JPH01187514A - Focus detector - Google Patents

Abstract

PURPOSE:To make probability that focus detection is possible high by setting the initial stopping position of a lens according to a photographing magnification which is used often before starting the focus detection. CONSTITUTION:If a lens 1 is in a position which is used often, the probability that the focus detection can be possible is high. Then, the initial stopping position Ns of the lens 1 is determined by a lens position determining means 3 based on a specified photographing magnification determined according to the lens 1. And a control means 6 controls a lens driving means 4 so as to drive the lens 1 to the initial stopping position Ns before a focus detecting means 2 performs a focus detecting action with the operation of an operating member 5. At the time of performing the focus detecting action, the lens 1 has already been set in the initial stopping position Ns determined based on the photographing magnification and the probability that the focus detection can be possible is made high.

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.

[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. If this operation is performed, there is a problem in 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 is possible to shorten the time. 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 inventors of the present invention have repeatedly conducted live shooting with lenses of various focal lengths, assuming frequently photographed scenes and shooting distances, and have found that the photographic magnification is closely related to the initial stop position of the lens. I found out that there is.

The present invention has been made based on such knowledge, and its purpose is to provide a focus detection device that has a high probability of being able to detect a focus and that takes a short time to detect the focus.

[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), and determining an initial stop position Ns of the lens (1) based on a predetermined imaging magnification β determined according to the lens (1). a lens position determining means (3) for driving the lens, a lens driving means (4) for driving the lens (1), an operating member (5) operated to operate the focus detecting means (2), and an operating member (5) for operating the focus detecting means (2). ), the lens driving means (4) drives the lens (1) to the initial stop position Ns determined by the lens position determining means (3) before the focus detecting means (2) performs the focus detecting operation. 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.

When the operating member (5) is operated, the focus detection means (2) is operated and the focus state of the lens (1) is detected.

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 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 of the subject is low, focus detection becomes impossible, but the contrast of the subject If it 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 lens (1
), the lens position determining means (3) determines the initial stop position Ns of the lens (1).
It is determined by 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. The control means (6) controls the lens drive means (4) to drive the lens (1) to the initial stop position Ns before the focus detection means (2) performs a focus detection operation by operating the operation member (5). control. Therefore, when the operating member (5) is operated and the focus detection means (2) performs a focus detection operation, the lens (1) has already been set to the initial stop position Ns determined based on the imaging magnification β. This increases the probability that the focus can be detected.

[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 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 (1=DC) inputs 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. . (ENC) is an encoder that detects the rotation amount of the motor (M>), and the microcomputer (ENC) detects the rotation amount of the motor (M>).
output a pulse to μC).

Here, the microcomputer (μC) uses a lens position counter N to know as an absolute amount the amount of lens extension from the infinity position, which is the most retracted state of the lens.
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 the pulse from NC). When the lens is extended to the closest position, the value of the lens position counter NL becomes N1=N+nax. This maximum extension amount N+nax differs depending on the lens, and is read into the microcomputer (μC) from the lens circuit (LEC) 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 capacitor (C1) is the terminal (RE S
)It is connected to the. When the power battery (BAT) is connected, the power terminal (Vcc) of the microcomputer (μC)
) and the ground terminal (GND), the microcomputer (μC) becomes active, but the charging voltage of the capacitor (cl), that is, the microcomputer's reset terminal (<RES) Until the voltage applied to 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) has a reset switch, and this switch
When the lens is reset to the initial position, the lens is reset to the initial position. (
S co ) 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 pressing the first button of the release button (not shown).

(SAF) is an AF mode switch. When this switch (SAF) is ON, the autofocus mode switch (SAF) drives the lens to the in-focus position based on the focus detection result. When the autofocus mode switch (SAF) is OFF, the focus detection result is Based on this, a manual focus mode is selected in which only in-focus or out-of-focus is displayed and the lens is not driven. (SMZ) is a macro zone switch, and Macro I! On a structured zoom lens, it is opened when the zoom ring is set to the macro zone. In the zoom lens with a macro function used in this example, when the zoom ring is set to the macro zone, the autofocus mode cannot be used, so in order to notify the microcomputer (μC) of this, , a signal SM indicating that the lens circuit (LEC) is a macro zone.
Output Z to a microcomputer (μC).

Next, the focus adjustment operation of the camera will be explained with reference to Flowchart 1. When a power-on reset is performed,
The microcomputer (μC) executes programs starting from #5 shown in FIG. First, reset all flags in step #5. Next, turn #1o and turn the main switch (SM) to
Determine whether it is N or not.

If the main switch (S M) is not turned on, repeat the judgment in #10 until it is turned on.
If M) is ON, #15 executes the lens initial position calculation subroutine (Fig. 9), #2° executes the (1) renormalization subroutine (Fig. 10), and #25 executes the lens initial position calculation subroutine (Fig. 10). After executing the subroutine (FIG. 11) for position set 1, it is determined at #3o whether the main switch (S4) is OFF. If the main switch (SM) is OFF,
#35 Execute the renormalization subroutine and return to #1o. If the main switch (SM) is not OFF at #3o, proceed to #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, the lens stator is input from the lens circuit (LEC).

The lens circuit (LEC) is a lens attachment signal IC.
P, macrosohn signal SMZ, macro lens attachment signal LCPR larger than 100%, maximum extension amount Nmax, focal pressure In
[, conversion coefficients, etc. are input into a microcomputer (μC). Here, the conversion coefficient ■ (is the defocus iD
This is a coefficient for converting F into a lens drive amount ΔN. #
1005 is the macro lens attachment signal LCPR larger than the same magnification.
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 where 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 DPb is the defocus amount from the infinity position to the lens position Nb determined according to the imaging magnification β. On the Kinio side, information on the lens position N11, which is preset in consideration of the commonly used photographic magnification β, is read from the R, OM table based on the information on the focal length f.

In Table 1, in the above table, when the 28-135vn zoom lens is at 135mm, t is 70-210mm, and when the m zoom lens is at 210m+n, the t is the 75-300in1o zoom lens. This is the take when is at 300 to +n.

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 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 lens initial position Cera 1 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. #1010 If DFb≦DFa, #1
020 Defocus amount D for lens initial position setting
Fs is set to DPI), the lens position set flag 5ETF is set to 1 in #1050, and the process returns 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 Nb to the infinity position determined according to the imaging magnification β is larger than the defocus amount DFa that allows focus detection. for,
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 sufficient to scan only in the direction in which the lens is extended. The same figure (b) shows the case where the telefocus 1DFb from the lens position N11 determined according to the imaging magnification β to the infinity position is less than the defocus amount DFa that allows focus detection. is set as DFs=DFb. In this case as well, lens initial position N5=DFs
In XI, the infinity position is the focus detectable range 2D.
If the focus cannot be detected, it is sufficient to scan only in the direction in which the lens is extended.

FIG. 10 is a flowchart I showing the contents of the subroutine for ω renormalization. When this subroutine is called, lens renormalization starts in #1100, and in #1105
Then, it is determined whether the infinite distance InN detection switch (Sω) is ON. #1105 If the switch (S■) is not ON, the switch (Sω) will be ON.
Repeat the judgment operation. #], If the lens is retracted to the infinite position at 105 and the switch (Sω) is turned on, lens retraction is stopped at #1110, and then at #11
At step 15, the lens position counter N is reset to 1, and the process returns to the step where the subroutine was called.

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 step 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. #1210 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 motor switch (SAF) is ON.

If the AF mode switch (SAF) is not turned on in #45, the flag MF indicating manual focus mode is set to 1 in #50, and the process proceeds to #80. #45teA
If the F mode switch (SAF) is ON, it is determined whether the flag MP is 1 in #55. #55 MF=1
If so, 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. #65 to #75, the above-mentioned lens initial position calculation,
Execute the ω renormalization and lens initial position setting subroutines to set the lens initial position, and then #1
Proceed to step 45. If MP = 1 in #55, it means that the switch (SAF) has been turned on before, #
Proceed to 80.

At #80, check the presence or absence of the lens attachment signal ICP -17-
, to determine. If no lens is attached in #80, #1
Flag LENO indicating that the lens is not attached at 00
Set F to 1 and proceed 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 #9o, it means that the lens has just been attached, and after setting the flag LENOF to 0 in #95 and setting the lens initial position in #65 to #75, #145 Proceed to. #90teL
If ENOF is not 1, it means that the lens was already attached, and proceed to #1o5.

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. #105 Macro zone switch (SM
Z) is not ON, that is, if it is in the macro zone,
#110 sets the flag SMZOFF indicating that the macro zone switch (SMZ) is OFF to 1, and #125
Proceed to. If the macro zone switch (SMZ) is ON in #1o5, 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.After setting the flag SMZOFF to 0 in #120 and setting the lens initial position in #65 to #75, Proceed to #145. If #115 does not have SMzOFF=1, the macro zone switch (SMZ) has been turned on.
Since this has been done, proceed to #125.

#] At 25, it is determined whether the reset switch (SR) is ON. If #125 reset switch (SR) is not ON, #130 reset switch (S+□
) is OFF, the flag 5ROFF is set to 1, and the process proceeds to #145. #125 Reset switch (SR
) is ON, it is determined in #135 whether the flag 5ROFF is 1.

If #135 and 5ROFF = 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 S ROF F = 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 #6
#14 without setting the lens initial position in steps 5 to #75.
Proceed to step 5.

Therefore, after performing the lens initial position cell l- (#15 to #25) immediately after turning on the main switch (SM),
Immediately after the AF mode I switch (SAF) is turned on,
Immediately after the lens is attached, or when the macro zone switch (S
Immediately after the MZ) is turned on, or the reset switch (
Immediately after the 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 the shooting preparation switch (Sl) is turned off (#
(see #155), lens initial position set (#65~
#75) is performed, and in other cases, lens initial position setting is not performed. Therefore, when the probability of focusing near the previous lens position is high, such as when photographing a similar scene or when taking a quick photo of multiple frames,
The lens initial position setting is not performed, and compared to the case where the lens initial position setting is performed every time the focus is detected, power consumption is reduced and the time required for focus adjustment is shortened.

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), AP 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 (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 camera to turn to N, but when the shooting preparation switch (Sl) is turned on in step #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 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 low in #185, #190 and #191 (Fig. 5), (N max - N L) / I > D
F a or N L/K > D F a
- Determine whether ■■ is satisfied. 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. 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 #190 or #191 is met, #
192, it is determined whether N + nax/ 2 K≦DFa (2) is satisfied. Here, Nmax/2
K is the amount of defocus (ie, DF+n/2) from the intermediate position to the final position of the photographic lens, and is determined depending on the lens attached. Further, as described above, 2DFa 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 force and melapod side. If condition #192 is satisfied, if the lens is in the middle position, the entire focus range of the lens is N.
+nax/K is included in the focus detectable range 2DFa, so there is no need to take the trouble to perform a low contrast scan. Therefore, in order to move the lens to the intermediate position N n + ax/2, in #193, the lens drive amount ΔN = Nmax/
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, continue #194 until the lens drive amount reaches ΔN.
Repeat the judgment operation in step 2.

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
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, the process proceeds to #255 (FIG. 7) without performing the low contrast scan, and displays that the focus cannot be detected. If 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 N+nax 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 Nmax, if it is extended to a position DFaXK in front of the user, the maximum extension position N+nax will also fall within the focus detectable range 2DFa. Next, to know the direction of the scan,
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 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,
First, proceed to #205, set FOWF=1 at $205, and proceed to #220. In #220, a signal is output to the lens drive circuit (LDC) to drive the lens (in the direction of lens movement), 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 at 3o, it is determined at #235 whether the lens drive amount has reached ΔN. In #235, the lens drive amount has not reached ΔN (if the lens drive amount has not reached ΔN, return to #225 and determine whether focus detection is impossible while continuing to drive the lens in the extending direction. In #235, the lens drive amount has not reached ΔN). If it has reached #240, the lens drive is stopped, and #245 determines whether the lens position set flag 5ETF is 1. If 5ETF = 1 in #245, the scan in the renormalization direction is not performed. Since it can be determined that the focus cannot be detected over the entire focus range of the lens, the process proceeds to #255 (FIG. 7) to display that the focus cannot be detected.

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 the focus can be detected 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 scanning in the feeding direction has already been completed, so the scanning amount in the feeding direction in #210 is ΔN = D Fa X K N
1. Calculated as This is because even if the infinity position is not renormalized, if the infinity position is renormalized to a position just before DFax, the infinity position will also fall 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 #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 FOWF = 1 is not set in #250, 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
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. In addition, if the focus becomes impossible to detect even though it is included in the entire focus range of the lens or 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, #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, all displays are turned off in #40 and the process returns to #30. #270 Shooting preparation switch (
SL) is ON, perform focus detection in #275 and #
280 to determine 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 SE'TF is set to 0 in #285, the low contrast scan end flag LSENDF is set to O in #290, and it is determined in #295 whether focus is achieved.

Focused on #295! If it is determined that the focus is not affected, the process proceeds to #300 to erase the focus and focus detection failure display, and then to #305 to defocus and adjust the lens drive amount ΔN = based on the IDE.
DFXK is calculated and lens driving is started in #310. In #311, it is determined whether the lens drive amount has reached ΔN. If the lens drive amount reaches ΔN in #311, the determination operation in #311 is repeated until the lens drive amount reaches ΔN. If the lens drive amount reaches ΔN in #311, the lens drive is stopped in #312, 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 step #295. #30 mentioned above
Since the lens is being driven toward the in-focus position in steps #5 and #310, there is a high probability that the lens will be in focus. 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, and a so-called focus lock state is established. 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. When 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).
l) was turned on and focus detection was performed, or focus detection was not possible.
This is a case where a lens position at which focus detection is possible cannot be found even after performing a low contrast scan, or a case where a lens position at which focus detection is possible cannot be found even when a low contrast scan is performed. In this place &, #157 flag LS
Return ENDF to O, set the lens initial position in #65 to #75, and proceed to #145. Note that when proceeding to #157, the photographing preparation switch (Sl) must be 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 fτ1 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 there is a need 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
30 and #335, the determination is made. The auxiliary light emitting device (ILM) 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)
It includes a focus detection optical system using the TL 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 from a predetermined distance in front of the photographic lens (varies depending on the angle of view), the focus detection The luminous flux range for the auxiliary light is completely included in the luminous 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.

Furthermore, when a long focal length lens is attached to the camera, the auxiliary light may be vignetted by the lens barrel, so that the auxiliary light may 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-in light may be reduced by adopting a TTL type fill-in light system, or the upper limit of the range in which focus detection is possible with fill-in light irradiation. Increasing the distance of the auxiliary light is at most about 10[1], so the remaining l
[JI can't wait. Therefore, in #330, it is determined whether the focal length f of the lens is 250 mm or more, and #330
If f≧250, it is determined that the auxiliary light may be vignetted due to the long lens length, so the auxiliary light is not emitted.
Proceeding to #190 (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 does not reach, so there is not much of a problem even if the auxiliary light emission is prohibited. #330 If f≧250, #335 equal magnification upper macro lens attachment signal LC
Determine whether there is a PR. #335 If a macro lens is attached to the same magnification lens, it will judge that the shooting is at a close range, which is closer than the lower limit of the range where focus detection is possible with the auxiliary light, and will not emit the auxiliary light. , the process proceeds to #190 (FIG. 5) to determine whether low contrast scanning is necessary. #335
#3 unless a macro lens is attached on the same magnification.
40 to emit the auxiliary light, #345 to perform focus detection,
In #350, 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. 411+>, or a distance (e.g. 31n) where there are relatively many photographic scenes) within the range where focus detection using the auxiliary light is possible. Lens driver ΔN − (f2
/D o) Perform the calculation of X K -N L, #36
0 and start lens driving. In #361, 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. #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 detection is impossible. If the focus is not detected in #380, the process proceeds to #395. If #380 indicates that focus cannot be detected, #385 displays that focus cannot be detected.
At #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 #400 is in focus, #4
20 indicates the focus, and #425 sets the shooting preparation switch (
SL) is ON. If the shooting preparation switch (Sl) is ON in #425, turn on the shooting preparation switch (Sl).
The determination in #425 is repeated until 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. #40
If it is not in focus at 0, calculate the lens drive amount ΔN = D F X K from the differential tDF in #405, and
At 410, lens driving is started. In #412, it is determined whether the lens drive amount has reached ΔN. If the lens drive amount has not reached ΔN in #412, the lens drive amount is ΔN.
The determination operation in #412 is repeated until the value is reached. #412
When the lens drive amount reaches ΔN, the lens drive is stopped in #413, and the shooting preparation switch (Sl) is turned OFF in #415.
Determine whether it is N. Press #415 to turn on the shooting preparation switch (
If SL) is ON, the process returns to #370; if it is not ON, the display is turned off in #40, and the process returns to #30.

Modification Example In the algorithm for determining the defocus amount DFb (#], 008) in the lens position calculation subroutine (Fig. 9) described above, the frequently used photographic magnification is determined according to the information on the focal length f. β is set in advance, and the defocus amount DFb from the lens position Nb to the infinity position is calculated in advance according to the photographing distance at which this photographic magnification β is obtained, and is stored in the Ui OM table (see Table 1). Here, a predetermined value of defocus JLDFb is selected for a lens having a focal length within a predetermined range. For example, when 35mm<f≦50mm, DFb=
When 1.1++un and 50+nm<f≦100man, D F j-2 and 5vn are set.

FIG. 13 is a flowchart showing a modification of this algorithm. In #1500, it is determined whether the focal length r is 28 mm or less. If r≦28+nm in #1500, set O as the imaging magnification β in #1510, and #
Proceed to 1570. If f > 28 vn in #1500, it is determined in #1-520 whether the focal path Nf is 2101 or less. If the distance is 11210 mm in #1520, the photographing magnification β is set to (1,/40) in #1530, and the process proceeds to #1570.

If f > 210 mm in #1520, #157
'! , 0, it is determined whether the focal length f is 600 mm or less.

#1550 if f≦600m+n in #15140
Set the shooting magnification β to (1/60) and select #1570.
Proceed to. If f>60Qmm in #1540, #1
．． 560, set (1/100) as the imaging magnification β,
Proceed to #1570. In #1570, the lens extension amount DFb from the infinity position to the lens position iNb is calculated by multiplying the photographing magnification β by the focal length f. In the algorithm shown in FIG. 13, when the focal length r is, for example, 35 mm to 105+n+n, the imaging magnification β-
The defocus amount DFb multiplied by (1/40) is selected. In other words, the lens is always initially set at a position where an imaging magnification of <1/40) can be obtained.

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, a lens circuit (LEC) is included in a lens (1), and a focus detection circuit (AFC) corresponds to focus detection means (2). #1008 and #102 in Figure 9
Step 0 (or # in Figure 13), 500 to #1
570 and step #1020 in FIG. 9) correspond to the lens position determining means (3). The lens drive circuit (LDC) in FIG. 2 corresponds to the lens drive means (4), and the photographing preparation switch (Sl) corresponds to the operation member (5). Further, the routine for setting the lens initial position shown in FIG. 11 corresponds to the control means (6).

[Effects of the Invention] As described above, the present invention sets the initial stop position of the lens according to the frequently used photographic magnification before starting focus detection, which increases the probability that focus detection will be possible. effective.

It should be noted that applying the present invention to an automatic focus adjustment device that has a low-contrast scan function that searches for a lens position where focus can be detected by driving the lens back and forth when focus cannot be detected is because there are fewer opportunities to perform low-contrast scans. This has the advantage that the time required for focus detection is shortened.

[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.
FIG. 12 is a flowchart showing the same operation as above, FIG. 12 is an explanatory diagram of the same operation, and FIG. 13 is a flowchart 1 of a modified example of the same. (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 working member, and (6) is a control means.

Claims (2)

[Claims] (1) A photographic lens, a focus detection means for detecting the focal state of the lens, a lens position determination means for determining the initial stop position of the lens based on a predetermined photographic magnification determined depending on the lens, A lens drive means to be driven, an operation member operated to operate the focus detection means, and an initial stop position determined by the lens position determination means before the focus detection means performs a focus detection operation by operating the operation member. 1. A focus detection device comprising: control means for controlling a lens drive means to drive a lens. (2) The focus detection device according to claim 1, wherein the lens position determining means is a means for determining an initial stop position of the lens based on an imaging magnification determined according to a focal length of the lens.