JPH0775401B2 - Focus detection device - Google Patents

Description

The present invention relates to a focus detection device such as a camera.

[Description of Prior Art]

Conventionally, as one type of focus detection device for a camera, the focus state of the shooting lens is divided by observing the relative position displacement of a plurality of images formed by the light flux that has passed through each pupil region by dividing the exit pupil of the shooting lens. There are known methods for detecting.

Specifically, the optical system for focus detection divides the exit pupil of the photographing lens into two, and each light flux that has passed through the two divided regions is a photoelectric conversion element array (for example, CCD sensor array) of the accumulation type. ) Form an image on top. Then, after the sensor output signal is A / D converted, the signals in the entire range or a part of the range are extracted and processed, whereby the relative position displacement of the two images can be known.

At this time, since the accumulation type sensor is used, the accumulation time must be appropriately set according to the brightness of the subject.

Controlling to an appropriate storage time is synonymous with adjusting the gain of the sensor, so the “AGC (Auto G
ain Control: Automatic gain control).

If this AGC does not work correctly, the output signal will be too small or saturated, and accurate focus detection will not be performed.

Therefore, usually, the photoelectric conversion output itself of a specific area of the sensor row is taken out for AGC, or the output of the photometric sensor for AGC provided in parallel with and near the sensor row reaches a predetermined level. End the accumulation,
Such a method is taken.

However, in the conventional methods, the area on the sensor array that is the target of AGC is fixed, and especially in the focus detection method that the sensor output range that is the target of focus detection processing is variable, the same range is on the sensor. If it does not match the region, there is a drawback that the AGC is incorrect for the same range.

[Object of the Invention]

The present invention aims to solve the above problems, the gist thereof is to prepare a plurality of AGC regions of the sensor array, and when the range of the sensor output that is the target of the focus detection process changes, the optimum sensor By setting the AGC area, correct focus detection is always possible.

〔Example〕

First, the principle of focus detection in the present invention will be described with reference to FIG. A field lens FLD is arranged with the same optical axis as the taking lens LNS whose focus is to be detected. Two secondary imaging lenses FCLA and FCLB are arranged at positions symmetrical with respect to the optical axis behind them. Further behind that is the sensor row S
AA and SAB are placed. Stops DIA and DIB are provided near the secondary imaging lenses FCLA and FCLB. The field lens FLD has two secondary imaging lenses FCLA and FC that are the exit pupils of the taking lens LNS.
It forms an image on the pupil plane of LB. As a result, the secondary imaging lens FC
The ray bundles respectively incident on LA and FCLB are emitted from the areas of the same area that do not overlap each other and correspond to the secondary imaging lenses FCLA and FCLB on the exit pupil plane of the taking lens LNS. The aerial image formed in the vicinity of the field lens FLD is detected by the secondary imaging lenses FCLA and FCLB as the sensor array S.
When re-formed on the surfaces of AA and SAB, the two images on the sensor arrays SAA and SAB change their positions based on the displacement of the aerial image position in the optical axis direction. Therefore, if the amount of displacement (deviation) between the relative positions of the two images on the sensor array is detected, the shooting lens LNS
You can know the focus state of.

FIG. 2 shows an example of photoelectric conversion outputs of two images formed on the sensor-specific SAA and SAB. Let SA (A) output be A (i) and SAB's output be B (i). In this example, the number of pixels of the sensor is 40 pixels (i = 0, ..., 39).

As a signal processing method for detecting the image shift amount PR from the image signals A (i) and A (i), there are Japanese Patent Laid-Open Nos. 58-142306 and 59-59.
The present applicant has proposed 107313, Japanese Patent Laid-Open No. 60-1015313, or Japanese Patent Application No. 61-160824.

It is FIG. 3 whether the focus adjustment of the photographing lens is performed based on the image shift obtained by the method disclosed in each of the above publications and the relationship between the two images in a so-called in-focus state is shown. The amount of deviation is Δ. This is 2 in the in-focus state caused by the adjustment of the secondary imaging optical system in FIG.
It is the amount of displacement of the optical image on one sensor row. In the present invention, this Δ is stored in the non-volatile memory in the processing device in the adjusting step as described later, and when the amount obtained by subtracting Δ from the detected image shift amount PR is within a predetermined value, I try to regard it as a rush.

Note that the photoelectric conversion signal examples shown in FIGS. 2 and 3 are AGC (Aut
o Gain Control) is effective in the central area of the sensor array SAA (hereinafter referred to as "central area AGC").
That is, the accumulation operation of the sensor is controlled by the brightness of the optical image formed on the pixel in the "AGC range" shown in the figure, and the photoelectric conversion signal in the range is controlled so as not to be saturated. The signals in Fig. 2 and Fig. 3 are proper output because the maximum value of the signal is in the central AGC range, but as shown in Fig. 4, the maximum value of the signal output is outside the central AGC range. If the output is within the AGC range, the signal outside the range is electrically saturated, and if the signal processing for image shift detection is performed using this image signal, the effect of the saturated part Will detect an incorrect image shift amount. So in this case
Expand the AGC range to the entire sensor array
It is possible to obtain an appropriate photoelectric conversion signal as shown in FIG.

An example of the line sensor device SNS capable of switching the AGC range is shown in FIG.

The sensor arrays SAA and SAB are known CCD line sensors, which correspond to the sensor array shown in FIG. φ ₁ and φ ₂ are the clocks for driving the CCD, and SH is a high potential (hereinafter abbreviated as “H” and a low potential is abbreviated as “L”) for a predetermined time, so that the charge accumulated in the photoelectric conversion element is A signal to be transferred to the CCD unit (charge transfer unit), CLR is a clear signal that clears the photoelectric conversion element in the "H" state. SSCNT is a control circuit inside the SNS that receives signals φ ₁ , φ ₂ , SH, and CLR and controls the photoelectric conversion element unit and the CCD unit. The photoelectric conversion output of the optical image formed on the sensor array SAA, SAB is transmitted through the conversion amplifier OAMP in synchronization with φ ₁ and φ _2.
It is output in time series as the OS.

ST ₁ , ST ₂ , and ST ₃ are photometric elements for AGC, and are output as a signal AGC via a conversion amplifier AAMP which is composed of a photodiode. The optical image formed on the sensor array SAA is ST ₁ , S
It is also formed on T ₂ and ST ₃ , so the same optical image as on SAA is AGC.
It will be used for control. MOS1 and MOS2 are photometric elements ST
This is a MOS transistor for switching the output of ST1 and ST3. It is conductive when the signal CAGC is "H", and the signal SAGC is the photometric element.
It is the sum of the outputs of ST1, ST2, and ST3. Signal CAGC
Is low, the MOS1 and MOS2 are non-conductive, and the signal SAGC is only the output of the central photometric element ST2. In summary, when the signal CAGC is "H", it is the entire area AGC, and when it is "L", it is the central portion AGC.

A specific method of AGC control will be described in detail using a flow chart described later.

FIG. 7 is a circuit diagram showing an embodiment of a camera provided with an autofocus device according to the present invention.

In the figure, PRS is a camera control device, for example, C
PU (Central Processing Unit), ROM, RAM, EEPROM (Electrically Erasable Programmable ROM) A single-chip micro computer with A / D conversion function, automatic exposure control according to the camera sequence program stored in ROM. It operates the camera such as functions, automatic focus detection function, film winding and rewinding. The EEPROM is a type of non-volatile memory, and various adjustment data are written in the process including the above-mentioned data of Δ.

The computer PRS uses the communication signals SO, SI, SCLK to communicate with the peripheral circuits and the lens and control the operation of each circuit and the lens.

SO is the data signal output from the computer PRS, SI is the data signal input to the computer PRS, SCLK is the signal S
This is a synchronization signal for O and SI.

The LCM is a lens communication buffer circuit, which supplies the lens power supply VL to the lens when the camera is operating.
When the signal CLCM from PRS is at high potential level, it becomes a buffer for communication between the camera and the lens.

When the computer PRS sets CLCM to “H” and sends the specified data from SO in synchronization with SCLK, the buffer circuit LCM sends the buffer signals LCK and DCL of SCLK and SO through the camera / lens indirect point. Output to the lens. At the same time, the buffer signal of the signal DLC from the lens is output to SI, and the computer PRS receives the SI signal in synchronization with SCLK and inputs the lens data.

SDR is a drive circuit of the line sensor device SNS for focus detection, which is selected when the signal CSDR is "H" and is controlled by the computer PRS by SO, SI and SCLK.

The signal CK is a clock for generating the CCD driving clocks φ ₁ and φ ₂ , and the signal INTEND is a signal for notifying the PRS that the accumulation operation is completed.

The output signals OS of the line sensor device SNS are clocks φ ₁ and φ ₂
6 is a time-sequential image signal described in FIG. 6, which is amplified by an amplifier circuit in the drive circuit SDR and then output to the computer PRS as an AOS signal. Computer PRS is AOS
A signal is input from the analog input terminal, and in synchronism with the signal CK, it is sequentially stored in a predetermined address of RAM after A / D conversion by an internal A / D conversion function.

SAGC, which is also an output signal to the device SNS, is an AG in the device SNS.
It is the output of the C control sensor (ST ₁ to ST _{3 in} FIG. 6), is input to the circuit SDR, and is used for storage control of the device SNS.
A series of operations of the circuit SDR will be described later.

The SPC is a photometric sensor for exposure control that receives light through the taking lens, and its output SSPC is input to the analog input terminal of the computer PRS and used for moving exposure control (AE) after A / D conversion.

DDR is a circuit for switch sense and display, and signal C
Selected when DDR is “H”, controlled by computer PRS using SO, SI, SCLK. That is, the switches of the cameras are switched based on the data sent from the computer PRS, and the switch group SWS that interlocks with various operation members such as a release button (not shown) (interlocked with the switches SW ₁ and SW2) and a mode setting button. The on / off state of the computer PRS
Contact.

MDR1 and MDR2 are drive circuits for the motors MTR1 and MTR2 for the film feeding and shutter charging, and the motors forward and reverse are executed by the signals M1F, M1R, M2F and M2R.

MG1 and MG2 are magnets for starting the first curtain and the second curtain of the shutter, respectively. The signals SMG1 and SMG2 amplify transistors TR1 and TR2 are energized, and the shutter is controlled by PRS.

The switch sense and display circuit DDR, the motor drive circuits MDR1 and MDR2 shutter control are not directly related to the present invention, and thus detailed description thereof will be omitted.

The AUT is an auxiliary light projecting unit, which is attached to the camera body by a member (not shown), and the transistor ATR is turned on in response to a signal SAL from the camera to energize the auxiliary light source LED and ALED to emit light. ALNS is a lens for appropriately illuminating the subject with ALED light.

The signal DCL input to the in-lens control circuit LPRS in synchronization with the synchronization signal LCK is command data from the camera to the lens FLNS, and the lens operation in response to the command is predetermined.

The circuit LPRS analyzes the instruction according to a predetermined procedure,
It performs focus adjustment and aperture control operations, and outputs various lens parameters (open F-number, focal length, coefficient of differential focus amount vs. extension amount, etc.) from the output DLC.

In the embodiment, an example of a single lens for the entire extension is shown, and when a command for focus adjustment is sent from the camera, the focus adjustment motor LMTR outputs a signal LMF, according to the drive amount and direction sent at the same time. Driven by the LMR, the optical system is moved along the optical axis to adjust the focus. The moving amount of the optical system is monitored by the pulse signal SENC of the encoder circuit ENC,
When the predetermined movement is completed, the signals LMF and LMR are set to "L" to control the motor LMTR.

When an aperture control command is sent from the camera, a stepping motor DMTR known for driving the aperture is driven in accordance with the number of aperture steps sent at the same time. Since the stepping motor can be open-controlled, an encoder for monitoring the operation is not required.

The operation of the camera having the above configuration will be described according to the flow of FIG.

When a power switch (not shown) is operated, power supply to the microcomputer PRS is started, and the PRS starts executing the sequence program stored in the ROM.

FIG. 9 (a) is a flow chart showing the overall flow of the above program.

When the execution of the program by the operation is started, the state detection of the switch SW ₁ which is turned on by the first stroke of the release button in step (002) is made, when the switch SW ₁ is turned off, step (003) In PRS RAM
All the control flags set in are cleared.
In addition, the detection of this switch SW ₁ is a signal from the computer PRS.
CCDR is set to H and no circuit DDR is selected, and the SO signal as a detection command of switch SW ₁ is transmitted to DDR, so that switch S
The state of W ₁ is detected by DDR, and the result is used as SI signal for P
Do this by telling RS. Above steps (002), (00
3) is repeatedly executed until the switch SW ₁ is turned on or the power switch is turned off. When SW ₁ is turned on, the process proceeds to step (004).

Step (004) means "AE controlled" saburtine. In this "AE control" subroutine, a series of camera operation controls such as photometric calculation processing, exposure control, and post-exposure shutter charge and film winding are performed.

The "AE control" subroutine is not directly related to the present invention, so a detailed description thereof will be omitted, but the outline of the function of this subroutine is as follows.

This "AE control" subroutine is executed while SW ₁ is on, and each time the camera mode setting, photometry and exposure control calculation, and display are performed. Second release button (not shown)
When the switch SW ₂ is turned on by the stroke, the release operation is started by the interrupt processing function of the microcomputer PRS, and the aperture or shutter time is controlled based on the exposure amount obtained by the exposure control calculation above.
After the exposure is completed, the shutter / charge and the film feeding operation are performed so that one frame of the film is photographed.

Now, when the "AE control" is completed at step (004),
The "AF control" subroutine of step (005) is executed.

FIG. 9B shows a flow chart of the "AF control" subroutine.

First, in step (102), the state of the flag PRMV is detected. P
RMV is a flag related to the lens control as described later, since all the flags at SW ₁ off in the step (003) as described above is cleared, SW ₁ on the first time from the step (005 When the "AF control" subroutine in (4) is called, the flag PRMV is also 0, so the routine proceeds to step (106).

At step (106), the state of the flag AUXJF is detected. AU
XJF is a flag related to auxiliary light control, and as described above, the flag AUXJF is also φ, so the process proceeds to step (108).

Step (108) is a subroutine of "image signal input", and by executing this subroutine, the A / D conversion signal of the image signal from the sensor device SNS is stored at a predetermined address on the RAM of the microcomputer PRS. .

The "image signal input" subroutine is shown in the flowchart of FIG. 9 (c), and the details will be described later.

At step (111), the state of the flag AUXMOD is detected.
The flag AUXMOD is a flag indicating that it is in the auxiliary light mode. The control regarding the auxiliary light will be described later.

As described above, since the flag AUXMOD is also 0, the process proceeds to step (112). Flag LLFLG in step (112)
The state of is detected. LLFLG is a flag set in the "image signal input" subroutine of step (108), and is set by 1 when the subject brightness is low. Here, the description will proceed assuming that the subject brightness is sufficient (LLFLG is 0). Since the flag LLFLG is 0, the process shifts to step (113), and since the subject brightness is sufficient, the auxiliary light mode flag is set.
Clear AUXMOD.

Next, in step (114), the "focus detection" subroutine is executed.

The flow chart of this subroutine is shown in FIG. 9 (e). In this subroutine, the focus of the taking lens is detected from the image signal data stored in the RAM, and if it is in focus, the focus flag JF Is set to 1, and if focus detection is impossible due to the low contrast of the object, the flag AFNG is set to 1 indicating that focus detection is impossible, and in any of the two cases, the lens drive is prohibited. Set the lens drive prohibition flag LMVDI to 1 and return. Also,
If the contrast is high and the object is out of focus, the defocus amount is calculated. At this time, the flag LMVDI is held at 0.

In the next step (115), a "display" subroutine for displaying the focus or the focus detection inability is executed. This is to transmit predetermined data to the display circuit DDR to display it on the display device DSP, but since this operation is not directly related to the present invention, further description will be omitted.

In the next step (116), the state of the flag LMVDI is detected. As described above, since LMVDI is set to 1 when lens driving is not necessary, if the flag LMVD is 1 at step (116), the "AF control" subroutine is returned at step (117). If LMVDI is 0, the process proceeds to step (118) to execute the lens drive subroutine "lens drive". This subroutine will be described later.

When the "lens drive" subroutine (118) is completed, the lens drive execution flag PRMV is set to 1 at step (119), and then the "AF control" subroutine is returned at step (120).

When the "AF control" subroutine is returned, the step (00
Returning to 2), as long as switch SW ₁ is on, the AE control and AF control subroutines are squeezed back.

If the "AF control" at step (005) is called again (second time) in the main flow of FIG. 9 (a), the state of the flag PRMV is detected at step (102).

If the focus or focus cannot be detected in the previous "AF control" routine, the flag PRMV has not been set to 1.
The above flow after step (106) is executed again. If the lens was driven last time,
In step 9), PRMV is set to 1, so step (1
Move to 03).

The step (103) communicates with the lens to detect the current driving state of the lens, and if the lens side notifies that the predetermined driving instructed in the step (118) has ended, a flag is set in the step (105). Set PRMV to 0 and set the step (10
6) Execute the subsequent flow. Note that this determination is made by detecting this signal SENC with the computer PRS because the monitor signal SENC is being sent from the encoder ENC during lens driving. If it is informed that the lens is still being driven, the process proceeds to step (104) and the "AF control" subroutine is returned.

Therefore, in the "AE control" subroutine, new focus detection operation and lens control are performed only when the lens is not driven.

That is, in normal mode, as long as switch SW ₁ is on, AE and A
If the F control subroutine is squeezed back, and the AF control subroutine detects the defocus amount based on the image signal and a low contrast judgment is made, focus detection cannot be displayed, and if a focus judgment is made, a focus display is made and out of focus. When the differential focus amount is obtained in step S1, the lens is driven by the differential focus amount and the focus state is brought about.

Next, the operation relating to the auxiliary fill light will be described.

If the subject brightness is low in the AF control subroutine, the flag LLFLG is set to 1 in the "image signal input" subroutine of step (108), and step (11)
When the LLFLG state is detected in 2), the process proceeds to step (121).

In step (121), the state of the auxiliary light unit AUT mounting member (not shown) is detected, and if the unit AUT is not mounted, the process proceeds to step (113) to perform the same operation as the normal operation described above. If the unit is installed, the process proceeds to step (122) and the auxiliary light mode flag AUXMOD is set to 1
To set.

Next, at step (123), the state of the flag AUXUSE is detected. AUXUSE is a step (10 with flag AUXMOD set to 1) when the auxiliary light is actually emitted.
This is a flag which is set to 1 when the "image signal input" subroutine of 8) is executed. In the situation I'm explaining now
Prior to that, the auxiliary light was not projected and the step (12
Return to "AF control" once in 4). That is, in this case, the image signal data input in step (108) is discarded without being used for focus detection, the image signal is input in the auxiliary light projection state in the next "AF control", and this is used for focus detection. It will be.

Now, when AUXMOD is set to 1 for the first time at step (122) and the "AF control" returns and the "AF control" subroutine is called again as described above,
In the "image signal input" subroutine of step (108), the image signal is input in the auxiliary light projection state, and in step (111), the state of the auxiliary light mode flag AUXMOD is detected and the step (12
Go to 1). If the auxiliary light unit AUT is not removed during this period, the process proceeds to step (122). If it has been removed, the process proceeds to step (113) to set the auxiliary light mode flag AUXMOD to 0, release the auxiliary light mode, and return to normal AF control.

The state of the auxiliary light use flag AUXUSE is detected in step (123) through steps (121) and (122). At step (108), the "image signal input" subroutine has already been executed in the auxiliary light projecting state, and since AUXUSE has been set to 1, the process proceeds to step (114) to execute the "focus detection" subroutine. After that, it is the same as the normal AF control.

As described above, in the case of low brightness, the auxiliary light mode is set only when the auxiliary light unit is attached, and the focus adjustment operation is performed based on the detected image signal under the auxiliary light emission. If in focus, step (114)
Auxiliary light focusing flag AUXJ in the "focus detection" subroutine of
F is set to 1. In this case, in the "AF control" flow, the state of AUXJF is detected in step (106), and the process proceeds to step (107), after which the "AF control" subroutine is returned. That is, when the focus is achieved in the auxiliary light projection state, the focus adjustment operation and the lens drive are not performed again until the switch SW ₁ is turned off.

FIG. 9C shows a flow chart of the "image signal input" subroutine.

In step (202), the state of the flag AGCFLG is detected. AGC
FLG is a flag that controls the AGC range on the sensor array and is cleared while switch SW ₁ is off. SW ₁ on in excisional clear is done in the "focus detection" subroutine. If the flag AGCFLG is 0, the operation proceeds to step (203), the output CAGC terminal of the microcomputer PRS is "L", and if the flag AGCFLG is 1, the operation proceeds to step (204) and the CAGC terminal is "H". That is, when the flag AGCFLG is 0, the sensor is the central portion AGC, and when it is 1, the sensor is the entire area AGC.

Therefore, in the first "AF control" subroutine, the central AGC
Becomes

In the next step (205), the state of the flag AUXMOD is detected,
In the case of 1 (auxiliary light mode), in step (206), the output SAL terminal of the micro computer PRS is set to "H" to emit the auxiliary light, and the auxiliary light use flag AUXUSE is set to 1 in step (207). . When AUXMOD is 0 (normal light mode), the process shifts from step (205) to (208) and the auxiliary light is not projected.

In step (208), the sensor device SNS is caused to start accumulating an optical image. Specifically, the micro computer PRS sets CSDR to H
In response, the sensor drive circuit SDR sends an "accumulation start command" as an SO signal, and the circuit SDR receives this command and sets the clear signal CLR of the photoelectric conversion element section of the sensor device SNS to "L".
Then, charge accumulation is started.

In step (209), the accumulation time counter INTCNT set in the RAM is initialized to 0. In step (210), the 1-millisecond clock timer is reset and the clock is started from the reset state. This 1 millisecond clock timer uses the timer function of the microcomputer PRS.

In step (211), the state of the input INTEND pin of the PRS is detected and it is checked whether or not the accumulation is completed. Sensor drive circuit SD
R sets the signal INTEND to “L” at the same time as the accumulation starts,
A structure in which the AGC signal SAGC is monitored, and when SAGC reaches a predetermined level, the signal INTEND is set to "H" and at the same time the charge transfer signal SH is set to "H" for a predetermined time to transfer the charge of the photoelectric conversion element section to the CCD section. have.

In step (211), the computer PRS detects the INTEND pin, and if the signal INTEND is "H", it means that the accumulation has ended, so the process moves to step (216), and if it is "L", it means that the accumulation has not ended yet. It moves to step (212). If not accumulated, it is checked in step (212) whether the previously reset 1 millisecond timer has clocked 1 millisecond.
If 1 millisecond has not elapsed, the process proceeds to step (211), and the accumulation ends or 1 millisecond has elapsed. If 1 millisecond elapses before the end of accumulation, the process proceeds to step (213). At step (213), the accumulation time counter INTCNT is counted up by 1, and the process proceeds to step (214). At step (214), the counter INTCNT is compared with the predetermined constant MAXINT.
MAXINT is the longest accumulation time expressed in units of 1 millisecond. If INTCNT is less than MAXINT, the process returns to step (210) and waits again for accumulation. When INTCNT matches MAXINT, the process proceeds to step (215) to forcibly end the accumulation. The forced accumulation end is executed by sending the "accumulation end command" as the SO signal from the microcomputer PRS to the sensor drive circuit SDR in the same manner as described above. SDR is PRS
When the "storage end command" is sent from, the charge transfer signal
The SH is set to "H" for a predetermined time to transfer the charges of the photoelectric conversion unit to the CCD unit. The accumulation of the sensor is completed by the flow up to step (216).

In step (216), set the PRS output SAL terminal to "L", and if the SAL terminal is in "H" in step (206), the auxiliary light is still emitting, so set it to "L". The light emission stops. That is, the auxiliary light is emitted only while the sensor is accumulating.

In step (217), the accumulation time counter INTCNT is compared with a predetermined constant AUXTINT. The constant AUXINT is the low-intensity storage time expressed corresponding to the storage time, and INTCNT is AUXINT.
If it is larger, the process proceeds to step (219) to set the low brightness flag LLFLG to 1, and if it is smaller, the process proceeds to step (218) to clear the LLFLG. That is, when the accumulation time is longer than the predetermined time, it is determined that the brightness is low.

In step (220), the signal AOS obtained by amplifying the image signal OS of the sensor device SNS by the sensor drive circuit SDR is subjected to A / D conversion and its digital signal is stored in RAM. More specifically, the circuit SDR generates CCD driving clocks φ ₁ and φ ₂ in synchronization with the clock CK from the computer PRS, and supplies them to the control circuit SSCNT inside the device SNS. SNS is controlled by φ ₁ and φ ₂ . The CCD unit is driven, and the charges in the CCD are output in time series from the output OS as image signals. This signal is amplified by the amplifier inside the SDR and then input as AOS to the analog input terminal of the PRS. The computer PRS performs A / D conversion in synchronization with the clock CK output by itself, and sequentially stores the digital image signal after A / D conversion at a predetermined address in RAM.

When the input of the image signal is completed in this way, the step (22
At 1), the "image signal input" subroutine is returned.

In this way, the image signal input subroutine controls the accumulation time of the image signal, and when the accumulation time is longer than the predetermined time, the flag LLFLG is set to 1 to allow the shift to the auxiliary light mode in the AF control subroutine. In addition, when the auxiliary light mode is entered, image storage is performed under the auxiliary light projection. Also, depending on the set state of the flag AGCFLG,
The switching operation of the central portion AGC or the whole area AGC is performed.

FIG. 9 (d) shows a flow chart of the "lens drive" subroutine.

When this subroutine is called, step (302)
Communicates with the lens in the two data "S", "PT
Enter "H". “S” is a coefficient of the “defocus amount” unique to the taking lens versus the “extending amount of the focus adjusting lens”. For example, in the case of a single lens of the whole extending type, the entire taking lens is the focus adjusting lens, and S = 1. However, in the case of a zoom lens, S changes depending on the zoom position.

"PTH" is an encoder E linked to the movement of the focusing lens
This is the amount of focusing lens extension per NC pulse.
The encoder is composed of a pulse plate or the like that outputs one pulse according to the unit movement amount of the lens.

Therefore, based on the current defocus amount DFE and the above information S and PTH, a so-called lens drive amount FP converted into the pulse number of the focusing amount encoder of the focusing lens is given by the following equation.

FD = DEF × S / PTH (1) In step (303), the equation (1) is executed as it is, and the pulse number FP from the encoder representing the lens drive amount according to the detected defocus amount DEF described later is obtained.

In the step (304), the FP obtained in the step (303) is sent to the lens to instruct the drive of the focus adjustment lens (in the case of a single lens of the whole extension type, the entire photographing lens), and the next step (305 ), The "lens drive" subroutine is returned.

The data "S" and "PTH" are input to the memory in the circuit LPRS, and CLCM is set to H by the computer PRS.
By transmitting the SO signal as the data read command to the circuit LPRS via the circuit LCM, the data "S" and "PTH" in the memory are input to the computer PRS as DLC and SI signals. Is read.

Similarly, the FP is also transmitted as a signal SO to the circuit LPRS, and the circuit LPRS sets either of the signals LMF and LMR to H in accordance with the input FP and rotates the motor in the direction corresponding to the FP to couple the lens. Move to the focal direction. At this time, the encoder SENC
Sends a number of pulses according to the amount of lens movement, counts the number of pulses with the counter inside the circuit LPRS, and inputs
When it coincides with FP, the signals LMF and LMR are set to L and the motor is stopped to drive the lens by the above FP.

Therefore, when the lens drive subroutine is called, the lens is driven by the detection differential amount as described above and moved to the in-focus position.

FIG. 9 (e) shows a flow chart of the "focus detection" subroutine.

When this subroutine is called at the step (114) during execution of the AF control subroutine, at step (402) the two data "LF" and "MAXDFE" are input from the lens by communicating with the lens by the above operation. . “LF” is the focal length data of the taking lens, and in the case of a zoom lens, the LF changes depending on the zoom position, which is natural.
"MAXDEF" is data called the maximum defocus amount, and is the defocus amount when the subject is measured at the closest distance of the lens when the shooting lens is in focus at infinity. is there. Therefore MAXDEF
Can be considered as the maximum value of the differential focus amount that occurs when the lens is attached.

These data are also input to the memory in the circuit LPRS. The idea of the maximum defocusing amount is presented by the applicant in Japanese Patent Application No. 60-272563. Generally, telephoto lenses and zoom lenses have a large MAXDEF.

At step (403), the flag AGCFLG is detected, and if AGCFLG is 1, that is, if the entire area is AGC, the process proceeds to step (420),
Executes the defocus amount detection subroutine "WPRED".

If AGCFLG is 0, that is, if it is the central AGC, the process proceeds to step (404). In the first "AF control" when switch SW1 is turned on, AGCFLG is 0, so first step (404)
The following will be described.

In step (404), the focal length LF and the constant CHLF are compared. CHLF represents a predetermined focal length. If the focal length of the taking lens is CHLF or more, the process proceeds to step (406), the defocus amount detection subroutine "MPRED" is executed, and if less, the process proceeds to step (405). The subroutine "N
Execute "PRED".

Both “MPRED” and “NPRED” are defocusing amount detection subroutines, but the number of pixels to be calculated when detecting the defocusing amount from the image signal is different, and the maximum defocusing amount that can be detected is also different. Figure 8 shows the correspondence between "WPRED", "MPRED", and "NPRED".
The sensor array SAA (SAB) is arranged as shown in the figure with respect to the so-called range-finding frame FFRM in the finder.

Further, the range of the central AGC described above is set to be substantially equal to the distance measurement frame FFRM. "WPRED", "MPRED", "NP
RED "Each of the calculation target regions (the defocus amount is detected based only on the image signal in the region) WRGN, MRGN, NRGN are as shown in FIG.

That is, "WPRED" covers the entire area of the sensor, "MPRED" has the same central AGC range inside, and "NPRED" is further inside. Based on these correspondences, when executing “WPRED”, the whole area AGC is changed to “MPRE” during the sensor accumulation process.
It can be seen that the central AGC must be selected when executing "D" and "NPRED".

Returning to FIG. 9 (e), the flow chart will be described again.

"NPRED" in step (405) according to the focal length of the lens
Alternatively, after "NPRED" is executed in step (406), the state of the flag LCFLG is detected in step (407). LCFLG is a differential focus detection subroutine "NPRE
Low contrast flag set in "D""MPRED",
Set to 1 when the contrast of the image signal in the detection calculation area is lower than a predetermined value.

If the flag LCFLG is 0 in step (407), it is determined that there is sufficient contrast, and the process proceeds to step (408) to clear the focus detection impossible flag AFNG to 0. Then, the absolute value of the defocus amount DEF detected in step (409) is compared with a predetermined constant JFFLD. JFFLD represents the upper limit of the defocus amount that can be regarded as in-focus, and is a so-called in-focus width. If the absolute value of the differential focus amount is less than JFFLD in step (409), the process proceeds to step (410) and both the focus flag JF and the lens drive prohibition flag LMVDI are set to 1, and if the absolute value of the differential focus amount is larger than JFFLD. At step (411), the flags JF and LMVDI are both cleared, and at step (414) the "focus detection" subroutine is returned. In the case of the in-focus state, the process further shifts to step (412) to detect the state of the auxiliary light mode flag AUXMOD. If AUXMOD is 0, that is, if it is not the auxiliary light mode, the "focus detection" subroutine is returned at step (414). If AUXMOD is 1, that is, if the auxiliary light mode, the process proceeds to step (413) to set the auxiliary light focus flag AUXJF to 1, and the subroutine returns.

The operation of the following focus detection subroutine is summarized as follows.

When the focal length is smaller than a predetermined value, NPRED detects defocusing, and when it is larger than a predetermined value, MPRED detects defocusing. Since the NPRED and MPRED routines are executed when the flag AGCFLG is 0, the signal CAGC is L and the central portion AGC is selected as described in the image signal input subroutine. Therefore, at this time, the central part AGC
The AGC is performed by the picture element output in the range that matches the defocus amount detection picture element range.

If it is determined that the defocus amount detection result is in-focus, the flag JFLMVDI is set to 1. Therefore, when returning to the AF control subroutine after that, the in-focus display is performed. When the focus determination is made in the auxiliary light mode, the flag AUXJF is set to 1, and subsequent image signal input focus detection and lens driving are prohibited. Also, if it is not determined to be in focus, the flag LM
Since VDI is set to 0, the lens drive subroutine is executed after the focus detection subroutine ends, and the NPRED or M
The lens is driven by the defocus amount calculated in the PRED subroutine.

Further, when the low contrast is determined by the NPRED or MPRED subroutine and the flag LCFLG is set to 1, the step (40
In 7), it is detected that the low contrast flag LCFLG is 1, and the process proceeds to step (415) to detect the state of the auxiliary light mode flag AUXMOD.

At this time, if AUXMOD is 1, that is, the auxiliary light mode, the operation proceeds to step (419), and if AUFMOD is 0 and is not the auxiliary light mode, the operation proceeds to step (416). At step (416), the maximum defocusing amount MAXDEF described above and the variable MD are compared. The variable MD is the defocus amount detection subroutine "MPRE
The values set in "D" and "NPRED", which will be described later, generally represent the maximum value of the defocus amount that can be detected in each subroutine. Therefore at step (416) MAXDE
Comparing F and MD is to determine whether the defocus amount that can occur in the currently mounted taking lens is equal to or higher than the detection capability of each defocus amount detection subroutine. That is, if MAXDEF ≦ MD, it is considered that the “MPRED” or “NPRED” differential focus detection capability is sufficient for the mounted lens.

Therefore, if MAXDEF ≦ MD in step (416), the process proceeds to step (419), it is determined that focus detection is impossible, the focus flag JF is cleared to 0, the focus detection inability flag AFNG is set to 1, and lens drive is prohibited. After the flag LMVDI is set to 1, the "focus detection" subroutine is returned at step (425). That is, in such a case, it is impossible to sufficiently detect the differential focus amount within the distance measuring range, and the contrast is low, and the signal from the distance measuring range appropriate for the subject has low contrast. LMVD
The I is set to 1, and the process returns to the AF control subroutine to display the focus detection impossible display and to execute the AF control subroutine again without driving the lens.

On the other hand, when it is determined that MAXDEF> MD in step (416), it is when the differential focus detection capability for the lens used in the relatively narrow distance measuring range of the subroutine "NPRED" or "MPRED" is insufficient. Therefore, in this case, for example, a case of a lens or a telephoto lens occurs, and if the focus detection is performed by setting an appropriate distance measurement range for the lens used, the contrast may not be low. Therefore, in this case, the process proceeds to step (417) and the AGC range selection flag AGCFLG
Is set to 1, and the "AF control" subroutine itself is returned at step (418). That is, in the above case, the focus or focus detection is not determined, and the subroutine "NP control" is executed in the next "AF control" subroutine.
Instead of "RED" and "MPRED", "WPRED" is used from the beginning to detect the amount of defocus.

Now, when the "AF control" subroutine is called again with the AGC range selection flag AGCFLG set to 1,
In the "image signal input" subroutine executed before the "focus detection" subroutine, as described above, the entire area AGC is used.
In this state, the image signal accumulated is input. Then, when the "focus detection" subroutine is called, the step (40
In 3), the state of the flag AGCFLG is detected, and this time, the process proceeds to step (420), and the differential focus detection subroutine "WPR
ED ”is executed. "WPRED" is "NPRED" or "MP
Compared to "RED", a wide area of the image signal is calculated, and the maximum value of the defocus amount detected by it is also large.

When the execution of the subroutine "WPRED" is completed, the flag AGCFLG is cleared in step (421). This is because the next "AF control" will again use the subroutine "NPRED" or "M
This is to execute "PRED".

Next, at step (422), the state of the low contrast flag LCFLG is detected. LCFLG is a flag created in "WPRED" of step (420). If LCFLG is 1, it is determined that the subject has low contrast and the process proceeds to step (419) to determine that focus cannot be detected. (425)
Then, the "focus detection" subroutine is returned. If the flag LCFLG is 0 in step (422), step (42
Go to 3) and compare the absolute value of the defocus amount DEF detected and the constant SDFLD. SDFLD represents the upper limit of the defocus amount that can be regarded as the vicinity of focus.

If | DEF |> SDFLD, move to step (424), focus flag JF, focus detection failure flag AFNG, lens drive prohibition flag
After clearing all LMVDI, the "focus detection" subroutine is returned at step (426). At step (423), if | DEF |> SDFLD is not satisfied, that is, if it is within the in-focus vicinity range, the process shifts to step (419) and focus detection is performed as in the case where LCFLG is 1 at step (422). It is impossible. This is because the subroutine "WPRED" is "NPRE
"WPRED" because it is executed when the differential focus detection result is low contrast in "D" and "MPRED".
The fact that the differential focus detection result is within the in-focus vicinity range is considered to be the detection of the differential focus amount of the subject outside the ranging frame FFRM shown in FIG. Therefore, if the focus determination or lens drive is performed with this defocus amount, the subject outside the range-finding frame will be focused, and in order to avoid it, the result is focused by the subroutine "WPRED" as described above. If it is within the vicinity range, the focus detection is forcibly impossible.

The operation of the "focus detection" subroutine is summarized with respect to Fig. 9 (e). Normally, the subroutine "NPRED" or "MPRED" (one of the two is selected according to the focal length of the lens) is used to determine the defocus amount. When detection is performed and the result is low contrast, recalculation is performed by the subroutine "WPRED" in the next "NF control" only when the telephoto lens is not mounted in the auxiliary light mode. Further, when “NPRED” and “MPRED” are executed, the sensor is accumulated in the central AGC state, and when “WPRED” is executed, the sensor is accumulated in the entire AGC state.

Further, when using the auxiliary light, if the low contrast is detected, the focus detection by the "MPRED" or "NPRED" is immediately performed in the auxiliary light mode without executing "WPRED".

That is, in the focus detection subroutine, first, the calculation target area of NPRED or MPRED is selected corresponding to the focal length, and the central AGC is selected as the AGC at this time to match the calculation target area with the AGC area. If the low contrast is not detected in the defocus amount detection of the image signal obtained in the area, the lens drive and the focus display according to the detected defocus amount are performed. In addition, when it is determined that the contrast is low, the differential focus detection capability in the calculation target region is larger than the maximum differential focus amount in the lens,
That is, there is sufficient differential focus detection capability, and the focus detection impossible display or the like is performed only when the detected differential focus amount for the target subject in the ranging frame properly represents the differential focus amount for the subject.

In addition, the above-mentioned diff orcus detection ability is smaller than the maximum diff orcus amount of the lens, that is, the maximum diff orcus amount of the lens used is larger than the diff orcus detection capability of the NPRED and MPRED routines, and the diff orcus detection originally suited to the maximum diff orcus amount of the lens used. If the low contrast determination is not performed if the defocus amount is detected with the ability (the calculation target area is large), the flag AGCFLG is set to 1, the calculation target area is set to be large, and the WPRED subroutine is executed. Sometimes the AGC is set as the whole area AGC to match the calculation target area. When the low contrast is determined by this WPRED subroutine, the focus detection impossible display is performed. Also, when the judgment of low contrast is not made,
When the diff orcus detected by the WPRED routine is large, the lens is driven based on the diff orcus amount, and when the diff orcus amount is within the in-focus vicinity, it is possible to determine that the subject outside the ranging frame is in focus. Since it is not focused on the original subject (subject captured in the ranging frame), it is determined that focus detection is impossible,
Display impossible.

Therefore, the AGC area matches the calculation target area, and it is possible to always perform an appropriate AGC operation. The differential focus amount can be correctly detected in the calculation target area that matches the lens used and the maximum differential focus amount, and the calculation target area can be measured. This makes it possible to prevent the subject outside the distance measuring frame from being in focus when switching from the inside of the distance frame to the area covering the outside.

In addition, the calculation target area is automatically selected according to the subject situation, and the focus detection operation is performed as appropriately as possible.

Also, select the calculation target area NRGN, MRNG according to the focal length of the lens, and when the focal length is small, NRGN is large and MR is large.
Since GN is selected, image processing is performed on the calculation target area suitable for the focal length, and proper focus detection is performed.

FIG. 9 (f) shows the differential focus detection subroutine "NP
The flow charts of "RED", "MPRE", and "WPRED" are shown.
The functions of the three subroutines are 2 from the given image signal.
The amount of image shift is detected, and then the amount of defocus is calculated, and a specific method has been previously disclosed by the present applicant in Japanese Patent Application No. 61-160824. Therefore, although detailed description is omitted, basic calculation is performed as follows.

A (I) and B (I) are signals of two images, respectively. f
{} Is a function of max {a, b}, min {a, b}, the former means extracting the larger value of a and b, and the latter means extracting the smaller value.

As described above, X (K) targets a specific range of the image signal, and the range is different between "NPRED", "MPRED", and "WPRED". The range is defined by the variables HB and NPX in the previous equation. Explaining with reference to FIG. 9 (f), when the defocus amount detection subroutine "NPRED" is called in the "focus detection" subroutine, the microcomputer computer P is called at step (502).
In the variable area HB set on the RAM of RS, the constant NHB is
If the constant NNPX is stored in and the "MPRED" is called, the constants MHB and MNPX are respectively set in the variables HB and NPX in step (513).
However, if "WPRED" is called, the constants WHB and WNPX are stored in step (515), respectively. More specifically with reference to FIG. 8, NPGN, MRGN, and WRGN in the figure represent calculation target areas on the sensor array of the subroutines “NPRED”, “MPRED”, and “WPRED”, respectively. In the embodiment, the number of pixels in the sensor array is 40, and [0] from the end,
If you assign numbers such as [1] ..., [39], you will see "NP
The calculation target area NRGN of “RED” is {[12] to [27]}.

Therefore, the constants NHB = 12 and NNPX = 16 are set. Similarly, "MP
Since the calculation target area MRGN of “RED” is {[10] to [29]}, MHB = 10, MNPX = 20, and the calculation target area WRGN of “WPRED” is {[0] − [39]}. WHB = 0, WNPX = 40.

By the way, in steps (502), (503), and (504), in addition to the variables HB and NPX, the value of the variable MD is set. Variable MD
Represents the maximum detected defocus amount in each defocus amount detection subroutine, as described in the explanation of FIG. 9 (e). The role of this variable MD will be described below.

In the calculation shown in Expression (2), the evaluation amount X (K) is KB ≦ K ≦
The amount of shift between the two images is detected by calculating in the range of KE, but according to equation (2), the evaluation amount X (K) with K as a variable is obtained as the absolute value of K increases. The number M of pixels to be calculated decreases according to the formula M = NPX− | K | −1.

As a matter of course, if M becomes too small due to the increase of | K |, then the S / N ratio of X (K) decreases. Therefore,
In order to secure the calculation accuracy depending on the number M of calculation pixels, it is necessary to set the upper limit of | K | according to the number NPX of calculation target pixels. If NPX becomes large, the upper limit of | K | can also be made large, which means that it is possible to deal with a large amount of deviation between the two images, and therefore the ability to detect the defocus amount can be increased. .

Constants NMD, M in steps (502), (513), and (515)
MD and WMD are the upper limit of | K | allowed from NPX in each subroutine converted into the defocus amount.

It is difficult to unambiguously determine how small the calculation pixel number M can be because it depends on the S / N and required accuracy of the entire focus detection system, but the number of pixels of the sensor array in the embodiment of the present invention is 40. Since it is a pixel, the lower limit of M is 10
Let's set it as a pixel. Then in each subroutine
The upper limit of | K | is determined by M = NPX− | K | −1 as follows. The upper limit of | K | in “NPRED” is 16−10−1 = 5,
20-10-1 = 9 for "MPRED" and 40-10-1 = 29 for "WPRED". By multiplying these values by a constant C that converts the image shift amount into the defocus amount, the maximum detected defocus amount in each subroutine can be obtained. The constant C is a value determined from the configuration of the secondary optical system for focus detection. For example, if C = 2, the maximum detected defocus amount NMD of the subroutine "NPRED" is 5 × 2 = 10, and the same amount MMD of "MPRED" is 9 × 2 = 18, the same amount WMD of "WPRED" is 29 × 2 = 54
Becomes

Returning to the explanation of the flow chart in FIG. 9 (f) again, the variable MD and the variable MAXDEF are compared in step (503), but the above-mentioned value is stored in the variable MD, and the variable MD is stored.
MAXDEF has already been stored in the first step of the "focus detection" subroutine of the maximum defocus amount that can be taken by the attached photographing lens.

If the result is MD> MAXDEF, go to step (504), MD ≦ MA
If it is XDEF, move to step (505).

At step (504), the value of the variable MAXDEF is stored again in the variable MD, and the process proceeds to step (505). Step (505)
Then, the variable MD is obtained by dividing the variable MD by the constant C described above. This variable MSFT represents the upper limit of | K |.

The reason why the variable MD and the variable MAXDEF are compared in step (503) is that the variable MSFT needs to be calculated from the variable MD when the maximum defocus amount of the mounted lens is smaller than the maximum detected defocus amount of the defocus amount detection subroutine at that time. However, it is sufficient to use the smaller value. Therefore, if MD> MAXDEF, the value of the variable MAXDEF is stored again in the variable MD in step (504).

Next, in step (506), the lower limit KB and the upper limit KE of K shown in equation (2) are set according to the following equations.

KB = -MSFT + △ (3) KE = MSFT + △ In equation (3), the constant △ is added to KB and KE.
Is the image shift amount between the two images at the time of focusing as described above, and is an offset when setting KB and KE from the maximum defocus amount of the lens.

Next, in step (507), the image shift amount PR and the contrast amount ZD are obtained by the method presented in Japanese Patent Application No. 61-160824 based on the equation (2).

In step (508), the defocus amount is calculated from the image shift amount PR obtained in step (507) as in the following equation.

DEF = (PR- △) ・ C (4) That is, after subtracting the image shift amount Δ at the time of focusing from the image shift amount PR, the defocus amount DEF is calculated by multiplying the image shift amount by the coefficient C of the defocus amount. obtain.

In step (509), the contrast amount ZD obtained in step (507) is compared with the constant LCLVL. LCLVL is the lower limit value of the contrast amount that enables correct focus detection, and ZD ≧
When LCLVL, the low contrast flag LCFLG is cleared to 0 in step (510) because the contrast is sufficient, and when ZD <LCLVL, the low contrast flag LCFLG is set to 1 in step (511) because the contrast is insufficient. The detection of the defocus amount is completed by the step as it is, and the defocus amount detection subroutine "NPRED", "MPRED", "WP" is performed at the step (512).
"RED" is returned.

Since each NPRED, MPRED, and WPRED routine is configured in this way, the defocus amount is detected by the image shift amount in the calculation area corresponding to each routine, and each of the above-mentioned steps based on the defocus amount in each step described above. Processing is done.

Further, since the offset amount Δ is added to the offset value in the calculation process, the correct image shift amount is always detected.

It should be noted that in the embodiment, a dedicated image sensor array is provided near the image signal sensor array.
Although the AGC sensor is provided and described, the AGC sensor does not need to be dedicated, and the present invention is effective even for a sensor device configured to output an image signal as an AGC signal as it is. it is obvious.

〔effect〕

As described above, according to the present invention, when the range of the sensor output that is the target of the focus detection process changes, the optimum AGC area of the sensor is set to enable correct focus detection at all times.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the principle of focus detection of the present invention, and FIGS. 2, 3, 4, and 5 are the sensor SAA of FIG.
FIG. 6 is a waveform diagram showing a state of photoelectric conversion output of SAB, FIG. 6 is a circuit diagram showing a configuration of a sensor device used in the present invention, and FIG. 7 is an embodiment of a camera having a focus detection device according to the present invention. FIG. 8 is a circuit diagram, FIG. 8 is an explanatory diagram of a positional relationship between a fiber distance measuring frame and a sensor, and FIGS. 9 (a) to 9 (f) are explanatory diagrams showing programs for explaining the operation of the present invention. . SAA, SAB …… Sensor array, ST _{1 to} ST ₃ …… Photometric element, PRS …… Computer

Claims (1)

[Claims] 1. A light beam passing through an imaging optical system whose focus is to be detected is received by a first and a second light receiving section, each of which is composed of a plurality of photoelectric conversion elements, and each photoelectric conversion element in the first light receiving section. From the first output column from the second output column from each photoelectric conversion element in the second light receiving section, the position of the image on the first light receiving section and the image on the second light receiving section In a focus detection device that obtains a relationship and detects the focus state of the imaging optical system, an output sequence from each photoelectric conversion element in the first range of the first and second light receiving units, or a first range including the first range. When the output column from each photoelectric conversion element in the first range is selected by the extraction unit that selects the output column from each photoelectric conversion element in the two ranges and outputs as the output for the correlation calculation, The amount of light received by the photoelectric conversion element in the first range Then, the storage time control for the first and second light receiving sections is performed, and when the output row from each photoelectric conversion element in the second range is taken out by the extraction means, the photoelectric conversion elements in the second range are output. A focus detection device comprising a control circuit for performing storage time control for the first and second light receiving units based on the amount of received light.