JPH032739A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To prevent the number of light emitting times from being limited more than needed and to execute an excellent automatic focusing operation by providing a time setting means for setting an interval from a preceding auxiliary light turning-off time to a current auxiliary light projection starting time in accordance with a preceding auxiliary light projecting time. CONSTITUTION:A microcomputer PRS communicates with a peripheral circuit and a lens by using signals for communication SO, SI and SCLK to control the action of each circuit and lens. When the auxiliary light is projected after the elapse of a time when images are accumulated under the preceding projection of auxiliary light. Therefore, when the auxiliary light is projected every AF action, the current auxiliary light projection starting time is shifted in accordance with the preceding auxiliary light projecting time. Thus, in the case that the auxiliary light projecting time of every AF action is made long, a time till the next start of the projection of the auxiliary light gets long and an auxiliary light source is prevented from receiving an adverse effect by generated heat.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an automatic focus adjustment device for a camera or the like, and particularly to an automatic focus adjustment device using auxiliary light.

[Conventional technology]

Conventionally, as a method for focusing a camera, a light flux from an object that has passed through a photographic lens is received and charged by a charge accumulation type photoelectric conversion element such as a CCD, and if the luminance is determined to be low at this time, A known method is to perform re-accumulation while illuminating the subject with auxiliary light, detect the focus state of the photographic lens from the output, and drive the photographic lens based on the result. There is.

[Problem that the invention is trying to solve]

LED light sources are commonly used as the light source for the above-mentioned auxiliary light, but in the case of LED light sources, an excessive amount of current passes through when emitting light, so if the light source is emitted frequently, the temperature of the light source will rise rapidly, damaging the LED. There is a risk of it being stored away. For this reason, the number of times the light is emitted for each focus detection is usually limited to a finite number of times, and control is performed to prevent the temperature of the light source from rising above a predetermined level.

However, even if the number of flashes is set to a small number to protect the light source, if the subject is difficult to focus on, the flash operation may end before achieving focus, resulting in failure to focus. There are some drawbacks that arise.

[Means to solve the problem]

The purpose of the present invention is to solve the above-mentioned problem, and its gist is to count the light emission time when the auxiliary light is emitted, and to provide a standby time corresponding to the light emission time before the next occurrence of the light source. By suppressing the temperature rise of the lens, it is possible to perform a good focus adjustment operation without unnecessarily limiting the number of times the light is emitted.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of a camera equipped with an autofocus device according to the present invention. In the figure, PH1 is a camera control device, for example, an internal ROM.

It is a 1-chip microcomputer with RAM and A/D conversion functions, and it controls camera operations such as automatic exposure control function, automatic focus detection function, and film winding/rewinding according to the programs described below stored in ROM. Is going.

Microcomputer PR8 has communication signal 5O1SI,
5CLK is used to communicate with peripheral circuits and lenses, and to control the operation of each circuit and lens.

SO is the data signal output from PH5, SI is PH1
The data signal input to 5CLK is the signal So, Sl
This is the synchronization signal.

LCM is a lens communication buffer circuit, and when the camera is in operation, the lens power supply VL is applied to the lens, and the signal CLCM from the microcomputer PR8 is at a high potential level (hereinafter abbreviated as "H", and a low potential is "L"). (abbreviated as “)”
In this case, it acts as a buffer for communication between the camera and lens. When the microcomputer PR8 sets the signal CLCM to "H" and sends out predetermined data as the SO signal in synchronization with the 5CLK signal, the circuit LCM is designated and the 5CLK signal and SO signal are transmitted through the camera-lens junction. buffer signal LCK.

Output DCL to the lens. At the same time, the buffer signal of the signal DLC from the lens (the part surrounded by the dashed line) is output as the Sl signal, and the computer PR3 outputs the 5CL signal.
Lens data as an Sl signal is input in synchronization with the K signal.

SDR is a drive circuit for the line sensor device SNS for focus detection, and the signal C5DR from the computer PRS is “
It is selected when the signal is H'' and is controlled by the computer PR3 using signals So, Sl, and SCI.

The SNS is, for example, a pair of CCD line sensors (CCD).

This is a sensor device including a CCD2. φl and φ2 receive the clock CK from the computer PR3, and drive circuit SD
A clock for driving the COD generated by R, SH is a line sensor CCD, a signal to transfer the charge accumulated in CCD 2 to the transfer section, CLR is a line sensor CCD
, , are clear signals for clearing the accumulated charges in the CCD 2, and these signals are formed by a drive circuit SDR controlled by a computer PR3.

The output signal O8 of the sensor device SNS is the clock φ1゜φ2
Sensor CCD, which outputs in time series in synchronization with.

It is an image signal accumulated in each power supply of CCD2, and the CCD
,.

Each bit of the CCD2 is outputted and amplified by the amplifier circuit in the circuit SDR, and then sent to the computer P as an AO3 signal.
It is input to R3. The computer PRS inputs the AO3 signal from the analog input terminal, synchronizes with the CK multiplied signal, and uses its internal A/D conversion function to sequentially store the signal at a predetermined address in the RAM after A/D conversion.

Same (the AGC signal which is the SNS output signal is the device SN
This is the output of the storage control sensor in S, is input to the circuit SDR, and is used to control the storage time of sensors CCD 2, CCD 2.

SPC is a photometric sensor that receives light through a photographic lens, and its output 5spc is input to the analog input terminal of computer PR3, and after A/D conversion, automatic exposure control (
AE).

DDR is a switch sense and display circuit, which is selected when the signal CDDR from the computer PR3 is "H", and communication with the computer PR5 is controlled by the So, 31, and 5CLK signals.

That is, the switch status of the switch group SWS that switches the camera display based on data sent from the computer PR3, and turns on and off in conjunction with various operating members including switches sw, , and sw2 that are linked to the release button. to computer PR5.

MDRI and MDR2 are drive circuits for film feeding and shutter charging motors MTRI and MTR2, and signal M
Execute forward/reverse rotation of the motor using IF, MIR, M2F, and M2R.

MCI and MG2 are magnets for starting the movement of the shutter front curtain and rear curtain, respectively, and the signals SMGI, 5MG2. The amplification transistors TRI and TR2 are energized, and the computer PR5 performs shutter control.

ALED is an auxiliary light source for projecting light onto the subject when the brightness is low, and the signal of the output terminal SAL of the microcomputer PR3 is set to "H".
Drive the drive transistor ATR by
Auxiliary light is projected through the optical system ALMS. The ALED
is composed of, for example, a light emitting diode.

In addition, switch sense and display circuit DDR.

The motor drive circuits MDRI, MDR2, and shutter control are not directly related to the present invention, so detailed explanations will be omitted. In-lens control circuit LP in synchronization with synchronization signal LCK
The signal DCL input to the RS is data of a command from the camera to the lens, and the operation of the lens in response to the command is determined in advance.

The control circuit LPRS analyzes input commands according to a predetermined procedure, performs focus adjustment and aperture control operations, and outputs various lens parameters (open F number, focal length,
(coefficient of defocus amount vs. feeding amount, etc.) is output.

In the example, an example of a single lens that is fully extended is shown, and when a focus adjustment command is sent from the camera, it is simultaneously sent (according to the drive amount and direction) to the focus adjustment motor LMTH. Signal LMF.

The LMR is sent out and the motor LMTR is driven to move the optical system in the optical axis direction and perform focus adjustment. The amount of movement of the optical system is monitored by the signal 5ENC of the encoder circuit ENC, and when the predetermined movement is completed, the signals LMF and LMR are set to L''.
to control motor LMTR.

When an aperture control command is sent from the camera, a known stepping motor DMTR that is linked to the aperture mechanism 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.

Next, the operation shown in FIG. 1 will be explained using FIGS. 2 to 4.

First, when a power switch (not shown) is operated, power is supplied to the microcomputer PR3, and the microcomputer PR3 executes a stored program.

FIG. 2 is a flowchart showing the overall flow of the above program. When the execution of the above storage program is started, the state of the switch SWI, which is turned on by the first step operation of the shutter button (not shown), is first detected in step (002), and when the switch SW1 is off, the state of the switch SWI is detected in step (002). 005), all flags inside the microcomputer PR3 are set to "0", and all variables described later are set to "0".
”.

The above steps (002) and (005) are performed by the switch S.
It is executed repeatedly until WI is turned on, and the switch SWI
When turned on, the process moves to step (003).

Step (003) is an AE sub-control subroutine,
This AE subroutine performs a series of controls such as photometric calculation processing, exposure control, shutter charging after exposure, and film winding. The AE subroutine described above has no direct relation to the present invention, so a detailed explanation will be omitted, but its outline is as follows. As long as the switch SWI is on, photometry and exposure control calculations are performed each time this AE subroutine is executed. Further, when the second stage operation of the shutter release button is performed and the switch SW2 is turned on, the release operation is performed by interrupt processing, and the aperture or shutter speed is controlled according to the exposure amount obtained by the above exposure control calculation. After exposure is completed, shutter charging and film feeding operations are performed.

Assuming that the shutter button is now operated in the first step, the process moves to step (004) after photometry and arithmetic processing are performed in step (003). The above-mentioned interrupt operation is permitted when the AF operation mode is the so-called "servo mode" or "manual mode" and the first photometry is completed from the power switch on, and when the AF operation mode is the "one-shot mode". When , permission is granted when focus is detected. That is, in the above-mentioned "servo mode" or "manual mode", the release operation can be performed at any time regardless of the focus adjustment operation, and in the "one shot mode", the release operation is possible only after in-focus is detected. The AF mode is selected by a mode switch (not shown). In the [one-shot mode], once focus is achieved, the AF operation is not performed again until the switch SWI is turned off, and in the "servo mode", the AF operation is always performed.

In the AF control step (004), the focus adjustment state of the photographic lens is detected, and if the mode is "one shot mode" or "servo mode", the photographic lens is driven so as to be in focus;
When in "manual mode", only in-focus or out-of-focus is displayed. Further, in the manual mode, AF control using auxiliary light is not performed.

In the above flow, as long as the switch SWI is on, the AE control (003) and the AF control (004) are alternately and repeatedly performed.

Step (004) is an AF control subroutine, and the AF control subroutine shown in FIG. 3 is executed.

Step (102): By shutter release operation,
It is determined whether this is the first AF control immediately after the shooting of one frame is completed (it is determined whether film feeding was performed in the AF control subroutine performed immediately before), and "Continuous shooting mode" is selected. ” or not. When it is determined that step (102) has been performed for the first time after the end of shooting, it is assumed that AF is in continuous shooting mode, and step (102) is performed.
At step 03), all flags in the microcomputer PR8 are set to "0" and all variables are set to "0". As a result, during the "continuous shooting mode", the past AF control status is initialized, and in the next step (104), the continuous shooting mode flag F
The AF is set to 1 to remember that AF control is being performed during continuous shooting, and the process moves to step (109). Further, in step (105), the set state of the flag PRMV is detected. The flag PRMV is a “lens drive flag”,
If the lens has not been driven in the previous AF control, the process moves to step (109) and AF control is performed again. Conversely, if the lens was driven last time, the next step (
In step 106), it is determined whether or not the lens has stopped driving.

In step (106), as explained in FIG. 1, the microcomputer PR3 operates as a lens communication buffer circuit, LCM.

It communicates with the lens LNS via the in-lens control circuit LPR3, and checks the status of the lens by receiving monitor communication. If the lens is not stopped now, the lens is being driven, so the AF control subroutine ends. Therefore, as long as the lens is in the driving state, the determination as to whether the lens has stopped is continued in step (106). In the present invention, AF control is not performed while the lens is being driven, and AF control is performed only when the lens is stopped, so the next step (
108), set PRMV to “0” and proceed to step (1
Proceed to 09).

Step (109): Determine the autofocus mode, and if it is manual mode, proceed to step (110) ("manual" is selected by a mode switch (not shown)). Step (110) is a subroutine for image signal input, and steps (111) and (112)
After executing the focus detection and display subroutine in step (113), the AF control subroutine is ended (each subroutine will be described later).

If it is determined in step (109) that the mode is not manual, it is determined in step (114) whether or not the mode is "one shot mode". If the mode is one-shot mode, proceed to step (115) and check the state of the focus flag JF.
It is determined whether or not the camera was in the "previously focused state". AP here
If the control mode is "one shot mode" and "previously focused", AF control is ended in step (116).

That is, in the one-shot mode, once the focus is achieved, new AF control is not executed until the switch SWI is turned off. Above step (1
15) If it is not in focus last time, go to the next step (117)
Move to.

Step (117): Execute the image signal input subroutine. In the image signal input subroutine, first the computer P
Set C3DR to H at R5 and select the drive circuit SDR,
The SO multiplied signal is transmitted to the drive circuit SDR. SO at this time
This is a double signal accumulation start command, and in response to this command, the drive circuit SDR transmits the CLR signal to the line sensor device SNS.
The image accumulation signal of the CD line sensor is cleared, and then an accumulation operation is performed on the image. Line sensor device SNS
The image light beams incident through the photographing lens are incident on the CDD line sensors CCD , , and CCD 2, respectively.
The image position on each sensor CCD 2 is determined according to the focus state. To explain in detail, when the subject is in focus, the same image pattern is projected at the same position on each sensor CCD 2, and when the front focus or rear focus is on, the image pattern on COD 2 is out of focus. The images are projected to symmetrically shifted positions depending on the direction and amount of shift. Therefore, by detecting the amount and direction of positional deviation between the image patterns on the CCD and the CCD 2, the direction and amount of out-of-focus can be detected.

After clearing the image signal, the image pattern projected to the position according to the focus state is transmitted to each CCD as described above.

The CCD 2 accumulates data for a predetermined period of time, and then the signal SH and the clock φ1. φ2 is the sensor device SNS
supplied to In addition, the accumulation time of the above image pattern is SNS
This is determined based on the output AGC of the storage control sensor in the storage control sensor.

When the signal SH and the clocks φl and φ2 are supplied to the sensor device SNS as described above, the image signals accumulated in each sensor CCD, . The signal AO3 is amplified by the amplification circuit in the drive circuit SDR and is sequentially input to the analog input terminal of the computer PR3. Computer PR3 outputs its own clock CK
The above signal AO3 is converted to A by the internal A/D conversion function in synchronization with
The digital image signals after /D conversion are sequentially stored at predetermined addresses in the RAM.

Through the above operations, image signals for each sensor corresponding to the image pattern on the sensors CCD 2 are stored as digital values in the RAM.

Details of the above image signal input subroutine are shown in Figure 4 (a).
). In this subroutine, first, when the image signal input in step (201) is called from the AF control routine, the flag AUXMOD is set in step (202).
(Flag set to 1 if it was in auxiliary light mode last time)
It is determined whether the previous AF control was in "auxiliary light mode" or not. If it is not auxiliary light mode, step (207)
If the mode is auxiliary light mode, the process proceeds to step (203).

Step (203): Determine whether or not the predetermined number of times the auxiliary light has been emitted has been completed using the flag AUXNOEM (a flag that is set to 1 when the emitted light has been emitted a predetermined number of times). If the predetermined number of times of light emitting has been completed, the process proceeds to step (207), but if not, the process proceeds to step (204).

Step (204): Determine whether or not focus was achieved under the previous auxiliary light projection using 7 lag AUXJF (a flag set when focusing in the auxiliary light mode). If the object is in focus, the process proceeds to step (207) without emitting the auxiliary light, and if the object is not in focus, the process proceeds to the next step (204, 1).

For this AUXJF, subroutine "Focus detection"
As will be explained in detail below, this flag AUXJF determines whether or not focus is achieved under the auxiliary light projection, and if AUXJF is 1
If flag AUXMOD is auxiliary light mode, flag A
The auxiliary light is not emitted even under the condition that the number of times UXNOEM is emitted is less than or equal to the predetermined number of times.

Step (204, 1): Here, the previous accumulation time counter INTCNT is referred to and the time represented by its contents is waited. Actually, since INTCNT is a value in units of 1 ms, an operation is performed in which a 1 ms timer counter, which will be described later, is counted by INTCNT.

Step (205): Turn on the auxiliary light.

By setting the output signal of the output terminal SAL of the microcomputer PR3 to 1'', a current flows to the auxiliary light source ALED via the transistor ATR, and the optical system ALNS starts emitting auxiliary light.

Step (206): Auxiliary light emission counter AUXCN
Count up T by one.

Step (207): Line sensor SNS for focus detection
Allow the device to start accumulating a light image. When the microcomputer PR3 sends an "accumulation start command" to the sensor drive circuit SDR, the sensor drive circuit SDR sets the clear signal CLR to the photoelectric conversion element section of the sensor SNS to "O" to start charge accumulation.

Step (208): Initialize the accumulation time counter INTCNT to an initial value of 0.

Step (209): Reset the 1 ms timer counter of the accumulation time timer. The counter is microcomputer PR
The timer function of 3 is used.

Step (210): This flag determines whether the sensor has finished accumulating. Check whether the signal INTEND from the sensor drive circuit SDR is "1". The sensor drive circuit SDR is connected to the line sensor SNS.
At the same time as the start of accumulation, the signal INTEND is set to "0", and the output AG of the accumulation control sensor from the sensor SNS is set to "0".
C signal is monitored, and when the AGC signal reaches a predetermined level, the signal INTEND from the sensor drive circuit SDR is
is set to "1", and at the same time the sensor drive circuit SDR
The charge transfer signal SH from the sensor SNS is set to "H" for a predetermined period of time to control the charge in the photoelectric conversion element section in the sensor SNS to be transferred to the CCD section.

Here, if the above accumulation is completed, the process moves to step (215), and if the accumulation is not completed yet, step (211) is performed.
).

Step (211): Determine whether the 1 m s timer has reached the accumulation time l m s. If l m s has not been reached, the process returns to step (210) and has already been completed.
If it has reached 1 ms, the next step (212) is to increment the accumulation time counter INTCNT by one.

Step (213): Compare the contents of the flag INTCNT with a predetermined number MAXINT. MAXINT is the longest accumulation time expressed in units of 1 ms, and if the INTCNT is less than MAXINT, the process returns to step (209) and waits for the accumulation to end again. If INTCNT matches the maximum storage time MAXINT, the storage is forcibly terminated in the next step (214).

The end of this accumulation is sent from the microcomputer PR3 to the sensor drive circuit SD.
The process is completed by sending an "accumulation end command" to R. When the sensor drive circuit SDR receives an "accumulation end command" from the microcomputer PR8, it outputs the charge transfer signal SH.
is set to "H" for a predetermined period of time to transfer the charge in the photoelectric conversion section to the CCD section.

Step (215): Determine whether or not it is the auxiliary light mode using the flag AUXMCD. If the flag AUXMOD indicates the auxiliary light mode, the projection of the auxiliary light is turned off in step (216). That is, the signal at the output terminal SAL of the microcomputer PRS is set to "0" to disable the projection light source ALED. Regarding step (216), there is no adverse effect even if this step is executed when the mode is not auxiliary light mode, so steps (215) and (216) may be omitted.

Step (217): Accumulation time counter INTCNT
A comparison is made between AUXINT and a predetermined constant AUXINT. Above AU
XINT is the low luminance accumulation time expressed in accordance with the accumulation time, and when INTCNT≧AUXINT(7), the low luminance flag LLFLG in step (219) is set to “1”.
is set, and when the INTCNT is less than AUXINT, the low luminance flag LLFLG is set to "0".

In step (220), the A-
D conversion and storage into a predetermined address of the RAM are performed in the microcomputer PR5, and in step (221) the process returns to the main routine, that is, step (118).

Step (118): Determine whether or not it is continuous shooting mode using flag FAF.

When the flag FAF is 1, that is, in continuous shooting mode, the process moves to the next step (121), and when it is 0, the process moves to step (11).
Proceed to 9). This shows the flow related to the auxiliary light after step (119), and when the flag FAF is 1, the process moves to step (121), so that no process related to the auxiliary light is performed for continuous shooting.

Step (119): Determine whether or not it is the auxiliary light mode using the flag AUXMOD.

Flag AUXM if the previous AF sub-control auxiliary light mode
OD is 1, and the process moves to step (128). When the flag AUXMOD is 0, the process proceeds to step (120), and it is determined whether the brightness is low based on the flag LLFLG. The flag LLFLG is a flag set in the subroutine "Image signal input" described above, and when the brightness is l, that is, the brightness is low, the step (
128), and if the brightness is not low, the process moves to step (121
).

Steps (128) to (135) are an auxiliary light control flow at low brightness.

Step (128): This flag determines whether the auxiliary light unit is attached to the camera. Here, the determination is made by detecting the state of a switch (not shown) that is turned on when the auxiliary light unit is attached to the camera.

If the auxiliary light unit is not attached to the camera, the process moves to step (121) and AUXMOD is set to “0”.
” to cancel the auxiliary light mode.

When the auxiliary light unit is installed, the step
129) Set the auxiliary light mode with AUXMODl:: "1"'e. Here, the step (11)
In step 9), the step (129) is executed even when the flag AUXMOD is in the auxiliary light mode, but this is done for convenience of the program sequence progress of the present invention. .

Step (130): Counter AUXCNT is “0”
Determine whether it is set to . This counter AU
XCNT is a variable that is counted in step (206) in the above-mentioned "image signal input" subroutine, and when an image signal is accumulated in the photoelectric conversion element under illumination of an auxiliary light, the count number increases by one. . Furthermore, this counter A
UXCNT is cleared in step (005) of the flowchart shown in FIG. 2 when switch SWI is off, and in AF sub-control in continuous shooting mode,
It is cleared in step (103) shown in the flowchart of FIG.

Therefore, counter AUXCNT="0" means that
This indicates that the auxiliary light mode is being used for the first time in the progression of the sequence, and if it is the first time that the auxiliary light mode is being used, the process proceeds to step (131), and the AF sub-control based on the current image signal input is completed.

That is, the image signal input in step (117) is discarded, and a new image signal is input under the next AF sub-control auxiliary light projection. Therefore, it can be considered that the image signal input in step (117) is used only for determining brightness.

On the other hand, if the counter AUXCNT is not '0'', it means that the auxiliary light mode has already been entered, so in step (132) the counter AUXCNT is compared with a predetermined constant AUUNNUM.This AUXNUM is the limit number of times the auxiliary light is emitted; When the counter AUXCNT is less than the limit number of light projections AUXNUM, the process moves to step (122), and a "focus detection" subroutine is executed.

The counter AUXCNT is AUXCNT≧AUXNU
M (However, in the actual sequence, AUXC
NT>AUXNUM does not occur) The process moves to step (133).

In step (133)+7 lag AUXNOEM, it is determined whether the number of times the auxiliary light is projected has been completed. Flag AUX
In NOEM, the number of times the auxiliary light is emitted has already reached the predetermined constant AU.
When it is determined that the auxiliary light has been emitted three times, the number of times the auxiliary light has been emitted is completed, and the auxiliary light is not emitted any more. That is, even if the flag AUXMOD is 1 in the subroutine for "image signal input" mentioned above and the auxiliary light mode is set, the flag A
When UXNOEM is 1 and the number of times the auxiliary light is projected has been completed, the auxiliary light is no longer projected during image signal accumulation.

In step (133), if the flag AUXNOEM indicates that the number of light projections has been completed, the process moves to step (134).

Step (134): Determine whether the brightness is low based on the flag LLFLG.

As mentioned earlier, this flag LLFLG is a low brightness flag that is set in the "image signal input" subroutine.
Determining the brightness using LFLG means determining the brightness in "a state in which the auxiliary light has already been emitted a predetermined number of times under the auxiliary light mode and is no longer emitted." If the flag LLFLG is not low brightness, the process moves to step (121), sets the flag AUXMOD to "0", cancels the auxiliary light mode, and proceeds to the next step (122). Here, determining that the flag LLFLG is not low brightness means that when the brightness increases in the above-mentioned state, the auxiliary light mode is canceled and the normal mode returns, and the AF control in the normal mode is restarted.

When proceeding to step (121) above, when it is determined in step (118) that the flag FAF is 1 and continuous shooting is in progress (no auxiliary light emission), and in step (119) the flag AUXMOD is set to auxiliary light mode. This is when it is determined in the next step (120) that the flag LLFLG is 0 and the brightness is not low. That is, when the AF control is not in the auxiliary light mode (and the subject brightness is not low brightness), the process moves to step (121).

On the other hand, if the flag LLFLG is 1 and it is determined that the brightness is low, the process directly proceeds to the next step (122), ``focus detection''.

In the above flow, in step (133) the flag AU
Flag L only when XNOEM has completed the number of times the auxiliary light has been emitted.
LFLG determines whether the brightness is low or not.

The reason for this is that when detecting the brightness of the subject under fill light projection, the brightness of the subject increases due to the influence of the fill light, and the true brightness of the subject cannot be determined. When the number of times of light projection is less than a predetermined number, determination as to whether the brightness is low or not is not made.

Next, the focus detection subroutine in step (122) will be explained using FIG. 4(b).

Step (303): Using the flag AUXJF, it is determined whether or not the focus was achieved under auxiliary light projection in the past.

When the focus is under the auxiliary light, the step (
304).

Step (304): The state of the flag LLFLG is detected, and it is determined whether the brightness is low when the auxiliary light is not emitted. Here, when the flag LLFLG is 1 and the brightness is low, the AF control is ended in the next step (305). On the other hand, when the flag LLFLG is O and the brightness is not low, the brightness of the subject has increased, so step (
306), and set the auxiliary light mode flag AUXMOD, the number of light emission completion flag AUXNOEM, and the focus flag AU.
Clear XJF to 0'' and further clear auxiliary light counter flag AUXCNT to 0''.

Here, the operations of steps (303) to (306) will be described in detail. The fact that the flag AUXJF is 01, that is, the focus was previously achieved under the projection of the auxiliary light, indicates that the current image signal is in a state where the auxiliary light is not projected. That is, when it is determined in step (204) in the above-mentioned "image signal input" subroutine that the flag AUXJF is 1 and focus is achieved under the projection of the auxiliary light, the auxiliary light is not turned on. Therefore, the flag LLFLG determined in the above step (304) determines the brightness without the auxiliary light being emitted. This indicates that even though the image has been focused, the subsequent brightness is still low. In this state, that is, after focusing under the auxiliary light projection,
At step (305), AF control is not performed when the brightness is low and focus is maintained, and the operation is the same as the one-shot mode of AF control at this time.

On the other hand, if the flag LLFLG is 0 and it is determined that the brightness is not low, it means that the brightness without the fill light is no longer low after focusing under the fill light, and step (306 ), flags and counters related to the auxiliary light are cleared and AF control is started again.

As described above, in the auxiliary light mode, the AF control mode operates in the one-shot mode regardless of whether the AF control mode is operating in the one-shot mode or the servo mode.

In this case, when the subject brightness is low, as described above,
One-shot mode continues, but if the subject brightness changes depending on the surrounding situation and is no longer low brightness, AF will start.
If the control mode is servo mode, start AF control in servo mode again as described above, and proceed to step (307).
).

Step (307): Defocus amount D of the photographing lens is determined from the image signal from the above-mentioned "image signal input" subroutine.
Perform the EF calculation.

Here, based on the sensor COD obtained in the image signal input subroutine described above and the digital value corresponding to the image pattern on the CCD 2, the amount of deviation and the direction of deviation until focusing are calculated as the defocus amount DEF. The specific method of calculating this defocus amount is not directly related to the purpose of this application, so a detailed explanation thereof will be omitted, but as mentioned above, the sensor C
Since the degree of coincidence between the image pattern on the CD and CCD2 is determined by the focus state, the degree of coincidence between the image patterns on the CD and CCD2 is determined by the focus state. The amount and direction of deviation, that is, the defocus amount DEF are determined.

Step (308): Defocus amount DEF and constant value J
Compare FFLD.

Here, when DEF>JFFLD, step (31
Step 0), set the focus flag JF to "O", complete the focus detection subroutine, and proceed to step (123) in Figure 3.
Shift to the display.

On the other hand, when it is determined that JFFLD>DEF, the focus flag JF in step (309) is set to l'' and the process proceeds to step (312).Here, JFFLD represents a constant focus state.

Step (312): Determine whether or not it is the auxiliary light mode using the flag AUXMOD.

If flag AUXMOD is auxiliary light mode, step (3)
13), the flag AU was activated due to focusing under the auxiliary light.
"l" is set in XJF, the focus detection subroutine is ended, and the process moves to "display" in step (123) in FIG.

Step (123): "r display" is a function of simply displaying whether or not the focus state of the above-mentioned AF control is in focus using the display member, so its explanation will be omitted.

Step (124): Determine whether or not focus is achieved using flag JF.

Flag JF is a flag stored in the above-mentioned "focus detection" subroutine, and when this flag JF determines the in-focus state, that is, when in focus, AF is activated in step (127).
When the control is completed and it is determined that the lens is not in focus, the process proceeds to step (125) and a lens drive subroutine is performed.

In the lens drive subroutine, the microcomputer PR3 outputs the signal C.
Set LCM to "1" to designate the buffer circuit LCM.

In addition, the lens driving amount is transmitted to the circuit LCM as an SO multiplied signal,
The SO multiplied signal is transmitted to the control circuit LPR3 as the DCL signal. The circuit LPR3 outputs a signal LM according to the lens driving amount.
F or LMR is set to H, motor LMTR is rotated in a predetermined direction, and photographing lens LNS is moved in the optical axis direction. The amount of movement of this lens is motored by an encoder ENC, which outputs a signal 5ENC corresponding to the amount of movement, and this signal 5ENC is compared with the signal representing the defocus etc. transmitted to the circuit LPR8, and when both signals match, Signal LMF, L
MR is set to L, rotation of the motor LMTR is stopped, and lens driving is completed.

The lens drive subroutine is ended by transmitting the lens drive amount to the lens, and in step (126) the lens drive flag PRMV is set to "1", and in step (127)
) to end AF control.

Next, the lens drive subroutine step (
401) will be explained in detail.

Step (402): Input the "coefficient S of the amount of defocus versus the amount of extension" from the photographic lens. The defocus amount is the aforementioned DEF, and the extension amount represents the amount of movement of the lens that performs focus adjustment in the optical axis direction.

The above coefficient S is S when the above photographing lens is a standard lens.
= 1, and when the photographic lens is a zoom lens, the coefficient S changes depending on the zooming position.

Step (403): Input the feed-out amount PTHJ corresponding to the l tooth of the r encoder. When the lens that performs focus adjustment moves, a pulse is generated from the encoder in conjunction with this movement, and the amount of extension PTH corresponding to the encoder l tooth represents the amount of movement of the lens per tooth.

Step (404): Previously detected defocus amount D
EF, the coefficient S of the defocus amount versus the feed-out amount described above, and the feed-out amount PTT corresponding to one encoder tooth (
An integer value FP representing the amount of movement of the focusing lens by the number of teeth of the encoder is calculated using the following equation.

FP=DEFxS/PTH Step (405): The integer value FP obtained in the above step (404) is sent to the photographing lens as a lens drive amount to instruct the lens to drive, and the above lens drive is ended in step (406). .

Since step (204, 1) in FIG. 4(a) is configured as described above, when the fill light is turned on in the fill light mode, the image accumulation time under the previous fill light projection, that is, the fill light is The auxiliary light is emitted after the content time of INTCNT representing the emitting time has elapsed. Therefore, when the auxiliary light is projected for each AF operation, the current auxiliary light projection start time is shifted according to the previous auxiliary light projection time. Therefore, if the auxiliary light projection time during each AF operation becomes longer, the time until the next auxiliary light projection starts also becomes longer, and the auxiliary light source is prevented from being adversely affected by heat generation. .

In the embodiments described so far, the previous accumulation time is directly used as the standby time, but this may be a value multiplied by a predetermined coefficient, for example, 1/2 of the time. Furthermore, since focus detection processing necessarily takes a finite amount of time, that value may be further reduced to make the ratio of light emission and non-light emission pure constant.

〔Effect of the invention〕

As explained above, according to the present invention, by providing a standby time of the non-emission period according to the emission time of the auxiliary light source, the temperature rise in the light source section is suppressed, thereby limiting the number of times the auxiliary light is emitted more than necessary. Good focus adjustment operation is possible without the need for

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment to which a focus detection device according to the present invention is applied, and FIGS. 2, 3, and 4(a). (b) and (C) are explanatory diagrams showing a program for explaining the operation of the first embodiment. PR3...Computer ALED...Auxiliary light source ATR...Transistor SNS...Sensor device

Claims (2)

[Claims] (1) An automatic system that uses an accumulation sensor to receive the luminous flux from the subject under fill-in illumination, accumulates a signal corresponding to the received luminous flux for a predetermined period of time, and adjusts the focus based on the accumulated signal. In the focus adjustment device, when repeatedly performing the accumulation operation by the sensor under the auxiliary light emission, the interval from the previous auxiliary light extinguishing point to the current auxiliary light emission start point is determined based on the previous auxiliary light emission. An automatic focus adjustment device characterized by being provided with a time setting means for setting according to a light projection time. (2) In a focus detection device that causes a storage type sensor to receive a luminous flux from a subject for a predetermined period of time and repeatedly detects a focus state according to the output of the sensor, the storage type sensor receives the luminous flux for a predetermined period of time. At this time, the auxiliary light means is kept in the flashing state for a predetermined period of time, and the sensor output for the luminous flux from the subject under the auxiliary light is obtained. What is claimed is: 1. A focus detection device comprising an adjusting means for adjusting according to the auxiliary light projection time.