JPS6350821A - Automatic focusing camera - Google Patents

Abstract

PURPOSE:To vary a coefficient of power variation with a distance ring position without providing any distance encoder by selecting the coefficient of power variation on the basis of the number of pulses from a reference position and the number of pulses characteristic to a photographic lens, and driving a photographic lens. CONSTITUTION:The ratio of the number of pulses which is obtained by counting output pulses of a photointerrupter indicating the rotational quantity of a motor 31 for driving the photographic lens as a distance ring position deciding means on the basis of the position where the photographic lens is set to infinity , and the number of pulses (maximum pulse) characteristic to the photographic lens corresponding to the movement from the closest position to the infinite distance position is used. Then, one of two kinds of coefficients of power variation is selected according to the result of comparison between the ratio and a certain decision level and the detected shift quantity of a focal surface is converted into the driving quantity of the lens. Consequently, variation in coefficient of power variation due to variation in lateral power which is ignored before is considered to improve the speed of AF.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an autofocus camera, and more particularly to an autofocus camera that takes into account changes in the magnification coefficient due to changes in the magnification of a photographic lens.

[Prior Art] Phase difference focus detection methods used in autofocus cameras are already well known. This focus detection method is shown in Figure 13~
It is constructed as shown in FIG. That is, FIGS. 13 to 15 show the principle thereof, and FIG. 13 shows the positional relationship between the focus detection sensor 100 and the optical system 101.

In this case, in the case of a TTL type reflex camera, the focus detection sensor 100 is placed at a position equivalent to that of the film. The focus detection sensor 100 is shown in FIG.
), (B), and (C), photoelectric conversion elements a, - are formed of CCDs and the like consisting of a group and b group arranged in pairs (al, b1 to an, bn), respectively. an, b, -b.

(see FIG. 15(A)) and each bear (al.

It is composed of lenslets C1 to Co (see FIG. 15(B)) arranged corresponding to the lenslets C1 to C0 (see FIG. 15(B)). The above lenslets C1 to C are photographic lenses 1
The light that passes through the exit pupil of 01 and reaches sensor 100 is divided into an upper A beam and a lower B beam across the optical axis of the photographic lens, and each is divided into an 8 group detection sensor and a b7!1 detection sensor. (See Figure 15 (C)).

Now, as shown in FIG. 13, assuming that the focal plane 102 is formed at a position ΔL away from the focus detection sensor 100 toward the photographing lens 101, the photoelectric conversion probes a1 to a□.

When the outputs of b1 to bn are expressed as the element number on the horizontal axis and the output value of the corresponding element on the vertical axis, the characteristic curve diagram shown in FIG. 14 is obtained.

At this time, the curve formed by the detection sensors of group b is shifted from the curve formed by the detection sensors of group a by a phase difference ΔX. This phase difference ΔX and the amount of deviation ΔL from the actual focal plane have a linear relationship via a certain coefficient. That is, ΔL− and ΔX (1) k: conversion coefficient.

Then, ΔX is derived from the data of this detection sensor in the following manner.

Whether the focal point is the front bin (the focal plane is behind the photographing lens), in-focus, or the rear bin (the focal plane is behind the sensor) can be determined by the following evaluation formula: can.

N: Number of sensor pairs In general, when F>0, the front bin F-0 is in focus, and when F<O, the rear bin holds true. However, it is not possible to obtain the phase difference ΔX using this evaluation formula.

The above formula (2) is an evaluation formula when the subscripts of the 8th group sensor and the b group sensor are the same, that is, when the shift is -0. Therefore, if we change this evaluation formula to a general formula that uses the shift number S as a function, when S≧0, F(S) = Σ (lan+s −bn+ll
lbn "n+5-It)'...ku5)n
−+ When SkuO, F(S)−Σ (l”n−bn−3+il 1bn−
8a, 1+11) - (3) n+1 N: Number of sensor bears, an evaluation formula that can calculate the phase difference ΔX, and the amount and direction of focal plane shift obtained by this phase difference focus detection method. When driving the lens to the focal point based on The lens is focused by moving it.

By the way, the coefficient that converts the focal plane shift amount into the lens drive amount (hereinafter referred to as the variable magnification coefficient) is the lateral magnification of the lens (the size of the image of the object perpendicular to the optical axis of the lens). It does not have a single value because it changes depending on the ratio (to the size).

Next, considering this in the case of a single lens, as shown in FIG. The following formula holds.

Δd−(1−β2)ΔΩ (4) However, β: lateral magnification, and this lateral magnification is calculated by the following formula.

β-! J/f ・・・・・・・・・(5) However, f
: Focal length of the lens Ω; Amount of extension of the distance ring when the point where the lens touches the infinity side is taken as the standard changes, and the ratio between the amount of lens extension and the amount of movement of the focal plane changes.

This is the reason why the scaling factor does not have a single value.

Furthermore, this is true not only for a single lens that focuses by extending the entire lens, but also for lenses that use a front group lens extension method, an internal focusing method, or a rear focusing method. In this case, the value of the variable magnification coefficient changes depending on the change in the lateral magnification of the focusing group lens for focus adjustment. .

For example, if we take the front group extension type zoom lens shown in FIG. 12 as an example, the following equation holds true.

In other words, the amount of movement of the image created by the focusing group lens is Δ
dp, Δd - (1-β, )ΔgF (6) However, ΔgF = the amount of extension of the focusing group lens from βF βF = the lateral magnification of the focusing group lens, and the amount of movement of the focal plane Let Δd be Δd−β
Δd ・・・・・・・・・(7)F However, βZ: Lateral magnification of the zoom group lens From the above formulas (6) and (7), Δd−(1−βF )β7 ΔgF ・・・・・・( 8
) holds true, and β, -ΩF/fF (9) However, fF
: Focal length of the focusing group lens ΩF: The amount of extension of the distance ring when the point where the lens touches the country side is used as a reference. Therefore, it can be seen that the magnification coefficient changes depending on the position of the distance ring even in the front group delivery method.

[Problems to be Solved by the Invention] Conventionally, for lenses such as macro lenses that have large changes in lateral magnification, a distance encoder has been provided to change the magnification coefficient depending on the position of the distance ring. It's here. However, in zoom lenses where the magnification coefficient changes depending on the focal length, the zoom encoder is biased, and it is difficult to install a distance encoder on top of it due to space constraints. Changes in the multiplication factor were ignored.

Therefore, the calculated lens drive amount is not accurate,
Sometimes the lens was not driven to focus quickly enough.

Therefore, the present invention focuses on the fact that the lateral magnification is a function of the amount of lens extension, and aims to provide an autofocus camera that changes the magnification coefficient depending on the position of the distance ring without providing a distance encoder or the like. do.

[Means and effects for solving the problem] In the present invention, in order to solve the above problem, the lens passes through the first portion and the second portion of the photographing lens that sandwich the optical axis of the photographic lens. A means for outputting the amount of deviation from the in-focus position of the photographic lens and its direction by detecting the correlation between the first and second images created by the photographic light beam, and a means corresponding to the amount of movement of the photographic lens. A pulse generating means for generating pulses, a counting means for counting the number of pulses from a reference position based on the pulses, a number of pulses peculiar to the lens corresponding to the movement of the photographing lens from a close position to an infinite position, and the said deviation. a two-light element having at least two types of variable magnification coefficients that change according to the magnification of the photographing lens, and a number of pulses from the base position and a number of pulses specific to the photographing lens, for converting the amount of light into the lens driving aperture; a selection means for selecting the magnification coefficient based on the selected magnification coefficient and the deviation amount,
The camera is equipped with a calculation means for calculating the amount of drive of the photographic lens, and a drive means for moving the photographic lens based on the output of the calculation means.

[Embodiment] An embodiment in which the present invention is applied to an interchangeable lens camera having an autofocus (hereinafter abbreviated as AF) function will be described below.

FIG. 1 is an overall block diagram mainly showing the power supply of a camera system to which the present invention is applied. Power battery 1
1 voltage■. C is D when the power switch 12 is closed.
5 by DC converter 13? Pressured, line g. ,
11 is constant voltage VDD. line f)
Main CPU 14 between o and D, bipolar circuit 15
．． Bipolar 1 circuit 16, strobe control circuit 17. The lens data circuit 18 and the data pack circuit 19 are connected, and the power supply control of the bipolar circuit 15 is controlled by the main C.
Power supply control for the PIPO91 circuit 16 to data pack circuit 19 is performed by a power control signal from the bipolar circuit 15.

Focus sensor 20. A/D converter 21. AF CPU
The AF block consisting of 22 is a power supply control transistor 2
Line g through 3. 9g1, and power supply control for this AF block is controlled by the main CPU 14.
This is done by controlling the transistor 23 on and off using a signal from the AF power control circuit.

The AF CPU 22 is a circuit for performing AF algorithm calculations, and is connected to an AF display circuit 24 that displays in-focus/out-of-focus status. The main CPU 14 is a circuit for controlling sequences of the entire camera such as film winding, rewinding and exposure sequences, and is connected to a display circuit 25 for displaying other than the above-mentioned focus display. The bipolar circuit 15 is a circuit that includes various drivers necessary for camera sequences such as film winding and rewind motor control, lens drive and shutter control, and is connected to an AF motor drive circuit 26, an AF auxiliary light circuit 27, etc. has been done. The bipolar 1 circuit 16 is a circuit mainly responsible for photometry, and is used for the photometry cable 28. The strobe control circuit 17 is for controlling the light emission of a built-in or external strobe 29. The lens data circuit 18 is a circuit that stores unique lens data necessary for AF, photometry, and other camera control, which differs for each interchangeable lens. Among the lens data contained in this lens data circuit 18, the data necessary for AF includes a lens magnification coefficient (zoom coefficient), macro identification signal, absolute distance coefficients a and b, power focus duty coefficient, and AF.
Accuracy threshold ETh.

Lens movement direction, maximum open F value 9 phase difference amount S
This is the maximum pulse MAX' representing the maximum value of the lens driving amount.

The bipolar circuit 15 monitors the state of the power supply voltage DD, and when the power supply voltage drops below the specified voltage, it sends a system reset signal to the main CPU 14, which supplies power to the bipolar circuit 15 to data pack circuit 19. , focus sensor 20° A/D converter 21 and A
The power supply to the AF block consisting of the F CPU 22 is cut off. Power is supplied to the main CPU 14 even if the voltage is below the specified voltage.

FIG. 2 is a system diagram showing the transmission and reception of signals centering on the AF block. The AF CPU 22 and the main CPU 14 transmit and receive data through a serial communication line, and the direction of the communication is controlled by a serial control line. The content of this communication is
These are unique lens data within the lens data circuit 18 and absolute distance information. In addition, from the main CPU 14, the AF C
Camera mode (AF single mode/AF
Information on sequence mode/power focus (hereinafter abbreviated as PF) mode/other modes is decoded through the model line. Furthermore, main CPU1
The AFENA (AF enable) signal from 4 to the AF CPU 22 is a signal that controls the start and stop of each AF and PF mode.
The EOFAF (end of AF) signal sent from 2 to the main CPU 14 is a signal that is issued at the end of the operation in the AF and PF modes, and is a signal that permits transition to the exposure sequence.

In addition, the bipolar circuit 15 is A FJ'll CP
It decodes the AF motor control line signal from U22 and drives the AF motor drive circuit 26. A
When the AF motor (lens drive motor) 31 is rotated by the output of the F motor drive circuit 26, the slits 32 provided at equal intervals in the rotating member of the lens barrel rotate, and the light emitting section 33a is opened across the passage of the slit 32. A photo ink printer 33, which includes a light receiving section 33b and a light receiving section 33b arranged opposite to each other, counts the number of slits 32. That is, the slit 32 and the photo ink clubber 33 constitute a pulse generating section 34, and the pulse signal (slit 3) generated from the pulse generating section 34 is
2 count signal) is waveform-shaped and sent to the AF CPU 22.
be taken in.

The sub-lamp (hereinafter abbreviated as S-lamp) signal sent from the AFCPU 22 to the bipolar ■ circuit 15 is a signal that controls the AF auxiliary light circuit 27, and when the subject is low light (low brightness) and low contrast, the S-lamp 27 is sent to the bipolar circuit 15.
Turn on a.

The AF display circuit 24 connected to the AF CPU 22 includes an LED (generator diode) 24a for indicating focus OK that lights up when focusing, and an LED that lights up when focusing is impossible.
It has D24b. Note that a clock oscillator 35° reset capacitor 36 is connected to this AF CPU 22.

Further, the AF CPU 22 and the A/D converter 21 exchange data via a pass line, and the direction of the data transmission is controlled by a pass line control signal. A sensor switching signal and a system clock signal are sent from the AF CPU 22 to the A/D converter 21. The A/D converter 21 is, for example, a C
A CCD drive clock signal and a COD control signal are sent to the focus sensor 20 consisting of a CD, and the focus sensor 20
Read the D output and display the read analog value on the CCD.
The output is digitally converted and sent to the AF CPU 22.

Next, a flowchart of the program operation of the microcomputer centered on the AF block shown in FIG. 2 of the camera to which the present invention is applied will be described. As shown in FIG. 1, in the AF block, when the AF power control circuit of the main CPU 14 is activated, the transistor 23 is turned on and the power supply voltage vDD is supplied. Begins execution of the on-reset routine.

When this power-on 0 reset routine is started, first, the AF block drive circuit is initialized in the <I10 initialization> subroutine. Specifically, the AF display circuit 24°, the AF motor drive circuit 26, the AF auxiliary light circuit 27, etc. are turned off, and the main CPU 1 is turned off.
Initialization of the serial communication line with 4 is performed.

Next, the mode line signal (mode signal) from the main CPU 14 is read out in the ``mode read'' subroutine, and after determining which lens drive mode is to be executed, the ``timer'' routine is used to After time,
The mode switching point is read through the mode read routine again. Then, the process returns to the first mode read until the mode switching is completed. The reason why the ``Mode Read'' subroutine is passed twice with a ``timer'' in between is to prevent reading errors at the time of mode switching.

When the mode has been reliably switched and the mode before and after the switch is the same, the mode after the switch is read and a transition is made to the subroutine for each mode. In other words, the lens drive modes are <lens reset>, <
PF (Power Focus)>, <AF'S IN (
AF Resin)>, <AFSEQ (AF Scene)>
When one of these modes is selected, the subroutine of the selected mode is executed, and then the process returns to the routine in Section 2 (10 Initialize).

Lens Reset>, <PF>, <AFSIN>.

When none of the <AFSEQ> modes is selected and the <Other> mode is selected, this is treated as mere noise, and the above ■10 initialization is performed in the <Timer> routine after a certain period of time. Return to >.

Here, the operation of the <lens reset> mode is to forcibly retract the lens to the infinite (flash) position, thereby changing the relative distance signal, that is, the distance measurement output signal output from the focus sensor 20. This is an initialization operation for replacing the pulse movement number from the position at infinity (oo) with the number of pulses and converting it into an absolute distance signal, that is, an operation for clearing the absolute distance counter. If Clear Lens Resent> is selected, for example, 5ms after clearing this absolute distance counter.
After that, the process returns to the I10 initialization operation. Also, <
In the PF> mode, the distance ring of the lens is driven not manually but by the lens drive motor 31, and the focusing operation of the lens is performed using manual focusing or focus aid. To be more specific, the operation switch SW1 for PFUP (up) and the operation switch SW2 for PFDN (down) will be described later.
On.

When the lens is turned off, the lens is extended and retracted. In addition, the <AFS I N> mode operates as a one-shot AF operation, in which the AF is applied to the subject.
The focus is locked after operation. Furthermore, <
The AFSEQ> mode is continuous AF, and in this mode, the AF operation will be performed continuously as long as the first stage of the release button continues to be operated.

By the way, as operation switches for each mode of lens drive, four operation switches SW1 to SW4 are used, as shown in Table 1 below.

Table 1 (*○Can be either N or OFF) First and second operation switch SW1゜SW shown in Table 1 above
2 is commonly used in the AF mode and the PF mode, and when the third operation switch SW3 is off, the AF mode is selected, and when it is on, the PF mode is selected. 1st in AF mode. When the second operation switches sw and sw2 are both off, the lens reset mode is set, when both are on, the AFSEQ mode is set, and when the first operation switch SW1
is off.

When the second operation switch SW2 is on, the AFSIN mode is entered. 1st in PF mode. Second operation switch sw
, sw2 are both off or on, the camera is in stop mode, and when the first operation switch SW1 is on, it is in PFUP (up) mode, in which the motor rotates the distance ring toward the short distance side and extends the lens.
When the second operation switch SW is turned on, the lens enters the PFDN (down) mode in which the distance ring is rotated toward the long distance side and the lens is retracted. Further, the fourth operation switch SW4 is
There is no change in any of the F modes and the stop mode in the PF mode, regardless of whether it is on or off, but when it is on in the PF mode, it becomes Hl (high speed) mode, and the lens drive motor 31 rotates at high speed to perform tn movement of the distance ring, and when it is off, the mode is set to LO (low speed), and the motor 31 (see FIG. 2) rotates at low speed to perform fine movement of the distance ring.

Next, we will explain the operation of each lens drive mode in Figures 4 to 1.
This will be explained using the flowchart shown in FIG.

First, if the <AFS IN> mode is selected,
The <AFS IN> routine shown in Figure 4 is executed,
It is detected whether the AFENA signal from the main CPU 14 is at "H" level (active). With the first operation of the release button, the AFENA signal becomes active, AF operation is started, and the <AFS IN2> subroutine is called. However, the second release button
The operation of the second step is accepted when the AF operation is completed, a focused state is obtained, and the exposure sequence is started. In <AFSIN2>, as will be described later, CCD integration of the focus sensor 20, performance of distance measurement output, lens driving, etc. are performed. And A of this <AFSIN2>
Focusing is the result of P movement.

Out-of-focus is displayed after the <AFSIN2> operation by viewing the AF status flag as 'Xi'. The AF status flags are the low contrast flag (a flag that is set to "1" when the subject is in low contrast, hereinafter abbreviated as the LC flag), and the movement flag (the flag that is set to "1" when the subject is moving). , abbreviated as the M flag) and the closest flag (a flag that is set to "1" when the lens is extended beyond the closest distance,
(hereinafter abbreviated as N flag), and when any of these flags is 0, focusing is possible, and if any of the above flags is set, focusing is not possible, so the AF status As a result of flag monitoring, if the AF status flag is 0, the LED 24a of the AF display circuit 24 will display that the focus is OK, and if the AF status flag is 0, the LED 24a will indicate that the focus is not possible.
Performed by ED24b. If in focus, EO
The FAF signal is issued, the AF operation ends, and the main CP
At U14, the camera enters a state of waiting for the second operation of the release button, that is, the start of the exposure sequence. In other words, even if the AFENA signal is active, after the -focus adjustment is completed, further lens operation is prohibited and the LE display indicating focus OK is disabled.
D24a remains lit and the focus is locked. The AFENA signal from the main CPU 14 is “
When the level reaches L0 (inactive), the process returns to the initial operation of the power-on reset flow shown in FIG.

While operating in the above <AFS IN> mode, <AFS IN>
The program operation of subroutine 2> is performed as shown in FIG. First, the previous 11-1 distance calculation value (
The RETRY flag is cleared to compare the current distance measurement calculation value (the previous output pulse of the focus sensor 20) and the A
The maximum number of distance measurements in a series of AF operations is set in the P small loop counter. Thereafter, the maximum value of the CCD integration time is set in the ITIME register so that CCD integration is reliably performed at brightness levels above a certain level. And A
The F status flag is cleared and the S lamp flag is also cleared. The operations in the flow up to this point complete the initialization operation before starting AF.

Thereafter, the lens read> routine is called, and after each lens data stored in the lens data circuit 18 is read out, the <AF> routine for distance measurement is called. In this <AF> subroutine, it is determined whether or not it is necessary to light the S lamp 27a during CCD integration. If it is necessary to light the S lamp 27a, the S lamp flag is set, and if it is not necessary, it is cleared. Ru. Further, a low light flag (a flag that is set to "1" when the subject is in low light, hereinafter abbreviated as LL flag) and LC flag are set or cleared.

The program operation of the <AF> subroutine is performed as shown in FIG. When the camera moves to <AF>, it first determines whether or not the S lamp flag is set, and if it is set, the S lamp is turned on.

Next, the AF CPU 22 sends an integration start signal to the focus sensor 20. Upon receiving the integration start signal, the focus sensor 20 performs photoelectric conversion and stores a charge corresponding to the contrast of the subject. At this time, the A/D converter 21 (second
(See figure) The charge is monitored by an internal AGC circuit, and when the charge becomes sufficient for the dynamic range of the A/D converter 21, integration is stopped. During this integration period, A F
The JIJ CPU 22 drives an internal timer to measure the integration time. This is used to determine the subject brightness level. Next, the S lamp is turned off and the I T I M E
When the integral time is longer than ITIME, the LL flag (low light flag) is set.

On the other hand, in the A/D converter 21, the focus sensor 20
The charges are sequentially A-D converted and the data is sent to the AF CPU 22.
Transfer to. Then, it is stored in RAM within the AF CPU 22. When inputting this sensor data is completed, the maximum value SMAx of the shift amount stored in the lens ROM is read. The calculation range of the order III difference is regulated by this SM□XX. Since calculations are performed in order from the negative side, S
The first number of is inverted and stored in S. Then, while increasing the value of shift H3 one by one, F (S
). This calculated value is stored in FLAST each time. If the phase difference cannot be detected even when the value of S reaches SMAX, the LC flag is set and the calculation ends. F
When the value of (S) becomes negative, an interpolated value is calculated using the previous F (S) value FLAST and the current F (S), and is added to the previous shift "5LAST. This calculated phase difference is It is stored in the CPU RAM as ERROR.

Next, it is determined whether the sensor data used for this calculation is appropriate or not based on the difference between MAX and MIN of the data, and when the difference is small, the LC flag is set as the contrast of the subject is insufficient.

Returning to Figure 5, if both the LL flag and LC flag are cleared after the <AF> distance measurement operation, the <Pulse> routine is called and the lens drive amount is calculated. be done.

This routine will be explained with reference to FIG. When entering the routine ``Pulse'', first the value of the absolute distance counter in which the number of drive pulses from position (3) of the distance ring is stored is read. Next, the lens data circuit reads the maximum number of pulses required to drive the range ring from flash to close range. Then, the scaling coefficient is selected based on the ratio of these two pulse numbers. That is, when the ratio is smaller than 0.5, the distance ring is closer to the flash position, so the smaller scaling factor, 1, is selected, and the ratio is Q, 5.
When it is larger, a scaling factor of 2 is selected. Based on the magnification coefficient selected in this manner, the number of pulses corresponding to the amount of lens drive is calculated.

After this, as shown in Fig. 5, the above AF calculation output value (
ERROR) is compared with the AF accuracy threshold ETh read from the lens data circuit 18, and the AF calculation output value (ERROR) is determined to be the AF accuracy threshold ET.
If it is larger than h, the process proceeds to (2) and the RETRY flag is determined. In the first AF operation, since the RETRY flag is 0, after the RETRY flag is set, the number of drive pulses is saved. Since the RETRY flag is set in the second and subsequent AF operations, the current number of drive pulses and the previous number of drive pulses are compared. At this time, if the number of pulses this time is smaller than the number of pulses last time, it means that the lens is driven closer to the in-focus point.
In the next lens drive, it will be even closer, so the current pulse will be saved instead of the previous pulse, and the <MDRIVAF> routine will be called.
Drives the lens.

The purpose of comparing the previous pulse and the current pulse is to
The purpose is to prevent divergent behavior of the entire sequence. Possible ways to compare the two are (current pulse number):(previous pulse number X O,5), or (current pulse number)=(previous pulse number X 1.5). If the AF sequence system is likely to be in a divergent state, it may be possible to perform the AF operation while the subject is moving, so in this case,
Immediately stop lens driving, set the M flag to prevent unnecessary AF operations, and proceed to ■<SD I 5CN
T>, calls the <CALDIS> routine.

After the lens is driven by <MDRIVAF>, 1 is subtracted from the distance measurement value of the AF operation set in the AF small loop counter. As a result, if the value of the AF small loop counter is not 0, the ITIM
Set the integration time in the E register, and then set the AFENA
When the signal is active (that is, the first operation of the release button is on), for the next AF operation,
Return to 0. In this way, each time the AF operation between 0 and 0 is repeated, the value of the AF small loop counter is decremented once, and as a result the value of the AF small loop counter gradually approaches the in-focus point, until the value of the AP small loop counter reaches 0. Even if the AF calculation output value (ERROR) is above the AF accuracy threshold ET
If it does not become smaller than h, it is assumed that it is impossible to focus and M
A flag will be set.

As a result of the AF operation between 0 and 0, if ERROR < ETh, that is, if the AF calculation output value (ERROR) falls within the focus error range, the AF status flag is cleared to indicate that the camera is in focus. and <5 DIscN
T>, calls the <CALDIs> routine.

Here, after the <AF> operation described above, if the LL flag or LC flag is set, the state of the S lamp flag is tested. At this time, if the S lamp flag had been set to "1" in advance, the low light and low contrast state would have occurred even though the S lamp 27a was lit during the integration operation for AF. Therefore, in this case, the LC flag is tested again, and in the case of low contrast, the only lens NF (unable to focus) routine is called to actively display the inability to focus. That is, in this lens NF> routine, the lens is first extended to the closest position, and then moved to infinity (oo).
The user is actively notified of the inability to focus by moving the lens significantly. Note that the lens indicating the inability to focus may be moved from an infinity (flash) position to the closest position. In addition, in this lens NF>, an absolute distance counter is used to save the number of drive pulses (number of movement address signals) from the infinity (flash) position of the lens distance ring by hitting the infinity (oo) position. is initialized. If the contrast is not low, it means that the AF calculation was performed even though the light was low, so in this case, the value returns to 0.

Also, if the S lamp flag was cleared in advance, it means that the S lamp 27a was previously off, so if the LL flag or LC flag is set, set the S lamp flag. , proceed to [F].

Therefore, the S lamp 27a will be lit in the second and subsequent AFil1 productions.

In any case, at the end of the <AFS IN2> operation, the <SDI 5CNT> routine is called and executed, and then <CALDIS> is called. <5DI
SCNT>, the absolute distance counter is set to infinity of the distance ring (o
o) Number of drive pulses from position is set. and,
In <CALDIS>, the absolute distance to the subject is calculated from the number of pulses set in the above-mentioned absolute distance counter and the absolute distance coefficients a and b in the lens data circuit 18. and the contents of the absolute distance counter are sent to the main CPU 4. This <CAL
The calculation of the absolute distance in DIS> will be described in detail later.

After <CALDIS> is executed, <
Return to the position after the operation of <AFS IN2> in the flow of <AFS IN>.

Next, in the flow shown in FIG.
> mode is selected, <AF mode shown in Fig. 8 is selected.
SEQ> routine is called. This <AFSEQ
> Then, when the first step of the release button is activated,
After this, the first AF operation until the EOFAF signal becomes active is exactly the same as in the case of <AFSIN>. In other words, <AFS IN> is also <A
FSEQ> also performs the operation <AFSIN2>, and when focusing is not possible, the lens is actively driven 5 times and the user is notified.

By the way, in <AFSIN2>, as mentioned above, the S lamp 27a is used to assist distance measurement for AF operation in low light and low contrast conditions, but in <AFSEQ> mode, AF If you use the S lamp 27a in the same way when operating continuously,
The S lamp 27a will be lit and emit light continuously during the CCD integration operation in <AF>, resulting in an increase in current consumption and a decrease in efficiency due to heat generation in the S lamp 27a. The abnormal driving occurs continuously, giving the user a sense of anxiety.

Therefore, in <AFSEQ>, after one AF operation is executed and the EOFAF signal is set, the AFENA signal is determined, and if the same signal is active, the operation of the first stage of the release button is continued. <AFS>
The routine EQ2> is called. If the AFENA signal is inactive, the process returns assuming that the first stage of the release button has been turned off, and the second stage of the release button has been turned on. In <AFSEQ2>, as will be described later, CCD integration of the focus sensor 20, AF calculation, lens drive, etc. are performed, but the S lamp 27a is used to actively display the inability to focus due to abnormal lens drive and to measure the distance. is not lit either. And this <AFS
As a result of the operation of EQ2>, the AF status flag is determined, and if the flag is 0, a display indicating that the focus is OK is displayed, and if it is not 0, a display indicating that the focus is not possible is displayed. Focus O
After K is displayed, the EOFAF signal is generated, and it becomes possible to start the exposure sequence by operating the second step of the release button. After this EOFAF signal is emitted or after the display shows that the focus is not possible, try again to use AFENA.
Since a signal test begins, as long as the first stage of the release button is kept on, AF operations centering on <AFSEQ2> will be performed continuously. And AFENA
When the signal becomes inactive, the process returns to the initial operation of the power-on contention reset flow shown in FIG.

Note that the EOFAF signal is cleared at I10 initialization (see FIG. 3) after CCp integration in the next AF operation or after return.

In the flowchart of the <AFSEQ> mode, the program operation of the <AFSEQ2> subroutine is performed as shown in FIG.

First, after the integration time is set in the ITIME register, the AP status flag is cleared and the S ramp flag is cleared. After this, the lens read subroutine is called, and the lens data circuit 18
The lens data within is read out. Then, in the <AF> routine, after A-i distance is performed, -1, AF
Turn off the display circuit 24 and turn off the focus OK indication LED 24a.
, and the out-of-focus display LED 24b are set not to light up. In other words, the AF display is not performed while the lens is being driven. Subsequently, after clearing the EOFAF signal, the LC flag is determined, and if the contrast is low, the process returns, and if the contrast is not low, the <pulse> subroutine is called. Note that even in low light, distance measurement calculations are possible if there is contrast, so the determination of the LL flag is intentionally omitted. As mentioned above, in the <Pulse>, the variable magnification coefficient is read from the lens data circuit 18 in order to convert the AF calculation output value obtained in the <AF> operation into the amount of distance movement for each interchangeable lens.
The number of drive pulses (number of addresses) is calculated from this and the AF calculation output value.

Then, the AF calculation output value (ERROR) is compared with the AF accuracy threshold ETh, which is lens data, and if the ERROR is larger than the threshold ETh, <MDRIVAF> is called and the lens is driven to the in-focus position. It is done. After this, <5D
ISCNT> is called and the absolute distance counter is set to the number of driving pulses based on the lens's renormalized position at infinity (beautiful), and then in <CALDIS>, the absolute distance counter is set to After the absolute distance to the object is calculated from the number of driving pulses set in and the absolute distance coefficients a and b in the lens data, the process returns. The calculated W value of this absolute distance and the number of drive pulses set in the absolute distance counter are sent to the main CPU 14.

Also, the upper 2 E RROR is the above threshold ETh
If it is sufficiently small that it falls within the focus error range, then A
Clear the P status flag and return.

Next, in the flow shown in FIG. 3, if the <PF> mode is selected, the <PF> routine shown in FIG. 10 is called. In this routine, the AFENA signal is first determined, and if the signal is not active, it returns; if it is active,
In other words, if the first stage of the release button is on, E
By setting the OFAF signal, the second stage operation of the release button can be accepted. In other words, it is possible to shift to the exposure sequence at any time during PF.

Thereafter, the lens read> is called, and lens data such as the power focus duty coefficient in the lens data circuit 18 is read, and then the state change flag is cleared. The status change flag is DIFSP (speed change), which is set when the speed changes.
There is a DIFMOD (mode change) flag that is set when the mode changes. After this, <Mode Read> is called, and here the instructions for the lens rotation direction and lens drive speed are read, and the lens rotation direction UP (up) and DN (down) are set or cleared, and SP A (speed) flag is set or cleared. That is, turning on the operation switch SW-8W4 regarding the lens drive mode shown in Table 1 above,
The off state will be read. In this <PF> mode, the operation switch SW3 is on, and the PF
When the UP operation switch SW1 is turned on, the lens rotation direction is the UP (lens extension) direction, and the PF
When the DN operation switch SW2 is turned on, the lens rotation direction becomes the DN (lens retraction) direction. and,
The SP flag is determined, but the operation switch S
When W4 is turned on, this SP flag is set, and in this case, the lens drive motor 31 (second
The on/off duty ratio of the pulse current that drives the lens (see figure) is set high, and the lens is extended or retracted at high speed. Since the SP flag is cleared when the operation switch SW4 is off, in this case, the duty ratio of the motor drive pulse current is set low and the lens is moved at a low speed. After this, <PDR
Call the subroutine of V>. In <PDRV>, the motor 31 is turned on and off based on the duty ratio set above, and the lens is driven for one pulse. Next, it is determined whether the lens has stopped at infinity (oo) or the nearest limit position, and if the lens has stopped at the limit position, the motor is activated for about 100 ms. Apply the brakes, <
5DISCNT> to set the absolute distance counter. Then, in this state, it waits while going around the mode change loop to see if there is any change in the mode signal. In this mode change,
The state changes (mode changes) of the PFUP operation switch SW, PFDN operation switch SW2 and the state change (speed change) of the speed operation switch SW4 are checked, and if there is a mode change, the DIFMO
Set the D flag and if there is a speed change,
The DIFSP flag is set. If the DIFMOD flag is set, this is determined and the process returns to [F].

On the other hand, in the case of normal power focus operation where the lens does not reach the limit position, the above motor is turned on and off in the <5PCTL> routine so that the lens drive speed becomes the determined coarse and fine movement speed. Fine-tune the off duty ratio. That is, speed adjustment by turning on and off the lens drive motor is performed by <PDRV> and <5PCTL>. After this, check the AFENA signal and if it is active, i.e.
When the first stage of the release button is on, call "Mode Change" and if the speed has been changed and the DIFSP flag is set, return to [F]. No speed change,
When the DIFMOD flag is set and a mode change is made, the brake is called to stop the motor, the absolute distance counter is set at DISCNT, and the process returns to [F]. If there is no speed change or mode change, it returns to <PDRV>, and as long as the first step of the release button remains on, ≧PDRV> and <5PCT.
The PF operation based on L> is continued.

When the first stage of the release button is turned off, the AFEN
The A signal becomes inactive, that is, the end of the PF operation is instructed by the main CPU 14, the brake> is called to stop the motor, and the absolute distance counter is set at <5DISCNT>. Then, from the contents of the set absolute distance counter, that is, the number of moving addresses from the infinite (flash) position and the absolute distance coefficients a and b in the lens data circuit 18, a calculation is performed using <CALDIS> to determine the absolute distance. The distance is calculated, and the calculated absolute distance information is sent to the main CPU 14. This <CALD
After IS>, the program returns and returns to the initial state of power-on reset.

[Effects of the Invention] As described above, according to the present invention, the distance ring position determining means uses the output pulse of the photo interrupter, which indicates the amount of rotation of the motor that drives the photographic lens, to determine the position where the photographic lens is placed against the flash. Using the ratio of the number of pulses counted as a reference and the number of pulses (maximum pulses) unique to the lens corresponding to the movement of the photographing lens from the closest position to the infinite position, the result of comparing this ratio with a certain judgment level is 2. One of the different magnification coefficients was selected so that the detected focal plane shift amount was converted into lens drive m.

Therefore, it is possible to provide an autofocus camera that can improve AF speed by taking into account changes in the magnification coefficient due to changes in lateral magnification, which have been ignored in the past.

In addition, since the value of the variable magnification coefficient does not change significantly with lenses other than macro, the variable magnification coefficient is changed into two types depending on the position of the distance ring, but with zoom lenses etc. that have a macro area, there are even more types. Of course, it may be changed to

[Brief explanation of drawings]

FIG. 1 is a schematic configuration block diagram of a power control circuit mainly showing the autofocus section of an autofocus camera to which the present invention is applied, and FIG. 2 shows signals of the autofocus circuit section in FIG. 1 above. FIGS. 3 to 10 are flowcharts showing program operations centered on the AF CPU shown in FIG. FIG. 11 is a diagram showing the case of a single lens, FIG. 12 is a diagram showing a case other than a single lens, and FIG. 13 is a diagram showing the phase difference. A diagram showing the positional relationship between the focus detection sensor and the optical system in the above method. Fig. 14 is an output characteristic curve diagram of the focus detection sensor shown in Fig. 13 above. Fig. 15 (A) (B) (C) is the above diagram. This figure shows the configuration of the focus detection sensor in Figure 13, and Figure 15 (
8) is a front view of the photoelectric conversion element arranged in each bear, the first
FIG. 5(B) is a side view showing the arrangement relationship between the photoelectric conversion element group and the lens red, and FIG. 15(C) is a diagram showing the luminous flux incident on the photoelectric conversion element through the lens red. 14... Main CPU 18... Lens data circuit (memory element)
22・・・・・・・・・CPU for AF Patent applicant Olympus Optical Industry Co., Ltd. %9 Figure %11 Figure 12

Claims (1)

[Claims] Detecting the correlation between the first and second images created by the subject light beams that have passed through a first part and a second part of the photographic lens, which sandwich the optical axis of the photographic lens. means for outputting the amount and direction of deviation of the photographic lens from the in-focus position; pulse generating means for generating pulses corresponding to the amount of movement of the photographic lens; and counting the number of pulses from the reference position based on the pulses. a counting means for the taking lens, a pulse number specific to the lens corresponding to the movement of the taking lens from a close position to an infinite position, and at least one pulse number that changes according to the magnification of the taking lens for converting the amount of deviation into a lens driving amount. a memory element having two types of magnification coefficients; a selection means for selecting the magnification coefficient based on the number of pulses from the reference position and the number of pulses specific to the photographic lens; 1. An autofocus camera comprising: a calculation means for calculating the amount of drive of a photographic lens based on the amount, and a drive means for moving the photographic lens based on the output of the calculation means.