JPH01187516A - Focus detector - Google Patents

Abstract

PURPOSE:To omit the insignificant setting of the position of a lens by driving a lens to an initial stopping position at the time of deciding that it is under condition that the driving of the lens should be performed in a condition decision means. CONSTITUTION:The initial stopping position Ns of the lens 1 is determined by a lens position determining means 3 in order to make probability that the focus detection can be possible high. And the condition decision means 5 decides whether or not the lens 1 is under the condition that the lens 1 should be driven to the initial stopping position Ns. Now, for example, a time when a main switch SM form power source is turned on is considered as the condition. In such a case, a control means 6 controls a lens driving means 4 so that the lens 1 is driven to the initial stopping position Ns. Thus, the initial setting of the position of the lens is performed under the specified condition and the probability that the focus detection can be possible is made high. Since the initial setting of the position of the lens is not performed when it is not under the specified condition, the quantity of current consumption can be reduced.

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 photographic lens and drives the lens to the in-focus position, the time required to drive the lens to the in-focus position after focus detection is In order to maintain the stability, it has been proposed to initially set the lens to an intermediate position each time a photograph is taken (U.S. Pat. Nos. 4 and 2).
65.528).

[Problems to be Solved by the Invention] However, initially setting the lens to an intermediate position every time photography is completed may not necessarily meet the objective of improving focus detection speed. For example, when shooting very similar scenes or shooting multiple frames in a short period of time,
Since the probability of focusing near the previous lens position is high, it is considered better not to move the lens after shooting. There is also the problem that if the lens position is set too frequently, power consumption increases.

The present invention has been made in view of these points, and an object of the present invention is to provide a focus detection device that makes it possible to omit meaningless lens position setting.

[Means for Solving the Problems] In order to achieve the above object, the focus detection device according to the present invention includes a photographing lens (
1), a focus detection means (2) for detecting the focus state of the lens (1), a lens position determination means (3) for determining the initial stop position Ns of the lens (1), and a drive for driving the lens (1). Lens driving is performed by the lens driving means (4), the condition determining means (5) for determining whether the condition is such that the lens (1) should be driven to the initial stop position Ns, and the condition determining means (5). The lens driving means (4) is configured to drive the lens (1) to the initial stop position IfNs when it is determined that the condition =3-.
The invention is characterized in that it comprises a control means (6) for controlling.

However, FIG. 1 is an explanatory diagram showing the configuration of the present invention in functional blocks, and in the embodiments described later, the main part of the above configuration is realized by a microcomputer program.

[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 detected as the amount of defocus (out of focus) from the in-focus position, and the defocus amount from the 9-in-focus position, whose sign distinguishes front focus and rear focus, is: If the value is larger than a predetermined value determined by the configuration of the focus detection means (2) or if the contrast of the subject is low, focus integration becomes impossible.
If the contrast of the subject is high and within the predetermined value, focus detection is possible. If the lens (1) is located in a commonly used position, there is a high probability that the focus can be detected. Therefore, in 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. The lens (1) is driven to the initial stop position by the lens drive means (4) under the control of the control means (6). During normal focus detection, this lens driving means (4) is for automatic focus adjustment, which drives the lens (1) toward the in-focus position based on the focus detection result of the focus detection means (2). All you have to do is divert it. Condition determination means (5)
Now, it is determined whether the conditions are such that the lens (1) should be driven to the initial stop position Ns. Here, the conditions for driving the lens (1) to the initial stop position Ns include, for example:
An example of this is when the main switch (SM) for power supply is turned on. In this case, since there is no need to maintain the previous lens position, it is meaningful to initially set the lens (1) to the position Ns where the probability that focus detection becomes possible is high.

When the condition determining means 6-(5) determines that the condition is such that the lens (1) should be driven, the control means (6) causes the lens (1) to be driven.
1) to the initial stop position Ns. If it is not determined that the condition is such that the lens (1) should be driven, the initial setting of the lens position is not performed.

[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 in the interchangeable lens, and transmits information specific to the interchangeable lens to the microcomputer (μC). (AF
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 displays the focus of the lens and indicates 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 focusing 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.
It has a built-in L. This lens position counter NL is reset to NL=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 counted up in response to a pulse from the encoder (ENC), and when the lens is retracted, it is counted down in response to a pulse from the encoder (ENC) by an internal command. When the lens is extended to the closest position, the value of the lens position counter N becomes Nl-Nmax. This maximum extension amount N max differs depending on the lens, and is read from the lens circuit (LEC) into the microcomputer (μC) as lens-specific information.

(BAT) has a power 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 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.
=8- charging voltage of capacitor (C1), i.e. reset terminal of microcomputer (
Until the voltage applied to RES) reaches a predetermined voltage,
The microcomputer (μC) does not work. When the voltage of the capacitor (C1) exceeds a predetermined voltage, the microcomputer (μC) is reset and starts operating 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 the main switch, which is turned on when using the camera. (
SL) is a photographing preparation switch, which is normally turned on by the first stroke of a release button (not shown). (SAF
) is the AF mode switch, and this switch (SAF
) is ON, the autofocus mode is selected to drive the lens to the focus position based on the focus detection result, and when the switch (SAF) is OFF'F, the autofocus mode is selected based on the focus detection result. A manual focus mode is selected in which only the out-of-focus state is displayed and the lens is not driven. (SMZ) is a macro zone switch, which is opened when the zoom ring is set to the macro zone in a zoom lens with a macro mechanism. 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 flowcharts 1-. When a power-on reset is performed,
The microcomputer (μC) executes programs starting from #5 shown in FIG. First, all flags are reset in #5. Next, at #10, the main switch (SM) is turned OFF.
Determine whether it is N.

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, in step #1000, lens data is input from the lens circuit (LEC).

From the lens circuit (LEC), the lens attachment signal IC
P, macro zone signal SMZ, equal magnification upper macro lens mounting signal LCPR1 maximum extension amount N max, focal length f, conversion coefficient 2, etc. are input to the microcomputer (μC). Here, the conversion coefficient includes the defocus amount D
This is a coefficient for converting F into a lens drive amount ΔN. #
1005, the macro lens attachment signal LCPR
Determine the presence or absence of.

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, DFm is the maximum defocus amount that covers the range from the closest position to the infinity position of the lens. If in #1005 a macro lens of equal or greater magnification is not attached, the defocus amount DFb is determined in #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 iNb, 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 t indicates when the 70-210mm zoom lens is at 210mm.
When there are 4 mm, the data at the end is when a 75-300 mm zoom lens is set at 300 mm.

Table 1 shows commonly used photographic magnification β and lens position i1 determined accordingly for lenses with various focal lengths.
The defocus amount DFb corresponding to b and the maximum defocus amount DF+n of the lens are shown. Note that DFa is a defocus amount that allows focus detection and is determined by the configuration of the focus detection circuit (AFC), and the focus detection range is 2DFa, which is twice that amount.

#1010, it is determined whether DFt]>DFa. If DFb>DPa in #1010, the defocus amount DFs for setting the lens initial position is set to DF in #1030.
a, and #1060 sets the lens position set flag 5ETF.
is set to 1 and returns to the step where the subroutine was called. #10], if DFb≦DFa in O, set the defocus amount DFs for lens initial position setting to DFb in #1020, set lens position set flag 5ETF to 1 in #1050, and return to the step where the subroutine was called. do.

FIG. 12 is a diagram for explaining the meaning of steps #1010 to #1030. Figure (a) shows a case where the defocus amount DFb from the lens position Nb to the infinity position determined according to the imaging magnification β is larger than the defocus amount DFa that allows focus detection. teeth,
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 that the defocus amount DFb from the lens position Nb to the infinity position determined according to the imaging magnification β is
The case is shown in which the defocus amount is less than or equal to the defocus amount DFa that allows focus detection, and in this case, DFs=DFb. Also in this case, lens initial position N5=DPsX
In K, the infinity position is the focus detectable range 2DFa
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 #i L
At O5, it is determined whether the infinite position detection switch (Soo) is ON. #1105 If the switch (Sω) is not ON, #110 until the switch (Sω) is ON.
Repeat the judgment operation in step 5. When the lens is retracted to the infinite position in #1105 and the switch (Sω) is turned on, the lens retraction is stopped in #1110, the lens degree position counter NL is reset in #1115, and the subroutine is called. Return to.

FIG. 11 is a flowchart showing the contents of the subroutine of lens initial position cellar 1. When this subroutine is called, the defocus amount DFs for setting the lens initial position is multiplied by the conversion coefficient K in #1200 to calculate the lens drive amount ΔN=DFsXK from the infinity position, and #
At 1205, lens extension is started. In #1210, it is determined whether the lens drive amount has reached ΔN. #121
If it is 0 and the lens drive amount has not reached ΔN, the determination operation in #1210 is repeated until the lens drive amount reaches ΔN. #12.10 When the lens drive amount reaches ΔN, #
At step 1215, 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 AF mode switch (SAF) is ON.

If the AP mode switch (SAF) is not turned on in #45, the flag MP indicating the manual focus mode is set to 1 in #50, and the process proceeds to #80. A at #45
If the P mode switch (SAF) is ON, it is determined in #55 whether the flag MF is 1. MP-1 with #55
If so, it means that the switch (SAF) has just been turned on, and the flag MF is set to 0 in #60 and the process proceeds to #65. In #65 to #75, the above-described subroutines of lens initial position calculation, ω renormalization, and lens initial position setting are executed to set the lens initial position, and then the process proceeds to #145. If MP is not 1 in #55, it means that the switch (SAF) has been ON before, and the process proceeds 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 photographic 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 LENOF is set in #95.
After setting F to 0 and setting the lens initial position in #65 to #75, the process proceeds to #145. If the lens is not LENOF-1 in #90, it means that the lens has been attached before, and the process proceeds to #105.

At #105, the macro zone switch (SMZ) is turned on.
In other words, it is determined whether the zoom lens is in the macro zone. If the macro zone switch (S-Z) is not ON in #105, that is, if it is in the macro zone,
In #110, the flag SMZ○FF 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. In #115, SMZOFF = 1, which means that the lever and macro zone switch (SMZ) has been turned ON, so in #120, the flag SMZOFF is set to 0, and after setting the lens initial position in #65 to #75, Proceed to #145. If #115 is not SMZOFF=1, the macro zone switch (8M7) has been turned ON.
There is a time when it was done, and we move on to #125.

In #125, it is determined whether the reset switch (SR) is ON. If the reset switch (SR) is not turned on in #125, turn on the reset switch (SR) in #130.
The flag 5ROFF indicating that is OFF is set to 1,
Proceed to #145. #125 Reset switch (SR)
If it is ON, it is determined in #135 whether the flag 5ROFF is 1 or not.

If #1355ROFF=1, it means that the reset switch (SR) has just been turned on, and #140
After setting the flag 5ROFF to O and performing the lens initial position setting in #65 to #75, the process proceeds to #145. #135
If 5ROFF is not 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, immediately after the lens is attached, or the macro zone switch (SMZ)
) 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) (#1
55), lens initial position set (#65 to #
75) 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 shooting preparation switch (Sl) is not turned on, press #40 to erase all displays and return to #30.Hereafter, #30, #45, #80, #105, #125
, while going around the loop passing through #145, set the main switch (SM), AP mode switch (SAF), lens attachment signal ICP, macro zone switch (SMZ), reset 1 switch (SR), and shooting preparation switch (Sl). Monitor status.

In the middle of this loop, the main switch (SM) is turned off.
When it is, as mentioned above, ω 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).
We are waiting for the response to be N, but if the shooting preparation switch (sl) is turned on in #145, we will start focus detection.
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 #18o whether focus cannot be detected. 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. If the brightness is low in #185, #
Proceed to step 330 (Figure 8). If the brightness is not low in #185, then in #190 and #191 (Figure 5), (Nmax - N 1-) / K > D Fa or N L / K > D Fa -,, ■ is satisfied. Determine what is being done. If condition (2) is not satisfied in #19o and #191, the entire focus range of the lens is included in the focus detectable range 2DFa. Despite this, the fact that focus cannot be detected means that there is no way that focus can be detected even if you perform a low-contrast scan (detecting a focus while driving the lens and searching for a position where focus can be detected). It is wasteful to perform a low contrast scan. 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, #
192, N + nax/ 2 K≦D Fa −■
Determine whether it is satisfied. Here, N max/
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 lens attached. 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, then,
If the lens is at the intermediate position, the entire focus range Nmax/K of the lens is included in the focus detectable range 2DFa, so there is no need to take the trouble of performing a low contrast scan. Therefore, in order to move the lens to the intermediate position W N max/2, in #193, the lens drive amount ΔN = N max/
2-NL is calculated, and lens driving is started in #1941. In #1942, it is determined whether the lens drive amount has reached ΔN. If the lens drive amount has not reached ΔN in #1942, #19 continues until the lens drive amount reaches ΔN.
42 is repeated.

If the lens drive amount reaches ΔN in #1942, #194
After the lens drive is stopped in Step 3 and focus detection is performed in Step #195, it is determined in Step #196 whether focus detection is impossible. #1
If focus cannot be detected at 96, focus cannot be detected even if a low contrast scan is performed, and it is wasteful to perform a low contrast scan. Therefore, without performing the low contrast scan, the process proceeds to #25'5 (FIG. 7), and a focus detection failure display is performed. If the focus cannot be detected, the process proceeds to #285 (FIG. 7) to perform focus determination.

If condition (■) is not satisfied in #192, the entire 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 max, if it is extended to a position just before DFaXK, the maximum extension position N max also falls 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, and in #205, the process is set as FOWF-1, and the process proceeds to #220. At #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 at #225, it is determined whether focus detection is impossible at #230. If the focus cannot be detected in #230, the flag FOWF is reset in #233, and the process proceeds to #285 (FIG. 7) to make a 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 step #235, the process returns to step #225 to continue driving the lens in the extending direction and determine whether focus detection is impossible. 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 can be 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 a scan was performed in the extension direction, but a lens position where the focus could be detected was not found, so return to #200 to scan in the retraction 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-Nt. This allows the DF to
This is because the infinity position is included in the focus detectable range 2DFa by renormalizing the position closer to ax.

In #215, the flag FOWF is set to 0 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) that drives the lens (in the retraction direction), and #225 to #2
After passing through 45, it reaches #250 again. This time, FOWF=
Since it is not 1, it does not return to #200, but #255
Proceed to (Figure 7). In other words, if #250 does not have FOWF = 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 the focus was detected in #255. This indicates that the vehicle is disabled.

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
60 and 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 unlikely that a lens position at which focus can be detected will be found. Next, in #265, a flag F indicating the scan direction
After returning OWF to 0, press #270 and press 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, perform focus detection 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 cannot be detected 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
], it is determined whether the lens drive amount has reached ΔN. #
If the lens drive amount has not reached ΔN in step 311, the determination operation in #311 is repeated until the lens drive 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 #27o.

If the shooting preparation switch (Sl) remains ON in #270, focus detection is performed in #275, and then in #28° to #290.
After that, focus determination is performed again in #295. #30 mentioned above
Since the lens is driven toward the in-focus position in steps #5 and #31o, 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 #32° whether the photographing preparation switch (Sl) is ON. At #320, the shooting preparation switch (sl) is set to O.
If N, the determination operation of #320 is repeated until the photographing preparation switch (sl) is no longer ON, and a so-called focus lock state is established. Although unrelated to the present invention, in a camera in focus priority mode, release is permitted in this focus locked state, and when the release button (not shown) is pushed to the second stroke,
A camera performs a release operation. If the photographing preparation switch (Sl) is no longer ON at #32o, the display is turned off at #4o and the process returns to #30. That is, by turning off the photographing preparation switch (Sl), 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 a case where a lens position where focus detection is possible cannot be found even after performing a low contrast scan, or a case where a lens position where focus detection is possible cannot be found even after performing a low contrast scan. In this case, the flag LS is set in #157.
Return ENDF to 0, 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 when the low contrast scan end flag LSENDF is 1,
Although the probability that the subject you want to photograph exists near the current lens position is low, and especially when low-contrast scanning is actually performed, the lens position is biased toward infinity or near the closest position. This is because it is necessary to return it to its proper position.

Next, when passing through #330 in Figure 8, it is determined that the brightness is low and focus cannot be detected in #185 and #180 (Figure 4), so auxiliary light emission is necessary. However, there are cases where it is useless to emit the auxiliary light, so #3
30 and #335, the determination is made. 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 the system. 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 illuminated 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. 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 illuminate 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 meters at most, so we can't expect much from it. Therefore, in #33o, it is determined whether the focal length f of the lens is 250 mm or more, and in #330, f≧
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 #19
0 (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. If f≧250 is not determined in #330, it is determined in #335 whether or not there is a macro lens attachment signal LCPR of equal or larger magnification. 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 #19'O (FIG. 5), it is determined whether a low contrast scan is necessary. If a macro lens of 100% magnification or higher is not attached to #335, #340
Emits the auxiliary light with #345, performs focus detection with #3
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 in #350, try #355 to adjust the lens position to an intermediate distance (e.g. 4 m) within which focus detection using the auxiliary light is possible, or a distance (e.g. 3 m) where there are relatively many photographic scenes. Lens drive amount ΔN − (f 2 / D
o) Calculate X K N t and start lens driving in #360. In #361, the lens drive amount is Δ
Determine whether N has been reached.

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. If the lens drive amount reaches ΔN in #361, #
At 362, lens driving is stopped. Then, in #370, the auxiliary light is emitted, in #375, the focus is detected, and in #380, the focus is detected.
Determine whether focus detection is impossible. If the focus is not detected in #380, the process proceeds to #395. If the focus cannot be detected in #380, a focus detection failure display is performed in #385, and
In #390, it is determined whether the photographing preparation switch (Sl) is ON. At #390, the 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 step #395, the display indicating that focus cannot be detected is erased, and in step #400, it is determined whether focus is achieved. If the focus is #400, #4
Press 20 to display the focus, and press #425 to turn on the shooting preparation switch (
SL) is ON. If the photographing preparation switch (Sl) is ON-35= in #425, the determination in #425 is repeated until the photographing preparation switch (Sl) is no longer ON. If the photographing preparation switch (Sl) is no longer ON in #425, the display is turned off in #40 and the process returns to #30. If not in focus at #400, #
At 405, lens drive amount ΔN=D from defocus amount DF
FXK is calculated and lens driving is started in #410. #
In step 412, it is determined whether the lens drive amount has reached ΔN. If the lens drive amount has not reached ΔN in #412,
The determination operation in #412 is repeated until the lens drive amount reaches ΔN. If the lens drive amount reaches ΔN in #412,
The lens drive is stopped in #413, and it is determined in #415 whether the photographing preparation switch (Sl) is ON. If the photographing preparation switch (Sl) is ON in #415, the process returns to #370; if not, the display is turned off in #40, and the process returns to #30.

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). The focus detection circuit (AFC) is a focus detection means (
2) is supported. In addition, the lens drive circuit (LDC)
corresponds to the lens driving means (4). The flowchart in FIG. 9 corresponds to the lens position determining means (3). In flowchart 1- of FIG. 3, #10, #4
5, #80, #105, #125. The steps #155 and #155 correspond to the condition determining means 5). Also,#
Steps 15 to #25 and #65 to #75 correspond to the control means <6).

[Effects of the Invention] As described above, the present invention has the effect that the initial setting of the lens position is performed under specific conditions, which increases the probability that focus detection is possible. Since the initial setting of the lens position is not performed when the conditions are not met, this has the effect of reducing current consumption compared to the case where the initial setting of the lens position is performed every time the focus is detected. When photographing an object, the lens is driven from a lens position corresponding to the previous focus detection result, which has the advantage of shortening the time required to achieve focus.

[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, and FIGS.
The figure is a flowchart showing the same operation as above, and FIG. 12 is an explanatory diagram of the same operation. (1) is a lens, (2) is a focus detection means, (3) is a lens position determining means, (4) is a lens driving means, 5) is a condition determining means, and (6) is a control means.

Claims (7)

[Claims] (1) A photographic lens, a focus detection means for detecting the focal state of the lens, a lens position determining means for determining the initial stop position of the lens, a lens driving means for driving the lens, and a lens driving means for driving the lens to the initial stop position. a condition determining means for determining whether or not the condition is such that the lens should be driven; and a lens driving device that drives the lens to an initial stop position when the condition determining means determines that the condition is such that the lens must be driven. 1. A focus detection device comprising: control means for controlling the control means. (2) Claim (1) characterized in that the condition for driving the lens is that the main switch for power supply is turned on.
The focus detection device described. (3) The lens driving condition is that the lens is driven by switching from a manual focus mode for performing a manual focus adjustment operation to an autofocus mode for performing an automatic focus adjustment operation. Focus detection device. (4) The focus detection device according to claim (1), wherein the condition for driving the lens is that the lens is attached. (5) The focus detection device according to claim (1), wherein the lens is a zoom lens with a macro mechanism, and the condition for driving the lens is that the lens exits the macro state. (6) The focus detection device according to claim (1), wherein the condition for driving the lens is that the reset switch is turned on. (7) A focus detection impossibility determining means for determining whether focus detection by the focus detecting means is impossible; and when the focus detecting impossibility determining means determines that focus detection is impossible, the lens driving means drives the lens; and a lens scanning control means for causing the focus detection means to perform a focus detection operation, and when focus detection is performed while driving the lens by the lens scanning control means, the focus is detected in a state where it is determined that there is no lens position where the focus can be detected. Claim (1) characterized in that the condition for driving the lens is that a switch for starting detection is turned on.
1) The focus detection device described above.