JPS62157016A - Auto-focus camera - Google Patents

Abstract

PURPOSE:To correct suitably an extent of defocus for stopping down by storing preliminarily data of the extent of defocus due to stopping-down at the photographing time after focusing in a storage element for a lens. CONSTITUTION:After data in the lens stored in a lens data circuit 18 are read out after the initializing operation before AF start, an extent DELTAx of focusing due to stopping down is corrected. That is, a CPU 22 for AF calculates an ERROR which is the extent of defocus in an AF algorithm on a basis of data of a focusing sensor 20. The CPU 22 receives an aperture value AV peculiar to the lens, which is forecasted in accordance with the luminance of an object, from a main CPU 14 and calculates a difference DELTA between an already read open F value AVMAX of lens data and the value AV. The extent of focusing corresponding to the forecasted DELTA is added to the ERROR calculated in the AF algorithm, and the lens is driven on a basis of this corrected ERROR.

Description

[Detailed Description of the Invention] [Prior Art] As is well known, a lens has a spherical aberration because it is formed of a spherical surface. For example, the first
As shown in Figure 0, the light incident on the convex lens L is ray 91~
As shown in g4, the central optical axis! The light enters from positions distant from Io, and focuses at positions f1 to f4 on the optical axis. In the case of a biconvex lens L having such a simple configuration, the incident light beam g is the central optical axis g. If it is further away, the focal point position f will also be farther away than fl. This can be expressed as the relationship between the incident ray g and its focal position f:Q
The characteristic curve shown in Fig. 11 is n, and the incident light gn is N4 (see Fig. 10).
The focus position is the shaded area a. determined by the incident ray g. When g2 (see Fig. 10), the focus position is the part indicated by the dot. determined by Therefore, this means that the thickness of the luminous flux of the lens,
In other words, this means that the focus position shifts depending on the FNo.

Next, problems caused by this focus movement in the case of a camera lens will be explained. The vertical axis in Figure 12 is MTF
(Modulation Transrer Fun
The horizontal axis shows the focus position. Therefore, it means that the higher the vertical axis direction, the clearer the contrast of the image can be obtained. Here, the curve indicated by the symbol F4 is the FNo. of a certain lens.
is the MTF curve at F4, and the film surface is set at Co, where the MTF output is highest. Next, the curve indicated by the symbol F8 is the MTF curve or line when this lens is stopped down to F8. At this time, the MTF output on this film surface is d, and generally co≦do, but in reality, the highest MTF output at F8 is eo, which is located at a position ΔX away from the film surface. There will be. This is based on the aforementioned focus movement.

Therefore, on the film surface, if you stop down to F8, even though it is a lens that can shoot with a contrast of eo,
This means that the photograph was taken because of this contrast. In other words, this indicates that the contrast may be significantly better when narrowed down.

[Problems to be Solved by the Invention] By the way, in order to achieve the contrast as described above, in the current state where humans focus with their eyes, they generally use open A111 light, so the above-mentioned focus is It is actually impossible to adjust the focus by correcting the deviation ΔX, and if you stop down and focus, the depth of field on the viewfinder becomes deeper, so it is impossible to get the peak of focus. It was virtually impossible.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an automatic focusing camera that can suitably correct the amount of out-of-focus when stopping down to improve contrast.

[Means and effects for solving the problem] In the present invention, a focus detection sensor for outputting a distance measurement signal according to the amount of defocus, a microcomputer for calculation, and a photographing lens are driven according to the distance measurement signal. In an automatic focusing camera having means, in order to correct the amount of focus deviation due to aperture during shooting after focusing, data on the amount of focus deviation to be corrected is stored in advance in a memory element (ROM) unique to the lens. After the aperture value is stopped, data corresponding to the aperture value is retrieved from the memory element, and the photographing lens is driven to the optimum focus position.

[Example] Hereinafter, the present invention will be explained in detail with reference to an illustrated embodiment.

FIG. 1 is an overall block diagram mainly showing the power supply of an automatic focusing camera to which the present invention is applied. Power battery 1
1 voltage V. 0 is DC/D when the power switch 12 is opened.
The voltage is boosted by the C converter 13, and the voltage between the lines gg is kept at a constant voltage vDD of 0'1. line (main CPU1 between lo.121
4. Bipolar ■circuit 15, bipolar 1 circuit 16, strobe control circuit 17, lens data circuit 18, and data pack circuit 19 are connected, and bipolar ■circuit 15
Power supply control is performed by signals from the power control circuit of the main CPU, and
Power supply control of the 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 connected to line g via a power supply control transistor 23. , 91, and the power supply control for this AF block is controlled by the main CPU1.
This is performed by controlling the transistor 23 on and off using a signal from the AF power control circuit No. 4. The AF CPU 22 is a circuit for performing AF algorithm calculations, and is connected to an AP 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 aI11 light, and has a photometric element 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 AP, 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), a macro identification signal,
Absolute distance coefficients a, b, power focus duty coefficient, AF accuracy threshold ETh.

These are the lens moving direction, the open F value, and the AV value at the time of stopping down according to the present invention, and the AE and other necessary data include the maximum value of the amount of phase difference.

The bipolar circuit 15 monitors the state of the power supply voltage vDD, and when the power supply voltage drops below the specified voltage, it sends a system reset signal to the main CPU 14 to supply power to the bipolar circuit 15 to data pack circuit 19.
Furthermore, the power supply to the AF block consisting of the focus sensor 20° A/D converter 21 and the AF 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. Also, the camera mode (AF single mode/A
Information on the F sequence mode/power focus (hereinafter abbreviated as PF) mode/other modes is decoded through the model line. Furthermore, the main CPU
The AFENA (AF enable) signal from 14 to the AF CPU 22 is a signal that controls the start and stop of each AF and PF mode.
An EOFAF (end of AF) signal sent from 22 to the main CPU 14 is a signal that is issued at the end of operation in the AF and PF modes, and is a signal that permits transition to the exposure sequence.

In addition, the bipolar circuit 15 decodes the AF motor control line signal from the AF CPU 22, and
Drives the F motor drive circuit 26. The AF motor (lens drive motor) is driven by the output of the AF motor drive circuit 26.
31 rotates, the slits 32 provided at equal intervals in the rotating member of the lens barrel rotate, and a photo ink printer is formed in which a light emitting part 33a and a light receiving part 33b are arranged opposite to each other with the passage of the slits 32 in between. 33 counts the slit 32. That is, the slit 32 and the photo ink printer 33
constitutes the address generation section 34, and the address signal (count signal of the slit 32) generated from the address generation section 34 is waveform-shaped and taken into the AP CPU 22.

The sub lamp (hereinafter abbreviated as S lamp) signal sent from the AF CPU 22 to the bipolar ■ circuit 15 is a signal that controls the AP auxiliary light circuit 27, and when the subject is low light (low brightness) and low contrast, the S lamp 2 is sent to the bipolar circuit 15.
Turn on 7a.

The AF display circuit 24 connected to the AP CPU 22 has an ED (generator diode) 24a for displaying focus OK that lights up when focusing, and L for displaying focus failure that lights up when focusing is not possible.
ED24b is combined. In addition, this AP CPU 22
Clock oscillator 35° Reset capacitor 36
is connected.

In addition, the CPU 22 for AF and the A/D converter 2
1 transmits and receives data through a path line, and the direction of data transmission is controlled by a path 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. Then, the A/D converter 21 sends a CCD drive clock signal and a CCD control signal to the focus sensor 20 made of a CCD, reads the CCD output from the focus sensor 20, and converts the read analog value
The CD 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 explained. 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 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
Initialization of the serial communication line with 4 is performed.

Next, in the subroutine of "mode read", the main C
After reading the model line signal (mode signal) from the PU 14 and determining what lens drive mode to execute, after a certain period of time in the Kutiman routine, the mote is switched again through the Mode Read routine. Reading the time. Then, the process returns to the first mode read until the mode switching is completed. mode/
The reason why the read> subroutine is passed through twice with the 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. That is, the lens drive modes include lens reset>, <PF
(Power Focus)>, <AFS IN (AP Resin)>, and <AFSEQ (AF Sequence)>. When one of these modes is selected,
After executing the subroutine of this selected mode, the process returns to the above routine (I10 initialization).

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

When none of the <AFSEQ> modes are selected and the <Other> mode is selected, this is treated as mere noise, and the <AFSEQ> routine is activated after a certain period of time. Return to Initialize.

Here, the operation of the lens reset mode is to forcibly retract the lens to the infinity (oo) position, thereby changing the relative distance signal, that is, the distance measurement output signal output from the focusing sensor 20. This is an initialization operation to convert the pulse movement number from the infinite (■) position to an absolute distance signal, that is, an operation to clear the absolute distance counter. If Lens Reset> 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. More specifically, the PFUP (up) operation switch SWl will be described later.

Turn on operation switch SW2 for PFDN (down).

When the lens is turned off, the lens is extended and retracted. Furthermore, the operation in the <AFS IN> mode is a one-shot AF operation, and the focus is locked after the AF operation for the subject. Furthermore, <A
The FSEQ> 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 sw-5w4 are used, as shown in Table 1 below.

[Table 1 (*Can be either ON or OFF) 1. Second operation switch SW1゜SW
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, and when both are on, the AFSEQ mode is set, and the first operation switch SWl
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 SW2 is on, the lens enters the PFDN (down) mode in which the distance ring is rotated toward the long distance side to retract the lens. Further, the fourth operation switch Sw4 is A
In any of the F modes and in the stop mode of the PF modes, there is no change whether it is on or off, but when the PF mode is on, it becomes HI (high speed) mode, and the lens drive motor 31 rotates at high speed to perform coarse movement of the distance ring, and when off, the mode is set to LO (low speed), and 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 9.
This will be explained using the flowchart shown in the figure.

First, when the <AFSIN> mode is selected, the <AFSIN> routine shown in FIG. 4 is executed, and it is detected whether the AFENA signal from the main CPU 14 is at the "H° level (active). When the first step of the release button is operated, the AFENA signal becomes active, AP operation is started, and the <AFS IN2> subroutine is called.However, the second step of the release button is not activated. This occurs when the AF operation ends, the focus state is obtained, and the exposure sequence begins.
At AFS IN2>, as will be described later, CCD integration of the focus sensor 20, distance measurement output calculation, lens driving, etc. are performed. And the AF of this <AFSIN2>
Focus is the result of movement.

Out of focus is displayed by monitoring the AF status flag after the <AFSIN2> operation. The AF status flags are a low contrast flag (a flag that is set to "1" when the subject is in low contrast, hereinafter abbreviated as the LC flag), and a movement flag (when the subject is moving).
The flag that is set to ``1'' (hereinafter abbreviated as the M flag) and the closest approach flag (the flag that is set to ``1'' when the lens is extended beyond the closest distance, hereinafter abbreviated as the N flag). Focusing is possible when any of these flags is 0, and it is impossible to focus when any of the above flags is set, so as a result of πi viewing of the AP status flag, If the AF status flag is 0, the LED 24a of the AP display circuit 24 will display that the focus is OK, and if the AF status flag is not 0, the LED 24a will indicate that the focus is not possible.
This is done by D24b. If in focus, EC)F
The AF signal is issued, the AF operation ends, and the main CPU
At 14, the release button is pressed to the 2nd step 1'', that is, the camera enters a state of waiting for the start of the exposure sequence. In other words, when focusing is completed, even if the AFENA signal is active, 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 “L”
When the level is reached (inactive), the process returns to the initial operation of the power-on reset flow shown in FIG.

While operating in the above <AFSIN> mode, <AFSIN2>
The program operation of the subroutine > is performed as shown in FIG. First, the RETRY flag is set to compare the previous distance calculation value (the previous output pulse of the focus sensor 20) and the current /lp1 distance calculation value (the current output pulse of the focus sensor 20). cleared, AF
The maximum total number of one distance in a series of AF operations is set in the 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 below a certain brightness. 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 the AP.

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. Additionally, 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.

Further, the focus movement amount ΔX is corrected by the narrowing down according to the present invention. That is, the correction of the focus movement amount ΔX is performed in <AF>, which calculates the focus shift flft (ERROR) by t times. The program operation of the <AF> subroutine is shown in FIG. 6. When the program jumps to <AF>, it is first determined 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 charge is monitored by the AGC circuit inside the A/D converter 21 (see Figure 2), and the charge is
When the amount becomes sufficient for the dynamic range of the converter 21, the integration is stopped. During this integration period, the AF CPU2
2 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, the integration time is compared with ITIME, and if the integration 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 the RAM within the AF CPU 22. Based on the data of the focus sensor 20 stored in this RAM, ERROR, which is the total out of focus, is calculated within the AF algorithm.

Next, the AFCPU 22 receives from the main CPU 14 the lens aperture value AV (apex calculation value) in the exposure sequence predicted from the current subject brightness. and,
Open F fIA of lens data that has already been read
Calculate the difference Δ between V MAX and AV value. Δ is the number of aperture steps, and the amount of focus movement (ERRORI to ERRORN) at each aperture step is stored in the lens data. Here, the amount of focus movement corresponding to Δ predetermined by a-1 is added to ERROR by the AF algorithm, and this result is stored as ERROR.

After returning from <AF>, this corrected ER
Lens driving is performed based on ROR.

Returning to Figure 5 again, after the <AF> distance measurement operation, LL
When both the flag and the LC flag are cleared, the routine ``Pulse'' is called and the lens drive amount is calculated. That is, in the routine of <Pulse>, the magnification coefficient is input from the lens data circuit 18 in order to convert the AF (distance measurement) calculation output value obtained in the operation of <AF> to the amount of distance movement for each interchangeable lens. Read information such as
A pulse (address signal) ¥I corresponding to the amount of movement to the in-focus point is calculated from the read magnification coefficient and the AF calculation output value.

After that, the AF calculation output value (ERROR) is compared with the AF accuracy threshold ETh read from the lens data circuit 18, and the AP calculation output value (ERROR) is compared with the AF accuracy threshold ETh read from the lens data circuit 18.
) is larger than the AF accuracy threshold ETh, then
Proceed to (2) to determine the RETRY flag. In the first AF operation, since the RETRY flag is 0, R
After the ETRY 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 current pulse number is smaller by the amount of movement compared to the previous pulse number, it means that the lens drive has approached the in-focus point, so in the next lens drive,
Furthermore, it was determined that the current pulse would be even closer, so the current pulse was saved instead of the previous pulse, and <MDRI
VAF> routine is called and the lens is driven.

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 dashing system seems to be in a divergent state, it is possible to perform AF operation while the subject is moving, so in this case,
Immediately stop lens driving, set the M flag to prevent wasted AP operation, and proceed to ■<5DISCNT>
, calls the <CALD I S > 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 O, 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 ■. In this way, each time the AF operation between ■ and ■ is repeated, the value of the AF small loop counter is decremented once, and the in-focus point is gradually approached, but the value of the AP small loop counter becomes 0. Even if the AF calculation output value (ERROR) is] - AF accuracy threshold E
If it does not become smaller than Th, it is determined that focusing is impossible and the M flag is set.

As a result of the AF operation between ◎ and ◎ above, 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 in-focus state has been reached. , <5DISCNT
>, 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, the S lamp flag is “1”.
In this case, even though the lever was set to 1° before F, and the S lamp 27a was lit during the integral operation for AP, it was in a low light, low contrast state. , the LC flag is tested again, and in the case of low contrast, the 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 (o
o) 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 the infinity (oo) position to the closest position. In addition, in this lens NF>, the absolute distance is set to save the number of drive pulses (number of moving address signals) from the jjjE extreme (oo) position of the lens distance ring by hitting the infinity (■) position. The counter is initialized. If it's low contrast! - If it is not the last, it means that the AF calculation has been performed even though the light is low, so in this case, return to step (2).

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 ■. Therefore, the S lamp 27a will be lit in the second and subsequent AF operations.

In any case, at the end of the operation of <AFSIN2>, <5
After the routine DISCNT> is called and executed, <CALDIS> is called. <5 DISCN
At T>, the number of driving pulses from the infinite (flash) position of the distance ring is set in the absolute distance counter. And <CAL
DIS>, the absolute distance to the subject is calculated from the number of pulses set in the absolute distance counter (1) and the absolute distance coefficients a and b in the lens data circuit 18, and the calculated absolute distance is The distance and the contents of the absolute distance counter are sent to the main CPU 14. <CALDIS
> is executed, <AFS I N
> returns to the position after the operation of <AFSIN2> in the flow. Next, in the flow shown in FIG. 3,
When the <AFSEQ> mode is selected, the <AFSEQ> routine shown in FIG. 7 is called. In this <AFSEQ>, when the first operation of the release button is performed, the first AF operation after this until the EOFAF signal becomes active is the AFS IN as described above.
Executes exactly the same operation as in >.

In other words, <AFS IN> and <AFSEQ> are both <AFS IN> and <AFSEQ>.
The operation IN2> is performed, and when focusing is not possible, the lens is actively driven abnormally 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>, which will increase current consumption and reduce the movement of the vehicle 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, it is assumed that the first stage operation of the release button is off or the second stage operation is turned on, and the process returns. < A F S E Q
2 > As described later, the CCD of the focus sensor 20
Integration, AF computation, lens driving, etc. are carried out, but active focusing failure display due to abnormal lens driving and S lamp 27a for distance measurement are not lit. As a result of this <AFSEQ2> operation, the AF status flag is determined, and if the flag is 0, the focus is
K is displayed, and if it is not 0, an indication that focusing is not possible is displayed. After the focus OK indication is displayed, an EOFAF signal is generated, and it becomes possible to start the exposure sequence by operating the second stage opening of the release button. After this EOFAF signal is emitted, or after the inability to focus is displayed,
The AFENA signal will be tested again, so as long as the first stage of the release button remains on, <AFSE>
AF operation centered on Q2> is performed continuously. Then, when the AFENA signal becomes non-active,
The process returns to the initial operation of the power-on reset flow shown in FIG. Note that the EOFAF signal is cleared at I10 initialization (see FIG. 3) after CCD integration in the next AF operation or after return.

In flowchart 1 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 AF 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 distance measurement is performed, the AF display circuit 24 is turned off, and the focus OK display LED 24a,
None of the out-of-focus display LEDs 24b is turned on. 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. In addition, even if it is lowlight,
Since distance measurement calculation is possible when there is contrast, determination of the LL flag is intentionally omitted. Pulse>
Now, as mentioned above, A obtained by the operation of <AF>
In order to convert the F calculation output value into a distance movement amount for each interchangeable lens, the variable magnification coefficient is read from the lens data circuit 18, and the number of drive pulses (number of addresses) is calculated from this and the AF calculation output value.
calculation is performed.

Then, the above AF calculation output value (ERROR) is compared with the AF accuracy threshold ETh, which is lens data, and the upper 3Q E RROR is the above threshold ET.
If it is larger than h, <MDRIVAF> is called and the lens is driven to the in-focus position. after this,
<SD I 5CNT> is called and the number of driving pulses based on the position of the lens renormalized to infinity (oo) is set in the absolute distance counter, and then <CAL
DIS>, the number of drive pulses set in the absolute distance counter and the absolute distance coefficient a, which is lens data,
After calculating the absolute distance from b to the subject, the process returns. The calculated value of the absolute distance and the number of drive pulses set in the absolute distance counter are sent to the main CPU 14.

Furthermore, if the ERROR is smaller than the threshold ETh to the extent that it falls within the focus error range, the AF status flag is cleared and the process returns.

Next, in the flow shown in FIG. 3, if the <PF> mode is selected, the <PF> routine shown in FIG. 9 is called. In the routine of this PF〉,
First, the AFENA signal is determined, and if the signal is not active, it returns; if it is active, that is, if the first stage of the release button is on, the EO
By setting the FAF signal, the second stage operation of the release button is enabled. 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 state change flag includes a DIFSP (speed change) flag that is set when the speed changes, and a DIFMOD (mode change) flag that is set when the mode changes. After this, <Mode Read> is called,
Here, the instructions for the lens rotation direction and lens drive speed are read, and the lens rotation direction is UP (up).
and DN (down) set or clear, and SP (
(Speed) flag is set or cleared.

That is, the on/off state of the operation switch sw-5w4 related to the lens drive mode shown in the garment 1 is read. In this <PF> mode, the operation switch SW3 is on, and when the PFUP operation switch SWI is turned on, the lens rotation direction is UP (
When the PFDN operation switch SW2 is turned on, the lens rotation direction is DN ().
lens renormalization) direction. Then, the SP flag is determined. When the operation switch SW4 is turned on, this SP flag is set. In this case, the pulse current that drives the lens drive motor 31 (see FIG. 2) is The on/off duty ratio is set high, and the lens is extended or retracted at high speed. Since the SP flag is cleared when the operation switch Sv4 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, the <PDRV> subroutine is called. 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
Apply the brake for about 0ms and call <5DISCNT> to set the absolute distance counter. Then, in this state, it waits to see if there is any change in the mode signal while going around the mode Φ change loop.

In this mode change>, the PFUP operation switch SW1. Change in state of PFDN operation switch SW2 (
mode change) and the status change of speed operation switch SW4 (speed change), and if there is a mode change, the DIFMOD flag is set.
If there is a speed change, the DIFSP flag is set. Then, if the DIFMOD flag is set, it is determined and [F]
Return to

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.
While the first stage of the release button is on, call the mode change>, and if the speed has been changed and the DIFSP flag is set, return to ■ and change the speed. There is no D
When the IFMOD 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 stage 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 <SD I 5CNT>. Then, the contents of this set absolute distance counter, that is, infinity (oo
) From the number of addresses moved from the position and the absolute distance coefficients a and b in the lens data circuit 18, calculation is performed in <CALDIS> to calculate the absolute distance, and this calculated absolute distance information is sent to the main CPU 14. It will be done. This <CAL
DIS> returns and returns to the initial state of power-on reset.

Note that the spherical aberration shown in FIG. 10.11 is only a simple example, and the spherical aberration is not as simple as this even though the lens has a complex structure such as a photographing lens of a camera. Further, FIG. 10.11 relates to the central image, and the curves related to the peripheral images are different. Therefore, when correcting the focus position, it is insufficient to correct only the central part, and it is necessary to take into consideration the movement of the peripheral images and balance the good image positions of both the central image and peripheral images. Since the amount of focus shift due to narrowing down the periphery and the MTF curves between the center and periphery can be easily determined at the lens design stage, the relationship between the focus correction amount and the contrast between the center and periphery can be known in advance. Therefore,
The data stored in the ROM inside the lens is data on the amount of focus correction that balances the center and periphery.

Furthermore, in the case of zoom lenses, each focal length generally has
Since this focus correction amount changes, the correction amount for each focal length is stored in the ROM inside the lens, and the address of the data to be recalled in the ROM according to the focal length is determined by the zoom encoder linked to zooming. It is to be determined.

Furthermore, since the spherical aberration curve generally changes depending on the focal position due to the magnification, the correction amount data for each focal position is stored in the lens ROM, and the focal position encoder is used to calculate the amount of correction data in the ROM according to the focal position. The address of the data to be called is determined.

However, the changes in the correction amount due to the zoom and the change in the correction amount due to the focus position are not necessarily necessary, and in some cases, in other words, if the amount of change can be ignored, it may be possible to use fixed data of only the FNo. and the amount of deviation. Of course it's a good thing.

FIGS. 13(A) and 13(B) are MTF curves of the central image and peripheral images after opening and closing the aperture. That is, FIG. 13(A)
is the MTF curve of the central image, where curve 1 shown by a solid line is the one with the aperture wide open, and curve 2 shown with the chain line is the curve after the aperture is stopped down. FIG. 13(B) shows the MTF curve of the peripheral image, where curve 3 shown by a solid line is the one when the aperture is fully open, and curve 4 shown by a chain line is the curve after the aperture is stopped down. Since the AF sensor focuses using the center image when the aperture is open, normally when focusing, the MTF output 5a corresponding to the peak line 5 of the center image
You will get . At this time, the peak line 6 of the peripheral image is slightly shifted from the peak line 5 described above.

Here, the deviation of the contrast peak when stopped down is ΔX in the central image and ΔXt in the peripheral images.

The MTF output after narrowing down at a position shifted by this ΔXc is 5b (>5a).

However, in the illustrated example, when the center image is focused, the MTF output of the peripheral image is 6a, and the output at a location shifted by ΔX is 6b (<6a), which simply means that the center image is in focus. If only the image is considered and the focus position is corrected by ΔX, the contrast of the central image will improve, but the contrast will actually decrease at the periphery.

Therefore, if ΔX is the amount of correction of the focus position when stopping down while considering both the change in contrast at the center and the periphery, the contrast output at the center is 5c (5a<5c
<5b), and 6c (6b<5a<
6c), and the contrast is improved both around the center 1. Of course, how to balance the center and the periphery is arbitrary, and it goes without saying that it is fine to emphasize only one of them. A value corresponding to this ΔX is set in the lens ROM as an ERROR value.

[Effects of the Invention] As described above, according to the present invention, it is possible to suitably correct the focus shift when stopping down to improve contrast, without increasing the cost. Performance (contrast characteristics) can be fully brought out. Therefore, it is possible to provide an automatic focusing camera that can take pictures with high focus accuracy.

[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 showing an embodiment of the present invention, and FIG. 2 is the autofocus circuit section shown in FIG. 1 above. The schematic block diagrams shown in FIGS. 3 to 9 show the transmission and reception of signals of the AF shown in the T52 diagram above.
10 is a line diagram for explaining the spherical aberration of the lens. 11 is a line diagram showing the relationship between the focus position and the incident light beam. The figure is a diagram showing the relationship between the focus position and MTF with respect to the film plane. Figure 13 (A) and (B) are diagrams showing the MTF curves of the central image and peripheral images when the aperture is wide open and after the aperture is stopped down, respectively. It is. , f: 180 Plan 13 Akebono Procedure Amendment (Voluntary) 1. ! If displaying 1985 patent application No. 299248 2
, Title of the invention: Automatic focusing camera 3, Name of the person making the correction (037) Olympus Optical Industry Co., Ltd. "Detailed explanation column of the invention in the specification" and drawings (
1) "Auto-focus camera" written on the first line of statement box 2.
After , add the following statement on a new line. 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an automatic focusing camera, and more particularly, to an automatic focusing camera that appropriately compensates for the amount of misalignment of the focus during aperture. (2) "rAV value" written in the second line from the bottom of the same page 700 will be changed to "amount of focus shift." (3) Figure 6 of the drawings attached to the application will be replaced with the attached drawing.

Claims (1)

[Scope of Claims] A photographing lens is attached, which has a fixed memory element that stores data indicating the amount of movement of the optimum imaging position according to the aperture value, and means for transmitting the data to the camera body before the photographing operation. a focus position detection device that outputs a value corresponding to the distance between the imaging position of the subject image formed by the photographing lens and the film surface; , means for determining the amount of focus movement when the aperture is opened and when the aperture is stopped down from the stored information from the fixed storage element of the photographing lens; and a calculation means for adding the determined amount of focus movement to the output of the focus position detection device; An automatic focusing camera characterized in that the camera body further comprises a drive control means for moving the photographing lens to an imaging position based on the output of the calculation means.