JPH03220535A - Focus detecting device - Google Patents

Abstract

PURPOSE:To eliminate such inconvenience that auxiliary light is not emitted when necessary or emitted when not necessary by deciding whether or not the auxiliary light is emitted according to the focus detection result of the center area among plural subjects in a picture plane. CONSTITUTION:When the focus of a photographic lens LNS is in front of a film surface, object images formed on respective couples of arrays of sensors SNS are mutually close and when the focus is behind the film surface, the subject images are mutually separate. The relative position shift quantity of the object images is in specific function relation with the out-of-focus quantity of the photographic lens LNS, so proper arithmetic for sensor outputs is performed by the respective sensor SNS array couples to detect the out-of-focus quantity of the photographic lens, i.e. the defocusing quantity. Consequently, focus detection becomes possible with auxiliary lighting when a main object is in the center of the picture plane even if a night scene picture, etc., is taken, and the auxiliary light is not emitted even when the focusing detection is disabled for the background at the periphery of the picture plane.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a focal point of a camera, etc., which has an auxiliary light source for illuminating a subject and performs focus detection of a plurality of subject areas within the screen of a photographic lens. This invention relates to a detection device.

[Conventional technology]

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

In the above method, since there is only one set of focus detection system (optical system, sensor), it is possible to detect only the defocus amount of one subject area within the screen. Many methods have also been proposed for detecting the amount of defocus in a subject area.

Even if there are multiple subject areas to be focus-detected, 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, two areas should be covered by the depth of field). (driving the photographing lens to an intermediate focus position), it is necessary to select the subject area using some selection method and focus the photographing lens based on the amount of defocus detected in the selected area.

A common selection method is to select a subject area that is determined to be closest to the camera.

In addition, with the conventional focus detection device described above, even if the subject is low brightness or not low brightness, the brightness (
Since the amount of defocus cannot be detected unless there is a change in the reflectance (reflectance), an auxiliary lighting device is often provided to illuminate the subject in a pattern when focus cannot be detected.

When there are a plurality of subject areas for which focus detection is to be performed, it is more useful for the illumination device to be configured to illuminate the plurality of areas.

[Problem that the invention is trying to solve]

However, in the conventional example described above, the following inconvenience may occur when focus detection is performed on a plurality of subject areas using an illumination device.

In other words, if the condition for operating the illumination device is that the focus cannot be detected in all subject areas, the illumination device will not work if there is even one detectable area, for example, in night photos. In a situation where a person is in the screen and the background is bright, even if the subject area where the person is located cannot be detected as a focus, it will not be illuminated and the background will be in focus, which is extremely inconvenient.

If the lighting device operating condition is that there is at least one subject area where focus cannot be detected, then meaningless lighting will be performed in a situation where focus cannot be detected on the subject area where the background is located. , which also significantly reduces operability.

Furthermore, if the illumination pattern generated by the illumination device is made common to each subject area for the sake of simplicity, it may be difficult in principle to detect that illumination pattern depending on the configuration of the focus detection system. There may be a subject area. Even if it is possible to detect focus in these areas due to illumination, since the subject is difficult to photograph in the first place, the amount of defocus detected often contains a large error, and the amount of defocus in this area is the final value. If a certain amount of defocus is selected, the focus will be incorrect.

[Means to solve the problem]

The present invention aims to solve the above-mentioned problems, and the gist thereof is as follows.

In other words, auxiliary illumination (hereinafter referred to as "auxiliary light") is used when focus cannot be detected.
) is effective because it focuses on the fact that subjects such as people are relatively close to the camera, and that such subjects have a high probability of being located in the center of the screen. The aim is to set the illumination condition for the auxiliary light to be that the focus cannot be detected in a certain subject area. As a result, even in a situation like the night scene photograph described above, if the main subject is located in the center of the screen, focus can be detected using the auxiliary light, and even if the background located at the periphery of the screen is unable to detect focus, the auxiliary light will not be illuminated. I can do it.

A further object of the present invention is to prevent incorrect focusing by not selecting a subject area whose illumination pattern is difficult to detect in principle when using the auxiliary illumination device. It is intended to do so.

〔Example〕

Hereinafter, the present invention will be explained 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 visual field mask, and a cross-shaped opening MSK-1. Vertical openings on both sides M S K
-2, MS K 3. FLDL is a field lens and the three apertures MSK of the field mask
-1, MSK-2, and MSK-3, it consists of three parts FLDL-1, FLDL-2, and FLDL-3. DP is a diaphragm, and in the center there are a total of four openings DP-1a, DPlb, DP-4a, and D
P-4b, and a pair of two openings D in the left and right peripheral areas.
P-2a, DP-2b and DP-3a, DP-3b are provided, respectively.

Each region FLDL-1, FLDL-2, FLDL-3 of the field lens FLDL functions to image these aperture pairs DP-1, DP-2, DP-3 near the exit pupil of an objective lens (not shown), respectively. have. AFL has 4 pairs of lenses AFL-1a, AFL-1bSAFL
4a, AFL-4b, AFL-2a, AFL-2
b, A secondary imaging lens consisting of AFL3a and AFL-3b, which are arranged behind each aperture of the diaphragm DP in correspondence with each aperture thereof. SNS has 4 pairs of 8 sensor rows 5NSl
a, 5NS-1b, 5NS-4a, 5NS-4b
, 5NS2a, 5NS-2b, 5NS-3a, 5N
It is a sensor consisting of S-3b, and each secondary imaging lens AF
It is arranged to receive the image corresponding to L.

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). The peripheral openings of the field mask other than the center MSK-2, MSK
It is also possible to measure the distance to an object located at a position corresponding to -3.

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 FIG. 3. 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) and ROM.

It is a one-chip microcomputer (hereinafter referred to as microcomputer) having RAM and A/D conversion functions.

The microcomputer PR3 performs a series of camera operations such as an automatic exposure control function, an automatic focus adjustment function, and film winding and rewinding according to a camera sequence program stored in the ROM. For this purpose, the microcomputer PR5 uses communication signals So, SI, and 5CLK.

Using communication selection signals CLCM, C3DR, CDDR,
It communicates with the peripheral circuits inside the camera body and the control device inside the lens to control the operation of each circuit and lens.

SO is the data signal output from the microcomputer PR5, SI
is a data signal input to the microcomputer PR8, and 5CLK is a synchronization clock for 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 PR3 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 CLK, the buffer circuit LCM transmits each buffer signal L of 5CLK and SO through the camera-lens communication contact.
Outputs CK and DCL to the lens. At the same time, the buffer signal of the signal DLC from the lens LNS is output as the signal SI, and the microcomputer PR3 outputs the signal S in synchronization with 5CLK.
Input ■ as the lens data.

DDR is a switch detection and display circuit, and the signal C
Selected when DDR is “H”, So, Sl.

Controlled by microcomputer PR8 using 5CLK.

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 PR5 performs photometry and automatic focus adjustment when SWI is turned on, and performs exposure control and subsequent film winding when SW2 is turned on.

Note that the switch SW2 is connected to the "interrupt input terminal" of the microcomputer PH1, and even if the program is being executed when the switch SW2 is 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/
It is a motor for down and shutter spring charging,
Forward rotation and reverse rotation are controlled by respective drive circuits MDRI and MDR2. Microcomputer PR8 to MDRl, MDR
The signal MIF input to 2.

MIR, M2F, and M2R are signals for motor control.

MCI and MG2 are magnets for starting shutter front curtain and rear curtain travel, respectively, and signals SMGI and 5MG2. The amplification transistors TRI and TR2 are energized, and the microcomputer PR3 performs shutter control.

In addition, the switch detection and display circuit DDR.

Since the motor drive circuits MDRI, MDR2, and shutter control are not directly related to the present invention, detailed explanations thereof will be omitted.

LPR3 is an in-lens control circuit, and LPR3 is connected to the LPR3 circuit.
The signal DCL input in synchronization with CK 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 LPR8 analyzes the command according to a predetermined procedure, and determines 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 optical axis direction to perform focus adjustment. The amount of movement of the optical system is determined by a pulse signal 5EN of an encoder circuit ENCF that detects the pattern of a pulse plate that rotates in conjunction with the optical system using a photocoupler and outputs a number of pulses according to the amount of movement.
Monitored by CF, counted by counter in circuit LPR3,
When the count value matches the movement amount sent to the circuit LPR3, the LPR3 itself outputs the signal LMF.

Control motor LMTR by setting LMR to "L".

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. Furthermore, the configuration is such that it is possible to send the contents of the counter to the camera if there is a request from 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 the circuit LPR3 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 when a request is received from the camera-side microcomputer PR3, parameters corresponding to the current zoom position are sent to the camera.

The SPC is a photometric sensor for exposure control that receives light from the subject through the photographic lens, and its output 5spc is input to the analog input terminal of the microcomputer PR3, and is used for automatic exposure control according to a predetermined A/D conversion program. used.

SDR is a drive circuit for the focus detection line sensor device SNS, and is selected when the signal C3DR is “H”.
Controlled by microcomputer PR5 using o, Sr, and 5CLK.

Signal φ5 given from drive circuit SDR to sensor device SNS
ELO, φ5ELI is the signal 5EL from the microcomputer PR8
O, 5ELL itself, φ5ELO-“L” φ5EL
When I="L", sensor row pair 5NS-1 (SNS-1a
, 5NS-1b), φ5ELO-“H”, φ5EL
When I is “L”, sensor row pair 5NS-4 (SNS-4a).

5NS-4b), φ5ELO=“L”, φ5ELI=
When “H”, sensor row pair 5NS-2 (SNS-2a,
5NS-2b), φ5ELO= “H”, φ5EL1
= “H”, sensor row pair 5NS-3 (SNS-3a,
5NS-3b).

After the accumulation is completed, set 5ELO and 5ELI appropriately,
By sending clocks φSH and φHR3, 5ELO
, 5ELL (φ5ELO, φ5ELI) are serially output from the output VOUT.

VPI, VF6. VF6. VF41:! Each sensor row pair 5NS-1 (SNS-1a, 5NS-1b
), 5NS-2 (SNS-2a, 5NS-2b), 5
NS-3 (SNS-3a.

5NS-3b), 5NS-4 (SNS-4a, 5N
The voltage of the monitor signal from the subject brightness monitoring sensor placed near S-4b) rises at the start of accumulation, thereby controlling the accumulation of each sensor array.

Signals φRES, φVR3 are sensor reset clocks, φHR3, φSH are image signal readout locks, φTl, φT2. φT3. φT4 is a clock for ending the accumulation of each pair of sensor columns.

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 the image signal, and differential amplification is performed between this and the image signal. Output VIDEO
is input to the analog input terminal of the microcomputer PR3, and the microcomputer PR3 sequentially stores the digital value of the signal from the A/D conversion station into a predetermined address on the RAM.

Signals /TINTEI, /TINTE2. /TINTE3
°/TINTE4 is the sensor row pair 5NS-1 (
SNS-1a, 5NS-1b), 5NS-2 (SNS-
2a, 5NS-2b), 5NS-3 (SNS-3a, 5
NS-3b), 5NS4 (SNS-4a, 5NS-4
This is a signal indicating that the charges accumulated in b) are appropriate and the accumulation has been completed. Upon receiving this signal, the microcomputer PR3 executes reading of the image signal.

The signal ETIME 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 vP1 to VP4 at the time this signal becomes "H". Determine the readout gain of the corresponding pair of sensor columns.

CKI, CK2 are the above clocks φRES, φVR3
゜To generate φHRS and φSH, microcomputer PR3
This is the reference clock given to the sensor drive circuit SDR from

The storage operation of the sensor device SNS is started by the microcomputer PR3 setting the communication selection signal C3DR to "H" and sending a predetermined "accumulation start command" to the sensor drive circuit SDR.

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 signals VPI to VP4 of the brightness monitoring sensor 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", respectively, independently.

In response to this, the microcomputer PR3 outputs a predetermined waveform to the clock CK2. The sensor drive circuit SDR generates clocks φSH and φHR3 based on GK2 and drives the sensor device S.
NS, the sensor device SNS outputs an image signal based on the clock, and the microcomputer PR3 converts the output VIDEO input to the analog input terminal using its internal A/D conversion function in synchronization with CK2 that it outputs. After A/D conversion,
The signals are sequentially stored as digital signals at predetermined addresses in the RAM.

The operations of the sensor drive circuit SDR and the sensor device SNS have previously been 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 be described here. A detailed explanation will be omitted.

AUXL is an auxiliary light unit for illuminating the subject when focus cannot be detected. Output terminal CAU of microcomputer PR3
When XL becomes “H”, transistor AT
R is turned on and the light emitting diode ALED is energized. A
The light beam emitted by the LED illuminates the subject through the action of the auxiliary light lens ACNS.

The state of illumination will be explained using FIGS. 4(a) and 4(b).

FIG. 4(a) is an explanatory diagram before illumination. VW represents the screen corresponding to the field of view, area 1 (RGNI),
Region 2 (RGN2), Region 3 (RGN3), Region 4
(RGN4) are the sensor rows 5M5-1 and 5M, respectively.
5-2° 5NS-3 and 5NS-4 represent the subject area within the screen receiving light. That is, the configuration is such that a light flux from the subject area of RGNI enters the sensors 5NS-1a, 1b via the photographic lens and the focus detection optical system.

Now, when the auxiliary light is activated when the focus cannot be detected, the subject is illuminated in a pattern as shown in FIG. 4(b). Each pattern is generated by a mask (not shown) located between the light emitting diode ALED and the lens ALNS, and the pattern APTI corresponds to the subject area RGNI,
RGN4 is illuminated, APT2 is illuminated to cover region RGN2, and APT3 is illuminated to cover region RGN3.

Each pattern has a similar shape with luminance variation in the vertical direction. This is area 1. 2. This is because area 1.2.3 has a configuration in which focus detection is performed based on luminance changes in the vertical direction, and in area 1.2.3, focus detection is possible based on the illumination pattern even if the pattern of the subject is poor. Therefore, in this pattern, unless there is a change in the brightness of the original subject in the horizontal direction, focus detection will not be possible in the area RGN4 even if the area is illuminated with auxiliary light.

As described above, the microcomputer PR3 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.

FIG. 6(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 (101) in FIG. 6(a). In step (102), the state of the switch SWI, which is turned on by pressing the release button in the first stage, is detected, and if it is off, the process moves to step (103), where variables and flags are initialized. If the switch SW1 is on, the process moves to step (104) and the camera starts operating.

In step (104), a ``rAE control'' subroutine for photometry, state detection of various switches, display, etc. is executed. A
Since the E control 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 (105).

In step (105), the "rAF control" subroutine is executed. Here, sensor accumulation, focus detection calculations, and automatic focus adjustment operations for driving the lens are performed. When the "subroutine rAF control" is completed, the process returns to step (102) and steps (104) and (105) are repeatedly executed until the power is turned off.

Note that the flowchart of this embodiment does not describe the release operation, but since the release operation is not directly related to the present invention, it is intentionally omitted.

FIG. 1 is a flowchart of the "subroutine rAF control" executed in step (105).

When "subroutine rAF control" is called, the process goes through step (001) and executes AF control from step (002) onwards.

In step (002), it is determined whether the current auxiliary light is emitted and focus detection is in the 133 mode (hereinafter referred to as "auxiliary light mode"), and if so, the process moves to step (003).

In step (003), the number of times the auxiliary light is emitted is checked, and if the auxiliary light has already been emitted twice, the process is branched off to step (005).
). That is, in this embodiment, the auxiliary light is set to be emitted only twice.

In step (003), if the number of times of light projection is less than two, the auxiliary light is turned on in step (004), and the process moves to step (005). As mentioned above, the method of lighting the auxiliary light is that the microcomputer PR5 sets the output terminal CAUXL to “H”.
” is executed.

In the following step (005), a subroutine "accumulation start" is executed. This subroutine is a routine that starts the accumulation operation of the sensor.

In the next step (006), a subroutine "image signal input and focus detection calculation" is executed. This subroutine monitors the accumulation status of the four sensors of this embodiment, sequentially inputs image signals from the sensor that has completed accumulation, and defocuses the subject area covered by that sensor based on the input image signals. This is a subroutine that detects the amount.

Regarding the specific calculations of the subroutines ``Start accumulation'' and ``Image signal input and focus detection calculations,''
Since this invention is disclosed in Japanese Patent Application No. 3-216905, Japanese Patent Application No. 61-160824, Japanese Patent Application No. 1-291130, etc., a detailed explanation of the present invention will be omitted.

It should be noted that through the above processing, the defocus amount is obtained for each of the four subject areas of the example, and it is also assumed that it is determined whether the focus is detectable or not, etc., using a known method based on the contrast of the image signal, etc. .

When the subroutine of step (006) ends, the process moves to step (007).

In step (007), it is checked whether the auxiliary light is on or not;
If the light is on, the process moves to step (021); otherwise, the process moves to step (OOS).

First, a case where the auxiliary light is not turned on will be explained.

In step (OOS), the area selection mode is determined. The area selection mode includes a mode in which one area is automatically selected from the four subject areas in this embodiment (referred to as "auto mode"), and a mode in which the photographer arbitrarily sets an area (referred to as "arbitrary mode"). ), and this mode setting is
This is done by the microcomputer PR3 shown in the figure recognizing the state of the switch group SWS via the switch detection circuit DDR. In other words, when a specific switch in the SWS is ON, it is in "automatic mode", and when it is OFF, it is in "arbitrary mode".
It can be determined as follows.

In the case of "arbitrary mode", the ON/OFF setting of a specific switch in the switch group SWS is done in the same way as the mode setting method.
It is determined in advance which subject area to arbitrarily select in the F state, and the state is detected via the switch detection circuit DDR to set the area to be selected.

Now, in step (008), if the selection mode of the subject area is set to "automatic mode", the process moves to step (009).

In step (009), it is determined whether focus cannot be detected in both area 1 and area 4, and if so, the process moves to step (010). Regions 1.4 are shown in Figure 4 (
This corresponds to the subject area RGNI,4 in a), and is the area at the center of the screen. Therefore, the process moves to step (010) when the focus cannot be detected on the subject area at the center of the screen.

In step (010), the number of times the auxiliary light is projected is checked, and if the auxiliary light has already been projected twice, the process branches to step (022).

If the number of times is less than 2, the process moves to step (011), and the accumulation time of the sensor 5NS-1 in the subject area 1 is checked, and if it is 10 msec or less, the process branches to step (022).

If the accumulation time is longer than 10ms, step (012
), and it is then determined whether the accumulation time of the sensor 5NS-1 in region 1 is longer than 100 msec.

If it is longer than 100 msec, the process branches to step (014) to set the auxiliary light mode, and then returns to the "rAF control" subroutine in step (015). The accumulation time of sensor 5NS-1 is from 10ms to 100msec.
If it is within m seconds, move to step (013),
The lowest value of the image signal in the subject area 1 is checked, and it is determined whether this value is smaller than a predetermined threshold value 8th. If it is smaller, the process branches to step (022), and if not, the process moves to step (014) to set the auxiliary light mode in the same way as when the accumulation time is longer than 100 msec.

If the selection mode of the subject area is "arbitrary mode", in step (OOS), the process moves to step (016).

In step (016), it is determined whether or not focus detection is possible in the preset selected area of the subject, and if detection is not possible, the process moves to step (017).

Steps (017) to (0
20) is the step (01) executed in “automatic mode”.
The processing content is the same as in 0) to (013), except that in the "automatic mode", the object to be processed is the object region l, whereas in the "arbitrary mode", the object is the selected region.

To summarize steps (OOS) to (020), when the area selection mode is "auto mode", consider area 1, which is the subject area in the center of the screen, in the same way as the selection area in "arbitrary mode", and Focus detection results and accumulation time,
Whether or not to use auxiliary light is determined based on the state of the image signal.

The meaning of the determinations in steps (013) and (020) will be explained using FIGS. 5(a) and 5(b).

FIG. 5(a) shows an image signal when focus detection is performed on a subject with little brightness change, and the lowest value B of this image signal exceeds a predetermined threshold value Bth.

FIG. 5(b) is an example of an image signal when focus detection is performed on, for example, a black and white edge-shaped object in a large defocus state. The lowest value B in this case is considerably smaller than the threshold value Bth. In most cases, it is correct to assume that the reason why the focus detection result becomes undetectable even though the image signal in this example has a considerable luminance change is due to a large defocus state. Therefore, by setting the threshold value Bth as shown in the figure and not using the auxiliary light when the lowest value B is even smaller than this, it is possible to prevent unnecessary projection of the auxiliary light.

Returning to FIG. 1 again, in this embodiment, even if focus cannot be detected when the accumulation time of the subject area of interest is 10 msec or less, the auxiliary light is not used and the focus is detected between 10 msec and 100 msec. A sequence is adopted in which the auxiliary light is used only when the minimum value of the image signal is greater than a predetermined value, and the auxiliary light is always used when the minimum value of the image signal is longer than 100 msec.

If it is determined in step (014) that the auxiliary light is to be used, the focus detection results up to this point are not used at all, and the subroutine "rAF control" is returned in step (015). Therefore, when the "next rAF control" subroutine is called, the auxiliary light is emitted from the beginning to perform focus detection.

Now, if the auxiliary light is on in step (007), the auxiliary light is turned off in step (021) without executing steps (OOS) to (020), and the process moves to the next step (022). do.

Focus detection using an auxiliary light is already in auxiliary light mode. Therefore, there is no need to perform the process of determining the use of the auxiliary light in steps (OOS) to (020), and there is no meaning in determining the accumulation time based on the state in which the auxiliary light is used.

In step (022), a subroutine "area selection" for selecting a subject area is executed.

A flowchart of the subroutine is shown in FIG. 6(b).

When the subroutine is called, the process goes through step (201) and then executes the processing from step (202) onwards.

If the selection mode of the subject area is "arbitrary mode" in step (202), the process branches to step (212), and the subroutine "Area Return "selection".

If the area selection mode is “auto mode”, step (2)
03), it is determined whether or not the focus of the subject area 1 can be detected, and if it is possible, the process branches to step (205).

In step (205), it is determined whether focus detection was performed using an auxiliary light, and if so, step (205) is performed.
The process branches to 9) and sets the subject area 1.2.3 as a candidate area for selection. That is, the areas 1, 2, and 3 are respectively the fourth
RGN 1 shown in figure (a).

RGN2. It is compatible with RGN3, and as explained earlier, the auxiliary light irradiation pattern is RGNI, RGN2゜RGN.
Since there is a brightness change in the vertical direction suitable for area 3, if area l, which is one of the areas at the center of the screen, can be focused, area 1.
2. One area is selected from among the three areas. For subject area 4, it is not expected that focus detection results will be improved much by using fill light, and if area 4 were to be detected and selected as a candidate, detection would be due to the illumination pattern that area 4 is not good at. The result may be adopted, and in this case, it is conceivable that the defocus amount with a large detection error is set as the final defocus amount. Taking this into consideration, this embodiment is configured to give priority to area 1 over area 4 even in the same central area of the screen when using the auxiliary light.

In focus detection without using auxiliary light, there is no difference between area 1 and area 4, so in step (206) it is determined whether focus detection is possible for subject area 4.

If the subject area 4 is focus detectable, step (21
0), and all subject areas are selected and set as candidates.

If the focus cannot be detected in area 4 in step (206), the process moves to step (209), and as a matter of course, area 1. 2. 3 is selected as a candidate.

In step (203), if focus detection is not possible for subject area 1, the process moves to step (204), and the detection result for area 4 is determined in the same manner as in step (206). Then, according to this determination, steps (207) and (208
) and set the selection candidates for each.

Once the selection candidates are set in steps (207) to (210), the process moves to the next step (211), where the selection candidate area is selected to be focus detectable and exhibiting the defocus amount of the most rear focus. Select the subject area. The fact that the area exhibits the most rear defocus amount means that the subject being observed in that area exists at the closest distance to the camera. Therefore, in this embodiment, the object closest to the camera is selected from among the plurality of objects.

When the selection in step (211) is completed, step (2
12), the defocus amount of the selected area is set as the final defocus amount, and the next step (213) is performed.
Returns the subroutine "area selection".

When the execution of the subroutine is finished, return to Figure 1 and
The process moves to the next step (023).

In step (023), it is determined whether the final focus detection result is impossible, and if so, step (03)
Branch to 2).

In step (032), it is determined whether the current focus detection was focus detection using an auxiliary light, and if so, the process branches to step (030) and returns to the "rAF control" subroutine. If the auxiliary light is not used, the process moves to step (027). Step (027)
The subsequent processing is related to search lens driving, which will be described later, and in this embodiment, step (032
) branch judgment is provided.

In step (027), it is determined whether one search lens drive has already been completed, and if it has already been completed, the process branches to step (030) and returns to the subroutine rAF control. If the process has not been completed yet, the process moves to step (028) and the subroutine "search lens drive" is executed.

This subroutine is an operation that repeatedly performs focus detection while driving the lens to the close-up side or to the infinity side when focus cannot be detected. Explanation will be omitted.

When the subroutine "search lens drive" is completed, the process moves to step (029), where the auxiliary light mode is canceled and the number of times the auxiliary light is projected is initialized. This is to provide another opportunity for focus detection using the auxiliary light at the end of the search lens driving operation. In other words, when the focus cannot be detected, first it is determined whether or not to use the auxiliary light, and if it is, the second
Focus detection is performed by emitting light up to 30 times, and if focus still cannot be detected, search lens drive is performed. Since the distance ring positions of the photographing lenses are generally different, it is possible to detect the focus by using the -degree auxiliary light at the distance ring position (continuity is at the infinite end position) after the search lens is driven. Since this can be expected, the above-mentioned operation is performed.

When step (029) is completed, step (030)
Then, the subroutine "rAF control" is returned.

Now, in step (023), if focus detection is possible, the process moves to step (024), where it is determined whether the final defocus amount is within a range that can be considered to be in focus, and the in-focus state is determined. If there is, the process branches to step (031), executes the subroutine "in-focus display", and displays the focus in the viewfinder; if it is not in focus, it branches to step (031).
25), the subroutine "lens drive" is executed, and the photographing lens is driven based on the amount of defocus.

The same subroutine was filed in Japanese Patent Application No. 61-1608 by the present applicant.
Since it is disclosed in Publication No. 24, etc., detailed explanation will be omitted.

When the subroutine "lens drive" in step (025) or the subroutine "focus display" in step (031) is completed, the process moves to step (026) and returns to the "rAF control" subroutine.

After the subroutine ends, as shown in the flowchart shown in FIG. 6(a), as long as the switch SW7 is ON, "AE control J rAF control" is executed alternately.

The operations in the above flow are summarized as follows.

If the focus can be detected, in this case step (002).

(005), (006), (007),'(008
), (009) or (016) to proceed to (022). Therefore, in (022), when the arbitrary mode is selected, the defocus amount of the selected area is selected, and when the automatic mode is selected, the defocus amount of the area of the rearmost bin among each area is selected, and steps (024), (025), (031)
), when the lens is in focus, an in-focus display is made, and when the lens is out of focus, the lens is driven to the above-mentioned defocus amount to perform focusing.

Step (009) or (016) during the above operation
), if it is determined that both the sensors in areas 1 and 4 are unable to detect focus, or if it is determined that the sensor in the selected area is unable to detect focus, steps (019) to (014) or (01) are performed.
7) to (020) are executed. Therefore, in automatic mode, the storage time of the sensor in area 1 is long (100ms).
or more) or the accumulation time is the appropriate time (10ms x 10
0 ms) and the lowest value of the image signal is equal to or higher than a predetermined level, the mode shifts to the auxiliary light mode.

Therefore, in the defocus state, auxiliary light projection is prohibited. On the other hand, in the arbitrary mode, the output of the sensor in the selected area is determined according to the same determination conditions as in the automatic mode, and it is determined whether or not to emit the auxiliary light.

If the auxiliary light mode is set, repeat step (002).
), return to (003), (004), (005
), (007).

(021) is executed and a focus detection operation is performed under the projection of the auxiliary light. After this (022), in the arbitrary mode, the amount of defocus in the selected area is determined, and in the automatic mode, the amount of defocus in the predetermined area is determined by the above-mentioned automatic selection. After that (023), when the sensor output of the selected area allows focus detection, focusing is performed based on the defocus amount.

On the other hand, when it is determined that focus detection is not possible even if the auxiliary light is projected, it is determined in step (032) that the auxiliary light has been projected for the current focus detection, and the process returns.

Thereafter, the focus detection operation is performed again under the projection of the auxiliary light, and even if the result is that the focus cannot be detected, the process similarly returns and executes the focus detection operation again. At this time, since the auxiliary light has already been emitted twice, step (004) is not executed, that is, focus detection is performed without the auxiliary light being emitted, and step (008), (009) or (008) is performed.
), (009), (010) or (008)
, (016) or (008), (016).

Proceed to (022) and (023) via (017). Even in this case, if focus cannot be detected (032)
The process proceeds to (027) and (028) via (027) and (028), where search lens driving is performed. In the search lens drive routine, the focus detection operation is performed while driving the lens, and if it is determined that the focus cannot be detected as a result, the subroutine directly returns to the AF control subroutine of step (001), and the focus detection operation described above is performed. resume. On the other hand, during search lens drive operation, the lens is moved over the entire drive range (from close range to infinity).
If the focus cannot be detected even if the lens is moved, hold the lens at a predetermined position (close or infinity) and proceed to step (029).
), cancel the auxiliary light mode, initialize the number of flashes, and then return. In this way, when the return is made after the search operation and the focus detection operation is restarted, the focus detection is performed without emitting the auxiliary light described above, and if an appropriate amount of defocus is detected as a result, then the The focus will be adjusted accordingly. On the other hand, if the focus cannot be detected even when the focus is not illuminated, the auxiliary light is emitted as described above and the focus is detected, and if the focus is still not detected, the auxiliary light is emitted again. Perform focus detection. If the focus cannot be detected even if focus detection is performed by emitting the auxiliary light twice after the end of the search operation, focus detection will be performed in the state in which the auxiliary light is not emitted.

In the embodiments described above, there are two subject areas located in the center of the drawing, but it is clear that the present invention is more simply effective in the case of one subject area.

Further, in the above embodiment, only one subject area is excluded, but depending on the configuration of the focus detection system, the effects of the present invention are obvious even if there are a plurality of subject areas.

Also, if there are multiple fill lights, each with a different lighting pattern, for example, avoid lighting them at the same time, and exclude subject areas that are not good at that lighting pattern when lighting each fill light. You should do it.

〔Effect of the invention〕

As explained above, according to the present invention, it is determined whether or not to illuminate the auxiliary light based on the focus detection result of the area in the center of the screen among a plurality of subjects within the screen. This makes it possible to eliminate inconveniences such as not lighting when necessary, or lighting when there is no point in lighting.

Furthermore, when using the auxiliary light, by not selecting a subject area whose illumination pattern is theoretically difficult to detect, it is possible to prevent a fixed focusing operation.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a flowchart for explaining the main operations of the focus detection device according to the present invention, and FIG. 2 is an explanatory diagram showing a specific configuration example when the device according to the embodiment of the present invention is incorporated into a camera. 3 is a detailed diagram of the focus detection system, FIGS. 4(a) and (b) are explanatory diagrams of the illumination pattern of the auxiliary light in the example, and FIGS. 5(a) and (b) are the detailed diagrams of the focus detection system. Detailed explanatory diagrams of the invention, FIGS. 6(a) and 6(b) are explanatory diagrams showing flowcharts for explaining the operation of the embodiment of the present invention. SNS...Sensor, PH1...Microcomputer, LNS...Lens, AUXL...Auxiliary light unit Fig. 4 (&) Male d Fig. (b)

Claims (4)

[Claims] (1) Defocus detection means for repeatedly detecting the defocus state of a plurality of subject areas within the screen of a photographic lens; a selection means for selecting at least one of the plurality of subject areas as selection candidates; and illuminating the subject. A focus detection device comprising: an illumination means, wherein the selection means selects by excluding at least one specific subject area from selection candidates when the illumination means is activated. (2) The subject area that the selection means excludes from selection candidates while the illumination means is in operation is an area in which it is difficult in principle to detect the illumination pattern generated by the illumination means. A focus detection device according to scope (1). (3) a defocus detection means for repeatedly detecting the defocus state of a plurality of subject areas within the screen of the photographic lens; and a determination of whether focus detection is possible or not possible for each subject area based on the results of the defocus detection means; illumination means for illuminating the subject; and control means for operating the illumination means based on the result of the determination means for at least one specific subject area among the plurality of subject areas. A focus detection device comprising: (4) The focus detection device according to claim (3), wherein the specific subject area targeted by the control means is a subject area located at the center of the screen.