JPH01187517A - Focus detector - Google Patents

Abstract

PURPOSE:To make probability that focus detection can be possible high both at the time of emitting light of auxiliary light and at the time of not emitting light thereof by switching the initial stopping position of a lens at the time of emitting light and at the time of not emitting light of the auxiliary light. CONSTITUTION:The initial stopping position Ns of the lens 1 is set in a position suitable for daylight photographing in which the auxiliary light is not used by a 1st lens position determination means 4 and a 1st control means 8 controls a lens driving means 6 so that the lens 1 is driven to the initial stopping position Ns before a focus detection means 2 performs focus detecting action with the operation of an operating member 7. When it is decided that the focus detection is impossible by a focus detection impossibility decision means 9, a 2nd control means 10 acts to control the lens driving means 6 so that the lens 1 is driven to a 2nd initial stopping position Ns2 suitable for a time for detecting a focus by using the auxiliary light determined by a 2nd lens position determination means 5 and to actuate an auxiliary light emission means 3 and the focus detection means 2. Thus, the probability that the focus detection can be possible is made high both at the time of emitting light and at the time of not emitting light of the auxiliary light.

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 fixed. It has been proposed to initially set the lens to an intermediate position each time a photograph is taken (U.S. Pat. No. 4,265)
, No. 528).

However, in this prior art, the initial stopping position of the lens is not determined in such a way as to increase the probability that focus detection becomes possible. Further, there is no mention of lens position setting when emitting auxiliary light.

On the other hand, Japanese Patent Application Laid-Open No. 59-136720 proposes performing focus detection after setting the lens position to the regular focus position when emitting auxiliary light.

However, in this conventional example, there is no mention of setting the lens position when the auxiliary light is not emitted.

After all, these documents do not disclose the idea of switching the initial stop position of the lens between when the auxiliary light is emitted and when it is not emitted.

[Problems to be Solved by the Invention] When focus detection is not possible, conventional focus detection devices drive the lens back and forth to search for a lens position where focus can be detected (so-called low-contrast scan). There is. When this operation is performed, there is a problem that the time required for focus detection becomes longer. Therefore, before starting focus detection, the lens is moved to a predetermined initial stop position to increase the probability that focus detection will be possible. It may be possible to shorten the time required. In this case, the problem is how to set the initial stop position of the lens in order to increase the probability that focus detection will be possible.

The present inventors have discovered that for daytime photography, if the initial stop position of the lens is determined according to the photographing magnification, the probability that focus can be detected increases.

By the way, in a passive focus detection device, when the subject is dark and it is difficult to detect the focus, focus detection is performed by irradiating the auxiliary light, but since the auxiliary light has a limited reach, The focus detection range is more limited than when it is not used. Therefore, the optimal initial stopping position of the lens is considered to be different depending on whether the auxiliary light is used or not.

-4~ The present invention has been made in view of the above points, and its purpose is to provide a focus detection device that has a high probability of being able to detect focus both when the auxiliary light is emitted and when it is not emitted. There is a particular thing.

[Means for Solving the Problems 1] In the focus detection device according to the present invention, in order to achieve the above objective number, as shown in FIG.
1), a focus detection means for detecting the focus state of the lens (1), 2), an auxiliary light emitting means (3) for irradiating an auxiliary light for focus detection onto the photographing area, and a lens when the auxiliary light is not emitted. A first lens position determining means (4) that determines the first initial stop position Ns of (1), and a second lens position determination means (4) that determines the second initial stop position MN S2 of the lens (1) when emitting the auxiliary light. a lens position determining means (5), a lens driving means (6) for driving the lens (1), an operating member (7) operated to operate the focus detecting means (2), and an operating member (7) for operating the focus detecting means (2). ) before the focus detection means (2) operates, the lens drive means drives the lens (1) to the first initial stop position Ns determined by the first lens position determination means (4). (6) First control means for controlling 8)
, a focus detection impossibility determining means (9) for determining whether or not focus detection by the focus detecting means (2) is impossible in a state in which the auxiliary light is not emitted; When it is determined that the lens is not possible, the lens driving means (6) is controlled to drive the lens (1) to the second initial stop position Ns2 determined by the second lens position determining means (5). The second control means (10) operates the auxiliary light emitting means (3) and the focus detection means (2).

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). When the operation member (7) is operated, the focus detection means (2
) is operated to detect the focal state of the lens (1).

The focus state of the lens (1) is usually detected as the amount of defocus (defocus amount) from the in-focus position, and front focus and back focus are distinguished by the sign. If the amount of differential shift 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 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. If the lens (1) is 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 first lens position determining means (4) so that the probability that focus detection becomes possible is increased. This initial stop position Ns is set at a position suitable for daytime photography without using auxiliary light. Initial stop position Ns
The lens (1) is driven by the lens driving means (6) under the control of the first control means (8). During normal focus detection, the lens drive means (6) drives the lens (6) based on the focus detection result of the focus detection means (2).
1) An automatic focus adjustment device that drives the lens toward the in-focus position may be used. The first control means (8) is a lens drive means configured to drive the lens (1> to an initial stop position Ns) before the focus detection means (2) performs a focus detection operation by operating the operation member (7). (6). Therefore, when the operating member (7) is operated and the focus detection means (2) performs a focus detection operation, the lens (1) is already suitable for daytime photography without using auxiliary light. This is set at the initial stop position Ns, which increases the probability that focus detection will be possible.

However, if the imaging area has low brightness or low contrast, focus detection may become impossible.

When this state is determined by the focus detection impossible determination means (9), the second control means (10) operates instead of the first control means (8), and the auxiliary light emitting means (3) takes pictures. Focus detection is performed by the focus detection means (2) while irradiating the area with auxiliary light for focus detection. Focus detection using this auxiliary light=7- The initial stop position N s 2 of the lens (1) suitable for exit is determined by the second lens position determining means (5).

The second control means (10) controls the lens drive means (6) to drive the lens (1) to the second initial stop position NS2 determined by the second lens position determination means (5). to operate the auxiliary light emitting means (3) and the focus detecting means (2). Therefore, when detecting the focus state of the lens (1) while irradiating the auxiliary light, the lens (1) is moved to the second initial stop position W suitable for focus detection using the auxiliary light.
It is set to N S 2, and in this case as well, the probability that the focus can be detected is high.

[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, which 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 illuminating 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. (EN
C) is an encoder that detects the amount of rotation of the motor (M) and outputs pulses to the microcomputer (μC) according to a predetermined amount of rotation of the motor (M).

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 pulse from the encoder (ENC) is reset by an internal command. When the lens is renormalized, the encoder (E
It is counted down in response to a pulse from NC). When the lens is extended to the closest position, the value of the lens position counter NL becomes N1=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) 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 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. , 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, the microcomputer (μC)
doesn't work. 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
oO) 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. <
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, the autofocus mode is selected based on the focus detection result. A manual focus mode is selected in which only the image 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, when the zoom ring is set to the macro zone,
Since the autofocus mode is disabled, 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 programs starting from #5 shown in FIG. Next, reset all flags 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, in #1000, lens data is input from the lens circuit <LEC).

From the lens circuit (L E C), the lens mounting signal circuit C
P, macro zone signal SMZ, equal magnification upper macro lens mounting signal LCPR1 maximum extension amount N max, focal length f, conversion coefficient, etc. are input to the microcomputer (μC). Here, the conversion coefficient includes the defocus amount DF
This is a coefficient for converting ΔN into a lens drive amount ΔN. #1
In step 005, it is determined whether or not there is a macro lens attachment signal LCPR of equal or greater magnification.

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, which is determined according to the imaging magnification β. In this embodiment, information on the lens position Nb, which is preset in consideration of the often used photographic magnification β, is read from the ROM table in addition to the information on the focal length f.

Table 1 shows commonly used photographic magnification β and 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 amount of defocus that can be detected by the focus detection circuit (AFC), which is determined by the configuration of the focus detection circuit.
It becomes DFa.

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

If DFb>DFa in #1010, use #]030 to set the defocus amount DFs for setting the lens initial position to DFa.
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 Defocus amount DFs for setting lens initial position
DFb, #1050 and lens position set flag 5
Set ETF to 1 and return to the step where the subroutine was called.

Table 1 However, in the above table, * means that the 28-135mm zoom lens is at 135mm, and ↑ means that the 70-210mm zoom lens is at 210mm.
When it is at nu□, the data at the end is when the 75-300mm zoom lens is at 300mm.

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,
DFs=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 W 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. In this case as well, lens initial position N5=DFsX
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 retraction is started in #1100, and it is determined in #1105 whether the infinity position detection switch (Soo) is ON. If the switch (Soo) is not ON in #1105, #110 until the switch (Sc+o) is ON.
Repeat the judgment operation in step 5. When the lens is retracted to the infinite position in #1105 and the switch (S(1)) is turned on, the lens retraction is stopped in #1110, and the lens retracting is stopped in #111.
In step 5, the lens position counter NL is reset and the subroutine returns to the called step.

FIG. 11 is a flowchart showing the contents of the subroutine for setting the lens initial position. When this subroutine is called, in #1-200, the defocus amount DFs for setting the lens initial position is multiplied by the conversion coefficient K, and the lens driving amount from the infinity position ΔN = D F s X
K is calculated, and lens extension is started in #1205.

In #1210, it is determined whether the lens drive amount has reached ΔN. If the lens driving amount has not reached ΔN in #1210, the determination operation in #1210 is repeated until the lens driving amount reaches ΔN. If the lens drive amount reaches ΔN in #1210, the lens drive is stopped in #1215 and the process returns to the step from which the subroutine was called.

Returning to the flow of FIG. 3, in #45, AP momo-l'
Determine whether the switch (SAF) is ON.

If the AF mode switch (SAF) is not ON in #45, the flag MF indicating that the manual focus mode is present is set to 1 in #50, and the process proceeds to #80. If the AF motor switch (SAF) is ON in #45, #55
Then, it is determined whether the flag MP is 1 or not. MF= at #55
If it is 1, 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, execute the above-mentioned lens initial position calculation, renormalization, and lens initial position setting subroutines to perform lens initial position cell 1~, and then,
Proceed to #145. If MF=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 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 LENOF 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 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. 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 lens initial position in #65 to #75, Proceed to #145. If SMZOFF=1 is not set in #115, the macro zone switch (SMZ) was already ON.
Therefore, proceed to #125.

In #125, it is determined whether the reset switch (SR) is ON. Reset switch (SR) with #125
is not ON, turn on the reset switch (SR) with #130.
) 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 performing the lens initial position setting in #65 to #75, the process proceeds 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 performing lens initial position cera+ (#15 to #25) immediately after turning on the main switch (SM), A
Immediately after the F mode switch (SAF) is turned on, immediately after the lens is attached, or the macro zone switch (3M2
) 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, 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 (S AF), (SMZ), and (SR) turns OFF.
N or when a lens is attached, lens initial position setting (#65 to #75) is performed each time.

In this way, the camera waits for the shooting preparation switch (Sl) to be turned on. When the shooting preparation switch (Sl) is turned on in #145, the camera waits for the shooting preparation switch (Sl) to be turned on in #155 (step #155) to start focus detection. Proceed to 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=0, 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 make a 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), (N max - N L) / K > D Fa or N L / K > D Fa - ■ is satisfied. Determine if there are any. If condition (2) is not satisfied in #190 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 low-contrast scanning (operation of detecting focus while driving the lens and searching for a position where focus can be detected) is performed. 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, Nmax/2K ≦ DFa
= Determine whether ■ is satisfied.

Here, N max/2 is the defocus amount (ie, DFm/2) from the intermediate position to the final position of the photographic lens, and is determined depending on the attached lens. Also, 2DFa
As mentioned above, is the amount of defocus 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 entire focus range Nmax/K of the lens is the focus detectable range 2D.
Since it is included in Fa, there is no need to go to the trouble of performing a low contrast scan. Therefore, in order to move the lens to the intermediate position Nmax/2, in #193, the lens drive amount ΔN = N
max/2-NL is calculated and lens driving is started in #1941. In #1942, the lens drive amount is Δ
Determine whether N has been reached. If the lens driving amount has not reached ΔN in #1942, the determination operation in #1942 is repeated until the lens driving amount reaches ΔN.

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 the focus cannot be detected in 96, the focus cannot 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 #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 (■) 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 have 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. are doing. 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 Nmax, 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, to know the scanning direction,
In #200, it is determined whether the flag FOWF is 1. This flag FOWF is a flag indicating that scanning is to be performed in the FOward direction. When a low contrast scan is performed for the first time, the flag FOWF is reset, so FOWF=1 is not set. therefore,
First, proceed to #205, set FOWF=1 in #205, and proceed 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 detection is impossible. If it is not possible to detect the focus in #230, reset the flag FOWF in #233,
The process advances to #285 (FIG. 7) to perform focus determination. #2
If the focus cannot be detected in step 30, it is determined in step #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=1 in 245, #250 flag F
Determine whether OWF 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 renormalization direction is ΔN = D Fa X K N
Calculate as L. This means that even if you do not retract to the infinite position, if you retract only to the position in front of DFa×,
This is because the infinite position also falls within the focus detectable range 2DFa.

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) 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 and #2
Proceed to 55 (Figure 7). In other words, at #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.

#255 (Fig. 7) When displaying focus detection failure, #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, in #265, a flag F indicating the scan 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 ON in #270, the entire display is erased in #40 and the process returns to #30. Press #270 to turn on the shooting preparation switch (
Sl) is ON, performs 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 0 in #285, the low contrast scan end flag LSENDF is set to 0 in #290, and it is determined in #295 whether focus is achieved.

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, focus determination is performed again in #295. #30 mentioned above
Since the lens is driven toward the in-focus position in steps #5 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. 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, resulting in a so-called focus lock state. Although unrelated to the present invention, in a camera in focus priority mode, when release is permitted in this focus locked state and 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 in #320, the display is turned off in #40 and the process returns to #30. That is, when the photographing 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 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,
This is because 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
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 the TTL phase difference detection method, and its optical axis coincides with the optical axis of the photographing lens. Therefore, the focus detection circuit (AFC>) The luminous flux region and the luminous flux region for focus detection have a balax, and the luminous flux region and the luminous flux region for focus detection have a balax, and the distance in front of the photographic lens (
(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 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 1.0 m at most, so I don't have much hope for it. Therefore, in #330, 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 #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. If r≧250 is not determined in #330, the macro lens attachment signal LCPR of equal magnification or higher is determined in #335.
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. 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 is not detected in #350, the process proceeds to #395. If focus cannot be detected in #350, adjust the lens position to an intermediate distance (e.g. 4 m) within the range where focus detection using the auxiliary light is possible, or a distance (e.g. 3 m) where there are relatively many photographic scenes, using #355. Then, lens drive amount -N-2/Do)xK-Nc is calculated, and lens drive is started in #360. In #361,
It is determined whether the lens drive amount reaches 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. #361 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 cannot be 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 #395, the focus detection failure display is erased, and in #400, it is determined whether focus is achieved. If #400 is in focus, #4
In step 20, the focus is displayed, and in step #425-38, it is determined whether the photographing preparation switch (Sl) is ON. If the shooting preparation switch (Sl) is ON in #425, the shooting preparation switch (Sl) is not ON until the shooting preparation switch (Sl) is turned ON.
425 is repeated. #425 If the shooting preparation switch (Sl) is no longer ON, turn off the display #40,
Return to #30. If it is not in focus at #400, change the lens drive amount ΔN = D F from the defocus amount DF at #405.
Calculate X l(, and start lens driving in #410. In #412, determine whether the lens driving amount has reached ΔN. If the lens driving amount has not reached ΔN in #412, lens driving starts. The determination operation in #412 is repeated until the amount reaches ΔN. If the lens drive amount reaches ΔN in #412, the lens drive is stopped in #413, and in #415 whether the photographing preparation switch (Sl) is ON or not. Determine. #41
If the shooting preparation switch (Sl) is ON in step 5, #370
Return to , if it is not ON, turn off the display with #40, and press #30
Return to

Finally, the correspondence between the basic configuration of the present invention shown in FIG. 1 and the embodiments shown in FIG. 2 and thereafter will be explained. The lens circuit (LEC) in FIG. 2 is included in the lens (1), and the focus detection circuit (AFC) corresponds to focus detection means (2). Further, the auxiliary light emitting device (ILM) corresponds to the auxiliary light emitting means (3).

The lens position calculation subroutine shown in FIG. 9 corresponds to the first lens position determining means (4). #355 in Figure 8
The step corresponds to the second lens position determining means (5). The lens drive circuit (LDC) in FIG. 2 corresponds to the lens drive means (6).

The photographing preparation switch (Sl) in the figure corresponds to the operation member (7). #65 to #75 and #145 in Figure 3 are the first
This corresponds to the control means (8). Steps #180 and #]85 in FIG. 4 correspond to the focus detection failure determining means (9). Steps #365 to #375 in FIG. 8 correspond to the second control means (10).

[Effects of the Invention] As described above, the present invention switches the initial stop position of the lens when the auxiliary light is emitted and when it is not emitted.
Compared to the case where the initial stop position of the lens is constant regardless of the presence or absence of the auxiliary light, this has the effect of increasing the probability that focus detection is possible both when the auxiliary light is emitted and when the auxiliary light is not emitted.

[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 an auxiliary light emitting means, (4) is a first lens position determining means, (5)
) is the second lens position determining means, (6) is the lens driving means, (7) is the operating member, (8) is the first control means, ku) is the focus detection failure determining means, and (10) is the second control means.

Claims (2)

[Claims] (1) A lens for photographing, a focus detection means for detecting the focus state of the lens, an auxiliary light emitting means for irradiating the photographing area with auxiliary light for focus detection, and a first auxiliary light of the lens when the auxiliary light is not emitted. a first lens position determining means for determining an initial stop position; a second lens position determining means for determining a second initial stop position of the lens when emitting auxiliary light; a lens driving means for driving the lens; An operating member that is operated to operate the detection means, and driving the lens to a first initial stop position determined by the first lens position determining means before the focus detection means is operated by the operation of the operation member. a first control means for controlling the lens drive means in such a manner;
a focus detection impossibility determining means for determining whether or not focus detection by the focus detecting means is impossible in a state in which the auxiliary light is not emitted; and a second control means for controlling the lens driving means to drive the lens to the second initial stop position determined by the second lens position determining means and operating the auxiliary light emitting means and the focus detection means. A focus detection device characterized by: (2) Focus detection according to claim (1), wherein the first initial stop position is determined according to the photographing magnification, and the second initial stop position is determined according to the reach distance of the auxiliary light. Device.