermined value, there is no problem even if it is assumed that the subject is continuing to move. Therefore, after the operation C ₃ is completed, the double-speed lens drive M ₅ is performed at the moving object following speed S ₃ .

However, if the overshoot exceeds a predetermined amount,
Since the moving speed of the subject becomes slow or stops, for example, as shown in FIG. 5, a check process for checking the situation without driving the lens is performed.

[0025] In FIG. 5, when a predetermined amount or more of excesses defocus pulse number DP ₄ was obtained by integration I ₄ during the calculation time t ₄ required for the operation C _4, waits without speed lens driving. Simultaneously with the start of the next integration I _5, perform follow-up lens drive M ₇ by the object following speed S ₃ obtained in previous calculation C _4. The data of the integration I _5, when the defocus pulse number DP ₅ within a predetermined amount resulting performs tracking AF process for normal speed lens drive.

However, if the subject image does not fall within the in-focus range even if the check for not driving the double-speed lens is repeated twice, the moving speed of the subject becomes slow, the subject stops, or the subject moves. Since it is considered that the direction has changed, the process exits from the moving object prediction AF mode, returns to the normal AF mode, and performs the processing shown in FIG. 2
By checking the number of times, it is possible to reliably detect that the state of the moving body has changed. In the present embodiment, the process exits from the moving object prediction mode when the number of times of overtaking is too large even if the check is repeated twice, but the present invention is not limited to this number. In the checking process, the tracking lens may not be driven.

[Calculation 1 of Moving Body Following Speed (Subject Image Moving Speed)] A specific method of calculating the moving body following speed S will be described with reference to FIG. 4 and FIG. Initial moving object following speed S ₁
Is calculated based on the number of defocus pulses DP ₁ obtained by the first integration I ₁ after entering the moving object prediction mode and the time T ₁ from the intermediate point of the previous integration I to the intermediate point of the current integration I ₁ It is obtained by the formula. Incidentally, X ₁ is an output period of the pulse encoder 41 outputs (ms). X ₁ = T ₁ / DP ₁ (ms) S ₁ = 1 / X ₁ = DP ₁ / T ₁ (pulses / ms)

The moving object following speed S obtained by the above equation
_By driving the double-speed lens M ₁ for a time corresponding to the integration interval T ₁ at twice the speed of ₁ , the focusing lens 53
Is quickly moved to near the focus. Thereafter, while integrating I ₂ is performed following lens driving M ₂ at a moving object following speed S _1, to follow the movement of the object.

[0029] In the moving object tracking operation "compute second moving object following speed Sn" obtains the moving object tracing speed S _n by the following equation. First, the time T ₂ of the midpoint of the previous integration I ₁ to the current midpoint of the integration I _2, the movement amount on the assumption that the subject image was moving at a moving object following speed S ₁ corresponding speed the lens driving pulse number MP ₁ the corresponding determined by the following equation. MP ₁ = T ₂ × S ₁ ...

Next, the time T ₂ from the intermediate point of the previous integration I _{1 to} the intermediate point of the current integration I ₂ , the number of pulses MP ₁ corresponding to the movement amount within the time T ₂ , and the current defocus pulse several DP ₂ Prefecture, determine the period X ₂ of AF pulses output the moving object following speed S ₂ obtained, obtains the moving object following speed S ₂ from the period X ₂ of the AF pulse output. X ₂ = T ₂ / (MP ₁ + DP ₂ ) (ms) ... S ₂ = 1 / X ₂ = (MP ₁ + DP ₂ ) / T ₂ (pulses / ms) ...

The moving object following speed S ₂ obtained by the above equation
In, between the time required for the calculation C ₂ t _2, performs lens drive M ₂ at double speed of the moving object following speed S _2, after the double speed driving ends, while doing the integral I _3, the moving object following speed S ₂ in performs a follow-up lens drive M ₃ follow the movement of the object.

In this calculation, since the number DP of defocus pulses is a scalar quantity, the sign changes between the front focus and the rear focus. Therefore, by subtracting the current defocus pulse number DP ₂ from the number of pulses MP ₁ corresponding to the amount of movement of the T ₂ hours when overshoot.

The following calculation is represented by the following general formula. MP _n-1 = T _n × S _n-1 ... X _n = T _n / (MP _n-1 ± DP _n ) (ms)... S _n = 1 / X _n (pulses / ms). , And the lens drive and integration based on the calculation result are repeated, whereby the moving object following shown in the figure becomes possible. In the calculation of the present embodiment, the calculated number of movement pulses MP _n−1 of the subject image and the number of defocus pulses DP _n in the calculation are absolute values, so the number of defocus pulses ± DP _{n on} the right side of the equation is Is plus (+) at the time of, and minus (-) at the time of overrun.

[0034] In the above lens driving, after the operation completion is only lens driving time required for the operation at double speed of the moving object following speed S _1, which is the next lens drive exits stop lens driving This is because the image plane is moved by an amount corresponding to the amount by which the subject image moves during this time. That is,
This is because the relationship of _Sn × (lens stop time + lens drive time) = lens drive speed × lens drive time is satisfied by a simpler calculation. Therefore, if the above expression is satisfied, the lens may be driven at another moving object following speed.

[Process at Release Switch ON] The operation when the release switch is turned ON during the moving object prediction AF process will be described with reference to FIG.

Generally, in a single-lens reflex camera, since the mirror is raised after the release switch is turned on, it takes a predetermined time from when the release switch is turned on to when the film is actually exposed. This is called release time lag RTL. Thus, when the subject is a moving object, since the object between the release switch SWR is turned on until the start of exposure is moved (between release time lag RTL), it is desirable to continue the follow-up lens driving.

Therefore, in the present embodiment, it is checked whether or not the release switch SWR is turned on at the end of the calculation.
When that has been turned on, the operation time t ₃ + release time lag RTL corresponding time, performs lens drive M ₃ at double speed of the moving object following speed S _3, release time lag RTL component,
The focusing lens 53 is moved forward.

When the double speed follow-up lens drive M ₃ is completed,
The photometric operation and the mirror-up operation are performed, the aperture is reduced to the value obtained by the operation, and the shutter mechanism 25 is driven at the shutter speed obtained by the operation.

[0039] Although is a process of when the object is approaching, too proactively when the object is moving away, it becomes the so-called after the pin. Since the depth of field is shallower on the near side than the focal point, the front focus is better than the rear focus. In addition, when the subject moves away and the moving speed of the subject is constant, the moving speed of the image plane is temporarily reduced.

Therefore, in this embodiment, when the subject moves away, the double-speed lens is driven only for half the time when the subject approaches. In FIG. 7, the operation C ₄
Only the calculation time t ₄ + release time lag RTL corresponding half hours of time required for, is performed lens driving at double speed of the object following speed S _3.

[Main Processing] Next, the operation of this embodiment will be described in more detail with reference to the flowcharts shown in FIGS. These processes are executed by the main CPU 35 based on a program stored in the internal ROM 35a of the main CPU 35. Further, parameters and the like necessary for the above calculation are stored in the E ² PROM 47.

FIG. 8 shows a routine relating to the main processing of the main CPU 35. When the main switch SWM is turned on, this processing starts, and step (hereinafter abbreviated as “S”) 1
At 01, a system such as each port and memory is first initialized. Next, a power-down process is performed to eliminate unnecessary power consumption, and it is checked whether the photometric switch SWS is turned on. The power-down process and the check process are repeated until the photometric switch SWS is turned on (S103, S105).

When the photometric switch SWS is turned on, the reference timer 35c is started, switch states such as the AF switch SWAF are checked, and lens communication is performed with the lens CPU 61 to open the aperture value, the maximum aperture value, and the focal length. And K value data (S107,
S109, S111). Note that K value data is
This is the number of pulses of the encoder 41 (the amount of rotation of the AF motor 39) required to move the subject image plane formed by the photographing lens 51 by a unit length.

Then, photometric data is input from the photometric IC 17, a shutter speed and an aperture value are calculated by a predetermined algorithm based on the data, the film sensitivity and the like, and the calculated shutter speed, aperture value and other photographing data are calculated. Is displayed on the display device 45 (S113, S11
5).

Next, AF processing is performed to check whether a predetermined loop time has elapsed, and the AF processing is repeated until the loop time has elapsed (S117, S119).
When the loop time elapses, the process returns to S109, and S109 to S
The loop processing of 119 is repeated.

While the loop processing is being repeated, each time the reference timer 35c times out, the reference timer interrupt processing of FIG. 9 is performed. In this reference timer interrupt process, various processes are executed. In this interrupt processing, after counting the loop time, the photometric switch S
WS and the state of the release switch SWR are input (S121, S123). When the release switch SWR is off, or when the release switch SWR is on but the release is not permitted, for example, when focusing is not performed, the process returns to the step before the interruption (S1).
25, S127).

When the release switch SWR is turned on and release permission has been issued, release processing is started. In the release process, first, the mirror motor 31 is activated to perform the mirror-up process, and the aperture mechanism 27 is activated to reduce the aperture to the value calculated in S113 (S13).
1, S133).

Wait until the mirror up is completed, and when the mirror up is completed, the shutter mechanism 25 is driven at the shutter speed calculated in S113 to perform exposure (S135, S
137). When the exposure is completed, the mirror motor 31 is activated to perform the mirror down process and the film winding motor 33.
Is started to wind up the film by one frame, and the process returns to S107 (S139).

[AF Process] Next, the AF process of this embodiment will be described with reference to FIGS. First, it is checked whether the focus mode is the AF mode or the MF (manual focus) mode. If the focus mode is the MF mode, the process jumps to S211 (S2).
01). Note that the AF mode is a mode for performing automatic focus adjustment, and the MF mode is a mode for the photographer to perform focus adjustment.

When the AF process is first entered in the AF mode, since the integration process is not performed, the camera is not in the AF locked state, is out of focus (the IN FOCUS flag is "0"), and the reintegration flag is cleared. Proceed to S211 (S20
5, S209). In the second and subsequent processes, if the AF is in the AF locked state, the process jumps to the AF lock process. If the AF is not in the AF locked state, the AF lock flag is set if the camera is in focus, that is, after waiting for a predetermined time after focusing once. The process proceeds to the reintegration process (S203, S205, S207). After the second time, since the reintegration flag is set, the process proceeds to the reintegration process (S209).

At the time of the first AF process or in the manual focus mode, the flow proceeds to S211 (S20).
1, S203, S205, S209). In S211,
In step S213, it is checked whether the camera is operating in the AF mode. During AF operation (AF1
If it is the first time), the process proceeds to S231, and the AF operation is not in progress.
If the MF operation is being performed, the distance measurement process and the in-focus / out-of-focus display process are performed (S215 to S227).

In S215, integration and calculation processing are performed, and it is checked whether the calculation result is valid (S217). If the calculation result is valid, the focus display processing is performed if the focus is achieved, and the focus display LE of the display device 45 is displayed.
D (not shown) is turned on, and furthermore, a process of emitting a sound indicating that the electronic buzzer 46 is in focus is performed, but if it is not in focus, the upper focus display process is not performed (S21).
9). Further, when the subject is low-contrast and out-of-focus processing is performed for the first time, the process jumps to S229, and if not, it is checked whether the subject is in focus (S221, S22)
3). If the camera is in focus, the release permission flag during AF is set, and the flow advances to S229 (S223, S22).
5) If not in focus, clear the secondary focus width, clear focus, release permission and AF lock flag,
The in-focus display on the display device 45 is turned off and the electronic buzzer 46 is turned off, and the process proceeds to S229 (S223, S227).

Even when the calculation result is invalid, the secondary focus width is cleared, the focus, the release permission and the AF lock flag are cleared, the focus display on the display device 45 and the electronic buzzer 46 are performed.
Is turned off and the process proceeds to S229 (S217, S227). S
At 229, the loop time is checked, and if the loop time has not elapsed, the flow returns to S211 to repeat the above processing, and returns to S109 of the main routine when the time has elapsed.

If the AF operation is being performed at the time of the check in S211, the process proceeds to S231 to start the AF process. In S231,
Performs integration and arithmetic processing. Then, it is checked whether the calculation result is valid, and if it is valid, the process jumps to the focusing check process (S233). If a valid calculation result has not been obtained, it is checked whether the mode is the auxiliary light projection mode . The auxiliary light emitting mode is an auxiliary light emitting device (not shown) for the object when the object brightness is lower than a certain value.
This is a mode in which auxiliary light (striped pattern) is projected from. In the auxiliary light projection mode, it is difficult to follow a moving object, so a moving object prediction mode prohibition flag is set (S237). Then, the auxiliary light is projected, integration and calculation are performed, and the calculation result is checked. If the calculation result is valid, the process proceeds to the focusing check process, and if not, the process proceeds to S243 (S23).
9, S241). If the mode is not the auxiliary light projection mode, the process jumps from S237 to S241 and proceeds to S243.

In S243, since the calculation result is not obtained, search integration and calculation for detecting the in-focus point are performed while the AF motor 39 is driven by DC (S24).
5) Check whether the calculation result is valid. If not, search integration and calculation are executed again. If valid, the process jumps to the driving direction check process (S245, S2).
47).

[Reintegration and Focus Check Processing] Next, a subroutine relating to the reintegration and focus check processing will be described with reference to FIGS. 11A and 11B.

The reintegration process is a second and subsequent integration processes. In the reintegration process, first, a reintegration flag is set, and then the integration and defocus amount calculation processes are performed (S25).
1, S253). If the calculation result of the defocus amount is invalid, the process jumps to the AFNG process, and if it is valid, the process proceeds to the focus check (S255).

In the focusing check process, it is checked whether or not the camera is in focus. If the camera is in focus, the focusing display LED of the display device 45 is turned on and the electronic buzzer 46 is activated. If nothing is done (S261).

Next, it is checked whether or not it is the first out-of-focus condition at the time of low contrast. If it is the first time, the process returns to S251 to repeat the above-described processing such as integration. If it is not in the moving object prediction mode, the release permission flag at the time of AF is set (S26).
3, S265, S267, S269). If it is not in the AF lock state (if the AF lock flag is not set), that is, the AF lock flag is set in the first processing after focusing, but if it is already set, the processing after the second focus is executed. so jump in AF lock processing (S28 2) (S271S273).

When the AF lock flag is set in S273,
Waiting for a release interrupt for a predetermined period of time on condition that the subject has a high contrast and the moving object prediction prohibition flag is falling, and if the release interrupt is not received within the predetermined time, clear the release permission flag during AF and release. Is prohibited, and the AF lock flag is cleared to enable the AF process (S275, S277, S279, S281).
Then, the process enters the AF lock process, waits for the elapse of the loop time, and returns to S109 of the main routine after the elapse of the loop time (S283). The AF lock process is a process in which the AF operation is not performed while the photometry switch SWS is on. If the subject is not high contrast,
If the moving object prediction prohibition flag is set, the process proceeds to the AF lock process without performing the weight process (S275, S277,
S283).

If it is determined in the focusing check process in S265 that the subject is out of focus, the process jumps to S285 to check whether or not the moving object prediction mode is set. Here, if the moving object prediction mode has not been entered, the flow proceeds to the moving object check processing in S301 and subsequent steps. If the moving object prediction mode has been entered, the flow proceeds to S321 (S285).

This moving object check process is a process for confirming whether or not the subject is a moving object (see FIGS. 2 and 3). In the moving object check processing, first, the flags of the secondary focus width, the focus, the release permission, and the AF lock are cleared, and the focus display LED of the display device 45 and the electronic buzzer 46 are turned off (S301).

Next, the reintegration flag is checked. If the reintegration flag is cleared, the process is the first process, so the process jumps to the pulse calculation process. (S303, S3
05). If the directions are the same, the moving object determination counter is decremented by 1 on the condition that the high contrast and the moving object prohibition flag are cleared (S307, S309,
S311, S313). The initial value of the moving object determination counter is set to "3". When the direction is not the same, when the contrast is not high, or when the prediction of the moving object is prohibited, the process directly jumps to the pulse calculation process without performing the counting process (S307, S309, S311).

When the moving object judgment counter is decremented, the counter value is checked. If the counter value is 0, the moving object prediction mode flag is set, and the moving object judgment counter is reset (set to 3 in this embodiment). From step (S315, S317, S319). Counter value is 0
If not, the process directly proceeds to the pulse calculation process (S31)
5).

If the moving object prediction mode has already been entered at the time of the moving object prediction mode check in S285, the in-focus flag, the release permission flag and the AF lock flag are cleared.
Focus display LED of display device 45 and electronic buzzer 46
Is turned off (S321).

Next, the number of defocus pulses is calculated based on the integration result in S253 (S323).
Note that the number of defocus pulses is a value for the subject at an intermediate point of the integration time.

Then, the calculated number of movement pulses of the object is
The moving speed (moving object following speed) of the subject image is calculated based on the current defocus pulse number and the time between the integration intermediate points, and when the calculation is completed, a moving object following flag is set to identify that the moving object is being followed ( S325, S32
7). Then, the number of defocus pulses is counted by a counter 35d.
, The AF motor constant speed control is started, and the process jumps to the constant speed control process (S329, S331).

In step S2 in the focusing check process,
In the moving object prediction mode check in step 67, if the moving object prediction mode has already been entered within the focusing range, the process proceeds to step S32.
Enter 3.

[Pulse Calculation and Backlash Driving] Next, pulse calculation and backlash driving will be described with reference to FIGS. 12A and 12B. The pulse calculation process is a process of calculating a pulse amount based on the defocus amount and a pulse amount for backlash removal. The backlash drive refers to a built-in gear of the AF motor 39 when the drive direction of the AF motor 39 changes.
This refers to driving for taking backlash in the joints 47 and 57 and the lens driving mechanism 55. In the present embodiment, the backlash drive is separately executed before the drive based on the defocus amount.

In the pulse calculation process, first, the amount of defocus pulse is calculated, and when the driving direction changes from the previous time, the number of backlash pulses is calculated, and a backlash driving flag is set (S351, S353). The backlash pulse amount is the number of pulses and the direction of rotation required to take backlash. The backlash amount of the camera body 11 is stored in the E ² PROM 43 in advance, and the backlash amount of the photographing lens 51 is
It is stored in the ROM of the PU 61 and is stored in the RAM 35 b of the main CPU 35 via the peripheral control circuit 23 by lens communication.

Next, when the backlash drive flag is not set, the number of defocus pulses is set to the counter as the number of AF pulses when the backlash drive flag is set, and the DC drive of the AF motor 39 is started (when the backlash drive flag is set). S355, S357). Note that the DC drive in the present embodiment means that the AF motor 39 is driven almost directly.

When the backlash drive is not performed (when the backlash drive flag is cleared) and when the mode is not the moving object prediction mode (when the moving object prediction mode flag is cleared), the count value of the counter and the predetermined number of pulses are set. When the count value is larger, the moving object prediction mode flag is cleared, the overlap integration is started, and the defocus pulse amount is calculated (S36).
9). Note that the overlap integration is a process of performing integration while driving a lens.

When the number of defocusing pulses is obtained, it is checked whether the number of defocusing pulses is valid. If the number is valid, the process returns to S363. If the number is valid, the process proceeds to the driving direction check processing (S373 to S375 ) (S373 to S375 ). S37
1).

In the driving direction check processing, whether the focus position is closer to the object image position than the subject image position based on the defocus amount is determined.
Further, it is checked whether it is within a predetermined range (S37).
3, S375). And the focus position is out of the predetermined range
If it is also before , the number of defocus pulses is calculated based on the defocus amount calculated in S369, set to the counter, and returns to S363 (S375, S377). Overtaking
If it is within the predetermined range , the AF motor 39 is braked to stop driving the lens, and the process returns to the reintegration process (S375, S379). Note that the brake of the AF motor 39 means that the input terminal of the AF motor 39 is short-circuited in this embodiment.

When the backlash drive is required, when the moving object predicting mode is entered, or when the counter value is smaller than a predetermined pulse, the AF pulse counter value is compared with a predetermined pulse number to perform the AF. Wait until the counter value becomes equal to or less than the predetermined number of deceleration pulses (S359 to S3
65, S381, S383).

When the AF pulse counter value becomes smaller than the predetermined number of deceleration pulses, the AF pulse counter is used when the backlash drive is not performed.
After the brake is applied to the motor 39, the process jumps to the constant speed control process (S385, S387).

At the time of backlash drive, the number of AF pulses is compared with a predetermined number of pulses. If the number of AF pulses is less than the predetermined number of pulses, the AF motor 39 is braked and the process proceeds to a constant speed control process (S389, S391, S38).
7). Then, backlash removal driving is performed by constant speed control.

If the number of AF pulses is equal to or greater than the predetermined number of pulses, the process waits until DC driving for backlash removal ends. Then, when this DC drive is completed, the brake is applied to the AF motor 39, the backlash drive flag is cleared, the backlash drive is completed, and the process returns to S355 (S391, S393, S395, S397). Then, the number of defocus pulses is set in the AF pulse counter, and lens drive processing for normal AF processing is performed.

With the above processing, driving for the backlash is executed before driving for the defocus. Moreover,
When the driving amount of the defocus pulse is larger than a predetermined value, the driving is executed in a short time by DC driving, and when the driving amount is smaller than the predetermined value, accurate driving without excessively moving is performed by constant speed control.

[Constant Speed Control] The constant speed control processing will be described based on the constant speed control processing shown in FIGS. 13A and 13B. The constant speed control process is a process of driving the AF motor 39 at a constant speed. In the present embodiment, the main CPU 35 controls the AF motor 39 to control the AF motor 39 at a predetermined constant speed based on the interval between pulses output from the encoder 41. Drive control. In the present embodiment, the AF motor 39 is driven at a constant speed at the moving speed S of the subject image or twice its speed.

In the constant speed control process, first, the constant speed control speed of the normal process is set (S401). Then, to check whether in motion tracking, if in the moving object tracking, sets the double speed 2S _n constant speed control speed S _n (S403, S405). If during the integration, proceeds after setting the constant speed control speed S _n in order to follow in moving object tracking speed S411, the process directly proceeds to S411 if not during the integration (S407, S409).

In step S411, it is checked whether the integration is being performed and the moving body is being tracked. If the integration is being performed and the moving body is being tracked, the process jumps to step S459 to check whether the integration is completed. If not, S413
(S411).

In S413, it is checked whether or not the constant speed control time has elapsed, and if it has elapsed, the process proceeds to a check process (S415) as to whether or not the end point has been reached, and if not, the process proceeds to S421. In S421, it is checked whether the AF pulse is output from the encoder 41. If the AF pulse is not output, the process returns to S411, and if it is output, the process proceeds to S423.

In S423, it is checked whether the pulse count has been completed or whether the drive time for moving object tracking has been completed. If any of them has been completed, the process proceeds to the brake process, and if none of them has been completed, the process proceeds to the end point check process (S423, S437, S425).

In S425, it is checked whether or not the focusing lens 53 has reached the end point, and the end point detection timer is reset. Then, for deceleration processing, it is checked whether the count value of the AF pulse counter has become smaller than the number of speed switching pulses, and when the count value has become smaller, the drive speed is switched to low speed, and then the AF motor 39 is braked. Proceed to S433 (S427, S4
29, S431). In step S433, it is checked whether the AF motor 39 is being driven.
After the brake is applied to No. 9, the process returns to S401. If the vehicle is not being driven, the process directly returns to S401.

In step S423, if the pulse count has ended or the driving time for following the moving object has ended, the flow advances to step S437 to brake the AF motor 39 in order to stop the AF motor 39. Then, it is checked whether the moving object prediction mode and the AF lock flag are set, and if so, the AF release permission flag is set, and the process proceeds to the release process (S439, S441, S441).
443). If the mode is not the moving object prediction mode or the AF lock flag is cleared, it is checked whether or not the backlash drive is being performed. If the backlash drive is performed, the process proceeds to the backlash drive end processing. To check the loop time, and when the loop time elapses,
Returning to the E process, the process proceeds to the reintegration process if the loop time has not elapsed (S445, S446, S447).

In the integration process, initialization is performed for integration and calculation, integration is started, and an integration flag is set (S451, S453, S455). If it is following the moving object, the process jumps to the constant speed control process (S401). If it is not following the moving object, it is checked whether or not the integration is completed (S457, S459).

If the integration is not completed, if the integration time is longer than the predetermined time, it is considered that the subject brightness is low. Therefore, the moving object prediction mode prohibition flag is set, and the process proceeds to S465. If the integration time is short, the process directly proceeds to S465 (S459, S461, S4).
63). Then, if not following the moving body, the process returns to S459,
It waits until the integration is completed (S459 to S465). If the moving object is being tracked, the process returns to S413 because the constant speed control is being performed. When the integration is completed, the brake is applied to the AF motor 39 if the tracking drive is being performed, the integration data is input from the distance measurement sensor unit 21, the defocus amount is calculated, and the process returns to the step next to the step where the integration was started. (S46
7, S469, S471, S473).

[Defocus Calculation] The defocus calculation processing will be described with reference to the calculation processing shown in FIG. First, a contrast calculation and a check process are performed (S501). The calculation of the contrast is a calculation for calculating the sum of the differences between the integrated data of the respective CCDs of the CCD ranging sensor unit. Then, it is checked whether the contrast is sufficient for calculating the phase difference. If the contrast is not sufficient, the process returns. If the contrast is sufficient, the process proceeds to the phase difference calculation process (S503, S505).

In S505, first, a phase difference is calculated by a correlation method or the like. If the mode is the 10-bit select mode, the process proceeds to S551 of the 10-bit select process. If the mode is not the 10-bit select mode, the process proceeds to S509 of the normal calculation process (S507). When entering first, the process proceeds to S509 because the 10-bit select mode has not been entered. In addition, 10
In the bit select mode, when the degree of coincidence (correlation) between the integrated data of the reference part and the reference part of the CCD line sensor is not very good, a 10-bit area of each of a plurality of areas is selected from the reference part and the reference part. This is a process of sequentially selecting and obtaining a region having a high degree of coincidence (high correlation).

In step S509, it is checked whether the phase difference calculation result is valid. If not, the process returns.
If it is valid, it is checked whether the matching degree is good (S509, S511). If the coincidence is good, the defocus calculation is executed (S511, S530 ). If the first out-of-focus flag at low contrast is set and the defocus amount is less than a predetermined amount, the previous and current defocus amounts are compared, and if the current defocus amount is smaller, The current defocus amount is set as an effective value, the defocus amount OK flag is set, and the process returns (S53).
5, S537, S539, S541, S543). If the first non-focus flag at low contrast is not set, the current defocus amount is made valid, the defocus OK flag is set, and the process returns (S533, S541, S543).

Even if the first low-conversion defocus flag is set, if the defocus amount is equal to or more than the predetermined value, the previous defocus amount is made valid, so that the defocus OK flag is set and the process returns (S533, S535, S535). S54
3). Even if the first non-focus flag at low contrast is set and the defocus amount is smaller than the predetermined value, if the defocus amount is larger this time than the previous time, the defocus O
The K flag is set, the previous defocus amount is maintained, and the process returns (S533, S535, S537, S53).
9, S543).

According to the above processing, when the subject has low contrast, the closer (smaller) of the two immediately preceding defocus amounts is used as the measured value. Flicker and erroneous activation of the AF motor 39 can be prevented.

If the degree of coincidence is not very good, the phase shift is compared with a predetermined value. If the shift is smaller than the predetermined value, it is checked whether or not the contrast is high. If the contrast is low, the flow proceeds to S530 ( S5
21, S523). 10 for high contrast
The first 10 bits are selected by setting the bit select mode flag and the moving object prediction mode prohibition flag, the number of checks is further set, and the process returns to S505 (S523, S525, S527, S529).

When the 10-bit select mode flag is set,
The process enters a 10-bit select process from S507. In the 10-bit select processing, first, it is checked whether or not the effective value of the defocus amount based on the selected 10-bit has been obtained at one time. If the previous
In order to invalidate the DATA, the 10-bit select defocus OK flag is cleared, and the process proceeds to S559 (S551, S551).
553, S555, and S557). If the 10-bit select defocus amount has not been obtained even once, the process proceeds to step S559.
The process proceeds to S559 without clearing the 10-bit select defocus OK flag (S551 to S557). If the contrast is smaller than the previous time,
Since 0-bit data is not used, the process jumps to S571 (S55).
1, S555).

In S559, it is checked whether or not the result of the phase difference calculation is valid. If the result is valid, the defocus calculation is performed on condition that the degree of coincidence is good (S55).
9, S561, S563). If the 10-bit select defocus OK flag is set, the closest (front) defocus amount between the previous time and the current time is selected, and the 10-bit select defocus OK flag is set.
The select OK flag is set, and the process proceeds to S571.
t If the select defocus OK flag is cleared, do nothing and set the 10-bit select OK flag and proceed to S571 (S565, S567, S569). Also, when the phase difference calculation result is invalid or the degree of coincidence is poor, the process proceeds to S571 without calculating the defocus amount (S559, S561).

In S571, the next 10 bits are selected. Then, the 10-bit select counter is decremented by 1. If the counter value is not 0, the process returns to S505 and repeats the processes of S507 and S551 to S575 until it becomes 0 (S573, S575). In addition, 10bi
t The initial value of the select counter is set to "4". If the value of the 10-bit select counter is 0, the low-contrast flicker countermeasure processing is performed on condition that 10-bit select defocus is OK ( S575, S57).
7, go to S533), if not OK, clear the 10-bit select mode flag and return (S575,
S577, S579).

The above S505, S507, S551 to S
575 CCD with good phase difference and degree of coincidence
The integral data from the sensor bit group can be selected. In this embodiment, the number of bits to be selected is 10
Although the bit is set, it is not limited to this, and may be set to an arbitrary number of bits.

[Calculation of Moving Object Tracking Speed] The calculation of the moving object tracking speed will be described with reference to the calculation processing shown in FIG. First, calculate the time T _n between the previous integration midpoint and the current integration midpoint (S601).
The reason why the integration intermediate point is used as a reference is that the integration time changes depending on the subject luminance.

Next, if it is not in motion follow-up, to return to calculate the object image moving speed S ₁ before tracking (S6
05). If the moving object is being tracked, the number of movement pulses MP _n−1 of the subject image that would have moved within the time T _n is calculated (S607). Then, by comparing the previous and current drive direction of the lens, to clear the flag overshoot body being followed if the same direction, by adding the current DP _n to MP _n-1 tracing speed correction calculation processing (S617) Go on (S609,
S611, S613, and S615). If the direction is different, the moving speed of the subject slows down or stops too much,
Alternatively, since it is considered that the moving direction of the subject has changed, the process proceeds to S637 (S609, S611, S637). If it is not the same direction or different direction, that is, if any abnormality occurs, the moving object prediction mode is cleared and the process proceeds to the reintegration process (S611, S613, S655).

[0102] In "tracing speed correction calculation 1" tracing speed correction calculation 1 first calculates the object tracing speed S _n by the following equation (S617). _{X n = T n / (MP} n-1 + DP n) S n = 1 / X n = (MP n-1 + DP n) / T n

Next, the moving object following time C _n (the sum of the integration data input time and the calculation time) is set (S621). Then, there the current calculation result in focus, and if the release switch SWR is turned on, and sets the AF lock flag, time lag correction time (integration data input time + calculation time C _n + release time lag equivalent time) When the subject moves away, the constant speed control time is set to の of the time lag correction time, and when the subject approaches, the constant speed control time is set to the time lag correction time and the process returns (S623, S625, S6
27, S629, S631, S633, S635).

If the focus switch is not in focus or the release switch SWR is not turned on even in focus, the follow-up operation is continued. Therefore, the flow jumps to S635 to set the constant speed control time to the moving body follow-up time. The process returns (S623, S625).

When the previous and current driving directions of the lens are different, if MP _n−1 −DP _n ≧ 0, MP _n−1 −DP _n is calculated, and the following equation is obtained: X _n = T _n / (MP _{n− 1} -DP _n) by _{S n = 1 / X n =} (MP n-1 -DP n) / T n perform the correction calculation of the moving object tracing speed S _n, checks the status of the release switch SWR (S639,
S641).

If the camera is in the in-focus state, the moving object following follow-up flag is reset and the process returns (S643, S64).
645). If it is not in focus, it is checked whether the moving object following passing flag has already been set, and if not, the following following flag is set, the calculation time C _n is set, and the calculation time C _{n is} waited. Before proceeding to the reintegration process (S647, S649, S651, S65
3). If the moving body following flag is already set, the moving body prediction mode is cleared and the process returns (S647, S655).

[Focus Check Process] The focus check process will be described with reference to FIG. In this focusing check process, the range of focusing is expanded when the moving object is being tracked , increasing the possibility of release.
You.

First, in the AF mode, a preset focusing width (a predetermined defocus amount regarded as focusing )
If the moving object prediction mode is set, the focusing width is expanded, and it is checked whether the current defocus amount is smaller than a predetermined amount (S701, S703, S705).

First, if the defocus amount is larger than a predetermined amount (an amount larger than the focusing width), the low-contrast out-of-focus 1
The process returns after resetting the second time flag (S719).

If the defocus amount is within the predetermined amount and the camera is in focus (less than the focus width), the focus flag is set, the low-conversion non-focus flag is cleared, and the display 45 is displayed. The focus indication LED is turned on, and the electronic buzzer 46
(S705, S707, S709, S71)
1, S713).

If the AF operation is being performed, the focus width corresponding to the predetermined moving speed of the image plane for checking the moving object is set, and the process returns. If the AF operation is not being performed, the process returns (S715, S717).

When the defocus amount is equal to or larger than the in-focus width and smaller than a predetermined amount, low-contrast flicker countermeasure processing is performed. If the first low-conversion in-focus flag has already been set, or even if it has not been set, in the moving object prediction mode, the low-con low-focus out-of-focus flag is cleared and the routine returns (S721, S723, S719).

If the first flag at low contrast has been cleared and the moving object prediction mode has not been entered, the routine directly returns to the auxiliary light projection mode (S721,
S723, S725). If the mode is not the auxiliary projection mode and the mode is the 10-bit select mode, the low-conversion first out-of-focus flag is set and the process returns (S7).
25, S733). When the mode is not the 10-bit select mode, if the integration time is longer than the predetermined value, the process returns as it is. Even if the integration time is shorter, the process returns as it is if the contrast is not low contrast. Set and return (S729, S731, S733).

As described above, when the process is not focused on for the first time, the low-contrast first out-of- focus flag is set at the time of low contrast, and the process returns. Even if the focus changes from in-focus to out-of-focus, the out-of-focus display process (the process of S301) is not performed at the first out-of-focus time, so that the in-focus display flicker is prevented. In this embodiment, the out-of-focus display is performed when the out-of-focus state is repeated twice. However, the number of times of the out-of-focus state changing to the out-of-focus state is arbitrary. In such a case, an out-of-focus display may be performed.

[End Point Detection Processing] Next, processing performed when the focusing lens 53 has reached the closest focus position or the infinity focus position will be described with reference to the end point detection processing shown in FIG. explain. This process
The AF motor is stopped by detecting a state where the end point has been reached or the end point has not been reached, but the focusing lens group 53 cannot be driven by some external force.

It is checked whether the AF motor is being driven,
If it is not driving, the process proceeds to the end point detection timer reset processing (S791). When the AF motor 39 is being driven, when the pulse interrupt flag is set (when a pulse is output from the encoder 41), the process proceeds to the end point check (S771). When the pulse interrupt flag is not set (when no pulse is output), the end point is detected. Proceed to timer count (S755).

The end point detection timer count process is performed when the pulse is not output from the encoder 41 for a certain period of time irrespective of the AF motor 39 being driven, the focusing lens 53 has reached the end point or cannot move. Therefore, this is a process for stopping the AF motor 39. Here, first, the pulse presence flag is cleared when the end point is detected, the counting flag during the end point detection is set, and the end point detection timer is counted down (S75).
5, S757, S 759). Then, it is checked whether or not the endpoint detection timer is 0. If the timer reaches 0, the process proceeds to the endpoint process. If the timer is not 0, the process returns (S801).

The end point check processing detects whether the focusing lens 53 has reached the end point by detecting a change in the pulse output from the encoder 41. Here, first,
The pulse interrupt flag is cleared (S771).

Then, it is checked whether or not the end point detection timer is counting. If the count is not being performed, or if the pulse presence flag is set when the end point is detected even if the end point detection timer is counting, the end point detection timer is set. The process proceeds to the resetting process (S775, S777). If the end point detection timer is counting and the end point pulse existence flag is not set, the end point detection pulse is set at the end point detection. If the constant speed control is being performed, the routine returns. If not, the flow proceeds to S757 (S777). , S77
9, S781).

The end point detection timer resetting process is a process for initializing data relating to the end point detection. The end point detection timer counting flag and the pulse presence flag at the time of the end point detection are cleared, and the end point detection timer data is set. The process returns (S791, S793, S795).

[Second Example of Moving Object Prediction AF] Next, a second example of the moving object prediction AF according to the present invention will be described with reference to FIGS. The second embodiment is characterized in that constant speed control is performed even during calculation. That is, a method of calculating a lens driving speed corresponding to a moving speed of a subject image and correcting the following speed by performing integration while controlling the focusing lens at a constant speed at the calculated speed. The basic principle is the first embodiment. Is the same as described above, except that the constant speed control is performed even during the predetermined calculation. In this embodiment, the CPU 36 for controlling the motor drive IC 37 is provided to execute the calculation and the constant speed control in parallel.

First, the DC lens driving M is performed based on the defocus pulse DP when it is determined that the moving object prediction mode is set (when the moving object prediction mode is entered). When the DC lens drive M is completed, the integration I ₁ is performed. In the operation C ₁ , the speed S ₁ at which the subject image moves during the time T ₁ between the intermediate points of the integrations I and I ₁ is calculated in the same manner as described above and the equation. The lens driving time is calculated by the following equation. _{(T 1 + (I 1/} 2) + C 1) / 2 ...

Then, for the driving time calculated by the above equation,
Performing constant speed control lens drive M ₁ at triple speed following speed S _1. The constant speed control lens drive M _1, can be moved to the vicinity of the focus of the focusing lens 53 in a short time. Incidentally, the 3-speed _{driving, (T 1 + I 1/} 2 + C
Substantially the same effect as ₁₎ time just to that lens driving at double speed of the object image moving speed S ₁ is obtained.

When the control lens drive M ₁ at the triple speed is completed, the integration I ₂ and the calculation C ₂ are performed while performing the constant speed control (lens drive M ₂ ) at the following speed S ₁ . In this operation C _2, the time T ₂ of the midpoint of the previous integration I ₁ to the current midpoint of the integration I _2, the subject image at a tracing speed S ₁ is of the object image when it is assumed to have been moved the number of pulses MP ₁ corresponding to the amount of movement calculated by the same equation as the above equation _{(MP 1 = T 2 × S} 1). Further, the speed S ₂ at which the subject image has moved during the time T ₂ is obtained by the following expression similar to the above and the expression. X ₂ = T ₂ / (MP ₁ + DP ₂ ) S ₂ = 1 / X _{2 During} integration I ₃ and calculation C ₃ , the constant speed control lens drive M ₃ is performed at the following speed S ₂ .

Thereafter, similarly, within the time T _n ,
_The number of pulses MP _n-1 corresponding to the amount of movement of the subject when it is assumed that the object is moving at the speed of _n-1 (MP _n-1 = T _n × S _{n-2 for the} second and subsequent operations during tracking) seeking tracing speed S _n, the integral I _{n + 1} and the calculation C _{n + 1} while performing, tracing speed S _n by (constant speed control) lens drive M
Perform _{n + 1} .

By the following control described above, a substantially in-focus state is always maintained for the moving subject. Further, when the release switch is turned on during the follow-up operation, while the mirror-up also performs constant speed control at a tracing speed S _n obtained immediately before (see Figure 19). By the constant speed control during the mirror-up operation, when the shutter first curtain actually starts running (exposure start), it is almost in focus.

Next, the second moving body following operation will be described with reference to FIG.
0 and the flowchart shown in FIG. First, calculate the time T _n between the previous integration midpoint and the current integration midpoint (S801).

Next, it is checked whether or not the moving object is being tracked.
If the moving object is not being followed, the moving speed of the subject image before following (following speed) S ₁ And returns (S803, S8)
05). Is under the moving object tracking, and if a follow-up during operation first, calculates the number of pulses MP ₁ that corresponds to the moving amount of the object image has moved during the time T _2, the second and subsequent being followed, the time T _n Is calculated, the number of pulses MP _n-1 corresponding to the movement amount of the subject image during (S803, S807, S80)
9, S811).

Then, the previous and current driving directions of the focusing lens 53 are compared with each other. If the driving directions are the same, the overshoot flag is cleared during the following of the moving object, and the calculated moving pulse number M of the subject image is calculated.
The current number of defocus pulses DP _n is added to P _n−1, and the process proceeds to S821 (processing of tracking speed correction calculation 2) (S81).
3, S815, S817, S819). If the driving directions are different, it is considered that the moving speed of the subject has become slow, the subject has stopped, or the subject moving direction has changed, and it is considered that the subject has gone too far, and the process proceeds to S833 (S81).
3, S817). Neither the same or different directions, that is,
If any abnormality occurs, the moving object prediction mode is cleared and the process proceeds to the reintegration process (S815, S817, S84).
9).

[0129] In the "following speed correction calculation 2" following speed correction calculation 2 first calculates the moving object tracing speed S _n by the following equation (S821). _{X n = T n / (MP} n-1 + DP n) S n = 1 / X n

Next, if the in-focus state and the release switch SWR are on, the AF lock flag and the AF release permission flag are set, and the routine returns (S825, S8).
27, S829, S831). If the camera is not in focus or the release switch SWR is not turned on, the process directly returns (S825, S827).

[0131] Further, when the driving direction of the lens are different, if _{MP n-1 -DP n ≧ 0} , obtains the object tracing speed S _n by the following equation (S815, S833, S
835, S837). _{X n = T n / (MP} n-1 -DP n) S n = 1 / X n = (MP n-1 -DP n) / T n

If the camera is in the in-focus state, the over-traveling flag during moving object tracking is cleared and the process returns (S839, S839).
841). If it is not in the in-focus state, it is checked whether the moving object overrun flag is set, and if it is already up, it is the second process since it is overrunning, so the moving object prediction mode is cleared and the process returns (S843, S849). In other words, there is a possibility of an error or the like if the vehicle goes too far during the following of the moving object.
Have . It should be noted that the configuration may be such that the user exits once, or the configuration may exit three or more times.

[0133] Unless standing body follow in excessive flag is still, so excesses with first processing, by setting the moving object tracking in excesses flag, sets the input and calculation time C _n integral data, calculation time C _n After waiting for minutes, the process proceeds to the reintegration process (S843, S845, S847).

[Constant Speed Control 2] Next, another constant speed control 2 will be described with reference to a subroutine shown in FIG. First, the pulse interval (X _n ) is set. If the moving object is being followed, the moving object following speed S _n (1 / X _n ) is set. In addition, if the first process enters the body follow-up, but re-set the 3-speed of a moving object following speed S _n, does not change if the second or subsequent processing (S853, S855, S857, S
859). If the operation is completed (operation end flag =
1), AF pulse, and an input and a set of data, such as moving object tracing speed S _n, and clear the calculation end flag S8
The process returns to S51 (S861, S863, S865).

If the calculation has not been completed (calculation end flag = 0), it is checked whether or not the constant speed control time has elapsed. If it has, the timer for detecting the end point is counted. If it is middle, the process returns to S861 (S867, S869, S871). AF motor 39
If not, the AF motor 39 is started to drive and S
The process returns to 851 (S871, S873).

If the constant speed control time has not elapsed,
It is checked whether an AF pulse has been output (S867, S875). If there is no AF pulse output, the process returns to S861, and if there is an output, the process proceeds to S877.

In S877, it is checked whether or not the mirror up has been completed, and if completed, the AF motor 39 is braked and stopped (S877, S879).
If the mirror-up has not been completed, check whether the AF pulse count has been completed.
Stop the AF motor 39, check the loop time,
If the loop time has elapsed, the AE process is performed. If the loop time has not elapsed, the process proceeds to the reintegration process (S879, S88).
1, S883).

If the AF pulse count has not been completed, the end point check and the end point detection timer are reset to check whether the AF pulse counter value has become smaller than the speed switching pulse (S879, S879).
885, S887). If it becomes smaller, the control speed is switched to a low speed to decelerate, and the AF motor 39 is braked to set S
Proceed to 893, and if not smaller, proceed directly to S893 (S887, S889, S891).

In S893, it is checked whether or not the AF motor is being driven. If it is not driving, the process returns to S851, and if it is driving, the brake is applied and the process returns to S851 (S895).

[Integration Processing] In the integration processing subroutine, integration is started after initial setting, and an integration flag is set (S90).
1, S903, S905). Then, the process waits while checking the integration time until the integration time ends (S907, S907).
909). At this time, if the integration time is longer than a predetermined value, the subject is too dark, so the moving object prediction mode prohibition flag is set (S909, S911).

When the integration is completed, the integrated data is input and the defocus amount is calculated (S907, S909, S9).
11). If the operation result is valid, the moving object following speed is calculated if the moving object prediction mode has been entered, the operation end flag is set, and the process proceeds to S925. If not, the process returns to S901, and the operation is valid. If it is not in the moving object prediction mode, the process directly proceeds to S925 (S919, S
921, S923). In step S925, it is checked whether the AF release permission flag is set. If the flag is not set, the process returns to step S901. If the flag is set, the process proceeds to the release process.

By the above processing, as shown in FIGS. 18 and 19, the focusing lens 53 is controlled at a constant speed even during the integration and the calculation, so that the movement of the subject can be more faithfully followed, that is, always. It is possible to maintain a focused state.

As described above, according to the present embodiment, the subject can be determined to be moving if it is out of focus in the AF processing after a predetermined time even if it is once focused. Even when the focusing lens moves from the short-distance in-focus position to the long-distance in-focus position when the object is approaching, it is possible to reliably determine that the subject is moving.

As described above, in the present embodiment, in the AF processing after focusing, when a three-time out-of-focus state is detected, it is determined that the subject is a moving object. However, the number of times is not limited to three. Further, in the AF process after focusing, a configuration may be adopted in which the moving object is determined when the subject is out of focus a predetermined number of times even intermittently, or when the subject is continuously out of focus a predetermined number of times.

[0145]

As described above, according to the present invention, when the specific subject whose defocus amount is measured has a low contrast, the defocus amount at that time is temporarily stored, and then the same specific subject is defocused again. The amount of defocus is measured and the re-measured defocus amount is compared with the stored defocus amount, and the smaller one is selected as the defocus amount. When it is determined that the lens is out of focus and the lens is driven, or when the fact is displayed when the lens is focused, the display is not switched between in-focus and out-of-focus, and flickering is eliminated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a single-lens reflex camera to which an automatic focusing device according to the present invention is applied.

FIG. 2 is a graph showing an AF operation mode before a moving object prediction AF mode operation of the automatic focusing apparatus.

FIG. 3 is a graph showing another AF operation mode of the automatic focusing apparatus before entering a moving object prediction AF mode operation.

FIG. 4 is a graph showing an AF operation mode in a moving object prediction AF mode operation of the automatic focusing apparatus.

FIG. 5 is a graph showing an AF operation mode in the case where the automatic focusing apparatus has gone too far in a moving object prediction AF mode operation.

FIG. 6 is a graph showing an AF operation mode when a release switch is turned on while operating in the same moving object prediction AF mode while a subject is approaching.

FIG. 7 is a graph showing an AF operation mode when a release switch is turned on while operating in a moving object prediction AF mode during separation of a subject.

FIG. 8 is a flowchart relating to a main operation of the automatic focusing apparatus.

FIG. 9 is a flowchart relating to a reference timer interrupt of the automatic focusing apparatus.

10A and 10B are flowcharts related to AF processing of the automatic focusing device.

11A, 11B and 11C are flowcharts relating to reintegration and moving object prediction AF in the same AF processing.

12A and 12B are flowcharts relating to defocus and drive pulse calculations in the same AF processing.

13A, 13B, and 13C are flowcharts showing a constant speed control process in the AF process.

14A, 14B, and 14C are flowcharts relating to defocus calculation, 10-bit select processing, and low-conversion flicker prevention processing in the same AF processing.

15A, 15B and 15C are flowcharts relating to a moving object following speed and a correction calculation in the same AF processing.

FIG. 16 is a flowchart of a focusing check and a low-contrast flicker countermeasure process in the AF process.

FIG. 17 is a flowchart relating to end point detection processing in the AF processing.

FIG. 18 shows a second moving object prediction AF of the automatic focusing apparatus of the present invention.
It is a graph which shows a processing operation.

FIG. 19 is a graph showing an operation when a release switch is turned on during the second moving object prediction AF processing operation.

20A, 20B and 20C are flowcharts relating to a moving body following speed calculation processing and the like in the second moving body prediction AF processing.

21A and 21B are flowcharts relating to constant speed control in the second moving object prediction AF process.

FIG. 22 is a flowchart related to integration processing in the second moving object prediction AF processing.

[Explanation of symbols]

 Reference Signs List 11 camera body 12 photographing lens 13 main mirror 14 sub-mirror 17 photometric IC 21 distance measuring CCD sensor unit 23 peripheral control circuit 25 shutter mechanism 27 aperture mechanism 35 main CPU 36 CPU 39 AF motor 41 encoder 45 display device 47 joint 51 Shooting lens 53 Focusing lens 55 Lens drive mechanism 61 Lens CPU

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B 7/28

Claims (4)

(57) [Claims] 1. A defocus amount measuring unit for measuring a defocus amount for a specific subject; a contrast determining unit for determining whether the specific subject has low contrast when the defocus amount is measured; means when it is determined that it is not low contrast select the defocus amount, re-operation of the defocus measurement means temporarily memory defocus amount at that time when the contrast determination unit determines that low contrast Let me defocus
Defocus amount selecting means for re-measuring , comparing the stored defocus amount with the re-measured defocus amount this time, and selecting a smaller one as the defocus amount. apparatus. 2. The focus detection device according to claim 1, further comprising: a focus determination unit configured to determine whether the object is in focus based on a defocus amount measured by the defocus amount measurement unit. A focus detection device, wherein the defocus amount selecting means selects the defocus amount irrespective of contrast when the focus determining means determines that the object is in focus. 3. The focus detecting device according to claim 1, further comprising lens driving means for driving a focusing lens based on the defocus amount selected by said defocus amount selecting means. A focus detection device. 4. The focus detection device according to claim 2, further comprising display means for displaying a focus when said focus determination means determines that focus has been achieved.