JPH03220514A - Focus detector - Google Patents

Abstract

PURPOSE:To eliminate a waste of time and save energy at the time of defocusing by providing a control means which operates a lighting means according to the results of a decision means, a measuring means, and a storage means. CONSTITUTION:An auxiliary light unit AUXL which lights a subject when focus detection is impossible turns on a transistor ATR through a resistance when the output terminal CAUXL of a microcomputer PRS goes up to 'H' to feed electricity to a light emitting diode ALED. The luminous flux emitted by the ALED lights the subject through the operation of a lens ALNS for auxiliary light. Further, when auxiliary light is emitted at the time of the failure in focus detection, the subject is lighted with a pattern. In this case, the microcomputer PRS receives image information on a subject image formed on respective sensor array couples and then performs specific focus detection arithmetic to know the quantity of defocusing of a photographic lens. Consequently, a waste of time originating from the auxiliary light projection is eliminated and the energy is saved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a focus detection device for a camera or the like having an auxiliary light source for illuminating a subject.

[Conventional technology]

Conventionally, a pair of light beams from a subject that have passed through different exit pupil areas of a photographic lens are received by a pair of accumulation-type sensor arrays.
A focus detection device that detects the amount of defocus of a photographic lens by determining the amount of relative positional displacement of the photoelectric conversion signal is well known. These passive focus detection devices cannot detect the amount of defocus if the subject has low brightness, or even if there is no change in brightness on the surface, so when focus cannot be detected, the subject cannot be detected in a pattern. In many cases, an auxiliary light source is provided for illumination.

[Problem that the invention is trying to solve]

However, in the conventional example described above, the condition for emitting the auxiliary light is that the focus cannot be detected and the brightness is low. However, if the subject brightness is even slightly low, the auxiliary light will be emitted, and in situations where focus cannot be detected due to large defocus, no matter how much auxiliary light is emitted, it will not be possible to detect the focus, and the auxiliary light will not be able to detect the focus. Responsiveness was wasted due to the accumulation time under floodlight, and energy was wasted due to lighting.

[Means to solve the problem]

The present invention aims to improve the drawbacks of the above-mentioned conventional example, and focuses on the fact that the minimum value of the image signal is sufficiently small when focus cannot be detected at the time of large defocus. The addition is made on the condition that the lowest value of the image among the output signals from the sensor is greater than a predetermined value, thereby providing a focus detection device that saves wasted time and energy during large defocusing. .

〔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 MSK-2 on the periphery of both sides
, MSK3. FLDL is a field lens, and the three apertures MSK-1, MSK of the field mask
-2, corresponding to MSK-3, three parts FLDL-1
, FLDL~2. It consists of FLDL-3. DP is a diaphragm, and there are a total of four apertures DP-1a, DP-1b, DP-4a, and DP-4b in the center, one pair each on the top, bottom, left, and right, and a pair of two apertures DP-2a in the left and right peripheral areas. ,
DP-2b, DP-3a, and 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, AF L -2b, AF
This is a secondary imaging lens consisting of L-3a and AFL-3b, and is arranged behind each aperture of the diaphragm DP, corresponding to each aperture. SNS has 4 pairs of 8 sensor rows 5NS-1a,
5NS-1b, 5NS-4a, 5M5-4b, 5
NS-2a, 5NS-2bSSNS-3a, 5NS-3
b, and is arranged 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). 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 1-chip microcomputer (hereinafter referred to as microcomputer) that has RAM and A/D conversion functions.

The microcomputer PR5 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 PR3 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 PR8, SI
is a data signal input to the microcomputer PR3, and 5CLK is a synchronization clock for signals So and Sl.

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 PR5 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 out as a signal SO in synchronization with CLK, the buffer circuit LCM outputs buffered signals LCK and DCL of S CLK and SO to the lens via the camera-lens communication contact. At the same time, the buffer signal of the signal DLC from the lens LNS is output as the signal S■, and the microcomputer PR3 outputs the buffer signal of the signal DLC as the signal SCLK.
The signal SI is input as lens data in synchronization with .

DDR is a switch detection and display circuit, and the signal C
Selected when DDR is H'', So, SI.

Controlled by microcomputer PR3 using 5CLK.

That is, based on the data sent from the microcomputer PRS, 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.
1 is turned on, and then SW2 is turned on at the second stage of depression. The microcomputer PR3 performs photometry and automatic focus adjustment when SW1 is turned on, and uses SW2 as a trigger to control exposure and subsequently advance the film.

Note that the switch SW2 is connected to the "interrupt input terminal" of the PRS, which is a microcomputer, and even if a 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 PR3 to MDRI, 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 LC is connected to this circuit LPRS.
The signal DCL input in synchronization with K is data of a command from the camera to the photographing lens LNS, and the operation of the lens in response to the command is determined in advance.

The control circuit LPR3 analyzes the command according to a predetermined procedure, and outputs the operation of focus adjustment and aperture control, 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 LPR5, 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 PR8, 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 controlled in an open manner, 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 requested by the camera-side microcomputer PR3, parameters corresponding to the current zoom position are sent to the camera.

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 microcomputer PR3, and after A/D conversion, automatic exposure control is performed according to a predetermined program. used for.

SDR is a drive circuit for the focus detection line sensor device SNS, and is selected when the signal C3DR is “H” and the SDR is
Controlled by microcomputer PR3 using ○, Sr, and 5CLK.

Signal φ5 given from drive circuit SDR to sensor device SNS
ELO, φ5ELL are signal 5EL from microcomputer PR3
O, 5ELI itself, φ5ELO="L" φ5EL
When 1=“L”, sensor row pair 5NS-1 (SNS-1a
, 5NS-1b), φ5ELO="H", φ5EL
When I = “L”, sensor row pair 5NS-4 (SNS-4
a.

5NS-4b), φ5ELO="L", φ5EL1=
When “H”, sensor row pair 5NS-2 (SNS-2a,
5NS2b), φ5ELO= “H”, φ5ELI−
When “H”, sensor row pair S N S -3 (S M S
-3a, SN S -3b).

After the accumulation is completed, set 5ELO and 5ELL appropriately,
By sending clocks φSH and φHR3, 5ELO
, 5ELI (φ5ELO, φ5ELL) are serially output from the output VOUT.

VPI, VF6. VF6. VF6 has each sensor row pair 5NS-1 (SMS-1a, 5NS-1b), SN
S-2 (SNS-2a, 5NS-2b), 5NS-
3 (SNS-3a,.

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

Signals φRES and φVR3 are sensor reset clocks, φHR3 and φSH are image signal readout clocks,
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 microcomputer PR8
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 PR8, and the microcomputer PR3 converts the same signal from analog to digital and sequentially stores the digital value at 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 (SMS-3a, 5
NS-3b), 5NS-4 (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 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. Normally, the circuit SDR calculates the timing from the voltage of the monitor signals VPI to VP4 at the time when this signal becomes "H". Determine the readout gain of the corresponding pair of sensor columns.

CKI and CR2 are reference clocks supplied from the microcomputer PR8 to the sensor drive circuit SDR in order to generate the above-mentioned clocks φRES, φVR8°φHR3, and φSH.

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 sets the signals /TTNTEI 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 CR2 and drives the sensor device S.
NS, the sensor device SNS outputs an image signal based on the clock, and the microcomputer PR3 uses its internal A/D conversion function to convert the output VIDEO input to the analog input terminal in synchronization with the CR2 output by itself. 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 WSNS 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 arrays, 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),
Area 2 (RGN2), Area 3 (RGN3), Area 4
(RGN4) are the sensor rows 5M5-1 and 5, respectively.
M5-2°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.

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

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
R5 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 SWI 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
E sub-control Since there is no direct connection with 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 l'-AF sub-control subroutine is executed. Here, sensor accumulation, focus detection calculations, and automatic focus adjustment operations for driving the lens are performed. subroutine rAF
When the control is completed, the process returns to step (102), and steps (104) and (105) are continued until the power is turned off.
Execute repeatedly.

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 the subroutine AF sub-control is called, the process goes through step (001) and executes the AF sub-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 for lighting the auxiliary light is that the microcomputer PR3 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 the present invention is disclosed in Japanese Patent Application No. 3-216905, Japanese Patent Application No. 61160824, 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 modes include a mode in which one area is automatically selected from the four subject areas of this embodiment (referred to as "auto mode"), and a mode in which the photographer arbitrarily sets an area (referred to as "automatic mode").
This mode is set by the microcomputer PR3 in FIG. 2 recognizing the state of the switch group SWS via the switch detection circuit DDR. It can be determined that the mode is "automatic mode" when the mode is ON, and the mode is "arbitrary mode" when the mode is OFF.

In the case of “arbitrary mode”, in the same way as the mode setting method, turning on a specific switch in the switch group SWS,
It is determined in advance which subject area is to be arbitrarily selected in the OFF state, the state is detected via the switch detection circuit DDR, and the area to be selected is set.

Now, in step (OOS), 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 l 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 5M5-1 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 l is checked, and it is determined whether this is smaller than a predetermined threshold value Bth. 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", the process proceeds from step (008) to step (016).

In step (016), it is determined whether or not the selected area of the subject that has been set in advance can be detected as a focus, and if the focus cannot be detected, 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), and the difference is that in the "automatic mode °', the object to be processed is the subject region 1, 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 l, which is the subject area at 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 "Toraguchi's 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 (008) 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 l is detectable, 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
RGNI 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 3, if area 1, which is one of the areas in the center of the screen, can be focus-detected, area 1.2 will be detected regardless of the detection result of area 4.
．． 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 area at the center 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 subject closest to the camera is selected from among the plurality of subjects.

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 not completed, step (
028), 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. The 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, if focus cannot be detected, it is first determined whether or not to use the auxiliary light, and if it is to be used, it is emitted up to twice to perform focus detection, and if focus still cannot be detected, the search lens is driven. However, since the distance ring position of the photographing lens is generally different when the auxiliary light is first emitted and when the search lens drive ends, the distance ring position after the search lens drive ends is different. Position (usually infinite end position)
However, it is expected that focus detection will become possible if the -degree auxiliary light is used, so the above-described 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.

Subroutine "Lens drive" in step (025) or subroutine "Focus display" in step (031)
When the rAF is completed, the process moves to step (026) and rAF
Returns the "control" subroutine.

After the subroutine ends, as shown in the flowchart shown in FIG. 6(a), as long as the switch SW7 is ON, rAE control J and "AF control" are 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), (
Proceed to (022) via (009) or (016).

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 most rear focused area among each area is selected, and steps (024), (025), and (031) are selected. ), 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 sensors in area 1.4 are unable to detect focus, or if it is determined that sensors in the selected area are unable to detect focus, steps (010) 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 (,10m s-
100ms) 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, if it is determined that the focus cannot be detected 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 returns in the same way and performs 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 advances to (027) and (028) via (027) and (028), where the search lens is driven. In the search lens driving 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 aforementioned focus detection operation is restarted. do.

On the other hand, in the search lens drive operation, if the lens does not become focus detectable even if it moves over the entire driving range (from close range to infinity), the lens is held at a predetermined position (close range or infinity) and the process proceeds to step (029), where the auxiliary light is emitted. Returns after canceling the mode and initializing the number of times of light emission. 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 embodiment described so far, the microcomputer PRS A/D converts the image signal VIDEO and imports it, and treats the lowest value of the digital image signal as the lowest value information itself, and compares this with a predetermined threshold value. However, the structure of the sensor device SNS was changed to output the lowest value of the output of the sensor array to the outside, and this was sent to the microcontroller PR3.
If it is treated as minimum value information, the object of the present invention can be more ideally realized.

〔Effect of the invention〕

As explained above, according to the present invention, the condition for using the auxiliary light is that the lowest value of the image among the output signals from the sensor is larger than a predetermined value, in addition to the conventional condition. Ineffective auxiliary light is not projected when focus cannot be detected by focus, and it is possible to save wasted time and energy caused by auxiliary light projection.

[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 main 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 12) Fig. i (b)

Claims (2)

[Claims] (1) An accumulation-type light receiving means that receives the light flux from the subject that has passed through the photographic lens; a defocus detection means that detects the defocus state of the photographic lens based on the output from the light reception means; , a determining means for determining whether focus detection is possible or not, a measuring means for measuring the accumulation time of the accumulation type sensor, a storage means for storing minimum value information of the output from the light receiving means, and an illumination means for illuminating the subject. A focus detection device comprising: a control means for operating an illumination means based on the results of the determination means, the measurement means, and the storage means. (2) When the result of the determination means is that the focus cannot be detected, the accumulation time that is the result of the measurement means is longer than the limit value, and the minimum value information that is the result of the storage means is greater than a predetermined value, The focus detection device according to claim 1, characterized in that the illumination means is operated at the same time.