JPH024207A - focus detection device - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention is directed to receiving a luminous flux passing through an imaging optical system to be focused and detecting the focus by a plurality of photoelectric conversion element arrays, and detecting the output of the photoelectric conversion element array. The present invention relates to an improvement of a focus detection device that detects the focus state of the imaging optical system using the above.

(Background of the Invention) This type of device installed in a conventional camera divides the exit pupil of a photographic lens and observes the relative positional displacement of a plurality of images formed by light beams passing through each pupil area.
A method for detecting the focal state of the photographic lens is known. Specifically, the exit pupil of the photographic lens is divided into two by a focus detection optical system, and each light beam that passes through the two divided areas is transferred onto an accumulation-type photoelectric conversion element array (for example, a CCD sensor array). Form as an image. After A/D converting the sensor output signal, all or a part of the signal is extracted to determine the relative positional displacement of the two images.

In this method, the focus position that is detected as being in focus is often different from the optimum focus position of the photographing lens. This is due to the spherical aberration and chromatic aberration of the photographic lens, and the bias in the spectral sensitivity of the photoelectric conversion element.

Furthermore, there are various types of interchangeable lenses for single-lens reflex cameras, and the original system is constructed by using these in various ways, but it is well known that the optimal focus position for each type of interchangeable lens is different. Therefore, due to these problems, it is necessary to correct the results obtained by signal processing in some way. This correction is necessary for each type of lens, and is called, for example, optimal focus correction, and has been conventionally performed using various methods.

In addition, cases where this type of correction is required include, for example, when the subject has low brightness or contrast and normal distance measurement is impossible, or when a lighting device for distance measurement called an auxiliary light is used. It is also necessary. This is because the auxiliary light generally uses light with a spectral component different from external light, that is, natural light, that is, normal (near) infrared light. In other words, since the sensitivity distribution of the photoelectric conversion element array described above is biased toward the infrared side, the output signal is biased toward the infrared component. Currently, there are two ways to correct this problem: one is to set two correction values for each lens: one for shooting with only external light, and one for only the auxiliary light component when using auxiliary light. No. 58-59413, JP-A-62-86318
As disclosed in the above issue, there is a method in which a dedicated light receiving section is provided for each of auxiliary light and external light, and information obtained from each is used.

However, in the former case, it is difficult to receive both external light and auxiliary light with a single sensor, and in an environment where both types of light are mixed (in a dim environment that requires auxiliary light), The problem is that images are taken without optimal correction according to the mixing ratio. Furthermore, in the latter case, providing a dedicated light receiving section for the auxiliary light as described above requires a very expensive hybrid sensor.

(Object of the Invention) An object of the present invention is to provide a focus detection device that can solve the above-mentioned problems and improve focus detection accuracy under auxiliary light while eliminating high costs.

(Features of the Invention) In order to achieve the above object, the present invention provides correction based on information from the photoelectric conversion means when using the auxiliary light and information from the photoelectric conversion means using only external light when using the auxiliary light. A correction value calculation means is provided which calculates the correction value and outputs the correction value to the calculation means for use in focus state detection calculation. The present invention is characterized in that when a photoelectric conversion means is used and when an auxiliary light is used, a correction value to be used in a focus state detection calculation is calculated by taking into consideration external light conditions that are mixed even when the auxiliary light is used.

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

FIG. 1 is a block diagram showing one embodiment of the present invention. In the figure, PRS includes a CPU (central processing unit), ROM, RAM, and EEFROM (electrically erasable programmable ROM).

It is a one-chip microcomputer (hereinafter referred to as microcomputer) with an A/D conversion section, and it advances operations such as AE and AF according to the camera sequence program stored in the ROM, and also processes various communication signals So and SI. , 5
Communicate with peripheral circuits and lens FLNS using CLK,
It controls each circuit and lens FLNS.

The EEFROM is a type of non-volatile memory, and various adjustment data are written therein during process steps. Further, SO is a data signal output from the microcomputer PR3, SI is a data signal input to the microcomputer PRS, and 5CLK is a synchronization signal of the data signals So and SI.

LCM is a lens communication buffer circuit, which applies lens power VL to the lens FLNS side when the camera is in operation, and serves as a communication buffer between the camera and lens FLNS when the signal CLCM from the microcomputer PR3 is H''.

When the microcomputer PRS sets the signal CLCM to "H" and sends out the data signal So in synchronization with the synchronization signal 5CLK, the lens communication buffer circuit LCM outputs each of the signals 5CLK and So through the camera-lens junction. Buffer signals LCK and DCL are output to the lens FLNS side.

At the same time, the signal DLC input from the lens FLNS side
The data signal SI, which is a buffer signal of
It is synchronized with K and output to the microcomputer PRS.

SDR is a drive circuit for the line sensor device SNS for focus detection, and is selected when the signal C5DR is "H" and is controlled by the microcomputer PRS using the signals So, SI, and 5CLK.CK is the COD drive clock. INTEND is a signal for generating signals φ1 and φ2, and INTEND is a signal to notify the microcomputer PR3 that the storage operation has ended.

The output signal O3 of the line sensor device SNS is clocked φ1. It is a time-series image signal synchronized with φ2, and after being amplified by the amplifier circuit in the drive circuit SDR, it is output to the microcomputer PRS as a signal AOS. Microcomputer PRS is signal A
The OS is input from an analog input terminal, A/D converted by an internal A/D converter in synchronization with the signal CK, and then sequentially stored at a predetermined address in the RAM. Similarly, the output signal 5AGC of the line sensor device SNS is the AGC in the device SNS.
This is the output of the control sensor, and is manually input to the drive circuit SDR and used for storage control of the device SNS.

SPC is a photometric sensor for exposure control, and its output signal 5spc is input to an analog input terminal of microcomputer PRS, A/D converted, and then used for AE control.

DDR is a switch sense and display circuit, and the signal C
Selected when DDR is “H”, signals So, SI, 5C
It is controlled by microcomputer PR3 using LK. That is, you can switch various types of camera information to be displayed on the display DSP based on data sent from the microcomputer PRS, and press release buttons (not shown) (switches swl, sw2).
The on/off status of various operating members such as the mode setting button and the like) are sent to the microcomputer PR3.

MDRI and MDR2 are drive circuits for film feeding and shutter spring winding motors MTR1 and MTR2, and perform forward and reverse rotation of the motors in accordance with signals MIF, MIR, M2F and M2R from microcomputer PR3.

MGI and MG2 are magnets for starting shutter front and rear curtain travel, respectively, and signals SMGI and 5M from the microcomputer PRS.
G2, transistors TR1 and TR2 are energized, and the microcomputer PRS performs shutter control.

AUT is an auxiliary light projecting unit, which is attached to the camera body by a member not shown. In response to the output SAL from the camera, a transistor ATR is turned on, and the auxiliary light source ALED is energized to emit light.

ALNS is a lens that allows the subject to be appropriately irradiated with light from the ALED.

The signal DCL input to the intra-lens control circuit LPRS in synchronization with the signal LCK is data of a command from the camera to the lens FLNS, and the operation of the lens in response to the command is determined in advance. The in-lens control circuit LPR3
analyzes the command according to a predetermined procedure, and outputs focus adjustment and aperture control operations and various lens parameters (open F-number, focal length, coefficient of defocus amount versus extension amount, etc.).

This example shows an example of a single lens that extends entirely, and when a focus adjustment command is sent from the camera, the focus adjustment motor is activated according to the drive amount and drive direction signals sent at the same time. The LMTR is driven by signals LMF and LMR 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 pulse signal 5ENC of the encoder circuit ENC, and when the predetermined movement is completed, the signals LMF and LMR are set to "L" and the motor LMT is activated.
Brake R.

When an aperture control command is sent from the camera, a known stepping motor DMTR for driving the aperture is driven according to the number of aperture stages sent at the same time. In addition, since the stepping motor DMTR can be oven controlled,
Does not require an encoder to monitor operation.

Next, the operation will be explained. Note that the switch sense and display circuit DDR, motor drive circuits MDR1 and MDR2, and shutter control system are not directly related to the present invention.
The details are omitted.

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

FIG. 2 is a flowchart showing the overall flow of the above program. When the execution of the program is started by the above operation, the state of the switch SW1, which is turned on at the first stroke of the release button, is detected in #2, and when the switch swl is off, the RA in the microcomputer PRS is detected in #3.
All control flags set in M are cleared. Above #2. #3 is repeatedly executed until the switch swl is turned on or the power switch is turned off, and when the switch swl is turned on, the process moves to #4.

#4 refers to the "rAE control" subroutine, and in this "rAE control" subroutine, a series of camera operation controls such as photometric calculation processing, exposure control, shutter charging after exposure, and film winding are performed. In addition, rAE control
Since the subroutine is not directly related to the present invention, a detailed explanation will be omitted, but an outline of the operational functions of this subroutine is as follows.

While the switch swl is on, this "rAE control" subroutine is executed, and each time the camera mode, photometry and exposure control calculations and display are performed. When the switch sw2 is turned on by the second stroke of the release button (not shown), the release operation is started by the interrupt processing function of the microcomputer PRS, and the aperture or shutter speed is adjusted based on the exposure amount determined by the above exposure control calculation. After the exposure is completed, shutter charging and film feeding operations are performed to complete the photographing of one frame of film.

When the “rAE control” subroutine ends in #4 above,
The #5 "rAF control" subroutine is executed.

FIG. 3 shows a flowchart of this rAF control subroutine.

First, in #102, the state of the lens drive execution flag PRMV is detected. This flag PRMV is a flag related to lens control as described later, but as mentioned above, all flags are cleared in #3 in Figure 2 while the switch swl is off, so 2
When the AF sub-control subroutine in Figure #5 is called, the flag PRMV is also O, so the process moves to #106.

In #106, the state of the auxiliary light focusing flag AUXJF is detected. The flag AUXJF is a flag related to auxiliary light control, and as described above, since the flag AUXJF is also 0, the process moves to #108.

#108 is the "image signal input" subroutine, and by executing this subroutine, the RA of the microcomputer PRS is
The A/D conversion signal of the image signal from the line sensor device SNS is stored at a predetermined address on M. A flowchart of the "image signal manual power" subroutine is shown in FIG. 4, and its details will be described later. In the next step #109, the state of the auxiliary light mode flag AUXMOD is detected. The flag A
UXMOD is a flag indicating the auxiliary light mode. Control regarding the auxiliary light will be described later. As mentioned above, since the flag AUXMOD is O, the process moves to #110.

In #110, the state of the low luminance flag LLFLG is detected. This flag LLFLG is set in the "image signal input" subroutine of #108, and is set to 1 when the subject brightness is low. Here, the explanation will proceed assuming that the subject has sufficient brightness (the flag LLFLG is O). Since the flag LLFLG is O, the process moves to #111, and the auxiliary light mode flag AUXMOD is cleared to O since the subject brightness is sufficient. Next, in #112, a "focus detection" subroutine is executed. The flowchart of this subroutine is shown in Fig. 5. In this subroutine, the focus of the photographing lens is detected from the image signal data stored in the RAM, and if the focus is on, the focus flag JF is set to 1, and the object is If focus detection is impossible due to low contrast, set the focus detection impossible flag AFNG to 1, and set the lens drive prohibition flag L to prohibit lens drive in either of the two states.
Set MVD I to 1 and return.

In the next step #113, a "display" subroutine is executed to display in-focus or inability to detect focus. This is to communicate predetermined data to the switch sense and display circuit DDR and display it on the display DSP, but since this operation is not directly related to the present invention, no further explanation will be given as mentioned above. Omitted.

Now, in the next #114, the lens drive prohibition flag LMVDI
Detect the state of. As mentioned earlier, when there is no need to drive the lens, the flag LMVDI is set to 1, so in #114, the flag LMVD I is set to 1.
If so, the "rAF control" subroutine is returned at #115. If the flag LMVDI is 0, the process moves to #116 and the "lens drive" subroutine is executed. This subroutine will be described later. When the "lens drive" subroutine (#116) is completed, the lens drive execution flag PRMV is set to 1 in #117, and then the "rAF control" subroutine is returned to #118.

In the main flow of Figure 2, #5 "AF control" is again performed.
When is called, the state of the lens drive execution flag PRMV is detected at #102 in FIG. In the previous rAF control subroutine, if in-focus or focus detection is not possible, the flag PRMV remains O, so the flow from #106 onwards is executed again. If the lens was driven last time, the flag PRMV is set to 1 in #117, so the process moves from #102 to #103.

#103 communicates with the lens FLNS, detects the current driving status of the lens FLNS, and transmits # from the lens FLNS side.
When it is notified that the specified drive specified in step 116 has ended, the flag PRMV is set to O in #105 and #106
Execute the following flow. If it is notified from the lens FLNS side that the lens is still being driven, the process moves to #104 and the ``rAF control'' subroutine is returned.

Therefore, in the rAF control subroutine, the lens FLNS
A new focus detection operation and release control are performed only when the lens is not driven.

Next, operations related to the auxiliary light will be explained.

If the subject brightness is low, use #108 "Image signal input"
In the subroutine, the flag LLFLG is set to 1, and when the state of the flag LLFLG is detected in #110, the flag LLFLG is set to #119.
to move to.

At #119, the attachment state of the auxiliary light projection unit AUT (not shown) is detected, and if the unit AUT is not attached, the process moves to #111 and the same normal operation as described above is performed. If the unit AUT is installed, #
120 and set the auxiliary light mode flag AUXMOD to 1.
Set to .

Next, in #121, the state of the auxiliary light use flag AUXUSE is detected. The flag AUXUSE is set to l in the "image signal input" subroutine of #108 when the auxiliary light is actually projected. In the situation described now, the auxiliary light mode is entered for the first time, so in #122, the process returns to "-rAF control". That is, in this case, the image signal data input in #108 is not used for focus detection and is discarded, and in the next rAF control subroutine, the image signal is input in the auxiliary light projection state and used for focus detection. . However, in the present invention, since it is used in the "correction calculation" subroutine described later, the accumulation time when the auxiliary light is not used is stored in a specific RAM in the "image signal input" subroutine of #108. .

Now, in #120, the auxiliary light mode flag AUXMOD
When the "rAF control" subroutine is called again with "rAF control" subroutine set to 1, the "image signal input" subroutine at #108 inputs an image signal in the auxiliary light emission state, and
#11 by detecting the state of the auxiliary light mode flag AUXMOD.
Move to 9. If the auxiliary light projection unit AUT has not been removed during this time (if it is still attached), #12
Transition to 0. If it has been removed, the process moves to #111, sets the auxiliary light mode flag AUXMOD to O, cancels the auxiliary light mode, and returns to normal AF control.

After passing through #119 and 120, the state of the auxiliary light use flag AUXUSE is detected in #121. Since the auxiliary light use flag AUXUSE has already been set to 1 in #108, the process moves to #112 and the "focus detection" subroutine is executed. In the "focus detection" subroutine, when the auxiliary light mode flag AUXMOD is 1, it is assumed that the auxiliary light is used, and a "correction calculation" is performed in the present invention.

On the other hand, in the "focus detection" subroutine of #112, if the contrast of the subject image is low and focus detection is impossible and no auxiliary light is used, it is determined that auxiliary light is necessary,
Set the auxiliary light mode flag AUXMOD to 1 and use rA
The ``F control'' subroutine is returned, and since the auxiliary light is being used this time, the ``rAF control'' subroutine is called again.

As mentioned above, in the case of low brightness and low contrast, the focus operation is performed using the auxiliary light, but if the focus is achieved with the auxiliary light emitted, the "Focus Detection" subroutine in #112 The auxiliary light focusing flag AUXJF is set to 1, and in this case, in the flow of "rAF control", #106
The state of the auxiliary light focus flag AUXJF is detected and #1
After moving to 07, the "rAF control" subroutine is returned. That is, when focusing is achieved in the auxiliary light projection state, the focus detection operation is not performed again until the switch swl is turned off.

FIG. 4 shows a flowchart of the "image signal input" subroutine.

The state of the auxiliary light mode flag AUXMOD is detected in #202, and if the flag AUXMOD is 1, the microcomputer PRS sets the output SAL to "H" in #2o3, causes the auxiliary light source ALED to emit light, and uses the auxiliary light in #204. Set flag AUXUSE to 1. Auxiliary light mode flag A
When UXMOD is O (normal light mode), the process moves from #202 to #205 and no auxiliary light is emitted.

In #205, the line sensor device SNS is caused to start accumulating optical images. Specifically, the microcomputer PR3 is the drive circuit SDR.
The drive circuit SDR sends the "accumulation start command" to
LR is set to "L" to start charge accumulation.

At #2o6, the accumulation time counter INTCNT set on the RAM is initialized to O. In #2o7, the 1 millisecond clock timer is reset. Note that this 1 millisecond clock timer utilizes the timer function of the microcomputer PRS.

At #208, the signal INTEN input to the microcomputer PR3
The state of D is detected and it is checked whether the storage has finished. The drive circuit SDR outputs the signal INTEND at the same time as the accumulation starts.
Set it to "L" and monitor the accumulation time control signal 5AGC from the line sensor device SNS, and when the signal 5AGC reaches a predetermined level, set the signal INTEND to "H" and at the same time set the charge transfer signal SH to "H" for a predetermined time. It has a structure in which charges in the photoelectric conversion element section are transferred to the CCD section.

If the signal INTEND is "H" in #208, it means that the accumulation has been completed, and the process moves to #209.

If the accumulation has not been completed, it is checked in #209 whether the 1 millisecond timer that was reset earlier has counted 1 millisecond. If 1 millisecond has not elapsed, the process moves to #208 and waits for the accumulation to end or for 1 millisecond to elapse. If 1 millisecond elapses before the accumulation ends, the process moves to #210. In #210, the accumulation time counter INTCNT is counted up by one, and in #21
Go to 1. In #211, the counter INTCNT and the predetermined constant MAXINT are compared, but the constant MAXI
NT is the maximum accumulation time expressed in degrees 1 millisecond;
The value of the counter INTCNT is the constant MAX IN
If it is less than T, the process returns to #207 and waits for the accumulation to end again. The value of the counter INTCNT is the constant MAXIN
If it matches T, the process moves to #212 and the accumulation is forcibly terminated. Forced accumulation ends from microcomputer PR3 to drive circuit SD
This is executed by sending an "accumulation end command" to R. That is, when the drive circuit SDR receives the "accumulation end command" from the microcomputer PRS, it sets the charge transfer signal SH to "H" for a predetermined period of time to transfer the charges in the photoelectric conversion section to the CCD section. In #213, the output SAL of the microcomputer PRS is set to “L”.
”, and if the output SAL is “°H” in #203, the auxiliary light continues to emit light, so the light emission is stopped by setting it to “L”. In other words, the auxiliary light is emitted only while the sensor is storing data. In #214, the accumulation time counter INTCNT is compared with a predetermined constant AUXINT. The constant AUXINT is the low luminance accumulation time expressed in correspondence with the accumulation time, and when the counter INTCNT is larger than the constant AUXINT, the process moves to #216 and the low brightness flag LLFLG is set to 1, and when it is smaller, the process moves to #215. The low brightness flag LLFLG is cleared to O. That is, when the accumulation time is longer than a predetermined time, it is determined that the brightness is low.

In #217, the state of the auxiliary light use flag AUXUSE is detected. This is when the auxiliary light is not used (AUXUS
E=O) and when used (AUXUSE=1),
This is to store each storage time ■NTCNT at a specific address on another RAM. The operation is performed in #218 and 219, and these two values are used in the "correction calculation" described later.
It is used for. In #220, the image signal O8 of the line sensor device SNS is amplified by the drive circuit S]:)R, and the signal AOS is
A/D conversion of the data is performed and the digital signal is stored in the RAM.

When inputting the image signal is completed in this way, the "image signal input" subroutine is returned at #221.

FIG. 5 shows a flowchart of the "focus detection" subroutine.

When this subroutine is called, the defocus detection subroutine rPREDJ is executed in #302. This involves detecting the amount of deviation between the two images from the given image signal, and then determining the amount of defocus. Various proposals have already been made regarding this, and this is not particularly relevant to this embodiment. Therefore, I will omit the details.

Now, if the defocus amount is found from the image signal in #302, the auxiliary light mode flag A is determined in #303.
Detects the state of UXMOD. This is because the contrast is stored separately when no auxiliary light is used (AAUXMOD=O) for "correction calculation". When auxiliary light is used, "correction calculation" is performed within this "focus detection" subroutine, so it is not specified explicitly.

In #305, the state of the low contrast flag LCFLG is detected. The flag LCFLG is a flag set in the defocus detection subroutine rPREDJ,
It is set to 1 when the contrast of the image signal is lower than a predetermined value. If the flag LCFLG is 0 in #3o5, it is assumed that there is sufficient contrast, and the process moves to #306, where the focus detection failure flag AFNG is cleared to O. Next, in #307, the auxiliary light mode flag AUXMO is set again.
The state of D was detected and the auxiliary light was used (AUXMOD=
1), the process moves to the "correction calculation" subroutine in #308.

In #3o9, the absolute value of the detected or detected liquid corrected defocus amount DEF is compared with a predetermined constant JFFLD. The constant JFFLD is a so-called focusing width that represents the upper limit of the amount of defocus that can be considered to be in focus. If the absolute value of the defocus amount is less than or equal to the constant JFFLD in #309, #
The process moves to #310 and both the focus flag JP and the lens drive prohibition flag LMVDI are set to 1. On the other hand, if the absolute value of the defocus amount is larger than the constant JFFLD, the process moves to #311 and both the flags JF and LMVDI are set to O. Clear, and return to the "focus detection" subroutine in #314. If it is in focus, the process moves from #310 to #312 and the state of the auxiliary light mode flag ALJXMOD is detected.

If the flag AUXMOD is O, that is, it is not the auxiliary light mode, the "focus detection" subroutine is returned at #314.

If the flag AUXMOD is 1, that is, the auxiliary light mode, the process moves to #313 and the auxiliary light focus flag AUXJF is set to 1.
Set to , and return from the subroutine.

Low contrast flag LCFLG is 1 in #305
If it is detected that this is the case, the process moves to #315 and the state of the auxiliary light mode flag AUXMOD is detected. If the flag AUXMOD is 1, that is, the auxiliary light mode, #31
9, and the focus flag J is determined to be impossible.
After clearing P to 0, setting the focus detection impossible flag AFNG to 1, and setting the lens drive inhibition flag LMVDI to 1, the "focus detection" subroutine is returned in #320. Also, if the flag AUXMOD is 0 in #315, that is, it is not the auxiliary light mode, the process moves to #316,
The flag AUXMOD is set to 1 to enter the auxiliary light mode, and the process moves to #317. In #317, the flag PLCFLG for "auxiliary calculation" is set to 1. This indicates that the contrast information of the subject image was low in contrast when the auxiliary light was not used. Then, in #318, the "focus detection" subroutine is returned.

FIG. 6 shows a flowchart of the "lens drive" subroutine.

When this subroutine is called, in #302 it communicates with the lens FLNS and sends two data rsJ, rP.
Enter THJ. rSJ is a coefficient of "defocus amount" specific to the photographing lens versus "extension amount of the focusing lens". rPTHJ is the amount of movement of the focusing lens per one pulse of the encoder, which is linked to the movement of the focusing lens.

Therefore, the current defocus amount DEF, data S, PT
The amount of extension of the focusing lens is determined by encoder EN using H.
The amount converted into the number of pulses of C, the so-called lens drive amount FP
is given by the following equation.

FP=DEF-S/PTH・・・・・・・・・・・・
(1) #403 executes the above equation (1) as is.

In #4o4, the lens drive amount FP obtained in #403 is sent to the lens FLNS side to command the focusing lens to be driven, and in the next step #405, the "lens drive" subroutine is returned.

FIG. 7 shows the "correction calculation" subroutine.

When this subroutine is called, a correction calculation based on the accumulation time and the peak value of the image signal is executed in #5o2. This is the accumulation time (T1°T2), image signal peak value (P!, P
2), and performs the following calculations, for example. Note that A is a correction value for external light, and B is a correction value for auxiliary light.

The correction amount X is the correction value A using the accumulation time and the image signal peak value.
, B is obtained by internally dividing the distance between them.

At #5o3, the state of the "correction calculation" flag PLCFLG is detected. This serves as a criterion for determining whether or not the contrast is low when the auxiliary light is not used. In other words, in the ``rAF control'' subroutine in Figure 3, the low brightness flag LLFLG was 1 in #110, leading to the use of the auxiliary light, or the brightness was not low, but in #305 in the ``focus detection'' subroutine, the subject image was low. Indicates whether the contrast flag LCFLG was 1 and the auxiliary light was used. If the flag PLCFLG is O in this #503, it can be determined that the fill light was used without performing a low contrast determination because the subject image was low brightness, and there is no contrast information when the fill light is not used. As such, the process moves to #506.

On the other hand, if the flag PLCFLG is 1, the auxiliary light stored in #304 in the "focus detection" subroutine is assumed to have been used because the object image was not low brightness but had low contrast. The process moves to #504 where a correction calculation is performed using the contrast information in the usage state.

#504 uses the contrast values (C1, C2) in the auxiliary light unused state and the auxiliary light used state, and performs the following calculation, for example.

Here, A and B are the same values as in equation (2) above. Correction ff1Y also uses the contrast value in the same way as X.
It is obtained by internally dividing the difference between correction values.

In #505, comprehensive correction is performed. This is X as mentioned above,
A summary calculation is performed on the correction value Y. For example, the following calculations are performed.

This is the average value of the correction values obtained in #502 and #504. This value 2 is adopted as the final correction value.

In addition, in #503, the flag PLCFL for "correction calculation"
If G is 0, the correction value calculated in #5o2 becomes the final correction value.

The correction value is calculated in this way, and the "correction calculation" subroutine is returned at #506.

In the above embodiment, in the "correction calculation" subroutine, "
When the flag PLCFLG for "correction calculation" is O, no contrast information is used.

However, even in this case, contrast information can be obtained when using the fill light, and it is also possible to perform correction calculations based on the contrast information using this contrast value and the contrast value (constant value; Co) of the fill light pattern itself. .

This flowchart is shown in FIG. 8, and the correction formula is as follows, for example.

On the other hand, when an infrared film is used, it is also effective to simply use the correction value using the auxiliary light without performing any correction.

According to this embodiment, - in the case of using an auxiliary light different from the extra-membrane light, focus correction can be obtained from the same light-receiving part as for the extra-membrane light without the need to provide a new light-receiving part exclusively for the auxiliary light. Corrections can be made when using auxiliary light using only the information. Therefore, it is possible to eliminate high costs, and when using an auxiliary light, the focus information is calculated only from the correction value of the auxiliary light.
Since the correction amount is calculated and the focus information is calculated by taking into account the conditions of the external light incident along with the auxiliary light, more appropriate focus information calculation is possible.

(Correspondence between Invention and Embodiment) In this embodiment, the portion that executes the operation shown in FIG. 7 or 8 corresponds to the correction value calculation means of the present invention.

(Effects of the Invention) As explained above, according to the present invention, when the auxiliary light is used, correction is made based on the information from the photoelectric conversion means when the auxiliary light is used and the information from the photoelectric conversion means using only external light. A correction value calculation means is provided which calculates the correction value and outputs the correction value to the calculation means for use in focus state detection calculation. A photoelectric conversion means is used, and when the auxiliary light is used, the correction value used in the focus state detection calculation is calculated by taking into account the external light conditions that are mixed even when the auxiliary light is used, which reduces the cost. It becomes possible to improve the focus detection accuracy under the auxiliary light while eliminating the auxiliary light.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIGS. 2 to 7 are flowcharts thereof, and FIG. 8 is a flowchart showing the operation of the main part of another embodiment of the present invention. PRS...Microcomputer, SNS...
...Line sensor device, SDR...Drive circuit, AUT...Auxiliary light projection unit, LCM...
...Lens communication buffer circuit, FLNS...
··lens. Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] (1) A photoelectric conversion means that receives a light beam passing through an imaging optical system whose focus is to be detected, and an arithmetic means that detects the focal state of the imaging optical system based on information from the photoelectric conversion means. In the focus detection device equipped with the above, when the auxiliary light is used, a correction value is calculated based on the information from the photoelectric conversion means when the auxiliary light is used and the information from the photoelectric conversion means using only external light, and the correction value is calculated based on the information from the photoelectric conversion means when the auxiliary light is used. A focus detection device comprising: a correction value calculation means for outputting the correction value to the calculation means for use in a focus state detection calculation.