JPS62139535A - Phase difference type focus detecting method - Google Patents

Abstract

PURPOSE:To prevent a wrong arithmetic result from being outputted by calculating the quantity of the phase difference between illuminance distributions of pieces of luminous flux which contain luminous flux from the same parts of respective bodies and travel through different paths having a parallax after being passed through different optical apertures. CONSTITUTION:The maximum value SMAX of the quantity of phase difference characteristic to a photographic lens is stored in the internal ROM of each lens as data characteristic to the lens or stored in the ROM of a camera-body side CPU for arithmetic so that it is led out as the identification signal of the lens. Then, the maximum value SMAX of the quantity of the phase difference characteristic to the photographic lens which is stored in the ROM is inputted to the arithmetic CPU in a camera body and this arithmetic CPU calculates the quantity of the phase difference within the range of the maximum value SMAX. Namely, the misoperation of the lens is eliminated by limiting shift arithmetic operation with the maximum value SMAX obtained selectively corresponding to the mounted lens or deciding whether the calculated phase difference x is effective or not for the maximum value SMAX.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a focus detection method using a phase difference method, and more specifically, a method for defining an autofocus calculation range in accordance with the maximum defocus amount of a photographing lens in a camera. The present invention relates to a method for doing so.

[Prior Art] As is well known, focus detection methods in cameras include a phase difference method, a contrast method, etc. Among them, a focus detection means using a phase difference method is shown in FIGS. 10 to 12. It is configured. That is, FIGS. 10 to 12 show the principle thereof, and FIG. 10 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 the film plane. The focus detection sensor 100 is shown in FIG.
)(b) and (C), the pair (al, b
, ~an, bn) photoelectric conversion elements a1 to a n formed of COD etc. consisting of a group and b group arranged in the form of
, b 1 to bn (see FIG. 12(a)), and each bear (al, b, to an.

b), and lenslets c1 to cn (see FIG. 12(b)) arranged corresponding to the lenslets c1 to cn (see FIG. 12(b)). The lenslet cl-cn is the photographing lens 101.
The light reaching the sensor 100 through the exit pupil of
It functions to divide the luminous flux and the lower B luminous flux and guide them to the 8th group detection sensor and the 5th group detection sensor respectively (see Fig. 12(c)).

Now, as shown in FIG. 10, assuming that the focal plane 102 is formed at a position shifted by 6 g toward the photographing lens 101 from the focus detection sensor 100, the photoelectric conversion elements a1 to an at this time.

When the outputs of b1 to b□ are expressed with the horizontal axis representing the element number and the vertical axis representing the output value of the corresponding element, the characteristic curve diagram shown in FIG. 11 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 Δχ. This phase difference Δχ and the amount of deviation Δg from the actual focal plane have a linear relationship via a certain coefficient. That is, Δg- and Δχ... (1) k: conversion coefficient.

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

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

F=Σ(1”n bn+tl 1bnarr+, 1)
--- River (2) N; Because of the sensor bare, generally speaking, when F>Q, the front focus is F-0, and when F<Q, the rear focus is in focus. However, it is not possible to determine the phase difference Δχ using this evaluation formula alone.

Next, we will explain how to calculate Δχ using Figures 13 and 14. Outputs from focus detection sensors that have the same corresponding subscript form a pair, but here we shift the subscripts one by one. Let us calculate the evaluation formula. Creating a pair of detection sensors so that the subscript of group b becomes smaller than the subscript of group a is defined as a positive shift, and the opposite is defined as a member shift.

By performing this shift, the curve formed by the group of detection sensors 5 can be moved as shown in the figure. Through this process, the positional relationship between the curves of the a-group sensor and the b-group sensor, which occurs when the detection sensor moves along the optical axis, can be calculated by calculation without moving the detection sensor.

Therefore, if shifts are performed in order from the negative side to the positive side, and an evaluation formula is calculated for each shift, and a matching point of F-0 is found, the number of shifts at that point becomes the phase difference Δχ. The above formula (2) is an evaluation formula when the subscripts of the a-group sensor and the b-group sensor are the same, that is, the evaluation formula when the shift is -0.

Therefore, if we change this evaluation formula to a general formula using the shift number S as a function, when S2O, F(S)=Σ(lan+5-bn+11 1')rl-
an+s-I I) "・"・(3) When Sku0, F(S)=Σ(lan-bn-n+11 Ibn-
5"n+1 I) -- (3) n+1 N: Number of sensor bears.

The limit values of the number of sensor bears, the dimensions between the sensor bears, etc. are determined by the sensitivity of the detection sensor, the manufacturing limit of Lens Red, etc. Therefore, it is difficult to find a shift number So that satisfies F(So)-0 only by calculation using the evaluation formula F (S). Therefore, it is necessary to set the intermediate value between hg based on the results of adjacent F(S).

In other words, this interpolation means that the result of the evaluation formula at a certain shift is F
If (S)>0, the result in the next shift is F(Sa+1
) is 0, the phase difference △χ is the following formula % Formula % [Problems to be Solved by the Invention] By the way, when detecting the phase difference using the focus detection principle described above, the following problem occurs. produce a point.

In other words, when there are two subjects, near and far, within the field of view of the detection sensor, group A is shown as shown in Fig. 15.

Since two matching points occur on the curve formed by the outputs of the sensors of group b, the two phase differences Δχ and Δχ2
occurs. Furthermore, if the contrast of the object that the detection sensor looks at is periodic, as shown in Figure 16, the phase differences △χ ′, Δχ ′, △χ
', Δχ4' will occur.

The reason why a phase difference other than the originally required 6% occurs is because
This is because shift operations are performed over a wide range.

In calculating the amount of defocus using the phase difference method, the calculation range generally extends to the detection limit of the sensor, regardless of the lens.

Generally, the maximum amount of movement of the focal plane of the photographic lens △gMA
X is determined by the magnification M and the focal length f.

F (M, f) - Δ'' MAX '''''' (5) Therefore, the necessary range of the shift amount (phase difference amount) is defined by ΔΩ MAX of the photographing lens used.

Therefore, whether the shift operation is performed only within this specified range or
Alternatively, only the necessary amount of phase difference can be obtained by performing shift calculation over a wide range but discarding calculation results outside the specified range. Further, on each side of the lens, the phase difference m (shift amount) corresponding to ψ to close distance varies depending on the focal length of the lens, and the value is small for a wide lens and large for a tele lens.

SUMMARY OF THE INVENTION An object of the present invention is to provide a phase difference focus detection method that avoids performing autofocus (AF) calculations and outputting incorrect calculation results over a range beyond that required by a photographic lens. .

[Means and effects for solving the problems] The present invention has the following features:
The maximum value SMAX of the amount of phase difference (shift filt) unique to the photographing lens is stored as lens-specific data in a memory element (ROM) built into each lens, or it is retrieved by the lens identification signal and stored in the camera. It is stored in the ROM of the calculation CPU next to the body, and the shift calculation can be limited by this maximum value SMAX, which is selectively obtained according to the attached lens, or the calculated phase difference △χ can be made effective by SMAX. This system is designed to eliminate lens malfunctions by determining whether the lens is invalid or not.

Furthermore, in a lens having a macro region, MAX changes depending on a signal from a member that discriminates the macro region.

For example, a distance encoder is provided on the lens side, and when the distance of the macro area is reached, a value corresponding to the distance is automatically selected for SMAX.

[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
When the power switch 12 is opened, the voltage VCC of 1 is DC/
It is boosted by the DC converter 13 and connected to line II.
Between lines 10 and 11, the main CPU 14,
Bipolar ■Circuit 15. Bipolar 1 circuit 16, strobe control circuit 17. A lens data circuit 18 and a data back circuit 19 are connected, and power supply control of the bipolar circuit 15 is performed by a signal from the power control circuit of the main CPU, and power supply control of the Pipo 91 circuit 16 to data back circuit 19 is performed. is bipolar■circuit 1
This is done by the power control signal from 5.

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. , Ω1, and power supply control for this AP block is controlled by the main CPU 14.
This is performed by controlling the transistor 23 on and off using a signal from the AP power control circuit.

The AP 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 includes an AF motor drive circuit 26, an AF hli light assist circuit 27, etc. is connected. The bipolar 91 circuit 16 is a circuit mainly responsible for photometry, and has a photometry element 28. The strobe control circuit 17 is built-in or externally attached to the strobe 2.
This is for controlling light emission for 9. 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 AP precision thread. Schold ETh.

These are the lens moving direction, the open F value, etc., and the AE, and other necessary data include the maximum value SMAX of the amount of phase difference.

The bipolar circuit 15 regards the state of the power supply voltage VDD as '<i', and sends a system reset signal to the main CPU 14 when the power supply voltage drops below the specified voltage.
The power supply to the bipolar circuit 15 to data pack circuit 19 and the AP labbook consisting of the focusing sensor 20° A/D converter 21 and AF CPU 22 are cut off. Power is supplied to the main CPU 14 even if the voltage is below the specified voltage.

Figure 2 is a system diagram showing the transmission and reception of signals centered on the AP lab book, and shows the system between the AFJiCr'U22 and the main CPU.
4 is a serial communication line for exchanging data, and the communication direction is controlled by a serial control line. The contents of this communication include unique lens data within the lens data circuit 18 and absolute distance information. Also, from the main CPU 14
F) Each piece of information about the camera mode (AF single mode/AF sequence mode/power focus (hereinafter abbreviated as PF) mode/other modes) is decoded by the CPU 22 through the model line. Furthermore, AFENA from the main CPU 14 to the AP CPU 22
The (AF enable) signal is a signal that controls the start and stop of each mode of AP and PF.
EOFAF from P CPU 22 to main CPU 14
The (end of AF) signal is a signal that is emitted at the end of the operation in the AP or PF mode and permits transition to the exposure sequence.

Further, the bipolar circuit 15 decodes the AF motor control line signal from the AFJ1 CPU 22 and drives the AF motor drive circuit 26. When the AF motor (lens drive motor) 31 is rotated by the output of the AF motor drive circuit 26, the slits 32 provided at equal intervals in the lens data rotating section 4a rotate.
A photo ink converter 33 in which a light emitting part 33a and a light receiving part 33b are disposed facing each other with a passage 2 in between is connected to the slit 32.
count. That is, the slit 32 and the photo ink printer 33 constitute an 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 sent to the AP CPU 2.
Incorporated into 2.

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 AFJlj CPU 22 has an LED (generation diode) 24a for indicating focus OK that lights up when focusing, and an LED 24b for indicating that focusing is not possible that lights up when focusing is impossible. In addition, this AFJllCP
A clock oscillator 35° reset capacitor 36 is connected to U22.

In addition, the CPU 22 for L-sight AF and the A/D converter 21
transmits and receives data through the 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 AFFCPU 22 to the A/D converter 21. Then, the A/D converter 21, for example,
A CCD drive clock signal and a COD control signal are sent to the focus sensor 20 consisting of a CCD.
Read the CD output and check the CC of the read analog value.
Convert D output into digital and AF 111 CPU2
Send to 2.

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 AP lab book, by putting the AP power control circuit of the main CPU 14 into operation, the transistor 23 is turned on and the power supply voltage vD1) is supplied. Begins execution of the power-on reset routine.

When this power-on reset routine is started, first, the AF block drive circuit is initialized in the subroutine (10 Initialize). Specifically, the AFF indicator circuit 24°, the AF motor drive circuit 26, the AFF auxiliary circuit 27, etc. are turned off, and the main CPU 1
Initialization of the serial communication line with 4 is performed.

Next, in the <mode read> subroutine, the main C
After reading the mode line signal (mode signal) from the PU 14 and determining what lens drive mode to execute, the <timer> routine passes a certain IIν period, and then the mode read> routine is executed again. The switching point is being read. Then, the process returns to the first mode read until the mode switching is completed. The reason why the subroutine ``mode read'' is passed through twice with the ``timer'' in between is to prevent z1 driving of reading 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 (A
There are AF Sequence)> and AFSEQ (AF Sequence) modes, and when one of these modes is selected, the subroutine of the selected mode is executed, and then the routine returns to the above (Step 10 Initialize). return.

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

When none of the <AFSEQ> modes are selected and the <Other> mode is selected, this is treated as noise, and the <AFSEQ> routine returns 1 after a certain period of time. Return to I10 Initialize.

Here, the operation in the lens reset mode is to forcibly retract the lens to the 1!1 (ultimate (oo) position), thereby producing a relative distance signal, that is, the measurement output from the focus sensor 20. This is an initialization operation to convert the distance output signal to an absolute distance signal by replacing the distance output signal with the number of pulses from the position at infinity (Ll), that is, an operation to clear the absolute distance counter. Lens Reset> is selected. If the absolute distance counter is cleared, the I10 initialization operation is returned to, for example, after 5 ms.Furthermore, <PF> mode means that the distance ring of the lens is driven not manually but by the lens drive motor 31. This attempts to perform a lens focusing operation using manual focusing or a focus aid.

More specifically, 1-7 includes a PFUP (up) operation switch SW, which will be described later.

Turn on operation switch SW2 for PFDN (down).

When the lens is turned off, the lens is extended and retracted. Further, the operation in the <AFS IN> mode is a one-shot AF operation, and is an AF movement operation-focus locking for the subject. Furthermore, <A
FSEQ>Mote is continuous AF, and in this mode, 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 of f.

■Table 1 1. shown in Table 1 above. 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. AF mode first. When both the second operation switches sw and sw2 are off, the lens reset mode is set, and when both are on, the mode is set to AFSEQ mode.The first operation switch SW
1 is off.

When the second operation switch SW2 is on, the AFS IN mode is entered. 1st in PF mode. Second operation switch s
When w and 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 PFDN (down) mode is set in which the distance ring is rotated toward the long distance side and the lens is retracted. Further, the fourth operation switch Sw4 is
In any of the AF modes and in the stop mode of the PF modes, there is no change whether it is on or off, but when it is on in the PF mode, Hl (
The lens drive motor 31 rotates at high speed and the distance ring moves up and down, and when it is off, it is in LO (low speed) mode.
mode, the motor 31 (see FIG. 2) rotates at a low speed to perform slight 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, if the <AFS IN> mode is selected,
The <AFS IN> routine shown in FIG. 4 is executed,
It is detected whether the AFENA signal from the main CPU 14 is at "H" level (active). When the first stage Ll of the release button is operated, the AFENA signal becomes active, AF operation is started, and the <AFSIN2> subroutine is called. However, the second stage of the release button 1
” operation is accepted when the AF operation is completed, a focused state is obtained, and the exposure sequence is started. At <AFS IN2>, as will be described later, CCD integration of the focus sensor 20, calculation of distance measurement output, lens driving, etc. are performed. Then, the focus is the result of the AF operation of this <AFSIN2>.

The out-of-focus state is displayed by setting the AF status flag to 'XrilJ' after the operation of AFSIN2>. AF
The status flag is the low contrast flag (a flag that is set to “1” when the subject has low contrast; above, L
(abbreviated as C flag), movement flag (a flag set to "1" when the subject is moving, hereinafter abbreviated as M flag), and closest approach flag (when an attempt is made to extend the lens beyond the closest distance) The camera has a flag that is set to "1" (hereinafter abbreviated as the N flag), and focusing is possible when any of these flags is 0, and some flag among the above flags is set. As a result of monitoring the AP status flag, the same A
If the F status flag is 0, the LED 24a of the AF display circuit 24 indicates that the focus is OK, and the A
If the F status flag is not O, the LED 24b indicates that focusing is not possible. If in focus, press E
The OFAF signal is issued, the AF operation ends, and the main C
The PU 14 enters a state of waiting for the second operation of the release button, that is, the start of the exposure sequence. That is, once focusing is completed, even if the AFENA signal is active, subsequent lens operation is prohibited and the LED 24a indicating "Focus OK" remains lit, resulting in a focus locked state. When the AFENA signal from the main CPU 14 becomes "L0 level (inactive)", the third
Return to the basic operation of the power-on reset flow shown in the figure.

While operating in the above <AFS IN> mode, <AFS IN>
The program operation of subroutine 2> is performed as shown in FIG. First, R
The ETRY (retry) flag is cleared, and the maximum number of A11l distances in a series of AF operations is set in the AF 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 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 reading each lens data stored in the lens data circuit 18, 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.

Then, the phase difference calculation according to the present invention is performed here. That is, the program operation of the <AF> subroutine is performed as shown in FIG.

When the camera jumps to AF>, it first determines whether or not the S lamp flag is set, and if so, lights up the S lamp. 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 (
(See Figure 2) The internal AGC circuit reduces the charge.
When the amount of charge becomes sufficient for the dynamic range of the A/D converter 21, the integration is changed to 1 [-]. During this integration period, the AF CPU 22 drives an internal timer to total the integration time A11l. This is used to determine the subject brightness level. Next, the S lamp is turned off and the ITI
ME and the integration time are compared, 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
Sequentially converts the charges from A to D and sends the data to the AFJII CPU.
Transfer to 22. And A F Jll CP U22
The data is stored in RAM within the system. When the manual input of this sensor data is completed, the maximum value SMAX of the shift peak stored in the lens ROM is read. The calculation range of the amount of phase difference is this S
Regulated by MAX. Since calculations are performed in order from the negative side, the sign of SMAX is inverted and stored in S. Then, F (S) is calculated using the evaluation formula (3) while increasing the value of the shift amount S one by one. This calculated value is FLAS
Stored in □ every time. If the phase difference cannot be detected even when the value of S reaches SMAX, the LL flag is set and the calculation ends. If the value of F (S) becomes negative, the previous F (S)
An interpolated value is calculated using the value FLAST and the current F (S), and added to the shift mS. This phase difference calculated by 1 is stored in the RAM of the CPU as ERROR. Next, it is determined whether the sensor data used for this calculation is suitable or not based on the difference between MAX and MIN of the data, and if the difference is small, the LC flag is set as the object has insufficient contrast. do.

Returning to Figures 1 and 50, now, after the distance measurement operation of AF,
When both the LL flag and the LC flag are cleared, the routine ``Pulse'' is called and the amount of lens drive is calculated. That is, in the routine of <Pulse>, the A obtained by the operation of <AF>
In order to convert the F (all distance) calculation output value into a distance movement amount for each interchangeable lens, information such as a magnification coefficient is read from the lens data circuit 18, and the read magnification coefficient and AF are
The number of pulses (address signals) corresponding to the mobile device reaching the in-focus point is calculated from the 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 AF 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 number of pulses this time is smaller than the number of pulses last time by the amount of movement, it means that the lens drive has approached the in-focus point, so in the next lens drive,
Furthermore, it was decided that the current pulse would be even closer, so the current pulse was saved instead of the previous pulse, and the IDR
IVAF> routine is called to drive 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 AP sequence system is likely to be in a divergent state, it may be possible to perform AF operation while the subject is moving, so in this case,
Immediately stop lens driving, set the M flag to prevent wasteful AP operation, and proceed to ■<SD I 5CN
T>, call 1 routine of <CALDIS>.

After the lens is driven by MDRIVAF, 1 is subtracted from the 71-1 distance 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,
Set the integration time in the ITIM E register, and when the AFENA signal is active (that is, the first operation of the release button is on), the next A
Return to ◎ for P action. In this way, AF between ◎-◎
Each time the operation is repeated, the value of the AF small loop counter is decremented once, which gradually brings the focus closer to the focused point. However, even if the value of the AF small loop counter reaches 0, the AF calculation output value (ERROR ) does not become smaller than the AF accuracy threshold ETh, 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) noted in - falls within the focus error range, the AF status flag is cleared and the in-focus state is reached. and <5DISCN
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, then retracted to the infinity (ψ) position, and the lens is actively moved to prevent focusing. Inform users. Note that the lens indicating the inability to focus may be moved from the infinity (OA) 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 (■) 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 has been performed even though the light is low, so in this case, the process returns to (2).

Also, if the S lamp flag was cleared 1# ago, it means that the S lamp 27a was previously off, so if the LL flag or LC flag is set, the S lamp flag Set and proceed to ■.

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

In any case, at the end of the <AFS IN2> operation, <
After the routine 5DISCNT> is called and executed, <CALDIS> is called. <5 DISC
NT>, the number of driving pulses from the infinite distance (■) position of the distance ring is set in the absolute distance counter. And <CA
LDIS>, the absolute distance to the limb object is calculated from the number of pulses set in the absolute distance counter and the absolute distance coefficients a and b in the lens data circuit 18. The distance and the contents of the absolute distance counter are sent to the main CPU 14. This<CALDI
The calculation of the absolute distance with S> will be described in detail later. <C
After the <ALDIS> is executed, the <AF
Return to the position after the operation of <AFSIN2> in the flow of <SIN>.

Next, in the flow shown in FIG. 3, <AFSEQ
> mode is selected, the <AF mode shown in Fig. 7 is selected.
SEQ> routine is called. This <AFSEQ
> Then, when the first step of the release button is activated,
After this, the first 11 AF operations until the EOFAF signal becomes active are performed exactly the same as in the case of <AFS IN>. In other words, both <AFS IN> and <AFSEQ> perform the operation of <AFSIN2>,
When focusing is not possible, the lens is actively driven abnormally and the user is notified.

By the way, in <AFS IN2>, as mentioned above,
S lamp 27a for low light and low contrast
is used to assist distance measurement for AF operation, but if you use the S lamp 27a in the same way when performing continuous AF operation in <AFSEQ> mode, the S lamp 27a will During the CCD integration operation in AF>, the light is emitted continuously, resulting in an increase in current consumption and a decrease in efficiency due to heat generation of the S lamp 27a, as well as continuous abnormal driving of the lens when focusing is not possible. This creates a sense of anxiety for the user.

Therefore, in <AFSEQ>, after the AP operation is completed once and the EOFAF signal is set, the AFENA signal is determined, and if the 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 operation of the first stage opening of the release button is OFF, and the operation of the second stage opening of the release button is turned ON, and the process returns. In <AFSEQ2>, as will be described later, CCD integration of the focus sensor 20, AP calculation, lens drive, etc. are performed, but active focusing failure display and il? due to abnormal lens drive are performed. The S lamp 27a for the J distance is also not lit. And this <
As a result of the operation AF S E Q 2 >, 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. After the focus OK indication is displayed, the EOFAF signal is generated, and it becomes possible to start the exposure sequence by operating the second stage 1 of the release button. After this EOFAF signal is emitted or after the display indicating that the focus is not possible is displayed, the AFENA signal test is started again, so as long as the first stage of the release button is kept on, <A
AF operation centered on FSEQ2> is performed continuously. Then, when the AFENA signal becomes non-active, the process returns to the cut-off operation of the power-on reset flow shown in FIG. Note that the EOFAF signal should be cleared after CCD integration in the next AP operation or after return! 10 initialization (see FIG. 3).

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 is called.
The lens data within is read out. And <AF>
In the 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 subroutine ``delete pulse'' is called. Note that even if it is a low light, distance measurement calculations are possible if there is contrast, so the determination of the LL flag is intentionally omitted. As described above, in the <Pulse>, the variable magnification coefficient is obtained from the lens data circuit 18 in order to convert the AF calculation output value obtained by the <AF> operation into the amount of distance movement for each interchangeable lens.
A drive pulse of 1 ft (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 viscosity 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 number of drive pulses based on the position retracted to infinity (■) of the lens is set in the absolute distance counter, and then in <CALDIS>, the number of driving pulses is set in the absolute distance counter. After the absolute distance to the object is calculated from the number of driving pulses and the absolute distance coefficients a and b, which are lens data, 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 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. after this,
lens read> is called and lens data circuit 1
After the lens data such as the power focus duty coefficient in 8 is read out, the state change flag is cleared. Status change flags include the DIFSP (speed change) flag, which is set when the speed changes, and the DIFMOD (mode change) flag, which is set when the mode changes.
There's a flag. After this, ``Kumote Read'' is called, and here the instructions for the lens rotation direction and lens drive speed are read, and the UP (up) and DN (down) of the lens rotation direction are set or cleared, and the SP A (speed) flag is set or cleared. That is, the on/off state of the operation switch sw-5w4 regarding the lens drive mode shown in Table 1 is read. In this <PF> mode, the operation switch SW3 is on, and when the PFUP operation switch SWl is turned on, the lens rotation direction is the UP (lens extension) direction, and when the PFDN operation switch SW2 is turned on, the lens rotation direction is the UP (lens extension) direction. The lens rotation direction is the DN (lens retraction) direction. Then, the SP flag is determined, and when the operation switch SW4 is turned on, this SP flag is set, and in this case, the lens drive motor 31 (see FIG. 2)
The on/off duty ratio of the pulse current that drives the lens is set high, and the lens is extended or retracted at high speed. S when operation switch SW4 is off.
Since the P flag is cleared, in this case, the duty ratio of the motor driving pulse current is set low and the lens is moved at a low speed. After this, the <PDRV> subroutine is called. In this <PDRV>, the duty ratio set in ! , ζ turns on the motor 31,
The off state is controlled and lens driving for one pulse is performed.

Next, it is determined whether the lens has stopped against the limit position at infinity (OA) or a nearby limit position, and if the lens has stopped against the limit position, then
Apply a brake to the motor for about 100ms, <5DIS
CNT> to set the absolute distance counter.

Then, in this state, there is no change in the mode signal (whether it is up or not, it waits while going around the loop of mode φ change).In this <mode change>, the PFU
P operation switch SW, PFDN operation switch SW
The state change (mode change) of 2 and the state change (speed change) of the speed operation switch SW4 are checked, and if there is a change in mode 1, the DrFMOD flag is set and the speed change is detected. In this case, D
IFSP flag is set. If the DIFMOD flag is set, it is set to 1'11 and the process returns to (2).

On the other hand, in the case of normal power focus operation in which 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 reaches the predetermined tll movement and fine movement speeds. Fine-tune the off duty ratio. That is, the quick adjustment by turning on and off the lens drive motor is performed in parallel with <PDRV> and <5PCTL>. After this, the AFENA signal is checked, and if the signal is active, that is, the first operation of the release button is not on, and the mode change is called, and at this time, the speed can be changed. is done and the DIFSP flag is set, it returns to [F] as it is, and if there is no speed liquefaction and the DIFSP flag is set and a mode change is made, the brake is called and the motor is stopped. Stop, set the absolute distance counter with 5DISCNT>, and return to [F]. If there is no speed change or mode change, return to <PDRV> and press the first release button.
As long as the operation of the second stage is turned on, <PDRV> and <
5PCTL> continues.

When the operation of the first stage 1 of the release button is turned off, the AFE
The NA 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, calculation is performed in <CALDIS> from the contents of the set absolute distance counter, that is, the number of moving addresses from the infinite (■) position and the absolute distance coefficients a and b in the lens data circuit 18. The distance is calculated, and the calculated absolute distance information is sent to the main CPU 14. This<CALDI
After S>, the program returns to the initial state of power-on reset.

[Effects of the Invention] As described above, according to the present invention, the shift I calculation is performed using the maximum value SMA of the phase difference fit (shift amount) specific to the photographic lens.
It is limited by This has the remarkable effect of being able to prevent abnormal movements of the lens due to the calculated results.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram of a power control circuit mainly showing the autofocus section of a camera system to which the phase difference focus detection method of the present invention is applied. FIG. 2 is the autofocus circuit shown in FIG. 1 above. A schematic block diagram showing the transmission and reception of signals between the parts, Figures 3 to 9 are 1,
A flowchart showing the program operation centered on the A Fl1i CPU shown in Fig. 2 above, Fig. 10 is a diagram showing the positional relationship between the focus detection sensor and the optical system in the phase difference method, and Fig. 11 is , the output characteristic curve diagram of the focus detection sensor shown in FIG. 10 above, and FIGS. Figure (a
) is a front view of the photoelectric conversion elements arranged in each pair, the 12th
Figure (b) is a side view showing the arrangement relationship between the photoelectric conversion element group and the lens left, Figure 12 (c) is a diagram showing the luminous flux incident on the photoelectric conversion element through the lenslet, Figures 13 and 14. 15 and 16 are output characteristic curve diagrams of the focus detection sensor, each showing a state in which the shift is performed. FIGS. 22...AFJIICPU (computation CPU) 4 Shift 1 to child number island 12 decoy island 11 figure to child number island 12 decoy direction 13 bs b2 bs
bs bN-4bs-s
bll-z bx-+S shift
bs b2---------
----- m-5-z bN-s-+ bs-s+I
I+)++1 Horse 14 figure; Schiff 44 a+ a2 03 04
−−−−−−−−−−−−−−−−−−−− 0N−
3aN-z QN-1ONQ seat 1)+
bz bs ba
bN-sbN-zbN-rbN Tsukasa shift bz
bs b4 bs b
N-1bm-2b+l bN-2 shift 1)3
ba bs bg bN,
sbN-gbN-+ bN-5 shift tn order+
bs*a bs*s −−−−−−−−−−−
-bN-+ bN1 procedure supplement +E book
(Voluntary) January 2811, 1985 1. Indication of the case 1985 Patent Application No. 2805
38 No. 2, Title of the invention Phase 7:: #j, i-point detection method 3, Name of the person making the amendment (037) Olympus Optical Industry Co., Ltd. 4, Agent 5, Subject of amendment ``Invention of the specification "Detailed explanation column" and drawing (1) Specification section page 4';
bn++l lb, ”n+11)・・・・・・-(
21J will be changed to . (2) rF(S)=Σ(Ian+5-bn+11 1bn-b
n+5-11 houses...(3)'', rF(S)=Σ
(Ian+5-bn+11 1bn-bn+5-II
)""" (Revised in March. (3)rl" (S) = Σ (Iafi-bn-8+11 1b
, -5-bn+11) "..." (March will be changed to . (4) Changed to written on page 6, line 14 of the same. (5) Changed to written on page 26, line 9 of the same. "Add to shift amount S." will be corrected to "Add to previous H shift"5LAST." (6) Among the drawings attached to the application, Figure 6 will be changed to the attached drawing.

Claims (1)

[Scope of Claims] Calculating the amount of phase difference between the respective illuminance distributions of the light fluxes from the object that each include light fluxes from the same part of the object and follow different paths having parallax through different optical apertures. As a result, in the phase difference focus detection method for focusing the photographic lens, the maximum value S_M_A_X of the amount of phase difference unique to the photographic lens stored in the storage element is loaded into the calculation CPU in the camera body, and this A phase difference focus detection method, wherein the calculation CPU calculates the amount of phase difference only within the range of the maximum value S_M_A_X.