JPH03153204A - focus detection device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Application of the Invention) The present invention provides a defocus amount detection means for repeatedly detecting the defocus amount of a plurality of subject areas, and a defocus amount detection means for repeatedly detecting the defocus amount of a plurality of subject areas, and The present invention relates to a focus detection device including selection means for selecting.

(Background of the Invention) Conventionally, as a focus detection device for a camera, a light beam from a subject area that has passed through different exit pupil areas of a photographic lens is imaged on a pair of line sensors, and the subject image is obtained by photoelectrically converting the image. A well-known method is to detect the amount of defocus of a subject area by determining the amount of relative positional displacement of a pair of image signals.

In the above method, since there is only one set of focus detection systems (optical system, sensor), it is possible to detect only the defocus amount of one subject area. However, by preparing multiple sets of such detection systems, the defocus amount of multiple subject areas can be detected. Many methods have been proposed to detect this.

In the latter method, since there are multiple subject areas, there are also multiple detected defocus amounts. However, the number of subject areas that you want to focus on with the camera is ultimately one, or at most two areas (in this case, for example, intermediate information between the two is used for focus adjustment), so it is necessary to set the subject area based on some judgment condition. It is necessary to select the area and focus the photographic lens using the amount of defocus corresponding to the selected area.

A common selection method is to select the closest subject area to the camera and hold that selected area while the release button is on to prevent inadvertent lens drive oscillation. be.

However, with the selection method described above, even if the subject changes and the selected subject area is no longer the closest subject, the selected area will not change, and conversely, the selected area will not be retained. However, as mentioned above, the focus adjustment operation of the photographic lens may oscillate, which is extremely inconvenient.

(Objective of the Invention) An object of the present invention is to solve the above-mentioned problems, to prevent focusing on objects other than the main subject, to prevent oscillation of the photographic lens, and to perform optimal focusing operation. An object of the present invention is to provide a focus detection device that can be used to focus images.

(Features of the Invention) In order to achieve the above object, the present invention provides a first method for determining whether or not a selected subject area falls outside of a predetermined selection condition during repeated defocus amount detection operations. Whether a predetermined time has elapsed since the determination means and the first determination means have determined that the object is out of alignment (or whether a defocus amount detection operation has been performed a predetermined number of times).
and a second determining means that determines that the defocus is not out of focus according to the first determining means, and that the second determining means determines that the predetermined time has not elapsed (or the defocus exceeds a predetermined number of times). If it is determined (that the amount detection operation is not being performed), the selection operation by the selection means is prohibited, and the first determination means determines that the selection operation is off, and the second determination means If it is determined that a predetermined time has elapsed since the defocus amount was removed (or that defocus amount detection operations have been performed more than a predetermined number of times), the operation control is performed to allow a new selection operation by the selection means. means, so that when a predetermined period of time has elapsed since the selected subject area deviated from the predetermined selection conditions (or when the defocus amount detection operation has been performed more than a predetermined number of times), a new selection operation is performed. It is characterized by being made to perform.

(Embodiments of the Invention) Hereinafter, the present invention will be described in detail based on illustrated embodiments.

FIG. 3 is a diagram showing a schematic configuration of a focus detection device which is an embodiment of the present invention.

In the figure, MSK is a field mask, with a cross-shaped aperture MS at the center -1 and a vertically elongated aperture MS at the periphery on both sides -2
, has -3 in MS. FLDL is a field lens, with three apertures MSK-1 in the field mask;
Three parts FLD, corresponding to -2 to MS and -3 to MS
It consists of L-1, FLDL-2, and FLDL-3.

DP is an aperture, and there are 4 in total in the center, one pair each on the top, bottom, left and right.
Two openings DP-1a, DP-1b, DP-1c,
DP-1d, and a pair of two openings DP-2a, DP-2b, DP-3a, and DP-3b in the left and right peripheral areas.
are provided for each. The field lens FL
Each area of DL FLDL-1, FLDL-2, FLDL-
3 are these aperture pairs DP-1, DP-2, DP, respectively.
-3 in the vicinity of the exit pupil of an objective lens (not shown). AFL has 4 pairs of lenses in total AFL-1
a, AFL-1b, AFL-4a, AFL-4b,
AFL-2a, AFL-2b%AFL-3a, A
This is a secondary imaging lens composed of FL-3b, and is arranged behind each aperture of the aperture DP, corresponding to each aperture. SNS
4 pairs of 8 sensor rows 5M5-1a, 5NS-1b
, 5NS-4a, 5M5-4b%5NS-2a,
The sensor is composed of 5NS-2b%5NS-3a and 5NS-3b, and is arranged so as to receive the image corresponding to each secondary imaging lens AFL.

In the focus detection system shown in Fig. 3, when the focal point of the photographing lens is in front of the film plane, the subject images formed on each pair of sensor rows are close to each other, and when the focal point is behind the film plane, the subject images are close to each other. In this case, the subject images are separated from each other. This amount of relative positional displacement of the subject image has a specific functional relationship with the amount of defocus of the photographing lens, so if appropriate calculations are performed on the sensor outputs of each pair of sensor rows, the amount of defocus of the photographing lens, It is possible to detect the so-called defocus amount.

By adopting the configuration described above, it is possible to measure even objects whose light intensity distribution changes only in one direction, vertically or horizontally, near the center of the range photographed or observed by an objective lens (not shown). This makes it possible to measure the distance to objects located at positions corresponding to the apertures MSK-2 and MS-3 on the periphery of the field mask other than the center.

FIG. 4 shows the arrangement of a focus detection device having the focus detection system shown in FIG. 3 housed in a camera.

In the figure, LNS is a photographing lens, QRM is a quick return mirror, FSCRN is a focus plate, PP is a pentaprism,
EPL is the eyepiece lens, FPLN is the film surface, SM is the submirror, MSK is the field mask, ICF is the infrared cut filter, FLDL is the field lens, RMl, RM
2 is the first. The second reflection mirror, S) IMSK is a light shielding mask, DP is an aperture, AFL is a secondary imaging lens, AFP is a prism member having a reflection surface AFP-1 and an exit surface AFP-2, SNS is a cover glass 5NSCG and light receiving Face 5NS
This is a sensor with PLN.

The prism member AFP has a reflective surface AFP-1 on which a metal reflective film such as aluminum is deposited, and has the function of reflecting the light beam from the secondary imaging lens AFL and deflecting it to the exit surface AFP-2. ing.

FIG. 2 is a circuit diagram showing an example of a specific configuration of a camera equipped with a focus detection device as shown in FIGS. 3 and 4. First, the configuration of each part will be explained.

In FIG. 2, PH1 is a camera control device, which includes, for example, a CPU (central processing unit), ROM, RAM,
The microcomputer PRS is a one-chip microcomputer (hereinafter referred to as microcomputer) that has an A/D conversion function.
A series of camera operations such as automatic exposure control function, automatic focus adjustment function, film winding and rewinding, etc. are performed according to the camera sequence program stored in the OM. For this purpose, the microcomputer PR3 uses communication signals SO, SL, 5.
CLK, communication selection signal CLCM, C3DR, CDOR
is used to communicate with the peripheral circuits within the camera body and the control device inside the lens, and to control the operations of each circuit and lens.

SO is the data signal output from microcomputer PR3, SI
is a data signal input to the microcomputer PRS, and SCL is a synchronous clock of signals SO and SI.

LCM is a lens communication buffer circuit, and when the camera is in operation, it supplies power to the lens power supply terminal VL, and the selection signal CLCM from the microcomputer PRS is set to a high potential level (hereinafter referred to as "H", low potential level). is “L”
), it becomes a communication buffer between the camera and lens.

The microcomputer PR3 sets the selection signal CLCM to “H” and the S
When predetermined data is sent as a signal SO in synchronization with CL, the buffer circuit LCM transmits each buffer signal LCK of SO to SCL via the camera-lens communication contact.
, outputs DCL to the lens. At the same time, lens L
The buffer signal of the signal DLC from NS is output as the signal Sl, and the microcomputer PRS outputs the signal Sl in synchronization with SCL.
Enter as lens data.

DDR is a switch detection and display circuit, and the signal CD
Selected when OR is “H”, So, Sl, SCL
It is controlled by the microcomputer PR3 using .

That is, based on data sent from the microcomputer PR3, the display on the display member DSP of the camera is switched, and the on/off states of various operating members of the camera are notified to the microcomputer PR3 by communication.

SWI and SW2 are switches that are linked to a release button (not shown), and when the release button is pressed in the first step, SW is activated.
I is turned on, and then SW2 is turned on at the second stage of depression. The microcomputer PRS performs photometry and automatic focus adjustment when 8w1 is on, and uses SW2 on as a trigger to control exposure and then advance the film.

Note that the switch SW2 is connected to the interrupt input terminal j of the PRS, which is a microcomputer, and even if a program is being executed when the switch SW2 is turned on, an interrupt is generated by turning on the SW2, and control can be immediately transferred to a predetermined interrupt program.

MTRI is for film feeding, MTR2 is for mirror up/
This is a motor for down and shutter spring charging, and forward and reverse rotation is controlled by respective drive circuits MDRI and MDR2. MDRI from microcomputer PR3.

Signals input to MDR2 MIF, MIR, M
2F.

M2R is a signal for motor control.

MCI and MG2 are magnets for starting the movement of the front and rear shutter curtains, respectively, and the signals SMGI, 5MG2. The amplification transistors TR1 and TR2 are energized, and the microcomputer PR3 performs shutter control.

In addition, switch detection and display circuit DDR.

Since the motor drive circuits MDRI, MDR2, and shutter control are directly related to the present invention, detailed explanations thereof will be omitted.

LPR3 is an in-lens control circuit, and LC is connected to this circuit LPR3.
The signal DCL input in synchronization with the camera is data of a command from the camera to the photographic lens LNS, and the operation of the lens in response to the command is determined in advance.

The control circuit LPRS analyzes the command according to a predetermined procedure, and calculates the operation of focus adjustment and aperture control, and the operation status of each part of the lens (driving status of the focusing optical system, driving status of the diaphragm, etc.) and various parameters from the output DLC. (Open F number, focal length, coefficient of defocus amount vs. movement amount of the focusing optical system, etc.) are output.

This embodiment shows an example of a zoom lens, and when a focus adjustment command is sent from a camera, the focus adjustment motor LTMR is activated according to the driving amount and direction sent at the same time.
is driven by signals LMF and LMR to move the focusing optical system in the direction of the optical axis to adjust the focus.The amount of movement of the optical system is determined by using a photocoupler with a pulse plate pattern that rotates in conjunction with the optical system. pulse signal 5E of the encoder circuit ENCF which detects the movement and outputs a number of pulses according to the amount of movement.
It is monitored by the NCF and counted by the counter in the circuit LPRS, and when the count value matches the movement amount sent to the circuit LPR3, the LPR3 itself outputs the signals LMF and LMR.
L" to control motor LMTR.

Therefore, once the focus adjustment command is sent from the camera, the microcomputer PRS, which is the camera control device, does not need to be involved in lens driving at all until the lens driving is completed. If there is a request from the camera, the contents of the counter can be sent to the camera.

When an aperture control command is sent from the camera, a stepping motor DMTR, which is known for driving an aperture, is driven in accordance with the number of aperture stages sent at the same time. Note that since the stepping motor can be oven controlled, it does not require an encoder to monitor its operation.

ENCZ is an encoder circuit attached to the zoom optical system, and circuit LPRS receives a signal 5ENCZ from the encoder circuit ENCZ to detect the zoom position. Lens parameters at each zoom position are stored in the control circuit LPR3, and upon request from the camera-side microcomputer PRS, parameters corresponding to the current zoom position are sent to the camera.

The SPC receives light from a subject via a photographic lens. It is a photometric sensor for exposure control, and its output of 5 spc is input to the analog input terminal of the microcomputer PRS, and the A/D
After conversion, it is used for automatic exposure control according to a predetermined program.

SDR is a drive circuit for the focus detection line sensor device SNS, and is selected when the signal C5DR is “H”.
Controlled by microcomputer PR3 using o, SI, 5CLK.

Signal φ5 given from drive circuit SDR to sensor device SNS
ELO, φ5ELI is the signal 5E from the microcomputer PRS
LO,5ELI itself, φ5ELO="L゛, φ5
When EL1="L-", sensor row pair 5M5-1 (SNS
-1a, 5NS-1b), φ5ELO="H", φ5
When EL1="L", sensor row pair 5NS-4 (SMS-
4a, 5NS-4b), φ5ELO="shi", φ5E
When LI = “H”, sensor row pair SNS-2SN5-2
(S, 5NS-2b), $5ELO="H",
When $5EL1="H", sensor row pair 5M5-3 (S
MS-3a, 5NS-3b).

After the accumulation is completed, set 5ELO and 5ELI appropriately,
Then, by sending clocks φSH and φHR3,
The image signals of the pair of sensor rows selected by 5ELO, 5EL1 (φ5ELO, φ5ELI) are serially output from the output vouT.

VPI, VF6, VF6, VF441 each sensor row pair 5M5-1 (SNS-1a, 5NS-
1b), 5NS-2 (SNS-2a, 5NS-2b)
, 5M5-3 (SMS-3a, 5NS-3b)
, 5M5-4 (SNS-4a.

The voltage of the monitor signal from the subject brightness monitoring sensor placed near the sensor 5NS-4b) rises at the start of accumulation, thereby controlling the accumulation of each sensor array.

Signals φRES and φVRS are clocks for resetting the sensor, φHRS and φSH are clocks for reading out image signals, and φTl, φT2, φT3, and φT4 are clocks for ending the accumulation of each pair of sensor columns, respectively.

The output VIDEO of the sensor drive circuit SDR is an image signal obtained by taking the difference between the image signal VOUT from the sensor device SNS and the dark current output, and then amplifying the difference with a gain determined by the brightness of the subject. The above-mentioned dark current output is the output value of the light-shielded pixels in the sensor array, and SDR is the output value of the light-shielded pixels in the sensor array.
The output is held in a capacitor by the signal DSH from VIDEO, and differential amplification is performed between this and the image signal.
is input to the analog input terminal of the microcomputer PRS, and the microcomputer PRS A/D converts the signal and sequentially stores the digital value at a predetermined address on the RAM.

Signal /TINTEI, /TINTE2, /TI
NTE3 and /TINTE4 are each sensor row pair 5
M5-1 (SNS-1a, 5NS-1b).

5M5-2 (SNS-2a, 5NS-2b), 5
M5-3 (SNS-3a, 5NS-3b), 5M
5-4 (SNS-4a, 5NS-4b) is a signal indicating that the charges accumulated are appropriate and the accumulation is complete.
The microcomputer PR3 receives this and reads out the image signal.

The signal BTIME is a signal that provides the timing for determining the readout gain of the image signal amplification amplifier in the sensor drive circuit SDR, and the circuit SDR normally calculates the timing from the voltage of the monitor signals vPO to VP3 at the time when this signal becomes "H". Determine the readout gain of the corresponding pair of sensor columns.

CKI, CR2 are above 0 tsuku $RES, φv
R3.

This is a reference clock given from the microcomputer PRS to the sensor drive circuit SDR in order to generate φHR3 and φSH.

The microcomputer PR3 sets the communication selection signal C3DR to "H" and sends a predetermined "storage start command" to the sensor drive circuit SDR, thereby starting the storage operation of the sensor device SNS.

Thereby, photoelectric conversion of the subject image formed on each sensor is performed by the four sensor row pairs, and charges are accumulated in the photoelectric conversion element portion of the sensor. At the same time, the brightness monitor sensor signals VPI to VP4 of each sensor rise, and when this voltage reaches a predetermined level, the sensor drive circuit SDR changes the signals /TINTEI to /TINTE4 to "L'" independently. .

The microcomputer PRS receives this and outputs a predetermined waveform to the clock C2. The sensor drive circuit SDR generates clocks φSH and φHR3 based on CK2 and drives the sensor device SN.
S, the sensor device SNS outputs an image signal based on the clock, and the microcomputer PRS outputs an image signal C by itself.
2, the output VIDε0 inputted to the analog input terminal is A/D converted by the internal A/D conversion function, and then sequentially stored in a predetermined address of the RAM as a digital signal.

The operations of the sensor drive circuit SDR and the sensor device SNS have been previously disclosed by the present applicant in Japanese Patent Application Laid-Open No. 63-216905 as a focus detection device having two pairs of sensor rows, so they will not be described here. Detailed explanation will be omitted.

As described above, the microcomputer PRS receives the image information of the subject image formed on each pair of sensor rows, and then performs a predetermined focus detection calculation, thereby being able to determine the amount of defocus of the photographing lens.

Next, the automatic focus adjustment device for a camera having the above configuration will be explained according to the flowchart below.

FIG. 5(a) is a very rough flowchart of the entire sequence of the camera.

When power supply starts to the circuit shown in Fig. 2, the microcomputer P
R3 starts execution from step (000) in FIG. 5(a). In step (001), the state of switch SWI, which is turned on by pressing the first step of the release button, is detected, and if it is off, step ( 002) to initialize the selected sensor. If the switch SWI is on, the process moves to step (003) and the camera starts operating.

In step (003), a ``rAE control'' subroutine for photometry, detection of various switch states, display, etc. is executed. A
E sub-control Since it is not directly related to the present invention, a detailed explanation will be omitted. When the "subroutine rAE control" is completed, the process then moves to step (004).

In step (004), the "rAF control" subroutine is executed. Here, when the subroutine rAF control, which performs sensor accumulation, focus detection calculations, and lens drive automatic focus adjustment operation, returns to step (001) again and repeats steps (003) and (004) until the power is turned off. Execute it.

Although the flowchart of this embodiment does not describe the release operation, it is purposely omitted because the release operation is not directly related to the present invention.

FIG. 5(b) is a flowchart of the "subroutine rAF control" executed in step (004).

When the subroutine "rAF control" is called, the process goes through step (010) and executes the AF sub-control from step (011) onwards.

First, in step (011), it is determined whether or not there is AF sub-control for the first time when the switch SWI is turned on, and if it is the first time, the process moves to step (012) to initialize the selected sensor. .

Next, in step (013), the subroutine "accumulation start" is executed.
Execute. This subroutine is a routine that starts the sensor storage operation, and specifically, the sensor drive circuit S
An accumulation start command is sent to DR to start the accumulation operation of the sensor device SNS, and at the same time, each sensor accumulation end signal /TINTEI to /TINTE3 is sent from the circuit SDR.
This is a subroutine that enables the interrupt function so that the microcomputer PRS can execute the "storage completion interrupt".

As a result, when each of the four sensors 5NS-IN 5NS-3 completes storage, each storage completion interrupt is executed.

The end of accumulation for each sensor is signal /TINTEI ~ /TINT
It can be detected by the falling edge of E3, and these signals can be detected by the "human input terminal with interrupt function" of the microcomputer PRS.
It is connected to the. In FIG. 5(b), the dashed line ■ represents interrupt control, and the signal /TINTE
If an interrupt occurs by I~/TINTE3,
Control is transferred to each side-in routine shown in FIG. 5(C) via ``■'' in the same figure. Therefore, for example, sensor 5M5-
1 becomes appropriate and the signal /TINTEI from the sensor drive circuit SDR falls, in response to which it is possible to move to the interrupt routine after step (OSO) in FIG. 5(C). .

The interrupt routine after step (050) in FIG. 5(C) is a routine for inputting the image signal of the sensor 5NS-1.

After inputting the image signal of the sensor 5M5-1 at step (051), the interrupt routine is returned at step (052). The input of the image signal is achieved by serially A/D converting the output VIDEO input to the analog input terminal of the microcomputer PR3, and sequentially storing the digital data in a predetermined RAM area.

When the accumulation of sensors 5M5-2, 3M5-3, and 5M5-4 is completed, interrupt control is also performed in steps (053), (056), and (056) in FIG. 5(c), respectively.
The process moves to (059), and image signals from each sensor are input.

Regarding the subroutine "accumulation start" and the specific method of inputting image signals, the present applicant previously published Japanese Patent Application Laid-Open No. 63-216.
Since it is disclosed in No. 905 etc., detailed explanation will be omitted.

Returning to FIG. 5(b), the explanation will be continued.

Since the image signal input processing of each sensor is controlled by interruption, processing is given priority at any time when accumulation is completed during execution of focus detection calculations, etc. in steps (014) to (02ft) in the figure.

Now, when the sensor storage operation is started in step (013), the process moves to step (014).

In step (014), it is determined whether the focus detection calculation of the sensor 5M5-1 has been completed, and if it has not been completed, the process moves to step (OtS).

In step (015), it is determined whether or not the image signal input of the sensor 5NS-1 has already completed the interrupt processing, and if it has been completed, the process moves to step (016) and the sensor 5NS-1
A focus detection calculation is executed based on the image signal of M5-1. A specific calculation method for detecting the amount of defocus is disclosed in Japanese Patent Application No. 160824/1983 filed by the present applicant, so a detailed explanation will be omitted.

If the focus detection calculation of sensor 5NS-1 is not completed in step (014), or if the input of the image signal of sensor 5M5-1 is not completed in step (015), or if step (old 6) After the focus detection calculation of the sensor 5M5-1 is completed, the process moves to step (017).

Steps (017), (018), (019
), the above-described processing is performed on the sensor 5M5-2.

Further steps (02G), (021), (0
22), step (02) is performed for sensor 5M5-3.
3), (024).

At (025), the above-described processing is performed on each sensor 5NS-4.

In step (026), it is determined whether or not focus detection calculations corresponding to all sensors have been completed. If not, the process proceeds to step (014), and if all have been completed, the process proceeds to step (027). ).

To summarize so far, after starting the accumulation operation in step (013), step (014) to (02) wait for the image signals of each sensor to be read by interrupt processing.
By repeating step 6), focus detection calculations are performed sequentially from the sensor from which the image signal has been read.

When the focus detection calculations for all sensors are completed, step (
In step 027), it is checked whether the focus detection results of all the sensors are valid or invalid. In other words, it is determined whether the detection results of each sensor are valid or invalid based on the contrast and degree of coincidence of image signals that are obtained simultaneously in the process of focus detection calculation, and if the detection results of all sensors are invalid and defocus detection is If it is not possible, the process moves to step (032).

In step (032), the selected sensor is initialized, and the process moves to step (033).

In step (033), a subroutine "search lens drive" is executed. This is a control that anticipates an increase in contrast while driving the lens when the contrast of the subject is low, and is disclosed in detail in the aforementioned Japanese Patent Application No. 160824/1983.

If defocus detection was possible with at least one sensor in step (027), step (028)
) executes the subroutine "judgment".

The subroutine "judgment" is a routine for selecting the sensor that provides the final resultant defocus amount, and its flowchart is shown in FIG.

When the subroutine “judgment” is called, step (1
00) and then moves to step (l old).

In step (l old), the sensor that provides the most rear defocus amount among the detectable sensors is determined. If the amount of defocus is in back focus, it means that the photographic lens is in focus in the back of the subject imaged on the sensor, so it corresponds to the sensor that provides the most amount of defocus in back focus. The subject to be photographed is the subject closest to the camera. Therefore, in this embodiment, a focus adjustment operation is performed to focus on the closest subject.

In the next step (102), it is checked whether the sensor selected in the previous AF sub-control can be detected by the current focus detection operation, and if it is not possible, the process proceeds to step (107), and if it is possible, the process proceeds to step (107). Move to (103).

First, we will explain if it is possible.

In step (103), it is checked whether the sensor selected in the previous AF sub-control and the sensor determined this time in step (101) are the same, and if they are the same, step (
107).

If they are not the same, the process moves to step (104) and the current time T is input from the timer built into the microcomputer PRS. Subsequently, in step (105), it is determined whether the difference between the pre-stored time Ts and T exceeds ro, 5J seconds when converted into actual time. rO,5
J seconds is not particularly limited to this value, and is an example of the time for temporarily locking the selected sensor. If it is within rO, 5J seconds, the "judgment" subroutine is returned at the next step (106) without switching the selected sensor.

On the other hand, if it is determined in step (105) that the time difference exceeds r0,54 seconds, the process moves to step (107). That is, since rO,5J seconds have passed since the subject area corresponding to the sensor that has been selected so far is no longer the closest among the subject areas, the process branches to step (107) to switch the selected sensor.

In step (107), the sensor determined in step (101) is set as the new selected sensor, and then in step (108), the amount of defocus provided by the selected sensor is set as the final defocus.

In the next step (109), a timer value is input as the time when the selected sensor is newly selected, and this is set as Ts and R
Stored in AM, and then "determined" in step (110)
Return subroutine.

Returning to FIG. 5(b), "judgment" in step (028)
After executing the subroutine, in the next step (029), it is determined whether the photographing lens is in focus based on the amount of defocus finally obtained.If the lens is in focus, it is determined in step (030). Execute the subroutine "focus display",
The focus is displayed in the viewfinder, and the next step (034
) to return the "rAF control" subroutine.

If it is determined in step (029) that the focus is not in focus, the process moves to step (031) to drive the lens, and then returns to step (035). This lens drive method was disclosed in the patent application filed in 16082-1982 by the applicant.
Since it is disclosed in Publication No. 4, etc., detailed explanation will be omitted.

According to this embodiment, the selected subject area is set to the selection condition (
When a predetermined period of time has elapsed since the sensor no longer represents the rearmost defocus, a new selection operation is performed (step (10) in Figure 1).
3)-(104)→(105)→(107)), focusing is performed on a subject other than the main subject,
Further, the inconvenience of the oscillating operation of the photographing lens is eliminated.

(Correspondence between the invention and the embodiments) In this embodiment, the part that performs the operations of steps (014) to (026) in the sensor SNS and the microcomputer PRS is replaced by the defocus amount detection means of the present invention, and the step (026) in the microcomputer PRS is 101), the part that performs the operation of step (107) serves as the selection means, the part that performs the operation of step (102) serves as the first discrimination means, the part that performs the operation of step (103) serves as the second discrimination means, Steps (103)-(107
) (103) →(104) →(tOS)
→ (106) or step (103) → (104)
The parts that perform the operations -(105)→(107) respectively correspond to the operation control means.

(Modified example) In this embodiment, the selection operation is redone when a predetermined period of time has passed since the object corresponding to the selected sensor is no longer the closest object, but the same effect can be obtained by setting the predetermined number of focus detection operations during this predetermined period of time. is obtained.

(Effects of the Invention) As explained above, according to the present invention, when a predetermined period of time has elapsed after the selected subject area deviates from the predetermined selection conditions (or the defocus amount detection operation is performed more than a predetermined number of times). Since the camera now performs a new selection operation, it is possible to avoid focusing on objects other than the main subject or causing oscillation of the photographic lens, and to perform the optimal focusing operation. It becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the operation of the main parts in an embodiment of the present invention, and FIG. 2 is a diagram showing an optical system and electric block, which is a specific example of the configuration when the device is incorporated into a camera. FIG. 3 is a diagram showing details of the focusing optical system of the device shown in FIG. 2, FIG. 4 is a diagram showing a schematic configuration of a camera including the optical system shown in FIG. 3, and FIGS. 3 is a flowchart showing the overall general operation in one embodiment of the present invention. SNS...Sensor, PR3...Microcomputer, LNS...Lens.

Claims (2)

[Claims] (1) A focus detection device comprising a defocus amount detection means for repeatedly detecting the defocus amount of a plurality of subject areas, and a selection means for selecting an area that satisfies a predetermined selection condition from among the plurality of subject areas, a first determining means for determining whether or not a selected subject area falls outside of the predetermined selection conditions during repeated defocus amount detection operations; a second determining means for determining whether a predetermined time has elapsed since the determination of the first determining means; If it is determined that the selection operation is not performed, the selection operation by the selection means is prohibited, and the selection operation is prohibited for a predetermined period of time after the first determination means determines that the selection operation is not performed, and the second determination means determines that the selection operation is not performed. a focus detection device comprising: operation control means for allowing a new selection operation by the selection means when it is determined that the selection means has elapsed. (2) A focus detection device comprising a defocus amount detection means for repeatedly detecting the defocus amount of a plurality of subject areas, and a selection means for selecting an area that satisfies a predetermined selection condition from among the plurality of subject areas, a first determining means for determining whether or not a selected subject area falls outside of the predetermined selection conditions during repeated defocus amount detection operations; A second determining means determines whether defocus amount detection operations have been performed a predetermined number of times since the determination of the defocus amount; If it is determined that the defocus amount detection operation has not been performed more than a predetermined number of times, the selection operation by the selection means is prohibited, and the first determination means determines that the defocus amount detection operation is off; and an operation control means for allowing a new selection operation by the selection means when the second determination means determines that the defocus amount detection operation has been performed more than a predetermined number of times since the defocus amount has been removed. A focus detection device characterized by: