JPH02812A - Camera with automatic focusing function - Google Patents

Abstract

PURPOSE:To ensure the quickness and reliability in deciding a moving body at the same time by switching the number of focal point detecting times, which is required for deciding a moving body, in response to the condition of a camera. CONSTITUTION:As a moving body deciding means 3 detects a focal point more frequently to decide a moving body, its reliability is improved, however, its quickness is deteriorated, and vice versa. Therefore, when quickness is required for deciding a moving body, a focal point detection time switching means 4 limits the number of times of focal point detection. On the other hand, when quickness in deciding a moving body is not required, the focal point detecting frequency switching means 4 increases the number of times of focal point detection. In such a way, the number of times of focal point detection, which is required for detecting a moving body, is switched in response to the condition of the camera, whereby a moving body is decided more quickly and more surely.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a camera with an automatic focus adjustment function, and is particularly suitable for an AFL reflex camera.

(Prior art) Conventionally, in cameras with an automatic focus adjustment function, when the previous and current defocus directions are the same, it is determined that the subject is moving, and tracking control is used to drive the lens in accordance with the speed of the subject. However, this conventional example does not disclose switching the number of focus detections for determining a moving object.

(Problems to be Solved by the Invention) Cameras with an automatic focus adjustment function are basically equipped with a one-shot AP mode in which focus adjustment is locked when focus is first achieved. This one shot AF
When using this mode, focus priority release mode is often used in which the shutter is not released until focus is achieved. By the way, even when using focus priority release mode in one-shot AF mode, it is still necessary to may be out of focus. This is because, for example, if the subject is moving in the direction of distance, the subject will deviate from the in-focus position by the time the camera is released.

Therefore, as in the conventional technology described above, when focus detection is performed multiple times and it is determined that the subject is a moving object, tracking control is performed to drive the lens in accordance with the speed of the subject. Proposed. However, if the number of focus detections for moving object determination is increased, the reliability of moving object determination increases, but there is a problem in that the speed of moving object determination is hindered.On the contrary, the number of focus detections for moving object determination increases. If the number is reduced, the speed of moving object determination increases, but there is a problem in that the reliability of moving object determination is hindered.

The present invention has been made in view of these points, and its purpose is to provide a camera with an automatic focus adjustment function that can determine whether or not a subject is a moving object, with the aim of quickly and accurately determining a moving object. The aim is to achieve both as much as possible.

(Means for Solving the Problems) In order to solve the above problems, in the present invention, as shown in FIG. A plurality of focus detection means (1) for detecting a focus, a lens drive means (2) for driving a lens toward a focus position based on at least the focus detection result of the focus detection means (1), and a plurality of focus detection means (1). In a camera having a moving object determination means (3) that determines whether or not the subject is a moving object based on the focus detection results of times, the number of focus detections for moving object determination is The present invention is characterized in that it is provided with focus detection frequency switching means (4) that switches the number of times of focus detection depending on whether the focus is in focus or out of focus.

However, FIG. 1 is an explanatory diagram showing the configuration of the present invention in functional blocks, and in the embodiments described later, all or part of means (1) to (4) will be implemented by a microcomputer program. It has been realized.

(effect) Hereinafter, the operation of the present invention will be explained with reference to FIG.

The focus detection means (1) detects the focus state of the lens on the subject to be focused at predetermined intervals. The lens drive means (2) drives the lens toward the in-focus position based on the focus detection result of the focus detection means (1). The moving object determining means (3) determines whether the subject is a moving object or not based on the results of multiple focus detections by the focus detecting means (1). If it is determined that the subject is a moving object, the lens driving means (2) applies correction to the focus position based on the focus detection result of the focus detection means (1) by predicting the amount of defocus based on the movement of the subject. It is preferable to drive the lens to a certain position.

Here, if the number of focus detections used by the moving object determining means (3) for determining the moving object is large, the certainty of the moving object determination increases, but the speed of the moving object determination is impaired.

On the other hand, when the number of focus detections is small, the speed of determining a moving object increases, but the reliability of determining a moving object is impaired. Therefore, in the present invention, when quickness of moving object determination is required, the focus detection number switching means (4) limits the number of focus detections to a small number to increase the speed of moving object determination. Also,
When quickness of moving object determination is not required, the focus detection number switching means (4) increases the number of focus detections to increase the reliability of moving object determination. Specifically, when there is a release request or in a state before focusing, quickness in determining a moving object is required, so the number of focus detections for determining a moving object is limited to a small number in order to quickly respond to a release request. On the other hand, when there is no release request or after focusing, the speed of moving object detection is not required, so the number of focus detections for moving object detection is increased to increase the reliability of moving object detection. It's expensive.

More detailed configuration and operation of the present invention will become clearer in the following description of embodiments. In the embodiment, the focus determination step #23 and the step #25
．． The step #38 of determining the release request realizes the focus detection number switching means (4).

(Embodiment) FIG. 2 is a block diagram showing the hardware of a camera according to an embodiment of the present invention. In FIG. (22) is a COD image sensor for AF, and the microcomputer (21) receives an integration start signal φI.
When cc is received, integration is started, and after the integration is completed, the output of each pixel is A/D converted and sent to the microcomputer (21). The microcomputer (21) performs calculations based on the output of each pixel transmitted from the COD image sensor (22), and calculates the amount of defocus of the subject image. Microcomputer (
21) calculates the amount of defocus of the subject and then drives the lens to make it zero. Here, the conversion coefficient that indicates the relationship between the amount of lens drive and the amount of defocus differs depending on the lens. Therefore, the conversion coefficients are stored in a lens circuit (25) built into each lens. The microcomputer (21) reads the value of the conversion coefficient from the lens circuit (25), and calculates the number of pulses required to drive the lens by multiplying the calculated defocus amount by the conversion coefficient k. The microcomputer (21) transmits the calculated number of pulses to the AF motor control unit (23) for driving the lens, and the AF motor control unit (23) transmits the calculated pulse number to the AF motor (24) for driving the lens. 21) is driven as many times as the number of pulses transmitted.

Reference numeral (26) is a display section, on which the figure shown in FIG. 3 is displayed. In FIG. 3, the LED (26A) displays in-focus or out-of-focus status. In other words, if the defocus amount is calculated and the lens is in focus after driving, the LED (26A)
D (26A) lights up in green to notify the photographer of focus. In addition, if the defocus amount is not calculated for the reason described later, the LED (26A) flashes in red,
Notifies the photographer that the camera cannot focus. Furthermore, LED (26B
) and (26C) are displays showing switching of the photographing mode of the camera in this embodiment. When the subject is stationary, the perfect point position after focusing is fixed, photography is performed in focus lock mode, and the LED (26B) is lit.

On the other hand, if the subject is moving, the tracking mode will be used to follow the subject's movement and always maintain focus.
ED (26C) lights up.

In FIG. 2, (Sl) is a switch that is turned ON when a release button (not shown) is pressed down to the first stroke. When the switch (Sl) is turned ON, interrupt processing by interrupt baud (INTI), which will be described later, is executed.
AP operation is performed. Further, (S2) is a switch that is turned on when the release button is pressed down to a second stroke, which is deeper than the first stroke. switch (S2) is O
When it reaches N, interrupt processing by an interrupt port (INT2>, which will be described later) is executed, and a release operation is executed.

Interrupts by this interrupt port (INT2) may be prohibited by a program. Therefore, the switch (S2) is also connected to the Kugata port (IF5) of the microcomputer (1), and even when interrupts by the interrupt port (rNT2) are prohibited, the microcomputer (21) is connected to the Kugata port (IF5). By scanning IF5), it is possible to determine whether or not the photographer has issued a release request. (S3) is a mirror up switch. This switch is used to raise the mirror (not shown) inside the camera body so that the photographer can observe the light that has passed through the photographic lens through the viewfinder. In order to allow the light that has passed through the camera lens to reach the film surface during exposure, it is a switch that is turned ON when the camera is completely removed from the photographic optical path.The shutter mechanism (not shown) is charged after photographing is completed. Reset to OFF state.

(27) is an LED that emits infrared light (auxiliary light) to irradiate the subject when the brightness of the subject is low, and is controlled by an auxiliary light control section (28). When the microcomputer (21) determines that the brightness of the subject is low, it activates the auxiliary light control unit (28).
), outputs the auxiliary light emission signal, and also outputs the COD
Integration start signal φIcc for image sensor (22)
is output, and when the integration is completed, the auxiliary light control section (28
) stops the auxiliary light emission signal that was being output.

As a result, the COD image sensor (22) performs CCD 8 minutes using the auxiliary light when the brightness is low. (29) is a timer for calculating the rate of change of the focal position for a dynamic subject, which will be described later. The timer value TM is cleared to zero when AP starts by turning on Sl), and then the timer value TM increases steadily, making it possible to monitor the time since AF start. end.

Next, we will explain the algorithm of this embodiment. In this embodiment, it is possible to distinguish between a stationary subject and a moving subject, and automatically switch between two shooting modes: "focus lock mode" and "following mode". I have to. Each shooting mode will be outlined below.

First, select r focus lock mode J as the shooting mode.
If you have set
The amount of defocus of the subject image in this focus frame is determined, and the lens is driven so that the subject image is brought into focus. During general photography, there are many cases where the photographer wants to frame the subject so that it is located in a different location from the focus frame in the viewfinder.In such cases, first,
The photographer moves the lens so that the subject he or she wants to focus on is within the focus frame, and then
After performing the motion, it is necessary to perform framing without changing the focal point position. The "focus lock mode" is a mode in which, in such a case, the release is performed without changing the focal position after focusing.

In this embodiment, a "following mode" is provided as another photographing mode. This is a shooting mode that corresponds to a case where the subject that the photographer wants to shoot is moving. When the subject is moving, the amount of defocus of the subject detected on the focus frame changes every moment. There is no problem if this change is small enough to fall within the depth of field on the film surface, but if the change in defocus exceeds the depth of field, the constantly changing defocus In this embodiment, it is necessary to follow the subject in order to change the focus position moment by moment according to the movement of the subject.In this embodiment, when the subject moves in this way, the following mode is set, and the image formation of the subject image changes moment by moment. It constantly tracks the position and maintains focus at all times. In addition, when the photographer presses the release button, "Following mode" takes into consideration the time lag between the timing of pressing the release button and the timing of the shutter curtain actually running and exposing the film surface. Also included is a predictive control method in which the amount of defocus is predicted and the lens is driven so that the subject image is in focus at the timing of exposure on the film surface. This “following mode”
With this feature, it is possible to always obtain in-focus photos even when the subject is moving.

This will be explained in detail below using a detailed flowchart.

When the release button is pressed down to the first stroke, the switch (
SL) is turned on, the AF start flow shown in FIG. 4 is executed. In the following description, the symbol "#" means a step of the program. In #1, interrupts from the interrupt baud (INT2) are prohibited to prevent the release routine from being called even if the release button is pressed down to the second stroke and a release request is made. Subsequently, in #2, the microcomputer (21) obtains a conversion coefficient (k) for converting the defocus amount into the number of pulses for driving the lens from the lens circuit (25) shown in FIG. Subsequently, in #3, a timer (29) for monitoring distance measurement time, which will be described later, is reset. Furthermore, focus detection calculation is performed in #4.

FIG. 11 shows a subroutine for focus detection calculation, #1
At #08, the timer value TM is read, and at #109, the start time of CCD integration, which will be described later, is stored in the memory in the microcomputer (21) as a memory value TM'. Subsequently, in #110, a low brightness flag is determined. When the brightness of the subject is low, the CCD image sensor (22) is not irradiated with sufficient light, so the above-mentioned auxiliary light is irradiated onto the subject.
The necessity of the auxiliary light irradiation is determined using the low brightness flag. A
Immediately after F start, the low brightness flag is cleared, so #111 auxiliary light emission is skipped, and #112 C
The CCD image sensor (22) that performs CD integration is an image sensor for obtaining object information for performing focus detection calculations, and by performing integration, brightness information of the object is accumulated in each pixel. In #113, the data of each pixel in the CCD image sensor (22) is sent to the microcomputer (21).
) data dump processing is performed. Below, #1
The correlation calculations, interpolation calculations, and focus shift pitch calculations in steps 14 to #116 represent the flow of a well-known focus detection calculation. Processing of 0 or more is performed in the focus detection calculation subroutine in #4.

When the focus detection calculation is performed in #4, if the reliability of the result is poor, focus detection becomes impossible.

Make the determination in #5. If focus detection is not possible here, proceed to #501; otherwise, proceed to #501.
Proceed to step 11. If you proceed to #501, check whether the brightness is low or not. First, before the focus detection calculation,
When CCD integration is performed, since the auxiliary light is not emitted, the subject brightness is low and focus detection may not be possible. If it is determined that the brightness is low in #501 and the low brightness flag is not set in #6, proceed to #7, set the low brightness flag, and return to #4. This time, the auxiliary light is emitted and the CCD On the other hand, if low brightness is not determined in #501, or if the low brightness flag is set in #6 and CCD integration is performed using fill light, the contrast of the subject image is It is determined that the condition is low.

In this case, proceed to #8. In #8, it is determined whether a low contrast scan was performed in the past, which repeats focus detection calculations while scanning the lens position. If this routine is entered for the first time, # 8 was determined as No,
Start low contrast scan in #9. If the low contrast scan has already been completed in #8, a low contrast display is performed in #10 to notify the photographer that focus detection is impossible. This is done by flashing the LED (26A) shown in FIG. 3 in red.

If it is determined in #5 that focus detection is possible, the process proceeds to #11. In #11, a low brightness flag is determined. Since the above-mentioned CCD integration time differs between when the auxiliary light is used and when the auxiliary light is not used, it is necessary to change the sampling period T0 when repeatedly calculating the defocus amount as described later. For this reason, #12. #13 is each sampling period T.

is set. In #14, the defocus amount is calculated from the result of the focus detection calculation. In #15, it is determined whether this defocus amount is within the focusing range, and if it is within the focusing range, the process proceeds to the AF mode determination routine from #441 onwards.
If the defocus amount is outside the focus range, proceed to the flow from #16 onwards.Normally, the lens position is not fixed when AF starts, so it is rarely within the focus range, and #
Proceed to 16 onwards.

In #16, the number of pulses for driving the lens is calculated using the defocus amount calculated in #14 and the conversion coefficient input in #2. Subsequently, the lens is driven in #17, and the lens is driven by the number of pulses calculated in #16. After this, a routine for detecting the state of the subject is entered.

In #18, the counter CN is cleared to zero. This counter CN is a counter for counting how many times focus determination has been performed in the routine after #19.

In subroutine #19, focus detection calculation is performed again. If the focus cannot be detected in #20, repeat #19 until the focus is detected.If the focus is detected, #21
The defocus amount is calculated in #22, the value of the counter CN is incremented by one, and the focus is determined in #23. At this time, if the subject is stationary, or if the focus position changes slowly even if it is moving, the defocus amount calculated in #21 is within the focusing range, and the process proceeds to #24, where the counter CN is If the value of + is 1, that is, if focus is achieved with one lens drive in #17, the process proceeds to the AF mode determination routine from #441 onwards.

However, if it is not in focus in the focus judgment in #23, it is assumed that the focal position of the subject image has changed during lens driving, or that the focus detection accuracy is low and the amount of defocus is inconsistent. , proceed to the routine after #30.

#30. If the value of the counter CN is 1 in #31, the lens has been driven once in the past, and after calculating the number of pulses for driving the lens again in #41, the lens is driven in #42. After this, After waiting time in #43, #1
Repeat the steps from 9 onwards.

The reason for waiting for time here is that when detecting the moving speed of a subject whose image focal position changes over time using the method described below, if the time interval between focus detection is short, the speed detection will be accurate. This is because it is not done well. In subroutine #19, the CCD integration start time TM' is set by the microcomputer (21).
Since the timer value TM is stored in the internal memory, a time wait is performed in #43 until the timer value TM reaches TM≧To+TM'.

After repeating the calculations in #19 to #22, focus determination is performed again in #23.

If it is determined in #23 that the image is in focus, the counter CN.

Since the value of is 2, it is determined in #24 that CN is not equal to 1, and in #25 the input port (IP2) of the microcomputer (21) is scanned to determine the presence or absence of a release request. Here, if there is no release request, A
Proceed to the F mode determination routine. If there is a release request, #26 to #
After processing 29, proceed to the release routine, #2
In step 6, it is determined whether the sign of the defocus amount DFb obtained last time is equal to the sign of the defocus amount DFa obtained this time. Defocus JiDFa and DFb having the same sign means that the focal position of the subject image shifts in the same direction, so if the previous defocus amount DFb and the current defocus amount DFa have the same sign, the subject is moving. After calculating the speed (2) in #27, a tracking mode flag for following the movement of the subject is set in #28, and release is permitted in #29, and the process enters the release routine.

In calculating the subject speed in #27, the defocus amount DFa calculated this time is used as the time interval (ta) between the current and previous focus detection.
-tb) and further multiplies that value by (1/2). This is because the subject speed is calculated with a weight of 1/2 so that the expected subject speed (2) is not estimated to be faster than the actual one when there are variations in the calculated defocus amount. Actually, since the defocus amount DFa is within the focusing range this time, the moving speed of the subject is not so large, and this tracking speed is sufficient.

On the other hand, if the signs of the current defocus amount DFa and the previous defocus amount DFb are opposite in #26, it means that the focal position of the subject image has shifted in the opposite direction, so it is not possible that the subject is moving in the same direction. It is not recognized and the release operation is performed without tracking.

Next, if the value of the counter CN+ is 2 in the focus judgment in #23 and the focus is out of focus, the judgment in #30 causes the #3
Processing moves to step 7. In #37, this time the defocus amount DFa
The sign of the previous defocus amount DFb is compared. Here, if the signs are the same, it is determined that the subject is moving in the same direction, and the process proceeds to #38. If the signs are opposite, it is not determined that the subject is moving in the same direction, so the lens drive In #38, it is determined whether there is a release request or not. If there is a release request, the subject speed V is calculated in #39. In #40, the tracking mode flag is set and the tracking is performed. Proceed to mode routine,
In the speed calculation in #39, the current defocus amount DFa is divided by the focus detection time interval (ta-Lb), and then (1/
2) It is doubled. This is the same as in the previous case, but here, since the defocus amount D-Fa is outside the focusing range and the speed of the subject is large, we do not immediately move to the release operation; The camera enters the following mode, and after accurately calculating the velocity V of the subject, the release routine is entered.

On the other hand, if there is no release request in #38, proceed to #41, calculate the number of pulses for driving the lens, drive the lens in #42, proceed to #43, and repeat the processing of #43 to #22. After that, the focus is determined again in #23. If it is in focus, proceed to #24 and below, and if it is out of focus, the value of counter CN is 3. , #30° and #31 are all determined to be NO, and #32
If the signs of the three defocus amounts match in #32, it is determined in #33 whether the absolute values of the three defocus amounts are all within l1. There is.

If the absolute value of the defocus amount exceeds 11.0, there is a high possibility that another subject was measured, so proceed to #41 and onwards and repeat focus detection again.
32. If YES in both #33, it is determined that the focus detection of the subject was normal all three times and that the subject is moving in the same direction, and the velocity V-(DFa-DF
After calculating b)/(ta-tb), the follow-up mode flag is set in #35, and the process shifts to follow-up mode. Also,
If the three defocus amounts do not have the same sign in #32, it is determined in #36 whether the signs of the current defocus amount DFa and the previous defocus amount DFb are the same, and in #36 the current defocus amount DFa and the previous defocus amount DFb
If the signs match, #41. After driving the lens again in #42, proceed to #43 and onwards to repeat the subject discrimination, and in #36, set the current defocus amount DFa.
If the signs of the previous defocus amount DFb and the previous defocus amount DFb do not match, it is determined that the accuracy of focus detection is low and the defocus amount varies, and the process enters the average mode (2).

FIG. 10 shows the flow of average mode (2). #9
9, the defocus amount DF is determined by the average value DF of the current defocus amount DFa, the previous defocus amount DFb, and the previous defocus amount DFe = (DFa+DFb
+DFc)/3 is calculated. In #100, it is determined whether this defocus amount DF is within the focusing range, and if it is in focus, the focus is displayed in #101, and in #102
After permitting release, the camera shifts to average mode I. In average mode I, after setting the average correction flag as shown in #66 of FIG. 7, a focus lock display is performed as shown in #67, and the camera waits for release.

On the other hand, in #100, there are large variations in each defocus amount, and the average defocus amount may exceed the focusing range. In this case, the number of pulses for driving the lens is calculated in #103, the lens is driven to a predetermined position in #104, and then focus detection calculation is performed again in #105. #10
If focus detection is not possible in step 6, repeat the focus detection calculation in #105 until focus is detected.If focus is detected, calculate the defocus amount in #107, and then repeat step #99.
Return to #9 until the average defocus amount is within the in-focus range.
Repeat steps 9 to #107.

As described above, after calculating the amount of defocus, the lens is driven to the expected focus position, and if it is not in focus, the movement speed of the imaging position of the subject image is fast and the lens drive cannot catch up, or the defocus Since the accuracy of the amount calculation is low, we have described a method of determining whether the defocus amount is either tracking mode or average mode by assuming that the amount of defocus is varying. Additionally, the sequence in the case where a release request occurs during determination has also been described.

If the subject is moving quickly, the tracking mode can be determined using the method described above, but if the subject is slow, it is possible to determine whether the subject is moving out of the focus zone or not, even if there is a time lag caused by driving the lens to the intended focus position. First, it may be determined that focus is achieved in #23. Therefore, even after the focus determination in #23, the tracking mode is determined in the AF mode determination routine from #441 onwards. This AF mode determination will be explained below.

In #441, a flag (A F M F ) indicating that the AF mode determination routine has entered is set. #4
In step 4, a focus display is performed to notify the photographer that the subject is in focus. In addition, when focusing, the prohibition of interrupts by the interrupt board (INT2) is canceled, and the release is always activated.
When a release request is made, a release operation is performed immediately. Next, in #46, the counter CN is cleared. The counter CN indicates the number of focus detections for determining the AF mode. In #47, focus detection calculation is performed, and in #48, it is determined that focus detection is impossible. If the contrast of the original subject is low, or the focus detection calculation was performed on another subject whose focus position is significantly different from that of the subject to be photographed after focusing, proceed to #55. , If the focus is detected normally in #48, the defocus amount DF is calculated in #481.
If IDFI>1 wheel is detected at 49, it is considered that focus detection was performed on another subject whose focus position is different from that of the subject to be photographed after focusing, so proceed to #55.
Steps 5 to #57 perform processing when such an irregular focus detection calculation is performed. In step #55, first, the previous ignore flag is checked. The previous ignore flag indicates that irregular focus detection has been performed consecutively. This flag is used to determine whether the
The determination in #55 is No, and the process proceeds to #56. In #56, a previous ignore flag is set so that the next time an irregular focus detection is performed, the determination in #55 is YES. #
If 55 is YES, it means that incorrect focus detection has been performed twice in a row, so in this case, #571
In step #57, the flag (A F M F ) is reset, indicating that the AF mode determination routine has been exited, and in step #57, a focus lock display is performed, and the camera waits for release.

Here, the reason why focus detection is performed only when irregular focus detection is performed twice in a row is as follows.

When photographing a moving subject in tracking mode, it is necessary to always follow the subject within the focus frame, but the subject may deviate from the focus frame due to camera shake or the like.

Therefore, if an incorrect focus detection is performed once, it is ignored. However, if this happens twice in a row,
It is determined that the photographer intentionally moved the subject out of the focus frame. This is because in focus lock photography, the photographer shakes the camera to decide on the composition after focusing on the subject. Therefore, if incorrect focus detection is performed twice in a row, focus lock mode is determined as AP mode, focus lock is displayed, and the camera waits for release.

#48. If the determination in #49 is NO, it is determined that the subject has not changed and the amount of defocus has been calculated reliably, and the process proceeds to #50, where the previous ignore flag is checked. Here, if the previous ignore flag was set, it means that the normal focus detection calculation was not performed last time, and in #51, the previous defocus amount DFc and the current defocus amount DFa are averaged. It is calculated by interpolating the focus amount DFb. Next, clear the previous ignore flag in #52, and #
On the other hand, if the ignore flag was not set last time in #50, there is no need for interpolation, so proceed to #53.
In #53, the counter CN is counted up, and in #54, the counter CN is counted up until the value of the counter CN reaches 4.
~ Repeat #54. If the value of the counter CN is 3 or less, the timer value TM is changed to the memory value TM' in #541.
A time wait is performed until To increases from .

After completing four focus detection calculations, reset the flag (A F M F ) indicating AP mode determination in #581,
The process proceeds to #58. In #58, the sign of the defocus amount for all four times is the same, and the defocus amount changes monotonically, and furthermore, in #59 to #61, two consecutive defocus amounts are detected. If it is determined that all the absolute values of the differences in amounts are equal to or higher than the predetermined determination threshold value 8, it is assumed that the subject is moving, and the camera shifts to the tracking mode. At this time, the initial velocity at the time of following is V − (D Fa − D F c)/
(ta - tc) and sets the tracking mode flag in #63 to enter the tracking mode. At this time, the speed ■ is the current defocus amount DFa and the previous defocus amount DFc.
What is calculated from is the focus detection time interval (ta −
This is because the longer tc) is, the higher the calculation accuracy is, and the newer the data, the more accurately the initial velocity V at the time of entering the tracking mode can be calculated.

On the other hand, if all four defocus amounts are not of the same sign or do not change monotonically in #58, then in #64 the stability of each defocus amount is determined by calculating the difference between the defocus amounts of the two focus detections. Determine whether the sign changes alternately or not, YE
In the case of S, it is assumed that the calculation of the defocus amount DF is unstable, and averaging processing is performed below #65. In #65, the defocus amount is the current defocus amount DFa, the previous defocus amount DFb, and the previous defocus amount. Quantity DFc of 3
The average defocus amount is the true defocus amount,
An average correction flag is set in #66, a focus lock display is performed in #67, and the camera waits for release. On the other hand, #6
If the defocus amount does not change alternately in step 4, or if the absolute value of the difference between successive defocus amounts is smaller than the predetermined determination threshold a in the determinations in #59 to #61, the subject does not move, and it is considered that the calculation of the defocus amount has been performed accurately, so no averaging process is performed, and the process proceeds to #67, where a focus lock display is performed and the camera waits for release.

This concludes the description of the routine from the start of AF to the completion of AF mode determination.

Next, the sequence after entering the tracking mode will be explained. In FIG. 8, first, in #68, the tracking mode is displayed, and then in #69, 2 is assigned to the counter CN, which notifies the photographer that the tracking mode has been entered.

Counter CN3 is used to determine when to exit the tracking mode. In #70, counters CN 4 and CN s
has been cleared.

Counter CN is a counter for counting the number of times that normal focus detection was not performed in the focus detection calculation after entering the tracking mode, and counter CN is a counter for counting the number of times that normal focus detection was performed. It is. #71
Now, add the value obtained by multiplying the moving speed of the subject by the period T0 of the focus detection calculation to the latest defocus amount DFa, and calculate the planned defocus amount DF' when the lens is not driven at the next time of focus detection. There is. Based on this planned defocus amount D F', the number of pulses for driving the lens is calculated in #72, and the lens is driven in #73.
In #74, wait until the timer value TM reaches the value obtained by adding the focus detection cycle T0 to the memory value TM' at the time of the latest focus detection calculation.Originally, the cycle T0 in #71 includes the lens driving time. The predicted period T0' should be used here, but to simplify the discussion, T is used here. =, T0°
and the lens drive time is set to almost no time.
In the lens drive in #73, the lens is driven by the planned defocus amount DF' when the lens is not driven, so when the focus detection calculation is performed in #75, the defocus amount is approximately It will be calculated as zero. #7
In step 6, it is determined whether or not focus detection is impossible. As mentioned above, if proper focus detection is not performed due to camera shake etc. of the photographer, proceed to #89, or proceed to #7.
If normal focus detection is performed in step 6, the defocus amount DF is calculated in #761, but if the absolute value IDFI of the obtained defocus amount is determined to be greater than lam in #77, the above-mentioned method is also calculated. Therefore, it is determined that proper focus detection has not been performed, and the process proceeds to #89.

In #89, the current defust focus amount DFa is set to zero as a result of the focus detection calculation.

This is because, as described above, the lens is driven so that the amount of defocus becomes approximately zero during the current focus detection calculation. Further, in #90, the value of the counter CN, which counts the number of irregular focus detection calculations, is incremented by one. This is so that if irregular focus detection calculations are frequently performed as described later, the tracking mode is exited at #87. #77 IDPI<1
If it is determined to be mm, the process proceeds to #78. In #78, the difference between the current subject position and the previous subject position is calculated as the defocus amount difference ΔDF.

FIG. 13 is a diagram for explaining a method of calculating the defocus amount difference ΔDF. In FIG. 13, the DFa origin is the lens position at the time of the current focus detection, and the DFb origin is the lens position at the previous focus detection. At the previous focus detection time tb, the lens was located at the origin of DFb, so the previous defocus ID Fb had occurred. The defocus amount DFb' for the previous lens drive is
The predicted movement amount of the subject is obtained by multiplying the elapsed time (ta-tb) from the previous focus detection time tb to the current focus detection time ta by the subject speed 2, and is obtained by adding the previous defocus amount DFb. Therefore, the current focus detection time ta
In , the lens position has reached the DFa origin, but
The subject actually deviates from the predicted position, causing a defocus amount DFa this time.

In this case, as is clear from the figure, the defocus amount difference ΔDF from the subject position at the previous focus detection time tb to the subject position at the current focus detection time ta is the current defocus amount DFa plus the previous defocus amount for lens driving. It is obtained by adding DFb' and further subtracting the previous defocus IDFb.

In #79, this defocus amount difference ΔDF and the moving speed ■
The signs of are compared. If the signs are different, it means that the subject is moving in the opposite direction to the direction calculated as the moving speed V, and it is assumed that proper focus detection has not been performed, and the value of the counter CN is increased by one in #88. It's increasing. Furthermore, even if the absolute value of the defocus amount is greater than or equal to the predetermined judgment darkness value in #80, this means that the actually measured defocus amount is significantly different from the expected defocus amount, and in the above case Similarly, it is assumed that proper focus detection has not been performed, and the process proceeds to #88, #79.
．． If the determination in #80 is YES, the process advances to #81, where a counter C indicating the number of times normal focus detection has been performed is displayed.
Increase the value of Ns by one.

If the value of the counter CN s is not 5 in #82, the process advances to #87.In #87, the counter CN s is set to 5.

A comparison is made between CN and CN. Initially, the value of counter CN is 2 due to the initial setting in #69, and the value of counter CN3 is compared with the value of counter CN, which indicates the number of irregular focus detections. That is, here, if the value of the counter CN is 2 or more, it is determined as YES, and the release is prohibited in #871, and the process returns to the AF mode determination, and this is repeated.This is because if the tracking mode is entered by mistake, The value of counter CN, and counter CN
This is to make it possible to compare the values of 3 and exit the tracking mode.

On the other hand, when the value of the counter CN becomes 5 in #82, the low brightness flag is checked in #83.As mentioned above, if the low brightness flag is set, the auxiliary light is emitted. Although CCD integration is performed, it is not desirable to perform focus detection calculations indefinitely because the use of auxiliary light increases power consumption.

For this reason, the tracking mode is exited when the value of the counter CN reaches 5. If the low-brightness flag is set, focus is determined in #91, and if the camera is in focus, release is permitted in #92, then focus lock is displayed in #94, and tracking mode ends. Notifies the photographer that focus lock mode is activated.

If the camera is not in focus, release is prohibited in step #93 and the process returns to AP mode determination. On the other hand, when the auxiliary light is not used, the tracking mode is continued because there is no need to worry about power consumption. In #84, the value of the counter CN is incremented by one. Furthermore, #85. At #86, counter CN 4, C
N, has been cleared.

The counter CN is a parameter used when escaping from the following mode in #87 described above. Since this counter CN increases in accordance with the elapsed time (the number of focus detections) after entering the tracking mode, the conditions for exiting the tracking mode in #87 gradually become stricter. In other words, the longer the time that has elapsed since entering tracking mode, the more the subject is definitely moving, and the camera is controlled to continue tracking even if the number of incorrect focus detections increases due to camera shake, etc. .

If it is determined in #87 that the tracking mode cannot be exited, a new tracking speed ■ is calculated in #95.

In #95, in order to improve the accuracy of calculating the tracking speed ■, the difference between the current subject position and the subject position before the previous one (defocus amount difference ΔDF) is calculated as the focus detection time interval (ta − t
Divide by c) to obtain the moving speed ■.

FIG. 14 is a diagram for explaining a method of calculating the defocus amount difference ΔDF. In FIG. 14, the DFa origin is the lens position at the time of the current focus detection, the DFb origin is the lens position at the previous focus detection, and the DFc origin is the lens position at the time of the previous focus detection. At the focus detection time tc of the previous focus detection time, the lens was located at the DFc origin, so the defocus i D F c occurred the second time before the previous focus detection time tc. The defocus amount DFc' for the lens drive before the previous time is the predicted movement amount of the subject obtained by multiplying the elapsed time (Lb - tc) from the focus detection time tc of the time before the previous time to the focus detection time tb of the previous time by the subject speed Vc. It is obtained in addition to the defocus amount DFc. therefore,
At the previous focus detection time tb, the lens position was DF.
b Although the origin has been reached, the subject is actually away from the predicted position, causing the previous defocus amount DFb. The defocus jiDFb' for the previous lens drive is calculated by multiplying the estimated movement amount of the subject by multiplying the elapsed time (ta - tb> from the previous focus detection time tb to the current focus detection time ta) by the subject speed vb. It is determined in addition to the focus amount DFb. Therefore, the current focus detection time t
At point a, the lens position has reached the DFa origin, but the subject is actually away from the predicted position, causing defocus HD Fa this time. In this case, the defocus amount difference ΔDF from the subject position at the focus detection time tc before the previous time to the subject position at the current focus detection time ta is, as is clear from the figure, the current defocus amount DFa plus the defocus amount for the previous lens drive. Add DFb' and the defocus amount DFc' for driving the lens before the previous time,
This can be obtained by further reducing the defocus amount DFc two times before. That is, the defocus amount difference ΔDF is ΔDF=DFa−DFc+DFb′+DFc′.

The tracking speed V is calculated by dividing the defocus amount difference ΔDF in the above formula by the focus detection time interval (ta-tc). After this, the focus is determined in #96, and if it is in focus, the release is permitted in #97, and if it is not in focus, the release is prohibited in #98, and the process from #71 is repeated. In the case of permission, if there is a release request, a release routine is called and a release operation is performed.

! & Later, the release routine will be explained.

First, in #117 of FIG. 12, it is determined whether the average correction flag is set or not. If the average correction flag is set, the process proceeds to #121, where the number of pulses for driving the lens is calculated from the calculated defocus amount, the lens is driven in #122, and the input port ( After monitoring IP3) and confirming that the mirror is up, the lens drive is stopped in #124, and then the shutter is run. If the average correction flag is not set in #117, it is determined in #118 whether the tracking mode flag is set.

Here, if the follow mode flag is not set,
In #125, it is determined based on a flag (A F M F ) whether or not the release was performed during the AF mode determination. If this flag (AFMF) is set, there is a possibility that the subject is moving during the above judgment mode in #126, so in order to correct this, the average amount of defocus obtained during the above judgment is Step # to drive this amount
Proceed to 121 0 For example, if two parfocal detection is performed and two defocus ff1 (DPI, DF2) are obtained, D
Let F=(DFI-toDF2)/2. The above flag (A
FMF) is not set, lens driving is not performed and the process proceeds to #123 and subsequent steps. If the tracking mode flag was set in #118, the process proceeds to #119.

In #119, time lag τ is calculated. The time lag τ is the time from when the latest focus detection calculation is performed to when the shutter is actually moved. In #120, the value obtained by multiplying the subject movement speed V by the time lag τ is the latest defocus I.
In addition to D Fa, a planned defocus JiD F' at the time of shutter movement is calculated. In #121, the number of pulses for driving the lens is calculated, and in #122, the lens is driven to the intended focus position when the shutter is running.

Below, #123. After performing the process of #124, shutter movement is performed, and thereby control is performed such that focusing is achieved during shutter movement. Exposure control is not related to the present invention, so a description thereof will be omitted.

(Effects of the Invention) As described above, in the present invention, in a camera with an automatic focus adjustment function that can determine whether or not a subject is a moving object,
The number of focus detections for moving object detection is changed depending on the camera status, for example, whether there is a release request or not, and whether the focus is in focus or out of focus. By limiting the number of focus detections to a small number, moving object detection can be performed quickly, and when speedy moving object detection is not required, the number of focus detections for moving object detection can be increased to ensure moving object detection. It has the effect of being able to

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of the present invention, FIG. 2 is a block circuit diagram of an embodiment of the present invention, FIG. 3 is a front view of a display section used in the same, and FIGS. 4 to 12 are A flowchart for explaining the operation of the same as above, and FIGS. 13 and 14 are diagrams for explaining the operation of the same. (1) is a focus detection means, (2) is a lens drive means, (3
) is a moving object determination means, and (4) is a focus detection number switching means.

Claims (3)

[Claims] (1) A focus detection means that detects the focus state of the lens on the subject to be focused at every predetermined time; and a lens drive means that drives the lens toward the in-focus position based on at least the focus detection result of the focus detection means. In a camera having a moving object determination means that determines whether or not a subject is a moving object based on the results of multiple focus detections by the focus detection means, a focus detection method that switches the number of focus detections for determining a moving object according to the state of the camera. A camera with an automatic focus adjustment function, characterized by having a number of times switching means. (2) The focus detection number switching means is a means for limiting the number of focus detections for moving object determination when there is a release request to be less than the number of focus detections for moving object determination when there is no release request. A camera with an automatic focus adjustment function according to claim 1. (3) A patent characterized in that the focus detection number switching means is a means for limiting the number of focus detections for determining a moving object before focusing to be less than the number of focus detections for determining a moving object after focusing. A camera with an automatic focus adjustment function according to claim 1.