JPS62133410A - Focus detecting system - Google Patents

Abstract

PURPOSE:To execute precisely focus detection even if any image forming optical system is loaded by changing an arithmetic range in which the 1st and 2nd signals are relatively changed based on of the positional information of the image forming optical system in its optical axis direction and making the arithmetic range include all the movable range of the image forming optical system in its optical axis direction. CONSTITUTION:The maximum defocusing variable MD of a lens loaded at present is obtained from a ROM in an intra-lens control circuit LPRS and the size of the arithmetic range of a relative displacement value (k) is set up in accordance with the information. Namely, the range of the relative displacement value (k) is increased at the loading of a lens such as a telephoto lens having a large maximum defocusing value MD, and at the loading of a lens such as a wide angle lens having a small maximum defocusing value, the range of the (k) is reduced. The positional information DV of a photographing lens LNF at the start of focus detection is obtained and the relative displacement value (k) is displaced in an effective direction to determine the arithmetic range. Consequently, the arithmetic range coincides with the movable range of the lens LNF and focus detection can be precisely attained even if any focus adjusting lens is loaded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention relates to an improvement in a focus detection method for detecting a focus state from the relative positional relationship between two images of an object.

(Background of the Invention) Conventionally, one type of camera focus detection device divides the exit pupil of a photographic lens and observes the relative positional displacement of two images formed by the light beams that have passed through each pupil area. For example, an aerial image formed on a predetermined focal plane (plane equivalent to a film plane) by two parallel imaging optical systems is guided to two sensor planes. , the secondary imaging method that detects the displacement of the relative position of the two images is
JP-A-55-118019, JP-A-55-155
It is disclosed in Publication No. 331 and the like.

A schematic view of the secondary imaging type focus detection device is shown in FIG. 6. A field lens 3 is arranged on the same optical axis 2 as the photographing lens 1 whose focus is to be detected. Behind it, two secondary imaging lenses 4a are placed at symmetrical positions with respect to the optical axis 2,
4b is placed.

Furthermore, photoelectric conversion element rows 5a and 5b are arranged behind it. Apertures 6a and 6 are located near the secondary imaging lenses 4a and 4b.
b is provided. The field lens 3 forms an image of the exit pupil of the photographing lens 1 approximately on the pupil plane of the two secondary imaging lenses 4a and 4b. As a result, the beams of light incident on the secondary imaging lenses 4a and 4b are distributed over areas of equal area on the exit pupil plane of the photographing lens l that correspond to the secondary imaging lenses 4a and 4b and do not overlap with each other. It will be ejected from. An aerial image formed near the field lens 3 is converted into a photoelectric conversion element array 5a by secondary imaging lenses 4a and 4b.
, 5b, the two images on the photoelectric conversion element arrays 5a and 5b change their positions based on the displacement of the aerial image position in the optical axis direction. FIG. 7 shows this state. As shown in FIG. 7(A), at the time of focusing, the two images are located at the center of the photoelectric conversion element arrays 5a and 5b, and as shown in FIG. 7(B). As shown, when the rear focus is on, the two images move in a direction away from the optical axis 2, and as shown in FIG. 7(C), when the front focus is on, the two images move in a direction toward the optical axis 2. If this image intensity distribution is photoelectrically converted and the displacement (shift) of the relative position of the two images is detected by electrical signal processing, the photographing lens l
It is possible to detect the focal state of

A method for processing the photoelectric conversion signals output from the photoelectric conversion element arrays 5a and 5b is disclosed in Japanese Patent Application Laid-Open No. 58-1423.
No. 06, US Pat. No. 4,333,007, etc. are disclosed. in particular.

The number of photoelectric conversion elements constituting the photoelectric conversion element row 5a or 5b is N, and the i-th (i=o, ..., N-1)
The image signals from the photoelectric conversion element arrays 5a and 5b are A(i)
, B(i), the following formula %( is calculated for k, ≦ and ≦ 2. Note that M is (M =
The number of pixels to be calculated is expressed as N-1kl-1). A
(i) OB('') is an operator for A(i), BU), for example, A (i) OB(j) = l A(i) - B(j)
I (2) A (1) OB (j) = I A (
i) -BU) I″L(3)A(i)OB(j)=
max[A(i).

B(j)] (4) A(i) 0B(j) = m E n [A(i).

B(j)] (5) etc. can be considered, and equation (2) is A(i), B(
Expression (3) expresses the absolute value of the difference between D, and Expression (4) expresses its power value.
Th L 4- Small L (Gl −+I↓ represents extraction of the small one, respectively. According to the above definition,
VL (k) and V2 (k) can be regarded as correlation quantities in a broad sense. Furthermore, according to equation (1), Vl(k) is actually the correlation amount according to the above definition at a displacement of (k-1), and similarly, V2(k) is the correlation amount at a displacement of (k+ 1), respectively. It means. Gatte, Vl (
k) , V2 (k) (7) Evaluation amount V 0 which is the difference
1) is the image signal A(i), B at the relative displacement k
(+) represents a change in the amount of correlation. This is because the amount of change becomes "0" at the peak of the amount of correlation.

lk) , V(k+ 1) <0 (8
), assuming that there is a peak of the correlation amount in the interval [k, +13], and interpolating the value of V(k), lk+1),
The amount of deviation between image signals A(i) and B(i) can be known. Figure 8 shows the number of photoelectric conversion elements as 16 (N= 16
), two image signals A(i) and B(i) are shown. In this case, there is a deviation amount of P. FIG. 9 shows the evaluation amount V (k) according to the above equation (2) when the relative displacement amount k is changed within the calculation range of -N/2≦≦N/2. As mentioned above, V(k)-V(k+1)<0
(k) and V(k+1) can be linearly interpolated to obtain the deviation amount P. Furthermore, FIG. 10 shows each evaluation amount V (k) when the relative displacement amount k is changed within the calculation range of -3≦≦3.
The correspondence between image signals A(i) and B(i) when calculating is diagrammatically shown, and the shaded area is the photoelectric conversion element to be subjected to the correlation calculation.

In the above calculation of the evaluation amount V (k), the calculation time varies significantly depending on the calculation range for the relative displacement amount. Therefore, it is desirable to perform calculations in a small range if possible, but if it is too small, the amount of deviation between the two images when the photographic lens is greatly defocused will deviate from the calculation range for the relative displacement amount, and it will not be accurate. In some cases, accurate focus detection could not be performed. Therefore, normally, the lower limit value of the calculation range is 1 and the upper limit value is 2, which corresponds to the number N of photoelectric conversion elements in the photoelectric conversion element array (the number of pixels of the sensor), k,=-N/2.

In many cases, k2 = N/2. However, if the photographic lens has a large maximum defocus amount, such as a telephoto lens, and the lens has a large defocus, the two images will be separated as described above. The probability that the shift amount P deviates from the relative displacement amount k increases, and focus detection cannot be performed.

(Objective of the Invention) The main object of the present invention is to provide a focus detection method that can reliably perform focus detection no matter what kind of imaging optical system is attached.

Another object of the present invention is to provide a focus detection method that can reliably perform focus detection, eliminate unnecessary calculations, and shorten focus detection time no matter what kind of imaging optical system is installed. It is to be.

(Features of the Invention) In order to achieve the above main object, the invention of claim 1 of the present application (hereinafter referred to as the invention of claim 1) provides a calculation range for relatively displacing the first and second signals. is changed based on positional information in the optical axis direction of the imaging optical system, so that the calculation range includes the entire movable range of the imaging optical system in the optical axis direction. do.

In order to achieve the object of the above function, the invention of claim 2 of the present application (hereinafter referred to as the invention of claim 2) sets the calculation range for relatively displacing the first and second signals to the imaging optical system. The displacement is made according to the maximum value of the defocus amount of the system and the positional information of the imaging optical system in the optical axis direction, and the smaller the maximum value of the defocus amount of the imaging optical system is, the more the displacement is made. The present invention is characterized in that the size of the calculation range is made small and the calculation range always matches the movable range of the imaging optical system in the optical axis direction.

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

FIG. 1 is a block diagram showing an example of a camera focusing device suitable for implementing the present invention. PRS is a camera control circuit that includes, for example, a CPU (central processing unit),
It is an l-chip microcomputer in which RAM, ROM, EEFROM (electrically erasable programmable ROM), input/output board, etc. are arranged, and the ROM and EEFROM are arranged.
A series of camera control software and parameters including AF amount control are stored in the EFROM.

DBUS is a data bus, and SHT is a data bus DBU while the control signal C3HT is input from the control circuit PR5.
The shutter control circuit APR accepts data input via S and controls the running of the shutter leading and trailing curtains (not shown) based on the data, and the APR connects the data bus DBUS while the control signal CAPR is input. The aperture control circuit, which receives data input via the data bus DBUS and controls an aperture mechanism (not shown) based on the data, receives data input via the data bus DBUS while the control signal CD5P is input. A display circuit for displaying various photographic information based on the data, and SWS are a group of switches (not shown) such as a release switch, a snapshot mode switch, and switches for setting various information.

SPC is a photometric circuit, and its output analog photometric signal 5spc is sent to the control circuit PR3, where it is A/D converted and used to control the shutter control circuit SHT and aperture control circuit APR. Used as photometric data. LCOM is a lens communication circuit that accepts data input via the data bus DBUS while the control signal CLCOM is input, and performs serial communication with the lens unit described later based on the data.
In synchronization with CK, data DCL for driving the lens is transmitted to the lens control circuit described later, and at the same time, from the lens control circuit, position information DV of the photographing lens (described later) or lens information such as maximum defocus amount is transmitted. Information DLC is input serially.

BSY is a signal to notify the camera side that a focusing lens, which will be described later, is moving, and when this signal is generated, the serial communication is not performed.

LNSU is a lens unit, and LPR3 is an in-lens control circuit that drives a motor MTR based on serially input data DCL to move the whole or a part of the photographing lens LNF. It has a ROM that stores information such as focal length and aperture f-number. ENC is 1, for example, photographing lens L
An encoder that detects a pulse signal generated as the lens barrel holding the NF moves, and outputs an encoder pulse signal EPL to the in-lens control circuit I and PR5 as the current position information DV of the photographing lens LNF. circuit,
SDR is a sensor drive circuit that controls a line sensor SNS, such as a CCD, which has two sensor arrays SA, A, and SAB according to each signal inputted from the control circuit PR3.

Next, the operation when using the position information DV of the line sensor SNS will be explained with reference to FIG. 2.3. Note that the shutter control circuit SHT, aperture control circuit APR, and display circuit DS
Since the operations of P and the photometric circuit SPC are not directly related to the present invention, they will be omitted here.

[Step l] Drive the line sensor SNS via the sensor drive circuit SDR to generate two image signals A(i),
Obtain B(i). To briefly explain the operations of the control circuit PR3, sensor drive circuit SDR, and line sensor SNS at this time, when the accumulation start signal STR is generated in the control circuit PR3, the sensor drive circuit SDR outputs a clear signal CL to the line sensor SNS. Then, the charges in each photoelectric conversion unit of the sensor arrays SAA and SAB are cleared. Then line sensor S
NS is an optical image formed on the sensor arrays SAA and SAB by the secondary imaging lens etc. (not shown in Fig. 1, but arranged as shown in Fig. 6) arranged at the front stage. photoelectric conversion and charge storage operations begin. When a predetermined time has elapsed since the start of the above operation, the sensor drive circuit SDR outputs a transfer signal SH to the line sensor SNS, and transfers the charges accumulated in the photoelectric conversion section to the CCD section. At the same time, the sensor drive circuit SDR outputs an accumulation end signal E.
ND to the control circuit PR5, and waits for the CCD drive clock CK to be input from the control circuit PR3. When the CCD drive clock CK is input, the sensor drive circuit SDR generates the CCD drive signals φ and φ2, and Outputs the signal to the line sensor SNS. When the CCD drive signals φr and φ2 are input, the line sensor SNS outputs an analog image signal 5SNS to the control circuit PR5 in accordance with these signals. As a result, the control circuit PR5 A/D converts the analog image signal 5SNS in synchronization with the COD drive clock CK, and stores it at a predetermined address in the RAM as two image signals A(i) and B(i). do.

[Step 2] Check the status of the continuous shooting mode switch in the switch group SWS, and if it is continuous shooting mode, step 11
If not, proceed to step 3.

[Step 3] Communicates with the lens driving lens LNSU via the lens communication circuit LCOM, obtains the current position information DV of the photographing lens LNF from the lens information DLC, and calculates the current relative displacement amount k( 7) -N/2+Dv
In the calculation range of ≦≦N/2+Dv, that is, + = -
Set N/2+DV, k2=N/2+DV. The position information DV has a value of O (zero) when the photographing lens LNF is located at the center of its range of motion, a value that is negative when it moves toward the closest position, and a positive value when it moves toward infinity. Therefore, the size of the calculation range for the relative displacement amount remains constant (as in the conventional case), and the displacement is made in a direction that covers the entire calculation range.

Here, the above explanation will be explained in more detail using FIG. 3. For example, the number of pixels in sensor arrays SAA and SAB is 24 (
Since N = 24), the calculation range for the relative displacement amount is set in advance to 112≦≦12, and at this time, the range of motion of the photographing lens LNF is 20 mm, and the sensor 1
The discussion will proceed on the assumption that the displacement of the pixel corresponds to the range of motion of the photographic lens of 1 mm. When the photographing lens LNF is at the position of arrow a (infinite position), the position information DV is r + tO.
Therefore, the calculation range becomes k, = -12 + 10K2, and 2 = 12 + 1O = 22. In this case, as shown in Figure 3, the size of the calculation range for the relative displacement remains constant, and the displacement in the nearest direction is There will be more. In other words, conventionally the relative displacement F as shown by the dotted line
Since it was within the calculation range of J3, it was impossible to detect the focus when there was a large defocus, but by using position information DV, it is now possible to cover areas that could not be covered conventionally within the calculation range. Inability to detect focus will no longer occur. Conversely, when the user is at the position of arrow C (close position), the position information DV is r-10J. from.

k, = -12 + (-10) = -22 to 2 = 12
+(-10)=2, and in this case, the number of displacements to be covered in the infinite direction increases. If you are at the position indicated by the arrow (center position of the range of motion), it is the same as before.

[Step 4] For example, a correlation calculation such as the above-mentioned equation (1) is performed to obtain focus detection information, that is, the amount of shift P between the two images at this time.

[Step 5] Even if the shift iP can be detected, if the contrast of the signal is low and the reliability of the result is poor, it is impossible to detect the focus, so in such a case, go to step lO.
If the focus can be detected, the process moves to step 6.

[Step 6] Compare the absolute value of the amount of deviation P with a predetermined value, and if the amount of deviation P is smaller than the predetermined value, that is, the amount of displacement that can be considered to be in focus, proceed to step 9; otherwise, proceed to step 9. moves to step 7.

[Step 7] Check whether the subject is in front or rear focus based on the sign (positive or negative) of the shift amount P, and send the data to the display circuit DSP to display the focus state at that time.

[Step 8] Calculate the amount of movement of the photographic lens LNF based on the shift amount P obtained in Step 4.

The data is output to the intra-lens control circuit LPR3 via the lens communication circuit LCOM. Lens unit at this time)
To briefly explain the operation on the L'NSU side, the in-lens control circuit LPR3 drives the motor MTR,
NF is moved to a position corresponding to the data, that is, until the number of encoder pulse signals EPL input from the encoder circuit ENC matches the data.

[Step 10] Move the photographing lens LNF by a predetermined amount,
A so-called search operation is performed.

[Step 11] In the case of quick shooting mode, focus detection must be performed in a shorter time than in single shooting mode,
Since it is expected that the defocus of the subject will not change much during quick shooting, the relative displacement amount kc is set in a relatively small calculation range, i.e., 1 = kc, 2 = kc.
to speed up the calculation.

[Step 12] Correlation calculation is performed to obtain focus detection information within the calculation range set in step 11.

[Step 13] As in step 5, determine whether focus detection is possible or not. If focus detection is not possible, proceed to step 14; if focus detection is possible, proceed to step 6. Then, the process moves to step 9 or step 7→step 8, as described above.

[Step 14] Since it is not preferable to perform a search operation during quick shooting, from the viewpoint of quick shooting performance, etc., data indicating that the focus cannot be detected is output to the display circuit DSP, and the data is displayed.

According to the embodiment shown in FIG. 2.3, the range of the relative displacement amount is set according to the position information DV of the photographing lens LNF at the start of focus detection, so that the maximum defocus amount MD reaches N/2. Even if a large photographic lens LNF is attached, focus detection can be performed reliably.

Next, the operation when using the position information DV and the maximum defocus amount MD of the photographing lens LNF will be explained with reference to FIG. 4.5.

[Step 21] Drive the line sensor SNS via the sensor drive circuit SDR to generate two image signals A(i)
, obtain B(i).

[Step 22] Check the state of the snapshot mode switch in the switch group SWS, and if it is the snapshot mode, proceed to step 33; otherwise, proceed to step 23.

[Step 23] Communicates with the lens unit LNStJ via the lens communication circuit LCOM and sends lens information D.
The maximum defocus amount MD' of the currently attached photographic lens LNF from the LC (the value of the maximum defocus amount MD of the actual photographic lens LNF).

For example, 1/2 value) and the current position information DV of the photographing lens LNF are obtained, and the relative displacement amount k at this time is determined according to each of the values.
into the calculation range of −MD′+Dv≦≦MD′+Dv, that is, kt =−MD′+pV, k2=MD′
+DVt;: Setting t6. As mentioned in section 6 before setting, the position information DV is O (zero) when the photographing lens LNF is located at the center of its range of motion, negative when it moves to the close side, and positive when it moves to the infinity side, so it is a relative value. When calculating the calculation range for the amount of displacement, it is known in advance that the maximum defocus amount MD', which is, for example, 1/2 of the value of the maximum defocus amount MD of the actual photographic lens LNF, may be used.
This value is set as the maximum defocus amount of the photographing lens LNF.

Here, the above description will be explained in more detail using FIG. 5. Maximum defocus amount MD of the photographing lens LNF at this time
' is 10mm (actual maximum defocus amount MD is 20m)
m), and the range of motion of the photographing lens LNS is 20 mm.
Let's proceed on the assumption that this is the case. When the photographing lens LNS is at the position of arrow a (infinite position), the position information DV
is r+10'', so the calculation range is k,=-10+10=O k2=lO+10=20. Therefore, as shown in FIG. 5, the range of calculation and the range of motion of the photographing lens LNS match, which not only prevents the inability to detect the focus, but also prevents unnecessary calculations. In other words, conventionally (in this case, it is assumed that the number of pixels is 24 (N = 24)), the calculation range for the relative displacement amount was as shown by the dotted line, so it took time to detect the focus. (not shown, but more noticeable with wide-angle lenses),
In addition, focus detection was not possible when there was a large defocus, but by using the maximum defocus iMD', the size of the calculation range matches the range of motion of the photographing lens LNF, and by using the position information DV, the conventional cover Since the portions that could not be detected can now be included within the calculation range, the focus detection time can be shortened and the inability to detect the focus will not occur. Conversely, if you are at the position of arrow C (close position), the location information DV is r-10.
Therefore, k+ = -10+ (-10) = -20 and 2 = 1
The calculation range is 0+(-10)=0, and the same holds true in this case. If you are at the position indicated by the arrow (center position of the range of motion), position information D
Because V is "0".

k,=-io+o=-i.

k2=lO+0=10 This is the calculation range.

[Step 24] For example, a correlation calculation such as the above-mentioned equation (1) is performed to obtain focus detection information, that is, the amount of shift P between the two images at this time.

[Step 25] Even if the deviation Bp can be detected, if the contrast of the signal is low and the reliability of the result is poor, the focus cannot be detected. In such a case, go to step 30; if the focus can be detected, go to step Move to 26.

[Step 26] The absolute value of the deviation amount P is compared with a predetermined value, and the deviation amount P is smaller than the predetermined value.

In other words, if the amount of displacement can be considered to be in focus, step 29
If not, the process moves to step 27.

[Step 27] It is determined whether the subject is in front or rear focus based on the sign (positive or negative) of the shift amount P, and the data is sent to the display circuit DSP to display the focus state at that time.

[Step 28] The amount of movement of the photographing lens LNF is calculated based on the shift amount P obtained in step 24, and the data is output to the intra-lens control circuit LPR3 via the lens communication circuit LCOM. Lens unit at this time) LNSU
To briefly explain the operation on the side, the in-lens control circuit LP
R3 drives the motor MTR to move the photographing lens LNS to a position corresponding to the data, that is, until the number of encoder pulse signals EPL input from the encoder circuit ENC matches the data.

[Step 29] Data indicating that the focus is in focus is sent to the display circuit DSP, and the data is displayed.

[Step 30] At step 25, it was determined that focus detection was impossible. Compare the maximum defocus amount MD obtained in step 23 with the fixed defocus amount MS,
If MD>MS, the process moves to step 32; if MD≦MS, the process moves to step 31.

[Step 31] If MD≦MS, it means that the maximum value of defocus of the currently attached photographic lens LNF is relatively small, and at this moment the photographic lens LNF
Even if the lens is moved by a predetermined amount 1, a so-called search operation is performed, and focus detection is performed again.

Since the amount of defocus is originally small, no increase in contrast can be expected, and as a result, the probability that focus will be detected next time is low.Therefore, in such a case, no search operation is performed, and the display circuit DSF is unable to detect focus. Output data indicating this and display it. After that, the process moves to step 21 again.

[Step 32] When MD>MS, there is a high probability that the focus can be detected by a search operation, contrary to the case when MD≦MS, so a search operation is performed.

[Step 33] In the case of quick shooting mode, focus detection must be performed in a shorter time than in single shooting mode,
Since it is expected that the defocus of the subject will not change much during quick shooting, the relative displacement amount kc is set in a relatively small calculation range, that is, = -kc, and 2 =k.
Set c to speed up the calculation.

[Step 34] Correlation calculation is performed to obtain focus detection information within the calculation range set in step 33.

[Step 35] Same as step 25.

It is determined whether focus detection is possible or not, and if focus detection is not possible, it is not preferable to perform a search operation during quick shooting from the viewpoint of quick shooting performance, so the process moves to step 31 and displays an indication that focus detection is not possible. If the focus can be detected, the process moves to step 26 to determine whether the focus is in focus.Thereafter, the process moves to step 29 or step 27→step 28, as described above.

According to the embodiment shown in FIG. 4, the maximum defocus amount MD of the currently attached lens is obtained from the ROM in the in-lens control circuit LPR3, and the size of the calculation range for the relative displacement amount is set according to this information. In other words, if a lens with a large maximum defocus amount MD is attached, such as a telephoto lens, it should be set large, and conversely, if a lens with a small maximum defocus amount MD is attached, such as a wide-angle lens, the teeth.

In addition, the position information DV of the photographing lens LNF at the start of focus detection is obtained, and the relative displacement amount k is displaced in an effective direction to determine the calculation range. The range of motion of the LNF matches, and no matter what kind of focus adjustment lens is attached, focus detection can be performed reliably, and unnecessary calculation time can be eliminated, reducing focus detection time. It can be achieved.

(Modification) In the embodiment shown in FIG. 1, the maximum defocus amount MD of the attached lens is obtained from the lens unit LNSU. Needless to say, the present invention can be applied to any zoom lens whose focal length can be selected.

(Effects of the Invention) According to the invention in item 1 of the present application, the calculation range for relatively displacing the first and second signals is changed based on the position information in the optical axis direction of the imaging optical system. Since the calculation range includes the entire range of motion of the imaging optical system in the optical axis direction, focus detection can be performed reliably no matter what kind of imaging optical system is installed. can.

According to the present invention, the calculation range for relatively displacing the first and second signals is determined by the maximum value of the defocus amount of the imaging optical system and the position of the imaging optical system in the optical axis direction. The smaller the maximum value of the defocus amount of the imaging optical system, the smaller the calculation range to be displaced, and the more the calculation range is changed in the optical axis direction of the imaging optical system. Since it always matches the range of motion, unnecessary calculations are not performed and focus detection time can be shortened.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an example of a focus adjustment device for a camera implementing the present invention, Fig. 2 is a flowchart showing the invention in Section 1, and Fig. 3 is a flowchart showing the invention in Section 1 using the position information of the photographing lens. Figure 4 showing the calculation range of the relative displacement amount when
The figure is a flowchart showing the second invention, FIG. 5 is a diagram showing the calculation range of the relative displacement amount when using the position information of the photographing lens in the second invention, and FIG. 6 is a general quadratic result. A layout diagram showing the optical system of the image-based focus detection device. Fig. 7 is a diagram showing the relationship between the focus detection state and image deviation. Fig. 8 shows the image signals output from two sensor arrays in the secondary imaging method. FIG. 9 is a diagram showing a change in the evaluation amount in the secondary imaging method, and FIG. 1O is a diagram showing the correspondence between two images during focus detection calculation in the secondary imaging method. PH1... Control circuit, LCOM... Lens communication [8, LNSU... Lens unit,
SDR...Sensor drive circuit, SNS...
・Line sensor, k...Relative displacement amount. Patent applicant Minoru Nakamura, Canon Co., Ltd. Figure 8 Figure 9

Claims (1)

[Claims] 1. Forming by an optical system first and second images whose relative positional relationship changes depending on the focal state of the imaging optical system whose focus is to be detected; The photoelectrically converted first and second signals corresponding to the second image are obtained by a plurality of photoelectric conversion means, and the first and second signals are computationally displaced relative to each other to obtain correlation information. In the focus detection method, the focus state of the imaging optical system is detected by determining the relative positional relationship between the first and second images based on the correlation information.
A focus detection method characterized in that a calculation range for relatively displacing the second signal and the second signal is changed based on positional information in the optical axis direction of the imaging optical system. 2. The optical system forms first and second images whose relative positional relationship changes depending on the focus state of the imaging optical system to be detected, and corresponds to the first and second images. The photoelectrically converted first and second signals are each obtained by a plurality of photoelectric conversion means, the first and second signals are calculated relative to each other to obtain correlation information, and the correlation information is In the focus detection method, the focus state of the imaging optical system is detected by determining the relative positional relationship between the first and second images based on the first image.
The calculation range for relatively displacing the second signal and the second signal is changed according to the maximum value of the defocus amount of the imaging optical system and the position information of the imaging optical system in the optical axis direction. Focus detection method.