JPS6318316A - Focus detecting device for camera - Google Patents

Abstract

PURPOSE:To perform accurate focus detection by providing a storage means for storing a correcting value for correcting an error in focus based upon the chromatic aberration of a split optical system in the use of a projection means and a correcting means for correcting a deviation quantity on the basis of the correcting value. CONSTITUTION:Light projected by the projection means 1 upon a subject 2 is reflected by the subject 2 and transmitted through a photographic lens 3 to enter a phase difference type focus state detecting device 4. This detecting device 4 has the split optical system which splits the incident light into pieces of subject luminous flux passed through the 1st and the 2nd parts of the photographic lens 3 respectively, and the phase shift between the 1st and the 2nd subject contrasts is detected to detect the deviation quantity of the photographic lens from the focusing point. The signal of the deviation quantity which is outputted by this focus state detecting device 4 is sent to the correcting means 5 and corrected on the basis of the correcting value DELTAfc for correcting the error in focus based upon the chromatic aberration which is stored in the storage means 6, so that the corrected signal is outputted.

Description

[Detailed Description of the Invention] [Field of Industrial Application] - The present invention relates to a focus detection device for a camera having a phase difference type focus detection device, and particularly relates to a focus detection device having a light projecting means for illuminating a subject when the subject contrast decreases. .

[Prior art]

Detecting the phase shift of the first and second object contrasts created from the object light beams that have passed through the first and second parts of the photographing lens, respectively, and detecting the amount of deviation from the in-focus point of the photographing lens. BACKGROUND OF THE INVENTION Phase difference focus detection devices are conventionally known.

This focus detection device will be explained below with reference to FIG. 11 and FIG. 13.

An output sensor array 105 is provided near the focal plane 103 from the subject 101 through the exit pupil of the photographic lens 102.
As shown in FIG. 11, the object light directed toward is divided into upper light beams A, ~AN and lower light beams B, ~Bi, depending on the positional relationship between the lenslet 104 and the sensor array 105.

Now, assuming that the object is in focus, the upper luminous flux A1 and the lower luminous flux B of the subject light emitted from one point C1 of the subject 101 intersect at a point on the focal plane f (hereinafter the focal plane is abbreviated as f). . The line sensor 105 and the lens left 104 have the following for the luminous flux A I"" A M , B r ~B9,
Since they are in the position shown in FIG. 12 (■), the outputs of elements a1 and S of the sensor array 105 are equal, and similarly, the outputs of elements a2 of other sensor arrays...aN+ b!・－・・
The same applies to bH. Therefore sensor array 1
The output difference between column a and column b of 05 disappears, and the phase difference becomes zero.

Next, if the positions of the line sensor 105 and lenslet 104 move by Δ as shown in FIG.
This is equivalent to the photographic lens 102 moving by Δβ), and the luminous flux AI and luminous flux B are at the focal plane f'. So-
It does not intersect the points.

If the output curves of rows a and b of the sensor array 105 are drawn at this time, they will be as shown in FIG. 13, and the output curves of row a and b
The column output curve produces a phase difference Δχ, and since this phase difference Δχ and the amount of deviation Δl of the focus plane are in a proportional relationship, the amount of deviation of the focus plane can be calculated by determining the phase difference Δχ.

As described above, this focus detection device can calculate the amount of deviation of the photographic lens by distance measurement in -degrees, and therefore has the advantage of being able to speed up the driving of the photographic lens to the in-focus point.

By the way, since this focus detection device detects the amount of out-of-focus based on the phase shift of the object contrast, it cannot detect an object with low contrast or when the brightness of the object is low and no contrast occurs.

Therefore, in order to solve this problem, a light source for projecting light is provided to project illumination light from the camera body onto a subject to increase the contrast of the subject.

Although a light bulb with an emission spectrum close to that of natural light is desirable as a light source for projecting light, it is difficult to use it in cameras due to problems such as responsiveness and power supply voltage fluctuations due to rush current at the start of light emission. Therefore, in general, LEDs with good luminous efficiency and high brightness are used.
(mitted diodes) are used.

[Problem that the invention seeks to solve]

However, unlike natural light, the emission spectrum of this LED is concentrated in a specific band, resulting in out-of-focus due to chromatic aberration.To simplify the explanation, the sensor array 105 is shown in FIG. 14 is an enlarged view of the focal plane f and its vicinity at this time.

The light that passes through the photographic lens 102 and enters the sensor array 105 is natural light, and this natural light includes various wavelengths, but for the sake of simplicity, λ6. λ2. It is assumed that it consists of three wavelengths, λ. Photography lens 10
2, the chromatic aberrations for these three wavelengths are almost corrected.

However, due to dimensional and manufacturing problems, the lens left 104 is composed of a single lens, and as a result, longitudinal chromatic aberration occurs in which the focal length varies depending on the wavelength, and the position considered as the focal plane from the sensor array 105 is It varies depending on the wavelength.

Each wavelength λ1. λ8. Let the focal plane corresponding to λ be f, λl+
fe λ! +fCλ, the focal plane fc for natural light is a weighted average of the above three focal planes. The sensor array 105 is then positioned with respect to the focal plane fC, which is a weighted average of the wavelengths included in the natural light. Using the sensor array 105 positioned in this manner, distance measurement is performed under LED light projection, and when photographing is performed using strobe light whose spectrum is equal to that of natural light, the focal plane and natural light ( Because the focus plane for the strobe light is out of focus, the photo becomes blurry.

The present invention has been made in view of the above-mentioned drawbacks, and an object of the present invention is to provide a focus detection device for a camera that can perform accurate focus detection even when distance measurement is performed by projecting light different from natural light.

[Means for solving problems]

The configuration of the present invention will be explained using FIG. 1. The light projected from the projection means 1 toward the subject 2 is reflected from the subject 2, passes through the photographing lens 3, and is transmitted to the phase difference type focal B detection device 4.
incident on .

The phase difference type focus state detection device 4 has a splitting optical system that splits the subject light flux that has passed through the first part and the second part of the photographic lens 3, and the first and second parts formed by this splitting optical system. This is a device that detects the phase shift of the subject contrast of No. 2 and detects the amount of shift from the in-focus point of the photographic lens.

A signal representing the amount of deviation outputted from the focus state detection device 4 is sent to the correction means 5, and a correction value Δf, which corrects the focus error based on chromatic aberration, is stored in the storage means 6.
It is corrected based on and output.

〔Example〕

Hereinafter, 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.

FIG. 2 is an overall block diagram mainly showing the power supply of the camera system to which the present invention is applied. The source battery 1
1 voltage VCC becomes D C/ when the power switch 12 is closed.
The voltage is boosted by the DC converter 13, and the line Ilo,
Main cPU 14° bipolar ■ circuit 15 between l+.
Bipolar 2 circuit 16. Strobe control circuit 17. Lens data circuit 18. The data back circuit 19 is connected, and the power supply control of the bipolar circuit 15 is performed by the main CP.
Power supply control for the bipolar circuit 16 to data bank circuit B19 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
3 via lines I,,1. The power supply control for this AP 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 the entire sequence of the camera, such as film loading, rewinding, and exposure sequences.The main CPU 14 is a circuit for controlling the entire sequence of the camera, such as film loading, rewinding, and exposure sequences. re depending on the number of film frames and wavelength
This circuit stores data Δfe and the like for correcting deviations, and can be read, written, and erased under the control of the main CPU. Bipolar ■Circuit 15 is for film winding,
Rewind motor control, lens drive and shutter control, etc.
This circuit includes various drivers necessary for camera sequences, and is connected to an AF motor drive circuit 26, an AF auxiliary light circuit 27, and the like. The bipolar 51 circuit 16 is a circuit mainly responsible for photometry, and includes a photometry 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 differs for each interchangeable lens.
This is a circuit that stores unique lens data necessary for F, photometry, and other camera controls. This lens data circuit 1
Among the lens data included in 8, the data necessary for AF includes a lens magnification coefficient (zoom coefficient), a macro identification signal, and absolute distance coefficients a and b.

Power focus duty coefficient, AP accuracy threshold ETh, lens movement direction, aperture F value, etc.
AE and other necessary data include the maximum value S□ of the phase difference amount and others.

1 in the above bipolar ■circuit 15! The state of the source voltage VDD is monitored, and when the taX pressure drops below the specified voltage, a system reset signal is sent to the main CPU 14, and power is supplied to the bipolar circuit 15 to data back 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. 3 is a system diagram showing the transmission and reception of signals centered on the AF block. The AF CPU 22 and the main CPU 14 transmit and receive data through a serial communication line, and the communication direction is determined by a serial control line.

The contents of this communication include unique lens data within the lens data circuit 18 and absolute distance information. Furthermore, information on camera modes (AF single mode/AF sequence mode/power focus (hereinafter abbreviated as PF) mode/other modes) is decoded from the main CPU 14 to the AF CPU 22 through the mode line. Furthermore, AF from main CPtJ14
The AFENA (AF enable) signal to the AF CPU 22 is a signal that controls the start and stop of each AF and PF mode. This is a signal issued at the end of the operation to permit 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 the photo interrupter 33 has a light emitting part 33a and a light receiving part 33b facing each other across the path of the slits 32. counts the slits 32. That is, the slit 32 and the photo ink printer 33
constitutes 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 taken into the AF CPυ22.

A 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 is composed of an LED when the subject is low light (low brightness) and low contrast. Turn on the S lamp 27a.

The AF display circuit 24 connected to the AF CPU 22 has an LED 24a for displaying focus OK that lights up when focusing, and an LED 24b for displaying focus failure that lights up when focusing is impossible. Note that this AF CPU 22 includes a clock oscillator 3.
5. A reset capacitor 36 is connected.

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 sends a CCD drive clock signal, a CO
A D control signal is sent, the CCD output is read from the focus sensor 20, and the read analog value CCD output is converted into digital 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. 3 of the camera to which the present invention is applied will be described. As shown in FIG. 2, in the AF block, the transistor 23 is turned on by activating the AF power control circuit of the main CPU 14, and the voltage V is supplied to the AF block.
As a result, execution of the power-on reset routine shown in FIG. 4 is started.

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. Turning off the AF motor drive circuit 26, AF auxiliary light circuit 27, etc., and turning off 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 (mode signal) from the PU 14 and determining what lens drive mode to execute, the <timer> routine waits a certain period of 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. That is, the lens drive modes include lens reset>, <
PF (power focus)>, <AFS IN (A
<AFSEQ (AF sequence)>
When one of these modes is selected, the subroutine of the selected mode is executed and then the routine returns to the above (I10 initialization). <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 timer routine returns to 110 Initialize as described above after a certain period of time has elapsed. .

Here, the operation of the <lens reset> mode is to forcibly retract the lens to the infinity (clo) 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 converting into an absolute distance signal by replacing it with the number of pulse movements from a position at infinity (ψ), that is, an operation to clear the absolute distance counter. If <Lens Reset> is selected, after clearing this absolute distance counter, for example 5m
After s has elapsed, the process returns to the I10 initialization operation. Also,
<PF> mode means that you can adjust the distance ring on the lens instead of manually.
The lens is driven by a lens drive motor 31, and the lens focusing operation is performed using manual focusing or a focus aid.

More specifically, the lens is extended and retracted by turning on and off a PFUP (up) operation switch SW+ and a PFDN (down) operation switch SW, which will be described later. Also, <AF S
The operation in the mode I N> is a one-shot AF operation, and the focus is locked after the AF operation for the subject. 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 ON or OFF) 1. Second operation switch SW, SW
t is commonly used in AF mode and PF mode, and when the third operation switch S W s is off, A
When F mode is on, PF mode is selected. 1st in AF mode. When the second operation switch SW+ and SWg are both off, the lens reset mode is set, when both are on, the AFSEQ mode is set, and when the first operation switch SW is off and the second operation switch SWt is on, the AFSIN mode is set. . 1st in PF mode. a second operation switch SW;

SW! When both are off or on, it is in stop mode, and when 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, and the second operation switch SW1 is in stop mode. When the operation switch S W t is on, the PFDN (down) mode is set in which the distance ring is rotated to the far side and the lens is retracted. Further, the fourth operation switch SW4 is
In any of the modes and in the stop mode of the PF mode, there is no change 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 The distance ring rotates at high speed and coarse movement is performed, and when it is off, the mode is set to LO (low speed), and the motor 31 (see FIG. 3) 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 5 to 1.
This will be explained using the flowchart in Figure 0.

First, when the <AFS IN> mode is selected, the <AFSIN> routine shown in FIG. 5 is executed.
It detects whether the AFENA signal from the main CPU 14 is at the "H" level (active).The AFENA signal becomes active with the first step of the release button, and the AF operation is started, and <AFSIN2> The subroutine is called.However, the operation of the second step of the release button is accepted only when the AF operation is completed, the in-focus state is obtained, and the exposure sequence is started.<A
FS IN2>, as described later, the focus sensor 20
CCD integral of.

Calculation of distance measurement output, lens driving, etc. are performed. The in-focus/out-of-focus display that is the result of the AF operation of <AFSIN2> is displayed after the AF operation of <AFSIN2>.
This is done by monitoring the P status flag. 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 LC flag), the movement flag (the flag that is set to @1 when the subject is moving, below) , abbreviated as the M flag) and a closest approach flag (a flag that is set to 1" when the lens is extended beyond the closest distance, hereinafter abbreviated as the N flag). Among these,
Focusing is possible when any of the flags is 0, and it is impossible to focus if any of the above flags is set.As a result of monitoring the AF status flag, if the AF status flag is 0, focusing is possible. An indication of OK is made by the LED 24a of the former AF display circuit 24, and if the AF status flag is not O, an indication of inability to focus is made by the LED.
If the 0 focus is done by 24d, EOFAF
A signal is issued, the AF operation ends, and the main CPU 14
Then, the camera waits for the second operation of the release button, that is, the start of the exposure sequence. In other words, when -degree focusing is completed, even if the AFENA signal is active, further lens operation is prohibited and the LED 24 indicating focus OK is disabled.
a remains lit, and the focus is locked. AFENA signal from main CPU14 is II L
When the level becomes W (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, in order to compare the previous distance measurement calculation value (the previous output pulse of the focus sensor 20) and the current distance measurement calculation value (the current output pulse of the focus sensor 20),
The TRY (retry) flag is cleared, and the maximum number of distance measurements in a series of AF operations is entered in the AF lube counter. After this, in order to ensure that COD integration is performed above a certain brightness, the C
The maximum value of OD integration time is cented. Then, the AF 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. After this, the <lens read> routine is called, and the lens data circuit 18
After each data in the lens 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 3 lamp 27a during COD integration, and if it is necessary to light it, the S lamp flag is set, and if it is not necessary, it is cleared. Ru. Further, a low light flag (a flag 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 switching to <AF>, first, it is determined whether or not the S lamp flag is set, and if it is set, the S lamp 27a is turned on.Next, the CPU for AF
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 AG inside the A/D converter 21 (see Figure 3)
The charge is monitored by the C circuit, and the charge is transferred to the A/D converter 2.
When the amount becomes sufficient for a dynamic range of 1, the integration is stopped. During this integration period, the AF CPU 22 drives an internal timer to measure the integration time. This means that the 0th order S lamp 27a used to determine the subject brightness level 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. cent.

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 this stored data, the AF CPU 2
2, the ERROR of the phase difference amount is calculated according to the evaluation formula. It is determined whether the S lamp flag is set again in the 0th order, and if it is not set, the process returns directly. If the S lamp flag is set, the LED used for the S lamp 27a
Since the photographic lens is focused by the light, the fc deviation is corrected according to the present invention. In other words, f depends on the wavelength of the LED stored in the data circuit 30 of the main body in advance.

The AF CPU reads out the deviation amount Δf through the main CPU, and performs correction by adding it to the calculated ERROR value.

Returning to Figure 6 again, after the <AF> distance measurement operation, LL
When both the flag and the LC flag are cleared, the <pulse> routine is called and the lens drive amount is calculated.

That is, in this <pulse> routine, the lens data circuit 1 is used to convert the AF (distance measurement) calculation output value obtained in the above-mentioned AF> operation into a distance movement amount for each interchangeable lens.
Information such as a magnification coefficient is read from 8, and the number of pulses (address signals) corresponding to the amount of movement to the in-focus point is calculated based on 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 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 5rd ETh, then
■Look at the equator and 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 aim is to prevent the divergence of the entire sequence.The way to compare the two is (current pulse number): (previous pulse number X O, 5), or current pulse number): (previous pulse number X 1 .5) etc. are possible. When the AF angle system is likely to be in a divergent state, it is possible to perform AF fishing operation while the subject is moving.
Immediately stop the lens drive, set the M flag to prevent wasted AF fishing operation, and go to the shrine <5 DISCNT>
, calls the <CALDIS> routine.

After the lens is driven by the above <MDRIVAF>, 1 is subtracted from the AF fishing operation distance measurement count value set in the AF loop counter.

As a result, if the value of the AF loop counter is not O, set the integration time in the ITIME register, and set the AF E N A (i. Each time the AF fishing operation is repeated, the value of the AF loop counter is decremented one by one, gradually approaching the in-focus point, but even if the value of the AF loop counter reaches 0, the AF calculation output value ( If ERROR) does not become smaller than the AF accuracy threshold ETh, it is determined that focusing is impossible and the M flag is set. Indicates that the AF status flag has been cleared and the focus has been reached, and <5DISCNT>, <CALD
IS> routine is called.

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 11'' in advance, it would have been in a low light, low contrast state even though the 3 lamp 27a was lit during the integration operation for AF. Therefore, in this case, the LC flag is tested again, and only in the case of low contrast, the <Lens NF (unable to focus)> routine is called to display the inability to focus, that is, this lens NF> In this routine, the lens is first extended to the closest position, then retracted to the infinity (flash) position, and the user is actively notified of the inability to focus by moving the lens significantly.

In addition, the lens that indicates inability to focus is infinity (oo).
It may be an operation to move from the position to the closest position. Also, in this <lens NF>, by hitting the infinity (■) position, the drive pulse from the infinity (oQ) position of the lens distance ring is An absolute distance counter is initialized to save the number (number of moving address signals). 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, return to ①a.

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. , ■e advances. Therefore, the AF fishing operation S lamp 27a will be lit for the second and subsequent times.

In any case, at the end of the <AFS IN2> operation, <
After the routine SD I 5CNT> is called and executed, <CALDIS> is called. <SD
I5CNT>, the number of driving pulses from the infinite distance (oo) position of the distance ring is set in the absolute distance counter. Then, in <CALDIS>, the absolute distance to the subject is calculated from the pulse number set in the above-mentioned absolute distance counter and the absolute distance coefficients a and b in the lens data circuit 18. The absolute distance and the contents of the absolute distance counter are sent to the main CPU 14. This<C
The calculation of the distance between one color in ALD"IS" will be explained in detail later.After <CALDIS> is executed, <AFSIN2> in the flow of <AFS IN> shown in FIG.
Return to the position after the operation.

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, <AFSIN> is also <A
FSEQ> also performs the operation of <AFSIN2>, 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>, 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 sent, 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 described later, the focus sensor 20
CCD integration, AF computation, lens driving, etc. are performed, but active focusing failure display due to abnormal lens driving and S lamp 27a for distance measurement are not lit, and this <AFSEQ2> As a result of the operation, AF
The status flag is determined, and if the flag is 0, a display indicating that the focus is OK is displayed, and if the flag is not 0, a display indicating that the focus is not possible is displayed.
The F signal is generated, and the exposure sequence can be started by operating the release button in the second step. After this EOFAF signal is emitted or after the display indicating that the focus is not possible is displayed, the AFENA signal will be tested again, so as long as the first stage of the release button is kept on, <
AF operation centered on AFSEQ2> 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. 4) after CCD integration in the next AF operation or after return.

In the flowchart for 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, a <lens read> subroutine is called, and the lens data in the lens data circuit 18 is read out. And <A
After distance measurement is performed in the routine F>, -d, A
Turn off the F display circuit 24 and turn off the focus OK display LED 24.
a. Make sure that none of the out-of-focus display LEDs 24b lights up. In other words, the AF display is not performed while the lens is being driven. Next, after clearing the EOFAF signal, the LC flag is determined, and if the contrast is low, return, and if the contrast is not low, <pulse>
Note that even in low light, if there is contrast, distance measurement calculations are possible, so the determination of the LL flag is intentionally omitted. As described 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, and this and the AF The number of drive pulses (number of addresses) is calculated from the calculated 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, <MDRI
VAF> is called and the lens is driven to the in-focus position. After this, <5DISCNT> is called and the number of drive pulses based on the position retracted to infinity (oo) of the lens is written to the absolute distance counter.
Next, in <CALDIS>, the absolute distance to the subject is calculated from the number of driving pulses set in the absolute distance counter and the absolute distance coefficients a and b, which are lens data, and then 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. 4, if the mode <PF> is selected, the routine <PF> shown in FIG. 10 is called. In this <PF> routine, first, the AFENA signal is determined, and if the signal is not active, it returns, and if it is active,
In other words, if the first stage of the release button is on, E
By receiving the OFAF signal, the second stage operation of the release button can be performed.

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 such as the nonowarf focus duty coefficient in the lens data circuit 18 is read, and then the state change flag is cleared. Status change flags include the DIFSP (speed change) flag, which is set when the speed changes, and the DI flag, which is set when the mode changes.
There is a FMOD (mode change) flag.

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) is set or cleared, and the SP (speed) flag is set or cleared. That is, the on/off states of the operation switches SW, ~SW a related to the lens drive modes shown in Table 1 are read. In this <PF> mode, the operation switch SW is on, and when the PFUP operation switch SWl is turned on, the lens rotation direction becomes the UP (lens extension) direction, and the PFDN operation switch SW is turned on.

When turned on, the lens rotation direction is the DN (lens retraction) 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. 3) 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 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.

Thereafter, the <PDRV> subroutine is called. In this <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 a nearby limit position, and if the lens has stopped at the limit position,
Apply a brake to the motor for about lQQms, <SD I
5CNT> to cent the absolute distance counter. Then, in this state, it waits through the <mode change> loop to see if there is any change in the mode signal. In this mode change, PF
UP operation switch SW, PEDN operation switch S
Changes in the state of W2 (mode change) and changes in the state of the speed scratching switch SW4 (speed change) are checked, and if there is a mode change, the D I FMO
If the D flag is set and there is a speed change,
The DIFSP flag is set. Then, if the DI FMOD flag is set, this is determined and the process returns to (8).

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 coarse and fine movement speeds. 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 operation of the release button is on, call up the mode change>, and at this time, if the speed has been changed and the DIFSP flag is set, continue as before. There is no DI
When the FMOD flag is set and a mode change is made, the brake is called to stop the motor,
Set the absolute distance counter at <SD I 5CNT> and return to ■Deaf. If there is no speed change or mode change, return to <PDRV> and continue to turn on the first step of the release button until <PDRV> and <5PCTL>.
PF operation continues.

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, an operation is performed in <CALI)IS> to calculate the absolute distance, and this calculated absolute distance information is sent to the main CPU 14. sent to. This <CA
After LD I S>, the program returns and returns to the initial state of power-on reset.

〔Effect of the invention〕

As described above, according to the present invention, accurate focus detection can be performed even when distance measurement is performed by projecting light different from natural light.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the basic configuration of a focus detection device for a camera according to the present invention; Fig. 2 is a block diagram of an electric circuit mainly for supplying power to a camera to which the present invention is applied;
The figure is a block system diagram showing the transmission and reception of signals centering on the AF block in Figure 2 above, and Figures 4 to 10 show the program operations centered around the AF CPU shown in Figure 3 above. The flowchart shown in FIG. 11 is as follows. A principle diagram showing the detection principle of the phase difference type focus state detection device, FIG. 12 is an enlarged view of the main part near the focal plane of FIG. 11 above, and FIG. 13 is an output diagram of the sensor array in FIG. 12 above. , FIG. 14 is an enlarged view of the main part near the focal plane of FIG. 11 above for explaining lens left chromatic aberration. 1-・-・--・-Light projecting means 4・-----------・-Phase difference type focus detection device 5...
・-----Correction means 6・-- Storage means

Claims (1)

[Scope of Claims] A splitting optical system that splits the subject light beams that have passed through a first portion and a second portion of a photographic lens, respectively;
A phase-difference focus state detection device detects the phase difference between the first and second object contrasts created by this split optical system and detects the amount of deviation from the in-focus point of the photographing lens, and a A light projection means for illuminating; a storage means for storing a correction value Δf_c for correcting a focus error based on chromatic aberration of the split optical system when the light projection means is used; and a storage means for correcting the amount of deviation based on the correction value Δf_c. A focus detection device for a camera, comprising: a correction means for: