JPH01187520A - Focus detector - Google Patents

Abstract

PURPOSE:To shorten a time required until it is decided that focus detection is impossible by limiting the direction of low contrast scanning to one direction just after setting a lens on an initial stopping position. CONSTITUTION:When it is decided by a focus detection impossibility decision means 6 that the focus detection by a focus detection means 2 is impossible, lens scanning (low contrast scanning) that the position of a lens in which the focus detection can be possible is seeked is performed by performing the focus detection by the focus detection means 2 while driving the lens 1 by a lens driving means 4 under the control of a lens scanning control means 7. However, when it is decided by a lens position setting decision means 5 that the setting of lens position has been just performed, a direction control means 8 drives the lens only in one direction (feeding out direction) toward other terminating position (for instance, the closest position) until the focus detection can be possible. Thus, the time required until it is decided that the focus detection is impossible can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a focus detection device used in a single-lens reflex camera with an automatic focus adjustment function.

[Prior Art] Conventionally, in an automatic focus adjustment device that detects the focus state of a lens for photographing and drives the lens to the in-focus position, when focus detection is impossible, it is possible to detect focus while driving the lens. It has been proposed to perform an operation to search for the lens position (so-called low contrast scan). In addition, when the focus cannot be detected, if the current position of the lens corresponds to the far-distance focusing position, it will move toward the near-distance focusing position; It has been proposed to drive a lens toward a focusing position on the far side (Japanese Patent Laid-Open No. 59-48719).

[Problems to be Solved by the Invention] When the focus detection device performs low contrast scanning, there is a problem that the time required for focus detection becomes longer.

Therefore, it is conceivable to move the lens to a predetermined initial stop position that allows focus detection at an infinite position before starting focus detection. In such a case, by extending the lens toward the short distance side from its initial stop position, it is possible to perform focus detection over the entire range. Therefore, low-contrast scanning only needs to be performed in one direction from the initial stop position toward the short distance side, which can eliminate unnecessary lens driving and reduce power consumption, as well as determine that focus cannot be detected. The time taken can be shortened.

However, the operation of setting the lens to the initial stop position is not performed every time focus is detected, so if the lens is not set to the initial stop position, focus detection of the entire range cannot be performed by simply extending the lens. It doesn't mean that it is. Therefore, in this case, it is necessary to perform the low contrast scan both on the near side and on the far side from the current position of the lens.

The present invention has been made in view of these points, and its purpose is to provide a focus detection device that can attempt focus detection over the entire range in as short a time as possible. be.

Means for Solving the Problem] In order to achieve the above object, the focus detection device according to the present invention includes a photographing lens (1), as shown in FIG. 1(a), A focus detection means (2) for detecting the focus state of the lens (1), and an initial state of the lens (1) such that one end position of the lens (1) (for example, an infinity position) is included in a focus detectable range. A lens position determination means (3) for determining the stop position Ns, a lens drive means (4) for driving the lens (1), and a determination as to whether or not the lens (1) has just been driven to the initial stop position Ns. A lens position set determination means (5), a focus detection impossible determination means (6) for determining whether focus detection by the focus detection means (2) is impossible, and a focus detection impossible determination means (6) for determining whether focus detection is impossible. When it is determined that the lens (1) is
and when it is determined by the lens position setting determination means (5>) that the lens position has just been set, the lens scanning control means (7) causes the focus detection means (2) to perform a focus detection operation. The lens is driven only in one direction toward the other end position (for example, the closest position) until the focus can be detected, and if it is determined that the lens position has not been set immediately after, the lens is driven in both directions until the focus can be detected. The present invention is characterized in that it comprises a direction control means (8) for controlling the direction of lens scanning so that the lens is driven in the direction in which the lens is scanned.

Further, as a modified example of the present invention, the lens position determining means (3) and the lens position set determining means (5) shown in FIG.
And instead of the direction control means (8), as shown in FIG.
A first output means (9) that outputs information regarding max, and a second output means (1) that outputs information regarding a defocus amount DFa that can be detected by the focus detection means (2).
0), a lens position detection means (11) for detecting the current position NL of the lens (1), and a lens position detection means (11) for detecting the current position NL of the lens (1).
The defocus amount NL, /K from to one end position is within the defocus amount DFa that allows focus detection, and the defocus amount (Nmax −N
L)/K is defocus iJ-D with focus detection
If it is not within F a, the lens is driven only in one direction toward the other end position until focus detection becomes possible, and the defocus amount N L/K , ( N+nax-Nl-)
/K is not within the defocus amount DFa that allows focus detection, a direction control means (12) is provided for controlling the direction of lens scanning so that focus detection is possible and the lens is driven in both directions. Also good.

However, FIG. 1 is an explanatory diagram showing the configuration of the present invention in a functional manner, and in the embodiments described later, the main part of the above configuration is realized by a microcomputer program. Note that one end position may be the closest position, and the other end position may be the infinitely far position.

[Effect] Hereinafter, the operation of the present invention will be explained with reference to FIG.

A photographic lens (1) forms an image of light from a subject.

The focus detection means (2) detects the focus state of the lens (1). The focal state of the lens (1) is usually defocused from the in-focus position! (out-of-focus amount), and front focus and back focus are distinguished by the sign. If the amount of defocus from the in-focus position is larger than a predetermined value determined by the configuration of the focus detection means (2), or if the contrast l- of the subject is low, focus detection becomes impossible, but the contrast of the subject is high and within the predetermined value, focus detection is possible. Lens (1)
If it is located at a commonly used position, there is a high probability that the focus can be detected. Therefore, according to the present invention, the initial stop position NS of the lens (1) is determined by the lens position determining means (3) so that the probability that focus detection becomes possible is increased. This initial stop position Ns is determined so that at least one end position of the lens (1) (for example, an infinity position) is included in the focus detectable range. Initial stop position Ns
The lens (1) is driven by a lens driving means (4).

During normal focus detection, this lens driving means (4), based on the focus detection result of the focus detection means (2),
An automatic focus adjustment device that drives the lens (1) toward the in-focus position may be used.

As described above, the initial stop position Ns of the lens (1) is determined so as to increase the probability that the focus can be detected, but there may still be cases where the focus cannot be detected.

Furthermore, after the lens (1) is moved from the initial stop position Ns, there may be cases where focus detection becomes even more impossible. In these cases, focus detection failure determination means (
6), it is determined that focus detection by the focus detection means (2) is impossible. If it is determined that focus detection is impossible, proceed to -9-. Under the control of the lens scanning control means (7), the focus detection means (2) is driven while the lens (1) is driven by the lens drive means (4). By performing focus detection, a lens scan (low contrast scan) is performed to search for a lens position where focus can be detected.

The direction of this lens scanning is controlled by the direction control means 8) according to the determination results of the lens position sensor 1 to the determination means (5). If it is determined that the lens position sensor 1 is not immediately after being performed, the lens is driven in both directions until focus detection becomes possible. In addition, if the lens position setting determination means (5) determines that the lens position has just been set, the camera moves in one direction toward the other end position (for example, the closest position) until focus detection becomes possible. The lens is driven only in the (feeding direction). This is lens (1)
When is set to the initial stop position Ns, one end position (infinity position) is included in the focus detectable range, so the renormalization direction is moved in the opposite direction toward this end position (infinity position). ) because there is no need to drive the lens.

By the above operation, the time required for low contrast scanning can be shortened as much as possible.

Moreover, in the modification shown in FIG. 1(b), the lens (
Information regarding the end position of 1) is output from the first output means (9). Information regarding this end position is lens-specific information. On the other hand, the defocus amount DFa that can be detected by the focus detection means (2) is determined by the configuration of the focus detection means (2), and is output from the second output means (10). The current position NL of the lens (1) is detected by the lens position detection means (11). The current position N of the lens (1) is usually detected as the amount of lens extension from the infinity position, and in this case, since the lens extension amount at the infinity position is 0, the first output means (9) is It is sufficient to output only the lens extension amount N max at the closest position. The information regarding the end position Nmax outputted from the first output means (9) and the lens position detection means (
11) The lens position N detected in step 11).

Based on the information, the amount of defocus from the current position NL of the lens (1) to the closest position (Nmax - NL)/, and the amount of defocus from the current position NL to the infinity position (NL/K) Seek. Here, K is a constant. The direction control means (12) controls these defocus amounts (Nma
x-N L)/K and (NL/K), when one is within the defocus amount DFa that allows focus detection and the other is not within the defocus amount DFa that allows focus detection, the cough that makes focus detection possible. The lens is driven only in one direction from the current lens position N toward the farthest end position, and if both are not within the defocus amount DFa that allows focus detection, the lens is driven in both directions until focus detection becomes possible. Control the direction of lens scanning to do so. With the above operation, regardless of whether or not the lens position is set, when the lens (1) is stopped within a defocus amount DFa that allows focus detection from one end position, the direction of lens scanning is changed to one direction. can be limited only to

[Embodiment] FIG. 2 is a block circuit diagram showing the circuit configuration of a camera as an embodiment of the present invention. However, illustrations of parts not directly related to the focus detection operation are omitted. (
μC) is a microcomputer that performs calculations and sequence control for focus adjustment. (LEC') is a lens circuit provided within the interchangeable lens, which transmits information specific to the interchangeable lens to the microcomputer (μC). (AP
C) is a focus detection circuit that photoelectrically converts the subject light that has passed through the lens and outputs focus detection data, which converts the focus detection data into a digital signal and outputs it to a microcomputer (μC). (DSP) is a display circuit that indicates that the lens is in focus and that the focus cannot be detected. (ILM)
is an auxiliary light emitting device for irradiating a subject with auxiliary light for focus detection. (M) is a motor for driving the four-force sync lens of the interchangeable lens, and extends and retracts the lens under the control of a lens drive circuit (LDC). The lens drive circuit (LDC) receives a motor drive speed signal, a motor drive direction signal, and a motor stop control signal from the microcomputer (μC), and drives the motor (M) based on these signals. (ENC) is an encoder that detects the amount of rotation of the motor (M).
The microcomputer (μ
Output a pulse to C).

Here, the microcomputer (μC) uses a lens position counter N to know the amount of lens extension from the infinity position, which is the most retracted state, as an absolute amount.
, is built-in. This lens position counter N, is reset to N,=O by an internal command when the lens is retracted to the infinite position, and when the lens is extended, the encoder (E N C) is reset by an internal command.
The count is increased from 1 to 1 in response to pulses from the encoder (ENC), and when the lens is renormalized, the count is counted down in response to pulses from the encoder (ENC) according to an internal command. When the lens is extended to the closest position, the value of the lens position counter NL is N (-= N ma
This maximum extension amount N+nax, which is 9, differs depending on the lens, and is read into the microcomputer (μC) from the lens circuit (LEC) as lens-specific information.

(BAT) is a power supply battery, and a microcomputer (
μC) and other circuits. Power battery (BA
A time constant circuit consisting of a series circuit of a resistor (R1) and a capacitor (C1) is connected to both ends of the resistor (T).
The connection point between R1) and the capacitor (C1) is connected to the power-on reset terminal (RES) of the microcomputer (μC). When the power supply battery (BAT) is connected, a power supply voltage is applied between the power terminal (Vcc) and the ground terminal (GND) of the microcomputer (μC), and the microcomputer (μC) becomes active.
The microcomputer (μC) does not operate until the charging voltage of the capacitor (C1), that is, the voltage applied to the reset terminal (RES) of the microcomputer reaches a predetermined voltage. When the voltage of the capacitor (C1) exceeds a predetermined voltage, the microcomputer (μC) is reset and starts operation from step #5 (see FIG. 3), which will be described later.

(SR) is a reset switch, and this switch is OFF.
When N is pressed, the lens is reset to the initial position. (S
ω) is an infinity position detection switch, which is turned on when the lens is retracted to the infinity position. (SM) is a main switch, which is turned on when using the camera. (S
l) is the shooting preparation switch, and normally the release button (
(not shown) is turned on at the first stroke. (SAF)
is the AP mode switch, and this switch (SAF)
When the switch (SAF) is ON, the autofocus mode is selected to drive the lens to the in-focus position based on the focus detection result, and when the switch (SAF) is OFF, the autofocus mode is selected based on the focus detection result. Display only,
A manual focus mode in which lens drive is not performed is selected. (SMZ) is a macro zone switch,
In a zoom lens with a macro mechanism, it is opened when the zoom ring is set to the macro zone. In the zoom lens with a macro mechanism used in this example, autofocus mode is disabled when the zoom ring is set to the macro zone, so in order to notify the microcomputer (μC) of this, the lens circuit <LEC) outputs a signal SMZ indicating the macro zone to the microcomputer (μC).

Next, the focus adjustment operation of the camera will be explained with reference to a flowchart. When the power-on reset is performed, the microcomputer (μC) executes the program from #5 shown in FIG. 3. First, all flags are reset in #5. Next, turn on the main switch (SM) with #10.
Determine whether

If the main switch (SM) is not turned on, the determination in #10 is repeated until it is turned on. Main switch (SM
) is ON, the lens initial position calculation subroutine (Figure 9) is executed in #15, the ω renormalization subroutine (Figure 10) is executed in #20, and the lens initial position set subroutine is executed in #25. After executing (Figure 11),
At #30, it is determined whether the main switch (SM) is OFF. If the main switch (SM) is OFF, the ω renormalization subroutine is executed in #35, and the process returns to #10. #
If the main switch (SM) is not OFF at 30, #
Proceed to step 45.

FIG. 9 is a flowchart showing the contents of a subroutine for calculating the lens initial position. When this subroutine is called, first, the lens circuit (L E C) is
Enter lens data from .

From the lens circuit (LEC), the lens attachment signal IC
P, macro zone signal SMZ, macro lens attachment signal LCPR of equal or greater magnification, maximum extension amount N max, focal length f, conversion coefficient I (etc.) are input to the microcomputer (μC).Here, the conversion coefficient I, This is a coefficient for converting the defocus amount DF into the lens drive amount ΔN.

In #1005, the macro lens attachment signal LCP
Determine the presence or absence of R.

If the macro lens of equal or larger magnification is attached in #1005, the defocus amount DFs for setting the lens initial position is set to DFm/2 in #1040, and the process returns to the step in which the subroutine was called. Here, D F m is the maximum defocus amount that covers the range from the closest position to the infinity position of the lens. If the macro lens is not attached at #1005, the defocus amount DFb is determined at #1008. This defocus amount DFb is the defocus amount from an infinity position to the lens position Nb determined according to the imaging magnification β. In this embodiment, information on the lens position Nb, which is preset in consideration of the frequently used photographic magnification β, is read from the ROM table based on the information on the focal length f.

(Left below) Table 1 However, in the table above, * indicates when the 28-135mm zoom lens is at 135mm, and ↑ indicates when the 70-210mm zoom lens is at 210mm.
↑ is data when a 75-300mm zoom lens is at 300mm.

=19- Table 1 shows the frequently used photographic magnification β and the lens position N determined accordingly for lenses with various focal lengths.
The defocus amount DFb corresponding to b and the maximum defocus amount DFm of the lens are shown. Note that DFa is the defocus amount that allows focus detection, which is determined by the configuration of the focus detection circuit (AFC), and the focus detection range is twice that amount.
It becomes DFa.

In #1010, it is determined whether DFb>DFa.

If DFb>DFa in #1010, set the defocus amount DFs for setting the lens initial position to DFa in #1030.
Then, in #1060, the lens position set flag 5ETF is set to 1, and the process returns to the step where the subroutine was called. If DFb≦DFa in #1010, #10
20 is the defocus amount DFs for setting the lens initial position.
is DFb, and #1050 is the lens position set flag 5.
Set ETF to 1 and return to the step where the subroutine was called.

FIG. 12 is a diagram for explaining the meaning of steps #1010 to #1030. The figure (,) shows a case where the defocus amount DFb from the lens position if N b determined according to the imaging magnification β to the infinity position is larger than the defocus amount DFa that allows focus detection. In this case, DPs=DFa. Therefore, at the lens initial position N5=DFsXK, the infinity position is included in the focus detectable range 2DFa, and if the focus cannot be detected, it is only necessary to scan in the direction in which the lens is extended. The figure (b) shows the defocus amount DF from the lens position Nb to the infinity position determined according to the imaging magnification β.
The case where b is less than or equal to the defocus amount DFa that allows focus detection is shown, and in this case, DFs=DFb. In this case as well, lens initial position N5=D
In FsXK, the infinity position is the focus detectable range 2.
It is included in the DFa, and if the focus cannot be detected, it is only necessary to scan in the direction in which the lens is extended.

FIG. 10 is a flowchart showing the contents of the ω renormalization subroutine. When this subroutine is called, lens renormalization starts at #1100, and #1.10
5, it is determined whether the infinite position detection switch (Sω) is ON. If the switch (Sω) is not turned on in #1105, the determination operation in #1105 is repeated until the switch (Sω) is turned on. When the lens is retracted to the infinite position in #1105 and the switch (S(X)) is turned on, lens retraction is stopped in #1110, the lens position counter NL is reset in #1115, and the subroutine is executed. returns to the step where was called.

FIG. 11 is a flowchart showing the contents of the subroutine for setting the lens initial position. When this subroutine is called, in #1200, the defocus amount DFs for setting the lens initial position is multiplied by the conversion coefficient K to calculate the lens drive amount ΔN=DFSXK from the infinity position, and #1
At step 205, lens extension is started. In #1210,
It is determined whether the lens drive amount has reached ΔN. #1210
If the lens drive amount has not reached ΔN, the determination operation in #1210 is repeated until the lens drive amount reaches ΔN. If the lens drive amount reaches ΔN in #1210, #12
At step 15, lens driving is stopped and the subroutine returns to the called step.

Returning to the flow of FIG. 3, in #45, it is determined whether the AP mode switch (SAF) is ON.

If the AF mode switch (SAF) is not ON in #45, the flag MF indicating Mayua J reflex focus mode is set to 1 in #50, and the process proceeds to #80. If the AP mode switch (SAF) is ON in #45, #55
It is determined whether the flag MF is 1 or not. #55 MP=
If it is 1, it means that the switch (SAF) has just been turned on, and in #60 the flag MF is set to 0 and the process proceeds to #65. In #65 to #75, the lens initial position calculation, ω renormalization, and lens initial position setting subroutines described above are executed to set the lens initial position, and then #
Proceed to 145. If MP = 1 in #55, it means that the switch (SAF) has been on for a long time.
Proceed to #80.

In #80, the presence or absence of the lens attachment signal ICP is determined.

If the lens is not attached in #80, the flag LENOF indicating that the lens is not attached is set to 1 in #100, and the process proceeds to #105. If the photographing lens is attached in #80, it is determined in #90 whether the flag LENOF is 1. If LENOF=1 in #90, it means that the lens has just been attached, and the flag LENO is set in #95.
After setting F to O and setting the lens initial position in #65 to #75, proceed to #145. If LENOF-1 is not detected in #90, it means that the lens has been installed before, and proceed to #105.

#105, macro zone switch (SMZ) is ON
In other words, it is determined whether the zoom lens is in the macro zone. Macro zone switch (SM) with #105
Z) is not ON, that is, if it is in the macro zone,
In #110, the flag SMZOFF indicating that the macro zone switch (SMZ) is OFF is set to 1, and in #125
Proceed to. If the macro zone switch (SMZ) is ON in #105, it is determined in #115 whether the flag SMZOFF is 1. If SMZOFF=1 in #115, it means that the macro zone switch (SMZ) has just been turned on, and after setting the flag SMZOFF to 0 in #120 and setting the initial lens position of #65 to #7 etc. , proceed to #145. #115 SMz.

If PF is not 1, the macro zone switch (
SMZ) was turned on, and #125
Proceed to.

In #125, it is determined whether the reset I switch (SR) is ON. #125 reset switch (SR)
is not ON, turn #130 to reset switch (SR
) is OFF, the flag 5ROFF is set to 1, and the process proceeds to #145. #125 is the reset switch (SR
) is ON, it is determined in #135 whether the flag 5ROFF is 1.

If 5ROFF=1 in #135, it means that the reset switch (SR) has just been turned on, and #140
After setting the flag 5ROFF to 0 and setting the lens initial position in #65 to #75, proceed to #145, #135
If 5ROFF = 1, it means that the reset switch (SR) has been turned on before, and the lens has already been set to the initial position, so #65 to #7
The process proceeds to #145 without performing the lens initial position setting in step 5.

Therefore, after setting the lens initial position (#15 to #25) immediately after turning on the main switch (SM),
Immediately after the P mode switch (SAF) is turned on or the lens is attached, the macro zone switch (SMZ) is
) is turned on, or the reset switch (SR
) is turned on, or when the focus cannot be detected even after performing the low contrast scan described below and the camera is turned on again after turning off the shooting preparation switch (Sl) (#15
5)), lens initial position setting (#65 to #7) is required.
5) is performed, and in other cases, lens initial position setting is not performed. Therefore, when there is a high probability of focusing near the previous lens position, such as when photographing a similar scene or when shooting multiple pictures in succession, the lens initial position setting is not performed and the focus Compared to the case where the lens initial position is set every time detection is performed, power consumption is reduced and the time required for focus adjustment is reduced.

In #145, it is determined whether the photographing preparation switch (Sl) is ON. If the photographing preparation switch (Sl) is not turned on, the entire display is turned off in #40 and the process returns to #30. Below, #30, #45, #80, #105, #125
, and #145, check the status of the main switch (SM), AF mode switch (SAF), lens attachment signal ICP, macro zone switch (SMZ), reset switch (SR), and shooting preparation switch (Sl). Monitor.

In the middle of this loop, the main switch (SM) is turned off.
When it is, as mentioned above, ■ Renormalization (#35)
and waits until the main switch (SM) is turned on again (#10). Also, in the middle of the loop, one of the switches (SAF), (SMZ), and (SR) is turned ON.
or when the lens is attached, the lens initial position setting (#65 to #75) is performed each time. In this way, the camera is set to the shooting preparation switch (Sl).
The camera is waiting for the signal to turn N, but when the shooting preparation switch (Sl) is turned on in #145, focus detection is started.
Proceed to #155 (Figure 4).

In #155, it is determined whether a low contrast scan end flag LSENDF, which will be described later, is 1.

Initially, since LSENDF=O, focus detection is performed in #175, and it is determined in #180 whether focus detection is impossible. If the focus cannot be detected in #180, the process proceeds to #285 (FIG. 7) to perform focus determination. If the focus cannot be detected in #180, it is determined in #185 whether the brightness is low. #185 If the brightness is low, the auxiliary light will be emitted, #
Proceed to step 330 (Figure 8). If there is no low brightness in #185, then in #190 and #191 (Figure 5), (N + nax - N + -)/K > D Fa or N L/K > D Fa - ■ is satisfied. Determine whether the #] If the condition (2) is not satisfied in 90 and #191, the entire focus range of the lens is included in the focus detectable range 2DFa. However, the fact that the focus cannot be detected means that there is no way that the focus can be detected even if you perform a low contrast scan (detecting the focus while driving the lens and searching for a position where the focus can be detected). It is wasteful to perform a conscan. Therefore, without performing the low contrast scan, the process proceeds to #255 (see FIG. 7), and a focus detection failure display is performed.

If condition ■ is satisfied in #190 or #191, #
At 192, it is determined whether Nmax/2K≦DFa−■ is satisfied. Here, Nmax/2 is the defocus amount (ie, DFm/2) from the intermediate position to the final position of the photographing lens, and is determined depending on the attached lens. Further, as described above, 2DFa is a defocus amount that allows focus detection, determined by the configuration of the focus detection circuit (AFC), and is a constant on the camera body side. If condition (■) is satisfied in #192, if the lens is in the intermediate position, the total focus range of the lens is Nm.
Since ax/K is included in the focus detectable range 2DFa,
There is no need to go out of your way to perform a low-contrast scan. Therefore,
#1 to move the lens to the intermediate position Nmax/2
In step 93, the lens driving amount ΔN=Nmax/2-NL is calculated, and in step #1941, lens driving is started. #
], 942, it is determined whether the lens drive amount has reached ΔN. If the lens drive amount reaches ΔN in #1942, the determination operation in #1942 is repeated until the lens drive amount reaches ΔN.

If the lens drive amount reaches ΔN in #1942, #194
3, the lens drive is stopped, focus detection is performed in #195, and then it is determined in #196 whether focus detection is impossible. #1
96, if the focus cannot be detected, there is no way that the focus can be detected even if the low-contrast scan is performed, and it is wasteful to perform the low-contrast scan. Therefore, the process proceeds to step #255 (FIG. 7) without performing the low contrast scan, and displays that the focus cannot be detected. If the focus cannot be detected, the process proceeds to #285 (FIG. 7) to perform focus determination.

If condition #192 is not satisfied, the total focus range of the lens is Nmax/no matter where you change the lens position.
K cannot be covered within the focus detectable range 2DFa. Therefore, in this case, a low-contrast scan is unavoidably performed, but we devised a way to shorten the time required for a low-contrast scan by limiting the range of the low-contrast scan to as narrow a range as possible. ing. That is, in #198 (FIG. 6), the scanning amount in the feeding direction is calculated as ΔN=Nmax-NL-DFaXK.

This is because even if the lens is not extended to the maximum extension position N+nax, if it is extended to a position DFaXK in front of the user, the maximum extension position Nmax will also fall within the focus detectable range 2DFa. Next, in order to know the scanning direction, it is determined in #200 whether the flag FOWF is 1.

This flag FOWF is a flag indicating that scanning is to be performed in the direction (FOWard). When a low contrast scan is performed for the first time, the flag FOWF is reset, so FOWF=1 is not set. Therefore, the process first proceeds to #205, sets FOWF=1 in #205, and proceeds to #220. In #220, a signal is output to the lens drive circuit (LDC) to drive the lens (in the extending direction), and after focus detection is performed in #225, it is determined in #230 whether focus cannot be detected. If the focus cannot be detected in step #230, the flag FOWF is reset in step #233, and the process proceeds to step #285 (FIG. 7) to perform focus determination. #
If the focus cannot be detected in 230, it is determined in #235 whether the lens drive amount has reached ΔN. If the lens driving amount has not reached ΔN in #235, the process returns to #225, and while continuing to drive the lens in the extending direction, it is determined whether focus cannot be detected. If the lens drive amount has reached ΔN in #235, the lens drive is stopped in #240, and it is determined in #245 whether the lens position set flag 5ETF is 1. If 5ETF=1 in #245, it is determined that focus cannot be detected over the entire focus range of the lens without scanning in the renormalization direction. Proceed to Figure).

If 5ETF is not 1 in #245, it is determined in #250 whether the flag FOWF is 1.

If FOWF=1 in #250, this means that the lens position where focus detection was possible was not found even though scanning was performed in the extending direction, so return to #200 to scan in the retracting direction. . If FOWF=1 in #200, it means that the scan in the feed-out direction has already been completed, so in #210, the scan amount in the retraction direction is calculated as ΔN=DFaXK-NL. This means that DFa can be calculated even without renormalization to the infinite position.
This is because the infinity position is included in the focus detectable range 2DFa when the position is retracted only to the position in front of x.

In #215, the flag FOWF is set to O to indicate that the scan is in the renormalization direction, and the process proceeds to #220. #
220 outputs a signal to the lens drive circuit (LDC) to drive the lens (in the retraction direction), and #225 to
After #245, the process returns to #250. This time, FOW
Since F=1, it does not return to #200, but #2
Proceed to step 55 (Figure 7). In other words, in #250, FOWF=
If it is not 1, it means that both the scanning in the extending direction and the scanning in the retracting direction were performed, but no lens position where the focus could be detected was found, so #25
5 indicates that focus cannot be detected.

If focus detection becomes possible in #230 during scanning in the retraction direction, the flag FOWF is reset in #233, and the process proceeds to #285 (FIG. 7) to perform focus determination.

When displaying focus detection failure in #255 (Fig. 7), #2
At 60, set the low contrast scan end flag LSENDF to 1
shall be. This flag is a flag to indicate that a lens position where the focus can be detected was not found even though the low contrast scan was performed. Note that if the focus cannot be detected even though the entire focus range of the lens is included in the focus detection range 2DFa (specifically, #191 or #19
6 to #255), the flag LSE is set in #260 even if low contrast scan is not actually performed.
Let NDF be 1. This is because even if a low contrast scan is performed, it is impossible to find a lens position where the focus can be detected. Next, #265 is the flag F indicating the scanning direction.
After returning OWF to 0, press #270 to turn the shooting preparation switch (
SL) is ON. If the photographing preparation switch (Sl) is not turned on in #270, the entire display is turned off in #40 and the process returns to #30. Press #270 to turn on the shooting preparation switch (
Sl) is ON, focus detection is performed in #275, and #
In step 280, it is determined whether focus detection is impossible. If the focus cannot be detected in #280, the process returns to #270. If the focus is not detectable in #280, the lens position set flag 5ETF is set to O in #285, the low contrast scan end flag LSENDF is set to 0 in #290, and it is determined whether focus is achieved in #295.

If it is determined that the focus is not in focus in #295, the process proceeds to #300, where the in-focus and focus detection failure display is erased, and the lens drive amount ΔN=DFX is determined based on the defocus amount DF in #305.
K is calculated and lens driving is started in #310. #31
In step 1, it is determined whether the lens drive amount has reached ΔN. #
If the lens driving amount has not reached ΔN in step 311, the determination operation in #311 is repeated until the lens driving amount reaches ΔN. If the lens drive amount reaches ΔN in #311, #3
At step 12, the lens drive is stopped and the process returns to #270.

If the shooting preparation switch (Sl) remains ON in #270, focus detection is performed in #275, and then in #280 to #290
After that, the focus is determined again in #295.1. #3 above
Since the lens is driven toward the in-focus position in steps #05 and #310, there is a high possibility that the focus will be achieved here. If the camera is in focus in #295, the focus is displayed in #315, and it is determined in #320 whether the photographing preparation switch (Sl) is ON. If the photographing preparation switch (Sl) is turned on in #320, the determination operation of #320 is repeated until the photographing preparation switch (Sl) is no longer ON, resulting in a so-called focus lock state. Although this is unrelated to the present invention, in the case of a camera in focus priority mode, if release is permitted in this focus locked state and the release button (not shown) is pushed to the second stroke, the camera will be released. It performs a release operation. #320 If the shooting preparation switch (Sl) is not ON, #40
Delete the display =37- and return to #30. In other words, the shooting preparation switch (
SL) is turned off, the above-mentioned focus lock state is released.

After the shooting preparation switch (Sl) is turned off, it is turned on again.
If so, it may be determined as LSENDF-1 in #155. This was previously set as the shooting preparation switch (S).
I turned on l) and performed focus detection, but the focus could not be detected.
This is the case when a lens position where focus detection is possible cannot be found even after performing a low contrast scan, or when there is no way that a lens position where focus detection is possible can be found even after performing a low contrast scan. In this case, #157 flag L
Return SENDF to O, set the lens initial position in #65 to #75, and proceed to #145. Note that the process proceeds to #157 only when the photographing preparation switch (Sl) is turned ON after being turned OFF.

At this time, the reason for setting the lens initial position is that the low contrast scan end flag L S E N D F 1
In this case, there is a low probability that the subject you want to photograph exists near the current lens position, and especially when performing a low contrast scan, the lens position may be near infinity or the closest position. Since it is biased,
This is because it is necessary to return it to its proper position.

Next, when passing through #330 in Figure 8, it is determined in #185 and #180 (Figure 4) that the brightness is low and focus cannot be detected, so auxiliary light emission is necessary. However, there are cases where it is useless to emit the auxiliary light, so #3
The determination is made in steps 30 and #335. Here, the auxiliary light emitting device (I LM) shown in Fig. 2 is usually a combination of a light emitting diode and a light emitting optical system mounted externally above the photographic lens of the camera, or installed on the front of the camera body. including systems. On the other hand, the focus detection circuit (AFC) includes a focus detection optical system using a TTL phase difference detection method, and its optical axis coincides with the optical axis of the photographic lens. Therefore, the luminous flux range of the optical system for auxiliary light projection and the luminous flux range for focus detection have a disparity, and a predetermined distance (
(changes depending on the angle of view), the light flux range for focus detection is completely included in the light flux range of the optical system for projecting the auxiliary light. This distance is the lower limit of the range in which the subject can be irradiated with the auxiliary light to enable focus detection, and it is useless to emit the auxiliary light for a subject that is closer than this distance. Also, if a long focal length lens is attached to the camera,
Since the auxiliary light is vignetted by the lens barrel, the auxiliary light does not hit the subject, and even if the auxiliary light is emitted, it may be wasted. Note that the lower limit of the range in which the subject can be illuminated to enable focus detection with fill light can be reduced by adopting a TTL fill light system, but the upper limit of the range in which focus detection is possible with fill light irradiation can be made smaller. The thing is, the reach distance of the auxiliary light is about 10" at most, so we can't expect much. Therefore, in #330, it is determined whether the focal length f of the lens is 250 mm or more, and in #330, f
If ≧250, it is determined that the auxiliary light may be vignetted due to the long lens length, and the auxiliary light is not emitted and #1
Proceeding to 90 (FIG. 5), it is determined whether a low contrast scan is necessary. Note that when shooting with a long focal length lens, there are many long-distance shots where the auxiliary light cannot reach, so there is not much of a problem even if the auxiliary light emission is prohibited. #330 If f≧250, use #335 to output the macro lens attachment signal LCPR
Determine the presence or absence of. If a macro lens of equal or larger magnification is attached in #335, it is determined that the shooting is at close range, which is closer than the lower limit of the range where focus detection is possible with auxiliary light irradiation, and the auxiliary light is not emitted. Proceeding to #190 (FIG. 5), it is determined whether a low contrast scan is necessary. #340 unless a macro lens of 1x or higher is attached to #335.
to emit the auxiliary light, perform focus detection in #345, and
At step 50, it is determined whether the focus cannot be detected. The auxiliary light is emitted only for a predetermined period of time for each focus detection. If the focus cannot be detected in #350, the process proceeds to #395. If focus cannot be detected with #350, try adjusting the lens position to an intermediate distance (e.g. 4m) where focus detection using the auxiliary light is possible, or a distance (e.g. 3m) where there are many photographic scenes. , #355 lens drive amount ΔN − (f2/D o
>X K N +- is calculated, and lens driving is started in #360. #361-41-.

. Now, it is determined whether the lens drive amount has reached ΔN.

If the lens driving amount has not reached ΔN in #361, the determination operation in #361 is repeated until the lens driving amount reaches ΔN. #36] When the lens drive amount reaches ΔN, #
At 362, the lens drive is stopped. Then, the auxiliary light is emitted in #370, the focus is detected in #375, and the focus is detected in #380.
Determine whether focus cannot be detected. If the focus is not detected in #380, the process proceeds to #395. If the focus cannot be detected in #380, the focus is not detected in #385, and
In #390, it is determined whether the photographing preparation switch (Sl) is ON. #390 Shooting preparation switch (Sl) is turned on
If so, return to #375. If the shooting preparation switch (Sl) is not ON in #390, turn off the display in #40,
Return to #30.

In #395, the focus detection failure display is erased, and in #400, it is determined whether focus is achieved. If the focus is #400, #4
20 indicates the focus, and #425 sets the shooting preparation switch (
SL) is ON. #425 If the shooting preparation switch (Sl) is ON, the shooting preparation switch (Sl) is turned on.
The determination in #425 is repeated until Sl) is no longer ON. When the photographing preparation switch (Sl) is no longer ON in #425, the display is turned off in #40 and the process returns to #30. #40
If 0 is not in focus, use #405 to defocus ff1D
A lens driving amount ΔN=D F x K is calculated from F, and lens driving is started in #410. In #412, it is determined whether the lens drive amount has reached ΔN. If the lens driving amount has not reached ΔN in #412, the determination operation in #412 is repeated until the lens driving amount reaches ΔN. #4
When the lens drive amount reaches ΔN at #12, the lens drive is stopped at #413, and the shooting preparation switch (Sl) is turned on at #415.
is ON. If the photographing preparation switch (Sl) is ON in #415, the process returns to #370; if it is not ON, the display is turned off in #40, and the process returns to #30.

Figure 13 is a flowchart 1 showing a modification of the low-contrast scan program shown in Figure 6, and is inserted before #198. In #2010, it is determined. #2010
If 5ETF=1, the process proceeds to #198, and the low contrast scan becomes one-way control only in the feeding direction. #201
If it is not 0 and 5ETF-1, #2020 and #205
0 (N1-/K)≦DFa or (N max N
L) / Determine whether the condition of K≦DFa is satisfied. If neither condition is met, the process proceeds to #198 with 5ETF=0 in order to perform low-contrast scanning in the feeding direction and the feeding direction. #2020 If (NL/Ig)≦DFa, the current position of the lens i
N, defocus amount from - to infinity position (N +
-/K) is within the defocus amount DFa that allows focus detection, low-contrast scanning in the renormalization direction is not necessary. Then, set #2030 to FOWF=O, and #2
At 040, set 5ETF=1 and proceed to #198&. In this case, low contrast scanning is performed only in the feeding direction as if immediately after the lens position Cera 1 is reached. Also, in #2050, (N + nax N +-)/≦D
If it is Fa, the defocus amount (N max - N L)/K from the current position NL of the lens to the closest position is within the defocus amount DFa that allows focus detection, so low-contrast scanning in the feeding direction is performed. is not necessary. Then, in #2060, set 5ETF=1 and proceed to #210. In this case, only low-contrast scanning in the renormalization direction is performed.

Finally, the correspondence between the basic configuration of the present invention shown in FIG. 1 and the embodiments shown in FIG. 2 will be explained. In FIG. 2, the lens circuit (LEC) is included in the lens (1) and includes first output means (9). The focus detection circuit (AFC) corresponds to the focus detection means (2). The amount of deficiencies DFa that can be detected by the focus detection means (2) is determined by a microcomputer (μC).
This memory is fixedly stored in the second memory.
It corresponds to the output means (10) of. #1010 to #1030 in the lens position calculation subroutine in FIG.
The step corresponds to the lens position determining means (3).

The lens drive circuit (LDC) in Fig. 2 is a lens drive means (
4) is supported. Step #245 in Figure 6, step #285 in Figure 7, and #1050 in Figure 9.
Steps #1060 and #1060 correspond to the lens position set determination means (5). Step #180 in FIG. 4 corresponds to the focus detection failure determining means (6). The program shown in FIG. 6 corresponds to the lens scanning control means (7). Steps #198 to #215 and #250 in the figure correspond to the direction control means (8).

Further, the encoder (ENC) shown in FIG. 2 and the lens position counter NL for counting its output pulses correspond to the lens position detection means (11). Furthermore, steps #198 to #215 and #250 in FIG. 6 and steps #2010 to #2060 in FIG.
12).

[Effects of the Invention] As described above, the present invention switches between one-way control and reciprocating control of the low contrast scan depending on whether or not the lens has just been set at the initial stop position. Immediately after setting to 1, the direction of low contrast scan can be limited to one direction and constant46, which shortens the time it takes to determine that focus cannot be detected, and the amount of lens drive is small. This has the effect of reducing power consumption.

Furthermore, according to the configuration shown in Fig. 1 ()), one-way control and reciprocating control of low-contrast scanning are performed depending on whether the lens is stopped within a defocus amount that allows focus detection from one end position. Therefore, when the lens is stopped within a defocus point where focus can be detected from one end position, the direction of low contrast scan can be limited to one direction, and it is determined that focus cannot be detected. This has the effect of reducing power consumption by reducing the amount of lens drive.

[Brief explanation of the drawing]

FIGS. 1(a) and 11 are block diagrams showing the basic configuration of the present invention, FIG. 2 is a block circuit diagram of an embodiment of the present invention, and FIGS. 3 to 11 are flowcharts showing the operation of the same. , FIG. 12 is an explanatory diagram of the same operation as above, and FIG. 13 is a flowchart of a modified example of the same. (1) is a lens, (2) is a focus detection means, (3) is a lens position determination means, (4) is a lens drive means, (5) is a lens position set determination means, and (6) is a focus detection impossible determination means. , (7) is lens scanning control means, (8) is direction control means, (9) is first output means, (10) is second output means, (11) is lens position detection means, (12) is a direction control means.

Claims (2)

[Claims] (1) A photographic lens, a focus detection means for detecting the focus state of the lens, and a lens position determination means for determining the initial stop position of the lens such that one end position of the lens is included in the focus detectable range. a lens drive means for driving the lens; a lens position set determination means for determining whether the lens has just been driven to the initial stop position; and a focus detection means for determining whether focus detection by the focus detection means is impossible. lens scanning control means for driving the lens by the lens driving means and causing the focus detecting means to perform a focus detecting operation when the focus detecting impossible determining means determines that the focus detection is impossible; and a lens position setting means. When the determination means determines that the lens position has just been set, the lens is driven in only one direction toward the other end position until focus detection becomes possible, and the lens position must be set immediately after the lens position is set. 1. A focus detection device comprising: direction control means for controlling the direction of lens scanning so that when it is determined, the lens is driven in both directions until focus detection becomes possible. (2) a photographing lens, a focus detection means for detecting the focus state of the lens, and a lens drive means for driving the lens;
a focus detection impossibility determining means for determining whether or not focus detection by the focus detecting means is impossible; and a focus detecting means for driving the lens by a lens driving means when the focus detecting impossibility determining means determines that focus detection is impossible. a lens scanning control means for performing a focus detection operation, a first output means for outputting information regarding the end position of the lens, and a second output means for outputting information regarding the amount of defocus that can be detected by the focus detection means. and a lens position detection means for detecting the current position of the lens; and a lens position detection means that detects the current position of the lens, and a defocus amount from the current position of the lens to one end position is within a defocus amount that allows focus detection, and a defocus amount from the current position of the lens to the other end position. If the defocus amount is not within the defocus amount that allows focus detection, the lens is driven in only one direction toward the other end position until focus detection becomes possible, and the defocus amount from the current position of the lens to each end position is A focus detection device comprising: direction control means for controlling the direction of lens scanning so that when the defocus amount is not within a defocus amount that allows focus detection, the lens is driven in both directions until focus detection becomes possible.