JPH02815A - Camera with automatic focusing function - Google Patents

Abstract

PURPOSE:To prevent the execution of control for photographing a moving body when a photographer does not intend to photograph a moving body by displaying only when an object is decided as a moving body. CONSTITUTION:Based on the result that a focal point detecting means 1 detects a focal point several times, a moving body deciding means 3 decides whether an object is a moving body or not. If so, a lens driving means 2 preferably drives a lens toward a position corrected by defocus quantity estimated based on the result of the focal point detecting means 1. When the object is decided to be a moving body, a display means 4 displays that fact. As a result, a photographer can realize that the object is decided to be a moving body on a camera side.

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, in this conventional example, when it is determined that the subject is moving, it is possible to follow the subject without displaying it. Since the camera has shifted to control, the photographer cannot know that the camera has shifted to control for photographing 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, a focus priority release mode is often used in which the shutter is not released until focus is achieved, even when using a focus priority release mode in one shot AP mode. However, the subject may not be in 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 prior art described above, focus detection is performed multiple times, and when it is determined that the subject is a moving object (dynamic subject), tracking control is performed to drive the lens in accordance with the speed of the subject. Proposed. However, when the camera determines that the subject is a moving object and automatically shifts to control for shooting moving objects, it is possible to control the motion shooting even when the photographer does not intend to shoot moving objects. Control may occur.

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, and to provide the result of moving object determination to the photographer. The goal is to make it possible to inform people.

(Means for Solving the Problems) In order to solve the above problems, in the camera with an automatic focus adjustment function of the present invention, as shown in FIG. a focus detection means (1) for detecting the focus state of the focus detection means (1), a lens drive means (2) for driving the lens toward a focus position based on at least the focus detection result of the focus detection means (1), and a focus detection means (
The apparatus comprises a moving object determining means (3) for determining whether or not the object is a moving object based on the focus detection result of 1), and a display means (4) for displaying when the object is determined to be a moving object. be.

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 with respect to the subject to be focused. Lens drive means (
2) drives the lens toward a focused 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. The display means (4), which preferably drives the lens to a position where the object is a moving object, displays this when it is determined that the object is a moving object. You can know that you have been judged.

More detailed configuration and operation of the present invention will become clearer in the following description of embodiments. In the embodiment, the display means (4) is realized by the step LED (26C) in FIG. 3 and step #68 in FIG.

(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 CCD image sensor for AF, and the integration start signal φI is sent from the microcomputer (21).
When cc is received, integration is started, and after finishing the separation, the output of each pixel is A/D converted and sent to the microcomputer (21). The microcomputer (21N) performs calculations based on the output of each pixel sent from the 1CCD image sensor (22), and calculates the amount of defocus (defocus M) of the subject image. After calculating the amount, the lens is driven to set it to zero.The conversion coefficient that indicates the relationship between the amount of lens drive and the amount of defocus differs depending on the lens, so the conversion coefficient has various values. It is stored in the lens circuit (25) built into the lens.The microcomputer (21) reads the value of the conversion coefficient from the lens circuit (25) and multiplies the calculated defocus amount by the conversion coefficient k. The microcomputer (21) calculates the number of pulses required to drive the lens.
The calculated number of pulses is sent to the motor control unit (23), and the AF motor control unit (23) controls the AF for driving the lens.
The motor (24) is driven by the number of pulses transmitted from the microcomputer (21).

Reference numeral (26) is a display section, on which the figure shown in FIG. 3 is displayed. In Figure 3, L E D (26A)
In other words, the amount of defocus is calculated, and if the lens is in focus after driving the lens, the LED (26A>) lights up in green to alert the photographer to focus. In addition, if the defocus amount is not calculated for the reason described later, the LED (26A) flashes in red to notify the operator that focusing is not possible.
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 is used to follow the subject's movement and always maintain focus, and the LED (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 the interrupt board (INTI), which will be described later, is executed.
AF 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 the time reaches N, interrupt processing by an interrupt port (INT2) to be described later is executed, and a release operation is executed.

Interrupts by this interrupt port (INT2) may be prohibited by the program. Therefore, the switch (S2) is also connected to the input port (IP2) of the microcomputer (1), and the microcomputer (21) uses the input port (IP2) even when interrupts by the interrupt port (INT2) are prohibited. By scanning, 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. This is a switch that turns ON when the light that has passed through the photographing lens reaches the film surface during exposure, and is turned ON when the light is completely removed from the photographing optical path.
is reset to the OFF state by charging.

(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 an auxiliary light emission signal to the CCD
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 CCD image sensor (22) performs CCDI using the auxiliary light when the brightness is low. The timer value TM is cleared to zero when AF 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 [Focus Lock Mode] 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, when the subject moves in this way, it is necessary to follow the subject in order to change the focus position 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 photographs 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 explanation, the symbol "#" shall mean a step in the program. In #1, the release button is pressed down to the second stroke by disabling interrupts from the interrupt port (INT2). The release routine is prevented from being called even if there is a release request.Next, in #2, the microcomputer (21) sets the conversion coefficient (k) when converting the defocus amount into the number of pulses for driving the lens. The input is from the lens circuit (25) shown in Figure 2.Next, in #3, a timer (29) for monitoring the distance measurement time, which will be described later, is reset.Furthermore, in #4, focus detection calculation is performed. conduct.

FIG. 11 shows a subroutine for focus detection calculation, #1
At #08, the timer value TM is read, and at #10, the start time of 11 minutes on the CCD, 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, but the necessity of irradiating the auxiliary light is determined by a low-brightness flag.

Immediately after AF starts, the low brightness flag is cleared, so the auxiliary light emission in #111 is skipped, and the CCD image sensor (22) performs the CCDI portion in #112.
This is an image sensor that obtains 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 (2).
1) Data dump processing is performed. below,#
The correlation calculations, interpolation calculations, and defocus pitch calculations in steps 114 to #116 represent the flow of a well-known focus detection calculation.The 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 was not determined in #501, or if the low brightness flag was set in #6 and CCD 11 minutes was 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. In #13, each sampling period T0 is set. In #14, the defocus amount is calculated from the result of the focus detection calculation. In #15, it is determined whether or not this defocus amount is within the focus range. If it is within the focus range, the process proceeds to the AF mode determination routine from #441 onwards, and if the defocus amount is outside the focus range. Proceed to the flow from #16 onwards 0 Normally, the position of the lens is not fixed at the time of AF start, so it is rarely within the in-focus range, and the process proceeds from #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 the focus is achieved with one lens drive in #17, then A after #441
Proceed to the F mode determination routine.

However, if the focus is not in focus in the focus judgment in #23, the focal position of the subject image may have changed while the lens was being driven, or the focus detection accuracy may be low and the amount of defocus may vary. It is recognized and the routine proceeds to #30 onwards.

#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 focus detection time is short, the speed detection may be delayed. This is because it is not performed accurately. 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≧T, +TM'.

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

If focus is determined in #23, the value of counter CN is 2.
Therefore, in #24, it is determined that CN is not 1, and in #25, the microcontroller (21) input capo) (IF5
) to determine whether there is a release request.

Here, if there is no release request, proceed to the AF mode determination routine; if there is a release request, proceed to the AF mode determination routine.
In order to quickly respond to this request, proceed to the release routine after performing the processing in #26 to #29. In #26, the sign of the defocus amount DFb obtained last time is equal to the sign of the defocus amount DFa obtained this time. Determine whether or not. The fact that the defocus amounts DFa and DFb have the same sign means that the focal position of the subject image shifts in the same direction, so the previous defocus amount DFb and the current defocus amount D
If Fa has the same sign, it is determined that the subject is moving,
After calculating the speed V in #27, a flag for a tracking mode 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 between the current and previous focus detection (La
-tb) and further multiplies that value by (1/2). This is to calculate the subject speed with a weight of 1/2 so that the expected subject speed V is not estimated to be faster than the actual one when there are variations in the calculated defocus amount. Actually, since the current defocus L D Fa is within the focusing range, the moving speed of the subject is not so large, and this is sufficient for the following speed.

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

Next, if it is out of focus when the value of the counter CN is 2 in the focus judgment in #23, then in the judgment in #30, #37
Processing moves to In #37, this time defocus JiLD
The signs of Fa and the previous defocus 1LDFb are 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 Proceed to #43 without doing
In #38, it is determined whether or not there is a release request, and if there is a release request, the subject speed V is calculated in #39, and in #40
Set the tracking mode flag with and proceed to the tracking mode routine. In the speed calculation in #39, the defocus amount DFa is divided by the focus detection time interval (tatb) and then multiplied by (1/2). . This is the same as the case described above, but here, since the defocus fiDFa is outside the focusing range and the speed of the subject is large, we do not immediately move to the release operation, but instead move to the release operation, which will be described later. 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° #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 11. There is.

If the absolute value of the defocus amount exceeds 1 mm, there is a high possibility that another subject was measured, so proceed to #41 and onwards and repeat focus detection again, #3
2. If #33 is YES, 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)/(La-tb), the follow-up mode flag is set in #35, and the process shifts to follow-up mode. Also,
If the three defocus amounts are not of the same sign in #32; in #36, it is determined whether the signs of the current defocus it D F a and the previous defocus amount DFb are the same;
If the signs of the current defocus l D F a and the previous defocus fi D Fb match in #36, select #4
1. After driving the lens again in #42, proceed to #43 and onward to repeat the subject discrimination, and in #36, set the current defocus MDF a and the previous defocus amount DFb.
If the signs do not match, it is determined that the accuracy of focus detection is low and defocus 1 varies, and the mode enters average mode (2).

FIG. 10 shows the flow of average mode (2). #9
Defocus at 9! As LDF, the average value DF of the current defocus amount DFa, the previous defocus amount DFb, and the previous defocus amount DFc = (DFa+DF
b+DFc)/3 is calculated. In #100, it is determined whether this defocus iDF is within the focusing range,
If it is in focus, press #101 to display the focus, and press #10
After the release is permitted in 2, the mode 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 fast, it is possible to determine the tracking mode using the method described above, but if the subject is slow, even if there is a time lag due to driving the lens to the intended focal position, the focus zone may be missed. 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 AP 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. Furthermore, when the camera is in focus, the prohibition of interrupts caused by interrupt 5 (interrupt baud) < INT2) is canceled, and release is always accepted, so that when a release request is made, the release operation is immediately performed. Subsequently, the counter CN2 is cleared in #46. Counter CN indicates the number of focus detections for AF mode determination. Focus detection calculation is performed in #47, and if it is determined that focus cannot be detected in #48, the contrast of the original subject is low, or
This may be the case when the focus detection calculation is performed on another subject whose focus position is significantly different from that of the subject to be photographed after focusing, and the process proceeds to #55. If the focus is detected normally in #48, proceed to #55. 481 calculates the defocus IDF,
If IDFI>1- is obtained in #49, it is considered that focus detection was performed on another subject whose focus position is different from that of the subject to be manipulated 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
If the determination in #55 is NO, the process proceeds to #56. In #56, if the next irregular focus detection is performed, #55
Set the previous ignore flag so that it becomes YES.

If YES in #55, it means that incorrect focus detection has been performed twice in a row, so in this case, check #57.
Step 1 indicates that the AP mode determination routine has been exited, and the flag (AFMF) is reset. Step #57 displays focus lock and 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 the AF 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 average of the previous defocus amount DFc and the current defocus Ji D F a is calculated. Therefore, the previous defocus amount DFb is interpolated and calculated. Next, in #52, the previous ignore flag is cleared and the process proceeds to #53.On the other hand, if the previous ignore flag is not set in #50, there is no need for interpolation, so the process directly proceeds to #53.In #53, the counter CN2 is cleared. is counted up, and #47 to #54 are repeated until the value of counter CN2 reaches 4 in #54. If the value of counter CN is 3 or less, the timer value TM is set to the memory value TM in #54I. ' to T, wait for a while until the number increases.

After completion of the four focus detection calculations, the flag (AFMF) indicating AF mode determination is reset in #581, and the process proceeds to #58. In #58, all four defocus amounts have the same sign, Moreover, the amount of defocus changes monotonically,
Furthermore, if the absolute values of the differences between the two consecutive defocus amounts in #59 to #61 are all determined to be equal to or greater than the predetermined determination amount value a, the subject is considered to be moving,
Shift to follow mode. At this time, the initial velocity at the time of following is V = (D F a D F c) / (t
a-tc) and sets the tracking mode flag in #63 to enter the tracking mode. At this time, the speed ■ is calculated from the current defocus amount DFa and the previous defocus amount DFc because the longer the focus detection time interval (ta-tc), the better the calculation accuracy, and because the data is newer. Cheng,
This is because the initial velocity V when entering the tracking mode can be calculated more accurately.

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 DFe 3
The average defocus amount of times is set as true defocus 1,
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 the AP to the completion of the 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 CN is used for determination when exiting from tracking mode. At #70, counters CN, CN, are 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 Ji D F a,
The planned defocus ff1D F' is calculated when the lens is not driven at the next time of focus detection. Based on this planned defocus amount DF', the number of pulses for driving the lens is calculated in #72, and the lens is driven in #73.In #74, the timer value TM is changed to the memory value TM at the time of the latest focus detection calculation. Wait until the time reaches the value obtained by adding the focus detection period T0 to T for simplicity. ! = iT0°, and there is almost no lens drive time. In the lens drive in #73, the lens is driven by the planned defocus amount DF' when no lens drive is performed, so focus detection is performed in #75. When the calculation is performed, the defocus amount will be calculated as approximately zero. In #76, it is determined whether 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.If proper focus detection is made in #76, the defocus amount DF is determined in #761. is calculated, but the absolute value IDFI of the obtained defocus amount is #77 and 11II
If it is determined that the value is M or more, it is determined that normal focus detection has not been performed as described above, and the process proceeds to #89.

In #89, the current defocus 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. IDFI<1 at #77
If it is determined to be m, 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 amount DFb had occurred. The defocus amount DFb' for the previous lens drive is the predicted movement amount of the subject 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 V. It is obtained by adding the 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 decreasing the previous defocus amount DFb.

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 ■, and it is assumed that proper focus detection has not been performed, and the value of counter CN4 is set to 1 in #88. It has increased by one. Furthermore, even if the absolute value of the defocus amount is greater than or equal to the predetermined judgment threshold in #80, this means that the actually measured defocus amount is significantly different from the expected defocus amount, and in the case described above. Similarly, it is assumed that proper focus detection has not been performed, and the process proceeds to #88, #7.
9. If both #80 and YES are determined, #81
Then, the value of the counter CNS indicating the number of times that normal focus detection has been performed is incremented 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 the counter CN3 is 2 due to the initial setting in #69, and the value of this counter CN3 is compared with the value of the 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, Counter CN s value and counter CN
This is to make it possible to exit the tracking mode by comparing the values of .

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 AF 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 CN4. Cleared CN.

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 following mode cannot be exited, the following speed V is newly calculated in #95.

In #95, in order to improve the calculation accuracy of the tracking speed V, 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-tc).
) to obtain the moving speed V.

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 1 at the time of the previous focus detection. At the focus detection time tc before the previous time, the lens was located at the DFc origin, so the defocus Ji D F c occurred the time before the previous time. The defocus 1DFc' for driving the lens two times before the previous time is calculated by multiplying the elapsed time (tb-tc) from the focus detection time tc of the previous time to the focus detection time tb of the previous time by the subject speed Vc, and then calculates the predicted movement amount of the subject. It is obtained in addition to the focus 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 amount DFb' for the previous lens drive is the predicted movement amount of the subject 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 vb. It is obtained in addition to the focus 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, the defocus amount difference ΔDF from the subject position at the previous focus detection time tc to the subject position at the current focus detection time ta
As is clear from the figure, this time the defocus JID
F a is the defocus amount DFb' for the previous lens drive.
and the defocus for driving the lens two times before the previous time] DFc', and further subtract the defocus JI D F c from the time before the last time. In other words, the defocus amount difference ΔD
F becomes ΔDF=DFa-DFc+DFb'+DFc'.

The tracking speed V is calculated by dividing the defocus amount difference ΔDF in the above equation 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, allowing the release. In this case, if there is a release request, a release routine is called and a release operation is performed.

Finally, the release routine will be explained.

First, in #117 of FIG. 12, it is determined whether the average correction flag is set. 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 by a flag (AFMF) whether or not the release was performed during AF mode determination. This flag (
If A F M F ) 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 defocus amount obtained during the above judgment is calculated. Step # to drive this amount
Proceed to 121 0 For example, if 2 parfocal detection is performed and defocus 1 (DFl, DF2) is obtained twice, DF=
(DPI+DF2)/2. The above flag (AFMF
) is not set, the lens will not be driven.
Proceed to #123 and subsequent steps; if the tracking mode flag was set in #118, proceed 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, a value obtained by multiplying the object moving speed V by the time lag τ is added to the latest defocus amount DFa to calculate the planned defocus amount DF' when the shutter is running. 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, the shutter is run, and as a result, control is performed to focus during the shutter run. 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 body based on the focus detection result, it is possible to determine that the subject is a moving body. Since the display is performed when the photographer does not intend to photograph a moving object, it is possible to prevent the control for photographing a moving object from being performed when the photographer does not intend to photograph a moving object.

[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 display means.

Claims (2)

[Claims] (1) Focus detection means for detecting the focus state of the lens with respect to the subject to be focused on, lens drive means for driving the lens toward the in-focus position based on at least the focus detection result of the focus detection means, and focus detection means A camera with an automatic focus adjustment function, comprising: a moving object determining means for determining whether or not a subject is a moving object based on a focus detection result; and a display means for displaying a display when the subject is determined to be a moving object. (2) When the subject is determined to be a moving object, the camera further comprises tracking control means for controlling the lens driving means so as to drive the lens in accordance with the speed of the subject. Camera with automatic focus adjustment.