JP2847703B2 - Focus detection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus detection device used for a single-lens reflex camera with an automatic focus adjustment function.

2. Description of the Related Art Conventionally, in an automatic focusing device that illuminates a low-luminance subject with auxiliary light and uses the reflected light to adjust the focus of an imaging lens, an image is captured before the auxiliary light is applied. It has been proposed to drive a lens to a normal focus position (see Japanese Patent Application Laid-Open No. 59-136720).

[Problems to be Solved by the Invention] Auxiliary light emitting devices for focus detection are usually mounted externally above an imaging lens or provided on the front surface of a camera body and a light emitting optical system. And On the other hand, the focus detection device usually includes a TTL type focus detection optical system, and its optical axis coincides with the optical axis of the taking lens. Therefore, the luminous flux area of the optical system for projecting auxiliary light and the luminous flux area for focus detection have a parallax, and the focus detection area is located beyond a predetermined distance (varies depending on the angle of view) in front of the taking lens. Is included in the light beam area of the optical system for projecting auxiliary light. This distance is the lower limit of the range in which the subject can be irradiated so that focus detection can be performed by the auxiliary light, and focus detection using the auxiliary light cannot be performed on a subject closer than this. Further, when a long focal length lens is attached to the camera, the auxiliary light is vignetted by the lens barrel, so that the auxiliary light may not be applied to the subject, and focus detection using the auxiliary light may not be performed. In such a case, it is useless to emit auxiliary light or to set the lens to an initial stop position suitable for capturing auxiliary light, which is wasteful and increases power consumption.

The present invention has been made in view of such a point,
It is an object of the present invention to provide a focus detection device in which power consumption is reduced by omitting useless auxiliary light emission and lens position setting.

[Means for Solving the Problems] In the focus detection device according to the present invention, in order to achieve the above object, as shown in FIG. Focus detection means (2) for detecting the focus state, auxiliary light emitting means (3) for irradiating the auxiliary light for focus detection to the shooting area, and whether the focus detection in the auxiliary light non-emission state is impossible. and it determines the focus detection is impossible judging means whether (4), the lens position determining means for determining the initial stop position Ns ₂ of the lens (1) when auxiliary light (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 auxiliary light for determining whether or not to inhibit the auxiliary light emission When the light emission prohibition determining means (8) and the focus detection impossibility determining means (4) determine that the focus cannot be detected and the auxiliary light emission prohibition determining means (8) determines that the auxiliary light emission is prohibited, the auxiliary light is not emitted. In this state, the focus detection means (2) is operated, and when it is determined by the focus detection impossible determination means (4) that the focus detection is impossible and when the auxiliary light emission prohibition determination means (8) determines that the auxiliary light emission is not prohibited, controls the lens driving means (6) to drive the initial stop position Ns ₂ determined by the lens position determining means (5) a lens (1), an auxiliary light emitting means (3) and the focus detection means ( 2) control hand to operate And a step (9).

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

[Operation] Hereinafter, the operation of the present invention will be described with reference to FIG. The photographing lens (1) forms an image of light from a subject. The focus detection means (2) detects a focus state of the lens (1).
When the operation member (7) is operated, the focus detection means (2) operates to detect the focus state of the lens (1). The focus state of the lens (1) is usually detected as a defocus amount (a defocus amount) from the in-focus position, and the sign is used to distinguish the front focus and the rear focus. At the time of normal focus detection, based on the focus detection result of the focus detection means (2),
The lens (1) is driven toward the focus position. The driving of the lens (1) is performed by lens driving means (6).

By the way, when the photographing area has low luminance or low contrast, focus detection may not be performed in some cases. This state is determined by the focus detection impossible determination means (4). When focus detection is not possible, the auxiliary light should be emitted. However, if the focal length of the lens (1) is longer than a predetermined length, or if the auxiliary light is emitted during macro photography, it is useless. In such a case, the auxiliary light emission is prohibited. Whether or not the auxiliary light emission should be prohibited is determined by the auxiliary light emission inhibition determination means (8).

If it is not determined that the auxiliary light emission is prohibited, the auxiliary light is irradiated to detect the focus state of the lens (1). Initial stop position Ns ₂ of the lens (1) suitable for the focus detection when using the auxiliary light is determined by the lens position determining means (5). Control means 9 controls the lens driving means (6) to drive the initial stop position Ns ₂ determined by the lens position determining means (5) a lens (1) and then the auxiliary light emitting means ( 3) and the focus detection means (2) are operated. Therefore, when detecting the focus state of the lens by irradiating auxiliary light (1) includes a lens (1) is set to the initial stop position Ns ₂ suitable when the focus detection using the auxiliary light, and allows focus detection Is more likely to occur.

If it is determined that the auxiliary light emission prohibition, the control means (9), without driving the lens (1) to the initial stop position Ns ₂ described above, the focus detection unit in the auxiliary light non-emission state (2) Make it work. Therefore, unnecessary auxiliary light emission and lens position setting are not performed.

Embodiment FIG. 2 is a block circuit diagram showing a circuit configuration of a camera as one embodiment of the present invention. However, parts not directly related to the focus detection operation are not shown.
(ΜC) is a microcomputer that performs calculation and sequence control for focus adjustment. (LEC) is a lens circuit provided in the interchangeable lens and transmits information unique to the interchangeable lens to a microcomputer (μC). (AFC)
Is a focus detection circuit that photoelectrically converts the subject light passing through the lens and outputs focus detection data. The focus detection circuit converts the focus detection data into a digital signal, and outputs the focus detection data to a microcomputer (μ).
C). (DSP) is a display circuit for displaying the in-focus state of the lens and the inability to detect focus. (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 driving circuit (LDC). The lens drive circuit (LDC) is a microcomputer (μC)
The motor (M) is driven based on the motor drive speed signal, motor drive direction signal, and motor stop control signal. (ENC) is an encoder which detects the rotation amount of the motor (M) and outputs a pulse to the microcomputer (μC) according to a predetermined rotation amount of the motor (M).

Here, the microcomputer (μC) is a lens position counter for knowing, as an absolute amount, the extension amount of the lens from the infinity position where the lens is fully retracted.
Built-in _NL . This lens position counter _NL is activated by an internal command when the lens is retracted to infinity.
When N _L is reset to 0 and the lens is extended, an internal command counts up in response to a pulse from the encoder (ENC). When the lens is retracted, the encoder (ENC) is activated by an internal command. ) Is counted down according to the pulse from. When the lens is extended to the closest position, the value of the lens position counter _NL becomes _NL = Nmax. The maximum payout amount Nmax differs depending on the lens, and is read from the lens circuit (LEC) as information unique to the lens into the microcomputer (μC).

(BAT) is a power supply battery for supplying power to the microcomputer (μC) and other circuits. Power battery (BA
At both ends of T), a time constant circuit consisting of a series circuit of a resistor (R1) and a capacitor (C1) is connected.
The connection point between the capacitor and the capacitor (C1) is connected to a power-on reset terminal (RES) of a microcomputer (μC). When a power supply battery (BAT) is connected, the power supply terminal (Vcc) of the microcomputer (μC) and the ground terminal (GN)
The power supply voltage is applied during D) to activate the microcomputer (μC), but the charging voltage of the capacitor (C1), that is, the reset terminal (RE) of the microcomputer
The microcomputer (μC) does not operate until the voltage applied to S) reaches a predetermined voltage. When the voltage of the capacitor (C1) becomes equal to or higher than a predetermined voltage, the microcomputer (μC) is reset, and a step # 5 described later is performed.
(Refer to FIG. 3).

(S _R ) is a reset switch, which is ON
Then, the lens is reset to the initial position. (S
∞) is an infinity position detection switch, which is turned ON when the lens is moved to the infinity position. (S _M ) is a main switch, which is turned on when the camera is used. (S1) is a shooting preparation switch, which is normally turned on by a first stroke of a release button (not shown). (S _AF ) is an AF mode switch. When this switch (S _AF ) is ON, the auto focus mode for driving the lens to the in-focus position based on the focus detection result is selected.
_{When AF} ) is OFF, a manual focus mode in which only focus or non-focus is displayed based on the focus detection result and lens driving is not performed is selected. (S _MZ ) 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 the present embodiment, when the zoom ring is set to the macro zone, the auto focus mode is disabled, so that the microcomputer (μ)
In order to notify C), the lens circuit (LEC) outputs a signal SMZ indicating a macro zone to the microcomputer (μC).

Next, the focus adjustment operation of the camera will be described with reference to a flowchart. When a power-on reset is performed,
The microcomputer (μC) executes the program after # 5 shown in FIG. First, all flags are reset in # 5. Next, it is determined whether or not the main switch ( _SM ) is ON in # 10. If the main switch (S _M ) is not ON
The determination of # 10 is repeated until it is turned ON. If the main switch (S _M ) is ON, the subroutine for calculating the initial position of the lens (FIG. 9) is executed in # 15, the subroutine for renormalization (FIG. 10) is executed in # 20, and the lens is executed in # 25. After executing the initial position setting subroutine (FIG. 11), it is determined in step # 30 whether the main switch (S _M ) is OFF. If the main switch (S _M ) is OFF, the subroutine of “∞” is executed in # 35 and the process returns to # 10. Main switch (S _M) is not the OFF at # 30, the process proceeds 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, at # 1000, lens data is input from the lens circuit (LEC). From the lens circuit (LEC), a lens mounting signal ICP, a macro zone signal SMZ, a macro lens mounting signal LCPR, a maximum payout amount Nmax, a focal length f, a conversion coefficient K, and the like are input to a microcomputer (μC). . Here, the conversion coefficient K is a coefficient for converting the defocus amount DF into the lens driving amount ΔN. # 1005
Then, the presence / absence of the macro lens attachment signal LCPR is determined to be equal to or greater than one. If the macro lens is attached at 1x or more at # 1005, the defocus amount for setting the initial lens position at # 1040
Set DFs to DFm / 2 and return to the step where the subroutine was called. Here, DFm is the maximum defocus amount covering the range from the closest position to the infinity position of the lens. If the macro lens is not mounted at the same magnification or larger in # 1005, the defocus amount DFb is determined in # 1008. The defocus amount DFb is a defocus amount from an infinity position up to the lens position Nb determined according to the imaging magnification β. In the present embodiment, the lens position Nb set in advance in consideration of the frequently used photographing magnification β from the information of the focal length f
Is read from the ROM table.

Table 1 shows frequently used photographing magnifications β for lenses having various focal lengths and lens positions determined accordingly.
A defocus amount DFb corresponding to Nb and a maximum defocus amount DFm of the lens are shown. DFa is a focus detection circuit (AFC)
Is a defocus amount that can be detected by the focus, and the focus detectable range is twice as large as 2DFa.

In # 1010, it is determined whether DFb> DFa. In # 1010
If DFb> DFa, the defocus amount DFs for setting the lens initial position is set to DFa in # 1030, the lens position set flag SETF is set to 1 in # 1060, and the process returns to the step where the subroutine was called. If DFb ≦ DFa in # 1010, #
In 1020, set the defocus amount DFs for setting the initial position of the lens to D.
Fb, the lens position set flag SETF is set to 1 at # 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. FIG. 6A shows a case where the defocus amount DFb from the lens position Nb to the infinity position determined according to the photographing magnification β is larger than the defocus amount DFa at which focus can be detected. Sets DFs = DFa. Therefore, at the lens initial position Ns = DFs × K, the position at infinity is included in the focus detectable range 2DFa, and when focus detection is not possible, only scanning in the direction in which the lens is extended may be performed. FIG. 6B shows a case where the defocus amount DFb from the lens position Nb to the infinity position determined according to the photographing magnification β is equal to or less than the defocus amount DFa at which the focus can be detected. Sets DFs = DFb. Also in this case, the lens initial position Ns = DF
In s × K, the focus detection range is 2DFa at infinity.
If the focus cannot be detected, only scanning in the direction in which the lens is extended may be performed.

FIG. 10 is a flow chart showing the contents of a subroutine for renormalization. When this subroutine is called, lens retraction is started in # 1100, and it is determined in # 1105 whether the infinity position detection switch (S #) is ON. #
If the switch (∞) is not ON at 1105, the switch (SＳ)
The determination operation of # 1105 is repeated until ∞) is turned ON. # 11
At 05, the lens is retracted to infinity and the switch (S
If ∞) becomes ON, stop lens retraction at # 1110,
In step # 1115, the lens position counter _NL is reset, and the process returns to the step where the subroutine was called.

FIG. 11 is a flowchart showing the contents of a subroutine for setting a lens initial position. 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 driving amount ΔN = DFs × K from the infinity position, and in # 1205 Start extending the lens. In # 1210, the lens drive amount is Δ
It is determined whether N has been reached. The lens drive amount is ΔN in # 1210
If not, the determination operation of # 1210 is repeated until the lens drive 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 where the subroutine was called.

Returning to the flow of FIG. 3, in # 45, it is determined whether the AF mode switch (S _AF ) is ON. If the AF mode switch (S _AF ) is not ON at # 45, the flag MF indicating manual focus mode is set at 1 at # 50 and #
Go to 80. If the AF mode switch (S _AF ) is ON in # 45, it is determined whether the flag MF is 1 in # 55. MF at # 55
If = 1, it means immediately after the switch (S _AF ) is turned ON, and the flag MF is set to 0 in # 60 and the process proceeds to # 65. #
In steps 65 to 75, the above-described subroutines for calculating the initial position of the lens, recalculating the lens, and setting the initial position of the lens are executed to set the initial position of the lens. If MF is not 1 in # 55, it means that the switch (S _AF ) has been ON before, and the process proceeds to # 80.

In # 80, the presence or absence of the lens attachment signal ICP is determined. # 8
If the lens is not attached at 0, the flag LENOF indicating that the lens is not attached is set at 1 at # 100, and the routine proceeds to # 105. If the photographing lens is attached in # 80, it is determined whether the flag LENOF is 1 in # 90. If LENOF = 1 in # 90, it means immediately after the lens is mounted, and # 95
The flag LENOF is set to 0 to set the lens initial position of # 65 to # 75, and then the process proceeds to # 145. If LENOF is not 1 in # 90, it means that the lens has been mounted before, and the process proceeds to # 105.

In # 105, it is determined whether the macro zone switch (S _MZ ) is ON, that is, whether the zoom lens is not in the macro zone. If the macro zone switch (S _MZ ) is not ON in # 105, that is, if it is in the macro zone, a flag SM indicating that the macro zone switch (S _MZ ) is OFF in # 110
Set ZOFF to 1 and proceed to # 125. If the macro zone switch (S _MZ ) is ON in # 105, it is determined whether the flag SMZOFF is 1 in # 115. If SMZOFF = 1 in # 115, it means immediately after the macro zone switch (S _MZ ) is turned ON. After setting the flag SMZOFF to 0 in # 120 and performing the lens initial position setting of # 65 to # 75 Proceed to # 145. At # 115
If SMZOFF is not 1, it means that the macro zone switch (S _MZ ) has been turned on before, and the process proceeds to # 125.

In # 125, it is determined whether the reset switch (S _R ) is ON. If the reset switch (S _R ) is not ON in # 125, the flag SROFF indicating that the reset switch (S _R ) is OFF is set to # 1 in # 130, and the process proceeds to # 145. If the reset switch (S _R ) is ON in # 125, the flag SRO is set in # 135
It is determined whether FF is 1. If SROFF = 1 in # 135, it means that immediately after the reset switch (S _R ) is turned on, the flag SROFF is set to 0 in # 140, and the lens initial position is set in # 65 to # 75. Go to # 145. In # 135
If SROFF is not 1, it means that the reset switch (S _R ) has been turned ON before and the lens has already been set to the initial position, so the lens initial position of # 65 to # 75 is not set. Then, proceed to # 145.

Therefore, after performing the lens initial position setting (# 15 to # 25) immediately after the main switch (S _M ) is turned on, whether the AF mode switch (S _AF ) is turned on or immediately after the lens is mounted. Immediately after the macro zone switch (S _MZ ) is turned on, immediately after the reset switch (S _R ) is turned on, or even when a low-con scan described later is performed, the focus cannot be detected and the shooting preparation switch ( Only when S1) is turned off and then turned on again (see # 155), the lens initial position setting (# 65 to # 75) is performed. In other cases, the lens initial position setting is not performed. Therefore, if there is a high probability of focusing near the previous lens position, such as when shooting similar scenes or when taking a series of photos, the lens initial position is not set and the focus is not set. Compared with the case where the lens initial position is set each time the detection is performed, the power consumption is reduced and the time required for the focus adjustment is shortened.

In # 145, it is determined whether the shooting preparation switch (S1) is ON. If the shooting preparation switch (S1) has not been turned ON, the entire display is turned off at # 40, and the process returns to # 30. Below, # 3
Main switch (S _M ), AF mode switch (S _AF ), lens mounting signal ICP, macro zone switch (S _MZ ) while going through a loop passing through 0, # 45, # 80, # 105, # 125, # 145 Monitor the status of the reset switch (S _R ) and shooting preparation switch (S1). If the main switch (S _M ) is turned off in the middle of this loop, as described above, the recall (# 35) is performed, and the process waits until the main switch (S _M ) is turned on again (# 10). ). In the middle of the loop, when one of the switches (S _AF ), (S _MZ ), and (S _R ) is turned on, or when a lens is attached, the lens initial position setting (# 65 to # 75).
In this way, the camera turns on the shooting preparation switch (S1)
The camera is ready for shooting.
When 1) is turned on, # 155 (fourth
(Figure).

In # 155, the low-con scan end flag L
Determine whether SENDF is 1. Initially, since LSENDF = 0, focus detection is performed in # 175, and it is determined whether focus detection is impossible in # 180. If the focus cannot be detected in # 180, the process proceeds to # 285 (FIG. 7) to make a focus determination. # 1
If the focus cannot be detected at 80, it is determined at # 185 whether the brightness is low. If the brightness is low at # 185, the process proceeds to # 330 (FIG. 8) to emit the auxiliary light. If the brightness is low in # 185,
In # 190 and # 191 (FIG. 5), it is determined whether (Nmax−N _L ) / K> DFa or N _L / K> DFa is satisfied. If the conditions are not satisfied in # 190 and # 191, the entire focus range of the lens is included in the focus detectable range 2DFa. Nevertheless, the fact that focus detection is not possible means that low-con scan (focus detection is performed while driving the lens,
Even if an operation of searching for a focus detectable position) is performed, focus detection cannot be performed, and it is useless to perform low contrast scanning. Therefore, without performing low contrast scan, #
Proceeding to 255 (see FIG. 7), a focus detection disabled display is performed.

If the condition is satisfied in # 190 or # 191, # 192
It is determined whether or not Nmax / 2K ≦ DFa is satisfied. Here, Nmax / 2K is the defocus amount (ie, DFm / 2) from the intermediate position to the end position of the taking lens, and is determined according to the attached lens. 2DFa is a focus detection circuit (AFC)
Is a defocus amount that can be detected by the focus and is a constant on the camera body side. If the condition is satisfied in # 192, 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 perform low contrast scanning. Therefore, in order to move the lens to the intermediate position Nmax / 2, the lens driving amount ΔN = Nmax / 2− _NL is calculated in # 193, and the lens driving is started in # 1941. In # 1942, it is determined whether the lens drive amount has reached ΔN. # 1942
If the lens drive amount has not reached ΔN, the determination operation of # 1942 is repeated until the lens drive amount reaches ΔN. #
If the lens drive amount reaches ΔN in 1942, the lens drive is stopped in # 1943, focus detection is performed in # 195, and it is determined in # 196 whether focus detection is impossible. If the focus cannot be detected in # 196, the focus cannot be detected even if the low contrast scan is performed, and it is useless to perform the low contrast scan. Therefore, without performing low contrast scan, # 255
Proceeding to (FIG. 7), a focus detection disabled display is performed. If the focus cannot be detected, # 285 (the seventh
(Figure).

If the condition is not satisfied in # 192, no matter where the lens position is changed, the entire focus range Nmax / K of the lens cannot be covered within the focus detectable range 2DFa. Therefore, in this case, low-con scan is unavoidably performed, but by limiting the range of the low-con scan to the narrowest possible range, the time required for low-con scan is shortened. ing. That is, # 198
(FIG. 6), the scan amount in the feeding direction is ΔN =
It is calculated as Nmax− _NL− DFa × K. This is because, even if it is not extended to the maximum extension position Nmax, if it is extended to the position before by DFa × K, the maximum extension position Nmax also falls within the focus detectable range 2DFa. Next, in order to know the scanning direction, it is determined whether the flag FOWF is 1 in # 200. The flag FOWF is a flag indicating that scanning in the forward (FOWard) direction is performed. When the low contrast scan is performed for the first time, the flag FOWF is reset, so that FOWF = 1 is not set. Therefore, the process first proceeds to # 205, sets FOWF = 1 in # 205, and proceeds to # 220.
In step # 220, a signal is output to the lens drive circuit (LDC) in order to drive the lens (extending direction). After performing focus detection in step # 225, it is determined in step # 230 whether the focus cannot be detected.
If the focus cannot be detected in # 230, the flag FOWF is reset in # 233, and the process proceeds to # 285 (FIG. 7) in order to perform focus determination. If the focus cannot be detected in # 230, it is determined in # 235 whether the lens drive amount has reached ΔN. If the lens drive amount has not reached ΔN in # 235, the flow returns to # 225, and it is determined whether or not focus detection is impossible while continuing the lens drive in the extending direction. If the lens drive amount has reached ΔN in # 235, the lens drive is stopped in # 240, and it is determined whether the lens position set flag SETF is 1 in # 245. SET at # 245
If F = 1, it is possible to determine that the focus cannot be detected over the entire focus range of the lens without performing scanning in the retraction direction. move on. If SETF is not 1 in # 245, it is determined whether the flag FOWF is 1 in # 250. # 2
If FOWF = 1 at 50, this means that scanning in the extension direction was performed, but a lens position capable of focus detection was not found, so the process returns to # 200 to perform scanning in the extension direction. If FOWF = 1 in # 200, it means that the scanning in the feeding direction has already been completed. Therefore, in # 210, the scanning amount in the feeding direction is ΔN.
= Calculated as DFa × K-N _L. This is because, even if the infinity position is not moved to the infinity position, if it is moved to the position before by DFA × K, the infinity position also falls within the focus detectable range 2DFa. In step # 215, the flag FOWF is set to 0 to indicate that the scan is in the rewinding direction, and the process proceeds to step # 220.
At # 220, a signal is output to the lens driving circuit (LDC) to drive the lens (retracting direction), and the process returns to # 250 via # 225 to # 245. This time, since FOWF is not 1, the flow does not return to # 200 but proceeds to # 255 (FIG. 7).
In other words, the case where FOWF is not 1 in # 250 means that both the scanning in the extending direction and the scanning in the extending direction were performed, but a lens position capable of focus detection was not found. The display is performed. If the focus can be detected in step # 230 during the scanning in the retraction direction, the flag FOWF is reset in step # 233, and the process proceeds to step # 285 (FIG. 7) to determine the focus.

When the focus detection disabled display is performed in # 255 (FIG. 7), # 260
Sets the low contrast scan end flag LSENDF to 1. This flag indicates that a low-contrast scan has been performed, but a lens position at which focus detection is possible was not found. If the focus cannot be detected even though the entire focus range of the lens is included in the focus detection range 2DFa (specifically, when the process proceeds from # 191 or # 196 to # 255), the actual Sets the flag LSENDF to 1 at # 260 even if the low contrast scan is not performed. This is because a low-contrast scan cannot find a lens position at which focus can be detected. Next, after returning the flag FOWF indicating the scan direction to 0 in # 265, it is determined in # 270 whether the photographing preparation switch (S1) is ON. If the shooting preparation switch (S1) is not ON in # 270, all the display is erased in # 40 and the process returns to # 30. In # 270, the shooting preparation switch (S1) is set to O
If N, focus detection is performed in # 275, and it is determined whether focus detection is impossible in # 280. If the focus cannot be detected in # 280, the process returns to # 270. If the focus cannot be detected in # 280, #
At 285, the lens position set flag SETF is set to 0, at # 290, the low-con scan end flag LSENDF is set to 0, and at # 295, it is determined whether the lens is in focus. If it is determined in step # 295 that the object is not in focus, the flow advances to step # 300 to eliminate the in-focus and focus detection disabled display. In step # 305, the lens driving amount ΔN = DF × K is calculated based on the defocus amount DF. At 310, lens driving is started. In # 311, it is determined whether the lens drive amount has reached ΔN. If the lens drive amount has not reached ΔN in # 311, the determination operation of # 311 is repeated until the lens drive amount reaches ΔN. If the lens drive amount reaches ΔN in # 311,
In step # 312, the lens driving is stopped, and the process returns to step # 270. If the photographing preparation switch (S1) remains ON in # 270, focus detection is performed in # 275, and focus determination is performed again in # 295 through # 280 to # 290. Since the lens is driven toward the in-focus position in steps # 305 and # 310 described above, there is a high possibility that the lens will be focused here. If the in-focus state is obtained in # 295, the in-focus state is displayed in # 315, and it is determined in # 320 whether the photographing preparation switch (S1) is ON. In # 320, the shooting preparation switch (S1) is set to O
If N, the determination operation of # 320 is repeated until the shooting preparation switch (S1) is not turned ON, and a so-called focus lock state is set. Although not related to the present invention, in the camera in the focus priority mode, when the release is permitted in the focus locked state and the release button (not shown) is pressed down to the second stroke, the camera is released. Perform the operation. If the shooting preparation switch (S1) is not turned on in # 320, the display is turned off in # 40 and #
Return to 30. That is, when the photographing preparation switch (S1) is turned off, the focus lock state is released.

When the photographing preparation switch (S1) is turned off and then turned on again, it may be determined that LSENDF = 1 in # 155. This is the case when the focus detection was previously performed with the shooting preparation switch (S1) turned ON, but the focus could not be detected, and the low-contrast scan did not find a lens position that could be detected. Is performed, there is no case where a lens position at which focus can be detected cannot be found.
In this case, the flag LSENDF is returned to 0 in # 157, and # 65
The lens initial position is set from # 75 to # 75, and the process proceeds to # 145.
When proceeding to step # 157, be sure to set the shooting preparation switch (S
Only when 1) is turned on after being turned off. At this time,
The reason why the lens initial position is set is that when the low-con scan end flag LSENDF is 1, the probability that there is a subject to be photographed near the existing lens position is low, and in particular, the low-con scan was actually performed. In such a case, since the lens position is deviated toward the infinity position or the vicinity of the closest position, it is necessary to return the lens position to an appropriate position.

Next, when passing through # 330 in FIG. 8, # 185 and # 18
In FIG. 0 (FIG. 4), since it is determined that the luminance is low and the focus cannot be detected, auxiliary light emission is required.
Even if the auxiliary light is emitted, there is a case where it is useless, so that the determination is performed in # 330 and # 335. Here, the auxiliary light emitting device (ILM) shown in FIG. 2 is usually equipped with a light emitting diode mounted externally above the taking lens of the camera or provided on the front of the camera body and a light emitting optical system. And On the other hand, the focus detection circuit (AFC) includes a TTL phase difference detection type focus detection optical system, and its optical axis coincides with the optical axis of the photographing lens. Therefore, the luminous flux area of the optical system for projecting auxiliary light and the luminous flux area for focus detection have a parallax, and a predetermined distance in front of the photographing lens (varies depending on the angle of view).
Beyond, the light flux area for focus detection is completely included in the light flux area of the auxiliary light projecting optical system. This distance is the lower limit of the range in which the subject can be irradiated to enable focus detection with the auxiliary light.
It is useless to emit auxiliary light. When a long focal length lens is attached to the camera, the auxiliary light is vignetted by the lens barrel, so that the auxiliary light may not be applied to the subject, and the auxiliary light may be wasted. The lower limit of the range in which the subject can be illuminated to enable focus detection by the auxiliary light can be reduced by adopting the TTL auxiliary light system, but the upper limit of the range in which the focus can be detected by the auxiliary light irradiation is increased. The reason is that the reaching distance of the auxiliary light is
Because it is about 10m, I cannot expect much. So, # 330
Then, it is determined whether the focal length f of the lens is 250 mm or more. If f ≧ 250 in # 330, it is determined that the auxiliary light may be vignetted due to the long lens length, and the auxiliary light is emitted. Instead, the process proceeds to # 190 (FIG. 5) to determine whether low-con scan is necessary. In addition, in photographing using a long focal length lens, since there are many long-distance photographings in which the auxiliary light does not reach, there is not much problem even if the auxiliary light emission is prohibited. If f ≧ 250 is not satisfied in # 330, it is determined in # 335 whether or not the macro lens attachment signal LCPR is equal to or greater than one. If the macro lens is attached at 1 × or more in # 335, it is determined that the shooting is performed at a close distance smaller than the lower limit of the range in which the focus can be detected by illuminating the auxiliary light, and the auxiliary light is not emitted. Proceed to # 190 (Fig. 5)
The necessity of low contrast scan is determined. If the macro lens is not mounted at the same magnification or larger in # 335, the auxiliary light is emitted in # 340, the focus is detected in # 345, and it is determined whether or not the focus cannot be detected in # 350. The auxiliary light is emitted only for a predetermined time for each focus detection. If the focus cannot be detected in # 350, the process proceeds to # 395. If focus detection is not possible at # 350, an intermediate distance (eg, 4
m) or the distance where the shooting scene is relatively large (for example, 3m) D
_In order to adjust the lens position to ₀ , the lens drive amount Δ in # 355
The calculation of N = (f ² / D ₀ ) × K−N _L is performed, and lens drive is started in # 360. In # 361, it is determined whether the lens drive amount has reached ΔN. If the lens drive amount has not reached ΔN in # 361, the process proceeds to # 361 until the lens drive amount reaches ΔN.
Is repeated. If the lens drive amount reaches ΔN in # 361, the lens drive is stopped in # 362. And # 3
Auxiliary light emission is performed at 70, focus detection is performed at # 375, and # 380
Is used to determine whether or not focus detection is impossible. If the focus cannot be detected in # 380, the process proceeds to # 395. If the focus cannot be detected in # 380, a focus detection disabled display is performed in # 385, and in # 390, it is determined whether the photographing preparation switch (S1) is ON. If the shooting preparation switch (S1) is ON in # 390, the flow returns to # 375.
If the shooting preparation switch (S1) is not ON at # 390, # 40
Press to clear the display and return to 30.

In step # 395, the focus detection disabled display is turned off, and in step # 400, it is determined whether the object is in focus. If the image is in focus in # 400, the in-focus display is performed in # 420, and it is determined in # 425 whether the shooting preparation switch (S1) is ON. At # 425, the shooting preparation switch (S1) is turned on
If so, the determination of # 425 is repeated until the shooting preparation switch (S1) is not turned on. If the shooting preparation switch (S1) is not turned on at # 425, the display is turned off at # 40 and the process returns to # 30. If not in focus at # 400, defocus amount at # 405
The lens drive amount ΔN = DF × K is calculated from DF, and the lens drive is started at # 410. In # 412, the lens drive amount is ΔN
Is reached. If the lens drive amount has not reached ΔN in # 412, the lens drive amount will reach #N until the lens drive amount reaches ΔN.
The determination operation of 412 is repeated. # 412: lens drive amount is ΔN
Is reached, the lens driving is stopped at # 413, and it is determined at # 415 whether or not the shooting preparation switch (S1) is ON. If the shooting preparation switch (S1) is ON at # 415, the process returns to # 370 and is ON
If not, the display is turned off at # 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 and thereafter will be described. The lens circuit (LEC) in FIG. 2 is included in the lens (1), and the focus detection circuit (AFC) corresponds to the focus detection means (2). The auxiliary light emitting device (ILM) corresponds to the auxiliary light emitting means (3). Steps # 180 and # 185 in FIG. 4 correspond to the focus detection impossible determination means (4). 8th
The step # 355 in the figure corresponds to the lens position determining means (5). The lens drive circuit (LDC) in FIG. 2 corresponds to the lens drive means (6). The photographing preparation switch (S1) in the figure corresponds to the operation member (7). # In Fig. 8
Steps 330 and # 335 correspond to the auxiliary light emission inhibition determination means (8). Step # 225 in FIG. 6 and steps # 365 to # 375 in FIG. 8 correspond to the control means (9).

[Effects of the Invention] As described above, the present invention prohibits the emission of the auxiliary light when it is useless to emit the auxiliary light, and at the same time, drives the lens to the initial stop position suitable for the auxiliary light shooting. Since the power for driving the light source of the auxiliary light and the power for driving the lens can be prevented from being wastefully used.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of the present invention, FIG. 2 is a block circuit diagram of one embodiment of the present invention, FIGS. 3 to 11 are flowcharts showing the operation of the above, and FIG. It is an operation explanatory view. (1) is a lens, (2) is focus detection means, (3) is auxiliary light emission means, (4) is focus detection impossibility determination means, (5) is lens position determination means, (6) is lens drive means, (7)
Is an operation member, (8) is an auxiliary light emission prohibition determination unit, (9)
Is control means.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshio Kaida 2-30-30 Azuchicho, Higashi-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Camera Co., Ltd. (72) Katsumi Kosakai 2-chome Azuchicho, Higashi-ku, Osaka, Osaka No. 30 Osaka International Building Minolta Camera Co., Ltd. (72) Inventor Hiroshi Otsuka 2--30 Azuchicho, Higashi-ku, Osaka City, Osaka Prefecture Osaka International Building Minolta Camera Co., Ltd. (56) References JP-A-63-172226 (JP, A) JP-A-62-215216 (JP, A) JP-A-63-172247 (JP, A) JP-A-63-103216 (JP, A) JP-A-63-82407 (JP, A) JP-A-59 -136721 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G02B 7/11

Claims (4)

(57) [Claims] 1. A lens for photographing, a focus detecting means for detecting a focus state of the lens, an auxiliary light emitting means for irradiating an auxiliary light for focus detection to a photographing area, and a focus detection in a state where no auxiliary light is emitted Operating the focus detection impossible determining means for determining whether or not the lens is impossible, the lens position determining means for determining the initial stop position of the lens when the auxiliary light is emitted, the lens driving means for driving the lens, and the focus detecting means The operation member operated to cause the auxiliary light emission to be inhibited is determined by the auxiliary light emission inhibition determination unit that determines whether or not the auxiliary light emission is to be inhibited. When it is determined that the auxiliary light emission is prohibited, the focus detection unit is operated in the auxiliary light non-emission state, the focus detection is disabled by the focus detection disabled determination unit, and the focus light is disabled by the auxiliary light emission inhibition determination unit. When it is determined that the auxiliary light emission is not prohibited, the lens drive unit is controlled so as to drive the lens to the initial stop position determined by the lens position determination unit, and the auxiliary light emission unit and the focus detection unit are operated. A focus detection device comprising control means. 2. The control means according to claim 1, wherein the control means simultaneously controls the lens driving means to scan the lens when the focus detecting means is operated in the auxiliary light non-emission state. Focus detection device. 3. The focus detecting device according to claim 1, wherein said auxiliary light emission inhibition determination means sets the auxiliary light emission inhibition determination condition that the focal length of the lens is equal to or longer than a predetermined length. 4. The focus detecting device according to claim 1, wherein the auxiliary light emission prohibition determining means sets the close-up photographing state as the auxiliary light emission prohibition determination condition.