JPH0215220A - Focus detecting device - Google Patents

Abstract

PURPOSE:To offer a focus detecting device capable of detecting a focus stably by switching a decided value according to a focal length, a lens position, magnification, etc., when a correlation obtained by comparing two picture signals is compared with the decided value to determine whether a focus can be detected or not. CONSTITUTION:The 1st and 2nd picture signals made incident on a light receiving means 14 through two parts over the optical axis of a photographing lens 2 from a object are compared with each other to calculate a correlation of a combination of things with the highest agreement. The relative interval between to images is detected from the correlation, and defocus quantity from the focusing position of the photographing lens 2 is calculated to detect a focus. To judge whether focus detection is possible or not, the correlation from picture data is compared with a set decided value. When the decided value is switched to a severe value, for instance, the feasibility of focus detection can be decided surely without mistakenly detecting the focusing position in an unfocused state, and the focus can be detected stably.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a focus detection device that calculates the amount of defocus from a focus position of a photographic rinse using a so-called phase difference detection method.

[Conventional technology]

In a focus detection device using the so-called phase difference detection method, the subject image within the focus detection area is separated into two images, each light image is received by a light receiving element, and these two image signals are compared to detect the image of the imaging lens. Since the amount of deviation to the focal point, that is, the amount of defocus, is calculated, for example, if the image signal is unreliable due to low brightness of the subject, or if the contrast is low, the reliability of the correlation value when comparing two image signals can be calculated. If not, accurate focus detection may not be possible.

Conventionally, various focus detection devices have been proposed to improve the problems of focus detection using the phase difference detection method. For example, Japanese Patent Application Laid-Open No. 61-282827 discloses a system in which a high-contrast image pattern is projected onto a subject using auxiliary light, and the image pattern is received.

Also, JP-A-60-243618, JP-A-60-24
No. 7210, Japanese Unexamined Patent Publication No. 6C)-247211,
Three types of judgment criteria are switched based on the subject brightness, the subject's Con1 Helast, and the judgment result of the previous focus detection, and if the defocus amount is less than the set judgment criterion, the focus detection is determined to be unreliable and the focus is detected. What has been determined to be impossible is shown. Specifically, if the reliability of the image signal or the correlation value in the previous focus detection is unreliable, the strictest judgment value is set to 1, and if it is reliable, the loosest judgment value is set to 3. is set. Also,
If the reliability of the image signal or the correlation value of the image signal is unreliable in this focus detection, the intermediate judgment value is set to 2 (
K1>K2>K3) is set and reliable, then
3 is set as the most lenient judgment value.

[Problem to be solved by the invention]

By the way, the method disclosed in Japanese Patent Application Laid-Open No. 61-282827 requires an auxiliary light, which complicates the camera configuration and is disadvantageous in terms of loss. Furthermore, it is difficult to detect the image pattern using the auxiliary light in a bright place, so there is a drawback that a sufficient effect cannot be obtained.

Also, JP-A No. 6C)-243618, JP-A No. 60-2
No. 47210 and Japanese Patent Application Laid-Open No. 60-247211, regardless of the number of focus detections, if the reliability of the image signal or the correlation value of the image signal is unreliable, focus detection is always performed using the strictest criteria. If the focus detection results are reliable, the previous focus detection results are taken into consideration and the criteria are relaxed. However, for example, if the photographic lens is far off from the focal point, that is, if the focus is quite low, even if the subject's own contrast is large, the light will not be received by the light receiving element. Since the high frequency components of image patterns are cut out, they often become repetitive patterns with low contrast.
The drawback is that it is easy to mistakenly detect the in-focus position as the in-focus position (false focus) when it is not the in-focus position, and the conventional method for switching the judgment criteria described above does not have a sufficient effect on the above-mentioned false focus. There is.

This defense has been made in view of the above-mentioned problems, and even when the received image signal has a repetitive image pattern, it is possible to reliably determine whether or not focus detection is possible without erroneously detecting the focus position, and to ensure stability. An object of the present invention is to provide a focus detection device that can perform focus detection.

(Means for Solving the Problems) In order to solve the above problems, a first invention provides a first invention that uses light beams from an object that have passed through the first and second parts of the photographic lens, which sandwich the optical axis of the photographic lens, respectively. a light-receiving means for receiving each of the first and second images to be created; a means for mutually comparing the first and second image signals to calculate a correlation value for a combination with the highest degree of coincidence; A focus detection device comprising means for detecting a relative interval between two images from a value and calculating a defocus amount from a focus position of the imaging lens, comprising: means for detecting a focal length of the imaging lens; and a determination method. a means for setting a value, a determining means for comparing the correlation value with the determination value to determine whether focus detection is possible, and a means for switching the determination value; This is to switch the above-mentioned judgment value.

The second invention also provides a light receiving means for respectively receiving the first and second images formed from the subject light beams that have passed through the first and second parts of the photographic lens, which are sandwiched by the optical axis of the photographic lens. and a means for comparing the first and second image signals with each other to calculate a correlation value for a combination with the highest degree of coincidence; and detecting a relative interval between the two images from the correlation value; A focus detection device comprising: means for calculating a defocus amount from a focus position of an imaging lens; means for detecting a position of the imaging lens; means for setting a determination value; The apparatus includes determining means for comparing and determining whether focus detection is possible, and means for switching the determination value, and switching the determination value based on the position information of the photographing lens.

Further, a third invention provides a light receiving means for respectively receiving the first and second images formed from the subject light beams that have passed through the first and second parts of the photographing lens, which are sandwiched between the optical axis of the photographic lens. and a means for comparing the first and second image signals with each other to calculate a correlation value for a combination with the highest degree of coincidence; and detecting a relative interval between the two images from the correlation value; In a focus detection device having a means for calculating a defocus amount from a focus position of an image carrier lens, a means for detecting a focal length of the photographing lens, a means for detecting a position of the photographing lens, and a determination value is set. determining means for comparing the correlation value with the determination value to determine whether focus detection is possible; and means for switching the determination value; This is to switch the above judgment value to the value of the focal length.

Further, a fourth invention provides a light receiving means for respectively receiving the first and second images formed from the subject light beams that have passed through the first and second parts of the photographic lens, which are sandwiched between the optical axis of the photographic lens. and a means for comparing the first and second image signals with each other to calculate a correlation value for a combination with the highest degree of coincidence; and detecting a relative interval between the two images from the correlation value; A focus detection device having a means for calculating a defocus amount from a focus position of an imaging lens, a means for detecting an imaging magnification, a means for setting a determination value, and a means for comparing the correlation value with the determination value. The apparatus includes a determination means for determining whether focus detection is possible, and a means for switching the determination value, and switches the determination value according to the photographing magnification.

Further, a fifth invention provides a light receiving means for respectively receiving the first and second images formed from the subject light beams that have passed through the first and second parts of the photographing lens, which are sandwiched by the optical axis of the photographic lens. and a means for comparing the first and second image signals with each other to calculate a correlation value for a combination with the highest degree of coincidence; and detecting a relative interval between the two images from the correlation value; A focus detection device having a means for calculating a defocus amount from a focus position of an imaging lens, a means for detecting a focal length of the imaging lens, a means for detecting an imaging magnification, and a means for setting a determination value. , comprising a determination means for comparing the correlation value with the determination value to determine whether focus detection is possible, and means for switching the determination value, and determining the determination value based on the photographing magnification and focal length values. It is something that can be switched.

[Effect]

In the first focus/detection device configured as described above, the judgment value is set by switching to a predetermined value depending on the value of the focal length of the photographing lens, and is obtained by mutually comparing two image signals. The correlation value is compared with the predetermined determination value to determine whether focus detection is possible.

In addition, in the second focus detection device, the determination value is switched to a predetermined value based on the position information of the photographing lens, and the correlation value is compared with the predetermined determination value to determine whether focus detection is possible. It is determined.

Further, in the third focus detection device, the determination value is switched to a predetermined value based on information on the focal length and lens position of the photographing lens, and the correlation value is compared with the predetermined determination value to perform focus detection. It is determined whether this is possible.

Further, in the fourth focus detection device, the determination value is switched to a predetermined value depending on the imaging magnification, and the correlation value is compared with the predetermined determination value to determine whether focus detection is possible. .

Further, in the fifth focus detection device, the determination value is switched to a predetermined value depending on the focal length and imaging magnification of the photographic lens, and the correlation value is compared with the predetermined determination value to enable focus detection. It is determined whether there is.

〔Example〕

FIG. 1 shows an embodiment of the schematic configuration of a camera incorporating a focus detection device according to the present invention. The automatic focus detection device 1 includes a photographic lens 2, a focus detection means 3, a defocus amount determination means 4, a lens position detection means 5, a lens drive means 6, and a control means 7.
It is composed of. This photographic lens 2 guides a light beam 9 emitted from a subject 8 to a focus detection means 3. The focus detection means 3 has a photoelectric conversion element array (not shown), and calculates the output of this photoelectric conversion element array to detect the relative displacement of the optical image caused by the subject 8 on the photoelectric conversion element array. be.

Further, the defocus amount determining means 4 is configured to include the focus detecting means 3
The amount of defocus of the photographic lens 2 is determined based on the displacement detection signal output from the lens. The lens position detection means 5 detects the position of the photographing lens 2. The lens driving means 6 is the defocus amount determining means 4.
The photographic lens 2 is driven based on the defocus amount signal. The control means 7 controls the lens driving means 6 so that the photographing lens 2 is driven to a position corresponding to the defocus amount, and also controls the photographing lens 2 when the focus signal is output from the focus detecting means 3. This is to stop the drive of the

FIG. 2 shows an embodiment of the mechanical configuration of the focus detection means 3. As shown in FIG. The focus detection means 3 is composed of a main mirror 10, a submirror 11, and a focus detection optical system 12. This main mirror 10 branches the light beam 9 that has passed through the photographing lens 2 into a finder optical system and a submirror 11 (not shown). The submirror 11 further branches the light beam 9 split by the main mirror 10 into a focus detection optical system 12 and a film 13.

The focus detection optical system 12 includes a photoelectric conversion element array 141.
142, 143, separator lens 15 and aperture mask 1
6, mogicor mirror 17, and condenser lens 181,
It consists of 182, 183 and one field stop.

The photoelectric conversion element arrays 141, 142, 14.3 are arrays of a plurality of COD imaging elements, etc., and are formed on one chip on the focal plane 14 of the separator lens 15.

The separator lens 15 is a pair of separator lenses 151°1
52.153, and the branched light beam 9 is projected onto the photoelectric conversion element array 141.142.143.

The aperture mask 16 has a circular or oval opening 161,
162 and 163, and limits the light flux 9 input to the leverator lens 15. module mirror 17
is for guiding the light beam 9 that has passed through the condenser lenses 181, 182, and 183 to the separator lens 15. The field stop 19 has rectangular openings 191, 192, and 193, and is arranged near the focal plane, and is connected to the focus detection optical system 12.
This is to limit the field of view of the light beam 9 input to the.

FIG. 3 shows the photoelectric conversion element arrays 14.1 and 142.1.
43 (hereinafter referred to as COD including the light receiving section, the storage section, and the transfer section of the photoelectric conversion element). This photoelectric conversion element array 141 includes a reference portion 141a and a reference portion 14.
Similarly, the photoelectric conversion element array 142 consists of a reference part 142a, a reference part 142b, and a photoelectric sensor 142C, and the photoelectric conversion element array 1
43 is a reference part 143a, a reference part 143b, and a photoelectric sensor.
143C. The photoelectric sensor 141C.

142c and 14.3c are reference parts 141a, respectively.

It is arranged in the longitudinal direction on one side of 142a and 143a, and outputs a signal according to the amount of light received. Then, the storage time in the storage section of the CCD is controlled using a signal corresponding to the amount of received light. Further, as shown in FIG. 4, the photoelectric conversion element arrays 141, 142, and 143 have focus detection areas 21, 22, and 23 (hereinafter referred to as first islands 21, 22, and 23, respectively) located at the center of the photographing screen 20 in the finder. A displacement detection signal is output based on the optical image of the subject 8 projected onto the second island 22 and third island 23).

An area 24 indicated by a dotted line in the center of the photographing screen 20 is for displaying to the photographer the area where focus detection is being performed.

Further, the display section 25 lights up when the image is in focus.

For example, as shown in FIG. In the array 143, the number of pixels X in the reference part is 34, and the number Y of pixels in the reference part is 44, and in the photoelectric conversion element array 142, the number X of pixels in the reference part is 44, and the number of pixels in the reference part is 44. Y is made up of 52 pieces.

Further, in the automatic focus detection device 1, the reference portion 141a.

The data of each pixel 142a, 143a is divided into a plurality of blocks, and each divided block is compared with all the data of the respective reference parts 141b, 14.2b, 143b to perform focus detection. Of the focus detection results in each block, the data of the rearmost focus is taken as the focus detection data of each island 21, 22.23, and roughly the focus detection data of each island 21, 22.23 and the photographing lens 2 are The photographic lens 2 is driven and focused based on the photographing magnification data.

Next, the photoelectric conversion element arrays 141, 142.14
．． Fig. 5 shows means for determining the range (tefocus range) for detecting the defocus amount (i.e., the amount of deviation in the optical axis direction between the intended focal plane of the imaging optical system and the subject image plane) from 3. 〜Explained using FIG. 7.

Figure 5 shows each island 21, 22, 23 shown in Figure 3.
Reference parts 141a and 142a corresponding to.

This is an enlarged view of the differential data area of 143a. In the figure, each reference portion 141a, 142a, 143
The numerical value shown in a is the reference part 141a shown in FIG.
, 142a, and 143a are detected every third pixel, and the difference (that is, spatial frequency component) obtained by calculating the difference between the data is shown. Further, this difference data indicates a specific spatial frequency component extracted (filtered) from the pixel data (first spatial frequency component extraction means). In addition, there are two difference data,
Or you can use every other one. However, the spatial frequency components are different from when every third spatial frequency component is taken, and the numerical values are also different.

Reference parts 141a, 14 of each island 21.22.23
2a, 143a are the values for the first island 2
In M3 island 23, there are 30 pieces, 40 pieces on second island 22, and 30 pieces on M3 island 23. Also, the reference part 141b
, 142b, 143b as well as the reference parts 141a, 14
It is obtained in the same way as the numerical value of the difference data of 2a and 143a. In other words, the numerical values of the reference parts 141b, 142b, and 143b are 40 in the first island 21 and 40 in the second island 2.
In the second island, the number is 48, and in the third island 23, the number is 40.

Next, block division in each island 21, 22, and 23 will be explained. That is, in the first island 21, 1 (1 to 20), K1 (11
-30) are divided into two blocks, respectively called a first block BL1 and a second block BL2. In the second island 22, 2 (1 to 20) from the leftmost differential data,
It is divided into three blocks, 2 (11 to 30) and 2 (21 to 40), and they are respectively referred to as a third block BL3, a fourth block BL4, and a fifth block BL5. In the third island 23, the difference data at the upper end is divided into two blocks, 3 (1 to 20) and 3 (11 to 30), and are respectively designated as a ninth block 819 and a tenth block BL10.

Furthermore, the second island 22 detects differential data whose extraction frequency is changed in order to focus on a subject consisting of low frequency components (second spatial frequency component extracting means), and transfers this differential data to the sixth block BL6, It is divided into a seventh block BL7 and an eighth block BL8 and used as focus detection data. That is, the data of each pixel in the reference part 142a and the reference part 142b is differenced, for example, every seventh pixel, the sum of the difference data between adjacent pixels is found, and the data of this sum is set as the sixth block BL6. That is, the number of differential data every seventh block is 36 in the reference section 142a and 44 in the reference section 142b, and the number of data in the sixth block 816 is 35 in the reference section 142a and 44 in the reference section 142b.
So there will be 43 pieces. 35 of this reference portion 142a.
The 25 pieces on the left side of the block are set as the 7th block BL7, and the 25 pieces on the right side are the 7th block BL7.
The 5 pieces become the 8th block BL8.

Note that in the above description, the interval between the differences was set every seven, but the larger the interval, the more low frequency components can be extracted. In other words, the interval between the differences may be set to an interval other than every seven.

In this focus detection means, when the optical images of the reference part and the reference part match, the rear focus is achieved when the image interval is larger than a predetermined interval, the front focus is achieved when it is smaller, and the focus is achieved at a predetermined interval. Therefore, in the defocus range of the divided blocks, the block far from the optical center within each island has the rear pin side.

FIG. 6 shows an enlarged view of the reference portion 142a and the reference portion 142b of the second island 22, and the defocus range of the fourth block BL4, which is divided into blocks, will be explained using this figure. In other words, the fourth block BL of the reference portion 142a
In order to focus on the image No. 4, 2 (11 to 30) match. From this, the images match the reference part 142.
The left side of b is the front pin, and the maximum number of deviation data for the front pin (hereinafter referred to as deviation pitch) is 14. On the other hand, when the images match on the right side of the reference portion 142b, the rear focus becomes a rear focus, and the maximum displacement pitch of the rear focus becomes 14 pieces.

The same applies to the first island 21 and the third island 23. That is, as shown in Figure 7,
In the third block BL3, there are 4 front pin side deviation pitches,
The rear pin side deviation pitch is 24, and the fifth block BL
In No. 5, the front pin side deviation pitch is 24 pieces, and the rear pin side deviation pitch is 4g.

Furthermore, in the first block BL1 and the ninth block BL9, the front pin side deviation pitch is 5 pieces and the rear pin side deviation pitch is 15 pieces, and in the second block BL2 and the tenth block BL10, the front pin side deviation pitch is There are 15 pieces, and the rear pin side deviation pitch is 5 pieces. Furthermore, the 6th block BL
In No. 6, the deviation pitch is 4 on both the front pin side and the rear pin side.

In the seventh block BL7, there are 4 front pin side deviation pitches,
There are 14 rear pin side deviation pitches, and the 8th block 81
8, the front pin side deviation pitch is 14 and the rear pin side deviation pitch is 4, but 1. Since the deviation pitch is the same as that of the sixth block B1.6, the seventh block B10 has a deviation pitch of 4 to 14 on the rear pin side, and the eighth block BL8 has a deviation pitch of 4 to 14 on the front pin side. Set the deviation pitch to the defocus range.

FIG. 8 shows an embodiment of a circuit block of a camera in which an automatic focus detection device according to the present invention is constructed using a microcomputer.

A central control circuit (hereinafter referred to as a microcomputer) 26 controls the entire camera, calculates exposure, etc., extracts the first spatial frequency component (secondary filter means), and adjusts the focus based on the extracted spatial frequency component. (first focus detection means) and further extracts a second spatial frequency component based on the extracted spatial frequency component (secondary filter means), and the spatial frequency component extracted by the second order filter means. Focus detection is performed based on (second focus detection means)
, the secondary filter means and the second focus detection means are operated (determination means) when it is determined that the focus cannot be detected by the first focus detection means. The lens circuit 27 transmits data specific to the photographing lens 2 (interchangeable lens) attached to the camera body (not shown) to the microcomputer 26. The focus detection data output circuit 28 corresponds to the focus detection means 3 in FIG. The lli degree detection circuit 29 is connected to the photographing lens 2.
The brightness of the subject 8 is detected by measuring the luminous flux 9 that has passed through it, and the apex value BVO corresponding to this brightness is determined.
is transmitted to the microcomputer 26. The film sensitivity reading circuit 30 reads the film sensitivity from a film (not shown) and determines the apex value SV corresponding to this film sensitivity.
is transmitted to the microcomputer 26.

The display circuit 31 displays exposure information and the focus state of the photographic lens 2. The encoder 32 detects the amount of rotation of the lens drive motor 33, and outputs the number of pulses corresponding to a predetermined amount of rotation of the lens drive motor 33 to a lens drive control circuit 34, which will be described later. Lens drive control circuit 34
inputs a motor drive direction signal and a motor stop signal from the microcomputer 26, and controls the drive of the lens drive motor 33 based on these signals.

Additionally, a counter is provided inside the microcomputer 26. This counter detects the extended position of the photographic lens 2 from the infinity position, and is designed to move up or down by 1 to 1 for the number of pulses. Further, when the power switch (main switch) SW+, which will be described later, is turned on and the photographing lens 2 is driven and retracted to the infinity position, the counter is reset to 1. There is.

The power supply battery 35 directly supplies power to the microcomputer 26 and switches described below, and supplies power to other circuits via a power supply circuit 36 described later. Power supply circuit 3
Reference numeral 6 supplies power to circuits such as the lens circuit 27 and the focus detection data output horn circuit 28 based on a control signal from the microcomputer 26.

The power switch SW1 starts or stops the operation of the camera when opened or closed. The one-shot 1-circuit 37 generates a predetermined pulse in conjunction with the opening/closing operation of the power switch SW1, and inputs this pulse to the microcomputer 26. Shooting preparation switch SW
2 is opened and closed by operating a release switch (not shown), and when this photography preparation switch SW2 is turned on, a focus detection operation is started. The limit switch SWa is turned on when the photographing lens 2 is retracted to an infinity position or extended to the most extreme position. The selection switch SW4 is for selecting automatic focus adjustment mode (hereinafter referred to as AF mode) or focus detection display mode (hereinafter referred to as FA mode).When this selection switch SW4 is turned on, FA mode is selected.
mode, and when turned off, it becomes AF mode.

Next, the operation of the camera with the above configuration will be explained.

First, when the power switch SW+ is turned on, a pulse is output from the one-shot circuit 37 to the interrupt input terminal INTO of the microcomputer 26, and the microcomputer 26 executes the interrupt operation flowchart shown in FIG.

That is, the microcomputer 26 prohibits the focus detection operation caused by turning on the photographing preparation switch SW2 (step #1), and determines whether this interrupt operation is caused by turning on or turning off the power switch SW1 via the interrupt input terminal IP of the microcomputer 26.
The determination is made based on the voltage input to step #1 (step #2).

And if this input voltage is high voltage, step #
The power to the lens circuit 27 and the like is stopped without performing the processes 3 to #11, and the microcomputer 26 enters an operation standby state (steps #12 and #13). If this input voltage is a low voltage, the power switch SW+ is determined to be on, and the operation of the counter in the microcomputer 26 is prohibited (step #3).
Initialize the flags used to execute flowcharts 1~ and the output terminals of the microcomputer 26 (step #4)
).

Next, the output terminal OP1 of the microcomputer 26 is set to a high voltage to supply power to circuits such as the lens circuit 27 (step #5). Next, the lens drive control circuit 34
The renormalization signal is input, and the photographing lens 2 is retracted toward the infinite position (step #6). Then, the photographing lens 2 is retracted to the infinite position and the limit switch SW3 is turned on (step #7). When the limit switch SW3 is turned on in step #7, the driving of the photographing lens 2 is stopped (step #8).

Along with this, a counter in the microcomputer 26 is reset to count the number of pulses corresponding to the amount of rotation of the lens drive motor 33 (steps #9 and #10). and,
Interruption of the focus detection operation by turning on the photographing preparation switch SW2 is permitted (step #11).

Then, the output terminal OP1 is set to a low voltage and the lens circuit 2
7, etc., and standby operation until the shooting preparation switch SW2, etc. is pressed (steps #12 and #13).
).

Further, when the photographing preparation switch SW2 is turned on during the operation standby state in step #13, the microcomputer 26 executes the interrupt operation flowchart shown in FIG.

That is, the microcomputer 26 initializes the flags used to execute the flowchart and the output terminals of the microcomputer 26 (step #21). Further, a timer provided in the microcomputer 26 is reset, and then this timer is started from 1 (step #22). Then, a flag AFSF indicating that this is the first focus adjustment operation is set (step #23), and the output terminal OP1 is set to a high voltage to supply power to the lens circuit 27 and the like (step #24). Next, data including coefficients for converting the focal length data, open aperture value, defocus amount, etc. of the photographing lens 2 into the number of pulses for driving the lens is input from the lens circuit 27 (step #25). Then, difference data is input from the focus detection data output circuit 28, and this difference data is stored (steps #26 and #27). Next, the defocus amount of each of the islands 21, 22, and 23 described above is calculated, and furthermore, exposure calculation is performed, and these calculation results are displayed on the display circuit 31 (steps #28 to 23).
#30).

Next, it is determined whether it is FA mode or AF mode (step #31), and if it is AF mode, the driving amount of the photographing lens 2 is calculated from the defocus amount, and the photographing lens 2 is adjusted based on this. Drive (step #32). On the other hand, if there is FAA mode in step #31, step #3
The process moves to step #34 without performing the process of step 2. In step #34, it is determined whether the photographing preparation switch SW2 is opened or closed.

Then, the photographing rate (if the book switch SW2 is on, the flag AFSF is reset from step #35), the process returns to step #25, and the processing from step #25 is repeated. On the other hand, in step #34, the shooting preparation switch SW2 is
If it is off, the power supply circuit 36 is turned off to stop the power supply to the lens circuit 27 etc. (Step #36), and the operation is put on standby until the photographing preparation switch SW2 etc. is pressed (Step #37). Then, when the photographing preparation switch SW2 or the like is pressed, the process shifts to the flowchart of FIG. 9.

Next, the subroutine for calculating the defocus amount for each island 21, 22, 23 shown in step #28 of FIG. 10 will be explained using FIGS. 11 to 14.

FIG. 11 shows the defocus amount of each island 21, 22.23 for the first island 21 (step #41), the second island 22 (step #41), and the third island 23.
(Step #41), and the 12th
1 to 14 show specific flowcharts 1 to 1 of the defocus amount calculation for each island 21, 22, and 23.

FIG. 12 shows the calculation of the defocus amount of the first island 21 (
The subroutine of step #41) is shown. As mentioned above, this first island 21 is connected to the first block B[
A predetermined value It K I+ is stored in variables DF1 and DF2 that store the respective defocus amounts of the blocks BLI and B10, respectively (steps #51 and #52). This predetermined value”
-K'' is the value of the front pin state that cannot be taken in each block BLI, B10, and
It is output as the defocus amount when focus cannot be detected (hereinafter referred to as low contrast).

Next, the flag LCF1 indicating the low contrast state at the first island 21 is set to 1~ (step #53). Then, the focus state (front focus state, rear focus state, in-focus state) of the first block BL1 is detected and the defocus amount DF is calculated (Step #54). If focus detection is possible from this calculation result, a flag is flagged. Reset the LCN to 1 and store the obtained defocus amount DF in the variable DFI that stores the defocus amount of the first block BL1 (step #55
~#57), then proceed to step #58.

On the other hand, if it is determined in step #55 that focus detection is impossible, steps #56 and #57 are not performed and step #
58.

Next, the focus state of the second block BL2 is detected and the defocus IDF is calculated (step #58), and if focus detection is possible from the calculation results, it is determined whether the flag LCFI is set.

Then, when the flag LCF1 has been reset, that is, when it is determined that no-point detection is possible in the determination at step #55, the process moves to step #62. Also,
When the flag LCFI is set to 1- in step #60, the defocus amount calculation subroutine for the second island 22 in step #42 shown in FIG. 11 (FIG. 13)
to move to.

On the other hand, if it is determined in step #59 that focus detection is possible, the process proceeds to step #62 without performing the process in step #60.

In step #62, an inter-block defocus amount (average processing width) ΔDF to be used in an average processing routine to be described later is determined. Next, it is determined whether the defocus amount DF1 is larger or smaller than the defocus amount DF2, and the defocus amount of the subject with the larger defocus amount, that is, the one closer to the photographing lens 2 (camera), is determined on the first island 21. Let the defocus amount be DFIS1. In other words, defocus M
When DFI is larger than the defocus amount DF2, the defocus amount DF1 is set as the defocus l DFISI of the first island 21, and conversely, when the defocus amount DF2 is larger than the defocus amount DF1, the defocus amount DF1 is set as the defocus amount l DFISI of the first island 21. DF2 is the defocus amount DF of the first island 21
ISI (steps #63 to #67).

Also, step #64. Defocus amount DN with #65
When the difference between the defocus amount OF2 and the defocus amount OF2 is smaller than the average processing width ΔDF, the defocus lDFl and the defocus amount [)F2 are averaged, and this average value is used as the defocus amount DFIS1 of the first island 21. (Step #68). After completing the processing in steps #66, #67, and #68, the process moves to step #42 in FIG. 11.

FIG. 13 shows a subroutine for calculating the defocus amount of the second island 22.

First, the third block BL3, the fourth block BL4, and the fifth block BL3.
Predetermined values ``'~K are set in variables DF3, DF4, and DF5 that store each defocus amount of block BL5, respectively.
” (steps #71 to #73),
Flag L indicating the state of low contrast at the second island 22
Set CF2 (step #74). Then, the focus state of each block BL3, B10, B10 is detected and the defocus amount DF is calculated (Sterap #7
5. #79. #83). That is, if focus detection is possible from the calculation result of the defocus amount DF of the third block BL3 in step #75, the flag LCF2 is reset and the determined defocus amount DF is stored in the variable OF3 (steps #76 to #78), the process moves to step #79. Conversely, if it is determined that focus detection is impossible, the process proceeds to step #79 without performing steps #77 and #78.

Similarly, the defocus amount DF of the fourth block BL4 is
If focus detection is possible from the calculation result in step #79, the flag LCF2 is reset, the defocus IDF is stored in the variable DF4 (steps #80 to #82), and the process moves to step #83. Conversely, if it is determined that focus detection is impossible, the process proceeds to step #83 without performing steps #81 and #82.

Similarly, for the defocus amount DF of the fifth block 8[5, if focus detection is possible from the calculation result of step #83,
Reset the flag LCF2, store the defocus 1iDF in the variable [IF5 (steps #84 to #86),
The process moves to step #87. Conversely, if it is determined that focus detection is impossible, the process proceeds to step #87 without performing steps #85 and #86.

In step #87, it is determined whether the low contrast flag LCF2 is set. And flag LCF
2 is not set, i.e. step #7
6, #80. When focus detection is determined to be possible in the determination at #84, an average processing width ΔDF to be used in an average processing routine to be described later is determined (step #88).

Next, each defocus amount [IF3 of each block 813.814.815.

The magnitudes of DF4 and DF5 are determined, and the largest defocus amount HAXDF is extracted (step #89). Then, the difference from the defocus amount HAXDF is the average processing width Δ
If there are no other blocks smaller than DF, then
Step #90. Set the defocus amount HAXDF to the defocus IDFIS2 of the second island 22. #9
1) If there is one or more other blocks whose difference is smaller than the average processing width ΔDF, the defocus amount) IAXDF and the defocus amount of the other block whose difference is smaller than the average processing width ΔDF. (average processing), and this average value is set as the defocus amount DFIS2 of the second island 22 (step #92). and,
Step #91. When the process of #92 is completed, the process moves to the defocus amount calculation subroutine for the third island 23 (FIG. 14) of step #43 shown in FIG. 11.

Further, when it is determined that the flag LCF2 is set in step #87, the difference data of every third point is reorganized into the difference data of every seventh point in order to focus on the subject consisting of low frequency components (step #87). #93). That is,
For example, pixel data Ql, ρ2. ...,Qn,・
..., then the difference data for every third data is d[)n-ρ
1-ρ5. ..., 450g, -, Qn-0n+4,
-... becomes. Also, the difference data for every 7th position is d[)m
=01-09. ..., 4m-12m+9. ...becomes... The difference data d[)m for every seventh difference is obtained by taking the sum of every third difference data dDn. In other words, the difference data for every 7th position is dDm = dl)4'+dl)5, -..., dDm
+d[)m+4, -1ρ1-ρ5+ρ5-ρ9.・
..., ρn-4ρn 10ρn-ρn+4. ... = ρ 1- ρ 9 , ... , ρ n-4-
ρ n+4.

-1! 1-Ng, =-,Qm-Qm
10B, -... However, n=m÷4.

Roughly, take the sum of the adjacent difference data dDm,
New data string d[)W(m)-d[)m +d[)n
++1 is calculated and used to perform focus detection in the sixth block BL6, and detects the focus state and defocus I.
To calculate DF, step #94), if focus detection is possible, reset flag LCF2 to
The defocus fiDF6 of L6 is set as the defocus fiDFIs2 of the second island 22 in step #43.
(steps #95 to #97) On the other hand, if focus detection is not possible in step #95, the seventh block BL7
Perform focus detection, calculate focus state detection d3 and defocus IDF to 3 (step #98), and if focus detection is possible (step #99), return to step #96 and set flag LCF2.
The defocus amount of the seventh block BL7 is set as the defocus IDEI32 of the second island 22, and the process moves to step #43.

On the other hand, if focus detection is not possible in step #99, the eighth
Perform focus detection in block BL8, detect focus state and calculate defocus IDF (Step #100)
, if focus detection is possible (step #101)
, returns to step #96, resets the flag LCF2, sets the defocus amount of the eighth block BL8 as the defocus amount DFIS2 of the second island 22, and proceeds to step #43.

On the other hand, if focus detection is not possible in step #101, step #96. The above step # without performing the process #97
43.

Fig. 14 shows the differential of the third island 23 by calculation of the amount of one waste (
The subroutine of step #43) is shown.

First, the 9th block BL9, the 10th block B1-10
A variable OF9 that stores each defocus amount.

A predetermined value 11 K j+ is stored in DFlo (steps #111 and #112). Next, the third island 23
Set the flag LCF3 indicating the low contrast state at ! - Step #113). And the ninth block B1-
Step #114) If focus detection is possible, reset the flag LCF3 and set the defocus amount DF found in the ninth block BL9 to the defocus amount DF9. It is stored (steps #115 to #117). Meanwhile, step #
If it is determined in step 115 that focus detection is impossible, step #1
16. The process moves to step #118 without performing the process in #117.

Next, step #118) to detect the focus state of the 10th block BLIO and calculate the defocus amount DF.
If focus detection is impossible from this calculation result, the flag LC
Determine whether F3 is set. and,
As long as the flag LCF3 is reset, that is,
If focus detection is determined to be impossible in step #115, the process moves to step #122. Further, when the flag LCF3 is set to 1~, the process moves to the exposure calculation subroutine of step #29 shown in FIG. 10 (steps #119 and #120>. On the other hand, step #
If it is determined in step 119 that focus detection is possible, step #1
The process moves to step #122 without performing the process of step #20.

In step #122, an average processing width ΔDF of an average processing routine to be described later is determined. Next, the defocus amount DF
9 and defocus l DFIO are determined, and the larger defocus amount is set as the defocus amount DFIS3 of the third island 23 (steps #123 to #127
).

Also, step #124. #125 Defono Js MD
When the difference between F9 and defocus fi DFlo is smaller than the average processing width ΔDF, the defocus amount DF9 and the defocus @ DFlo are averaged, and this average value is set as the defocus IDFIS3 of the third island 23 ( Step #128). And step #126. #
127. After completing the process in #128, the process moves to step #29 in FIG.

Next, the exposure calculation subroutine shown in step #29 of FIG. 10 will be explained using FIG. 15.

First, an open brightness value (apex value) BVO corresponding to the brightness of the subject 8 is input from the brightness detection circuit 29 to the microcomputer 26 (step #131).

Subsequently, a film sensitivity value (apex value) Sv corresponding to the film sensitivity is input from the film sensitivity reading circuit 30 to the microcomputer 26 (step #132). Next, these open brightness value BvO, film sensitivity value Sv, and first
The exposure value EV (E
V=BVO+SV-1-AVO) is calculated (step #133).

Next, the control aperture value AV and shutter speed TV are determined based on the exposure value EV (step #134), and then the process moves to step #30 shown in FIG. 10.

Next, the photographing lens 2 shown in step #32 of FIG.
The process of calculating the drive amount will be explained. In the process of step #32, patterns are divided into how the subject is distributed from each defocus amount of each island 21, 22, 23, and the optimum defocus amount calculation procedure is selected for each pattern. In this way, the optimum amount of driving of the photographing lens 2 is obtained. Here, the means for selecting the calculation procedure will be briefly explained.

First, it is determined whether the mode is FA mode or AF mode. In the case of FA mode, priority is given to the distance measurement of the second island 22, and if the second island 22 is capable of distance measurement,
The driving amount of the photographic lens 2 is determined based on the defocus amount DFIS2 of the second island 22, and the second island 2
2, the amount of drive of the photographing lens 2 is determined based on the amount of defocus of the nearest island.

In other words, ``In A mode, you often shoot with a stationary subject in the center, and if you calculate the amount of defocus based on distance measurement over a wide range, it will be clear which island is selected and displayed. Therefore, the defocus amount DF of the second island 22 that performs distance measurement in the center of the shooting screen
We decided to give priority to IS2.

On the other hand, in the case of AF mode, each island 21.22
．． When the focus of any one of the 23 subjects 8 can be detected, the defocus amount of the nearest island, that is, the island with the maximum defocus amount,
The photographing magnification is calculated based on the focal length data of the photographic lens 2 and the distance to the subject, and the procedure for calculating the amount of defocus is changed depending on the result of this calculation. That is, basically, if the photographing magnification is large, the main subject is necessarily present in the center of the photographic screen, and priority is given to the defocus amount DFIs2 of the second island 22.

Also, if the shooting magnification is small, the background will be included in the shot, and the distance distribution to the subject will vary widely.Furthermore, since the main subject is often located close to the camera, priority will be given to the side with a closer distance distribution. do. FIG. 16 shows an example of a value that serves as a standard for determining the imaging magnification and a procedure for selecting a calculation means based on this value.

That is, for example, in the case of the AF mode, the calculation means is selected when the focal length f of the photographic lens 2 reaches 35 degrees. Then, the focal length f is 35 seconds or more, and the imaging magnification βdf of the nearest island is a predetermined magnification βH (for example, a magnification of 1
/25>, the driving amount of the photographing lens 2 is determined based on the defocus amount of the nearest island.

On the other hand, when the photographing magnification βdf exceeds the predetermined magnification β■, priority is given to the defocus li DFIS2 of the second island 22, and if the second island 22 cannot be used for distance measurement, the defocus amount of the nearest island is used. Shooting lens 2
Determine the amount of drive.

Further, if the focal length f is less than 35M, the driving amount of the photographing lens 2 is determined based on the defocus amount of the nearest island. This is because as the focal length f becomes shorter, the depth of field becomes deeper, so even if you focus on the subject on the nearest island in the distance distribution, objects detected on other islands will be within the depth of field to a considerable extent. This is because it can be included in

In addition, in the case of Tom mode, the defocus amount D[IS
If distance measurement is not possible for the second island 22, the driving amount of the photographing lens 2 is determined based on the defocus amount of the nearest island.

Here, the above-mentioned means for calculating the imaging magnification βdf will be explained.

This photographing magnification βdf is determined by the following equation based on the focal length f and the subject path 11x from the camera.

βdf=f/x Since the data of the focal length 1IiItf is input from the photographing lens 2, when the subject distance X is calculated, the photographing magnification β (H is calculated. Using the defocus amount DFx from the infinity position to the subject position, it is determined as in the following formula.

X=f2/DFX However, the photographing lens 2 is not a single thin ideal lens, but has principal points at the front and back, and the principal points differ depending on the change in focal length, so from the above equation, the subject distance x is an approximate fraction. Desired.

On the other hand, the defocus amount DF from the infinity position to the current position of the photographing lens 2 is the rotation amount (number) N of the lens drive motor 33 stored in the counter inside the microcomputer 26.
It is determined from the number of pulses depending on the number of pulses, and the relationship is as shown in the formula below.

N = k - DF.

DFo=N/, where the ratio of the coefficient is determined based on the number of pulses and the like.

The defocus amount DFx is the defocus amount DF,
and the defocus amount DF from the current position of the photographing lens 2 to the in-focus position of the subject, DFx = DFo -1
-D F yells. From these equations, the object path ll1ltx is x=
f2/DFx = f2/ (+DF to N/) Therefore, the imaging magnification βdf is βdf=f/x= (+DF to N/)/f.

In addition to the above formula, the photographing magnification βdt' is the driving amount ΔN from the current position of the photographing lens 2 to the subject position (ΔN=DF
-k), it can also be obtained as βdf=(N+ΔN)/f-.

Next, go to flowchart 1 of the second island 22 for the subroutine that performs the averaging process (step #8 in FIG. 13).
8. #92) will be explained as an example.

The average processing width ΔDF in step #88 in FIG.
This is determined according to the subroutine shown in FIG. first,
It is determined by the flag WZF2 whether or not the previous averaging process was performed (step #141).

In other words, when the previous averaging process is performed, the flag ``2'' is set. If the previous averaging process was performed, the coefficient is set to 1 to ``1.5'', and the previous averaging process is performed. If not, set the coefficient to 1 (steps #142 and #143). The reason for setting the coefficient to 1 is
In order to prevent averaging processing from being performed or not performed due to variations in distance measurement values, if -degree averaging processing is performed, the averaging processing width can be widened and averaging processing can be performed from the second time onwards. This is to increase the probability (probability).

Next, the photographing magnification βdf detected during the previous distance measurement is determined, and when the photographing magnification β (H is ``1/20'' or more, 2 is set to 1'' in the coefficient, and the photographing magnification βd [is ”
In the case of 1/20" to "1/50", set the coefficient 2 to "0.5" and set the shooting magnification βdf to "
If it is less than 1/50", set 2 to O" in the coefficient. Steps #145 to #"149), Step #1
50. The reason why the coefficient is set to 2 is that when the imaging magnification βdf is high, there is a high possibility that the same subject will occupy multiple blocks within the same island.

Next, in step #150, the aperture value FNo.
The reference average processing width ΔDFI is set based on the following. That is, the depth of focus δ, which is determined by the product of the aperture value FNo at the time of photographing and the allowable circle of confusion diameter ε, is set as 〇F1 to the reference average processing width for preserving the resolution of the photographed image.

Then, by multiplying the reference average processing width 〇FI by the coefficient 1 and the coefficient 2, the average processing width ΔDF is determined, and the flag -Zr2 is reset (step #151). Thereafter, the process moves to step #89 shown in FIG.

In addition, the first island 21 and the third island 23 also have flags for determining whether or not the previous averaging process was performed, similar to the flag WZF2, and when the previous averaging process was performed, the flag WZF2 is It is set and reset if no averaging was performed last time.

Next, the calculation of the defocus amount of each block and the determination of whether or not focus detection according to the present invention is possible will be performed in the third block BL.
3 will be explained using FIG. 18(a) as an example (steps #75 to #78 in FIG. 13).

First, the front pin side deviation pitch is at four positions (deviation pitch "
While shifting the data of the reference part 142b while shifting the data of the reference part 142b while shifting the data in the defocus range from "~4") to a position shift pitch of "'24") where the rear focus side shift pitch is 24), the data of the third block 813 at each shift position is Step #161) for calculating the correlation function H3(I) between the data and the data of the reference unit 142b.

This correlation function H3(1) is expressed by the following formula.

H3(I)-(1 to 2(1)-32(5+I) l
+l K2(20)-32(24+l)l)
/2+ΣIK2(,,1)-82(4+j+I)J:λ However, K2 indicates the difference data string of the reference part 142a,
S2 indicates a differential data string of the reference section 142b.

Next, the phase pApA number H3 at each shift position described above
The best correlation among (I), that is, the correlation function 1-
The shift position IH where the value of 13(1) is the minimum is extracted (step #162). Next, interpolation calculations between each pitch are performed using the values at each point of the correlation function H3(I) (step #163).

The interpolation pitch XM obtained by this interpolation calculation is as shown in the following equation (see Japanese Patent Laid-Open No. 60-247211).

XH=I M+(83(IN-1)-H3(1M+1
1)/[2・(MIN(83(IN-1), H3(IN
+1)) -83([) months The reason for performing this interpolation operation is 1
Converting the pitch deviation to defocus amount is about 10
This is because the pitch is as large as 00 μm, and by compensating for this pitch, accurate distance measurement can be performed.

The thus obtained interpolation pitch X)l is multiplied by a coefficient α determined by the pitch length of the optical system and the photoelectric conversion element array to convert it into defocus IDF (DF=XHα) (step #164).

Next, the contrast (brightness) value C(3) of the data of the third block BL3 is determined as the sum of the differences between adjacent data of the reference portion 142a (step #165).

This contrast value C(3) is expressed by the following formula.

Next, calculate the interpolated value YH of the minimum value of the correlation function H3(I), and calculate the ratio of this interpolated value YM and the contrast value C(3). The value R(3) is determined (step #167).

These interpolated values Y)l It becomes like this.

Y H= 1-(3(IM)- and the ratio 1iiIR (3) is the following formula H3(IN 1)-H3(1M+1)/2 R(3)=C(3)/YH Thus obtained Focus detection is possible only when the contrast value C(3) and the ratio value R(3) both satisfy the set value, and the contrast value C(3) or the ratio value R(3)
), it is determined that focus cannot be detected (low contrast determination). That is, first, it is determined whether the focus of the third block BL3 was able to be detected in the previous routine processing using the detection flag NLB3 (step #168). This is to reduce the determination level when focus detection was possible last time, and to prevent the determination of whether focus detection is possible from becoming unstable for a subject whose focus detection determination level is at the very edge. That is, for a subject whose focus is on the edge of the focus detectable level, the determination levels Cth and Rth are set to predetermined values C1 and R1, respectively (step #169).

Then, in step #168, if the previous focus cannot be detected or the first routine processing is performed, that is, the detection flag NLB3
If has been reset, the eye shadow magnification β[S when photographing is performed at the current position of the photographic lens 2 is calculated (step #170).

This imaging magnification βLS is determined by the calculation of the imaging magnification βdf described above.
That is, it is obtained by substituting O'' into the defocus amount DF of βdf=(N/+DF)/f.

Then, the product of this photographing magnification βLS and the focal length 111f is calculated, and this product is a predetermined value of 1tFJ f·βth (for example, 3
In the case of a 0ttvn lens, βth is 1/15 or more), the determination levels Cth and Rth are set to predetermined values C1 and R1J, respectively: Rimo large key predetermined mc4. FJ is determined for R4 (steps #171 and #172). In other words, the determination level c th is higher than in the case of step #169.

Rth will be tough.

If the predetermined value f·βth is not vortexed in step #171,
Maximum local contrast of third block BL3]・value CL
A calculation of t l+ is performed (step #173). Then, if the local contrast 1 to the last value CL t 11 is thicker than a preset predetermined value (in other words, if the flag C to be described later is
(If - is set, the judgment level (:tll is set to a predetermined value C2, and if it is smaller than the predetermined value, that is, if the flag CL is reset, the judgment level Cth
Set a predetermined value C3 to (steps #174 to #176
). However, the relationship between predetermined values C2 and C3 is C1<C2<
It is set in advance so that C3<C4.

Next, it is determined whether the flag AFSF is set, and if the flag AFSF is set, the determination level Rtl is set.
) is set to a predetermined value R2, and if the reset has been performed, a predetermined value R3 is set to the determination level Rth (step #1
77~#179). However, the relationship between the predetermined values R2 and R3 is set in advance so that R1<R2<R3<R4.

After each of the determination levels Cth and Rth is set to a predetermined value (steps #169 and #172,
#178. #179) When the contrast value C(3) is larger than the judgment level cth and the ratio value R(3) is larger than the judgment level Rth, the detection flag N is set.
If LB3 is set to Sera 1~, Con1-Las)~(ic(3) or ratio value R(3) is either one, the judgment level is C.
th or the determination level RthG, the detection flag NLB3 is reset (steps #180 to #182). After that, the first
The fourth block BL shown after step #79 in Figure 3
Processes such as calculating the defocus amount and determining whether or not focus can be detected in step 4 are performed.

Note that the detection flag NLB3 may be set for each island, and the determination level may be relaxed based on this detection flag NLB.

In other words, when a large amount of defocus is detected with no -degree detected, the image interval approaches the basic image interval due to lens driving. Therefore, the image of the reference part itself, for example,
The images in the 5th and 5th blocks are shifted to the 3rd and 4th blocks by increasing the image interval due to lens drive.
-I have something to do. In such a case, focus detection becomes impossible in the third block. Therefore, a flag LCF indicating the remote control for each island may be stored in a separate flag LCFH, and this flag LCFN may be determined during ranging of each island instead of the detection flag NLB.

Here, the reason why the determination levels Cth and Rth are made stricter when the value is equal to or greater than the predetermined value f·βth in step #172 will be explained.

In other words, in the case of a long focal length lens with an extremely large lens drive range (lens extension amount of 40 haze or more), the lens position must satisfy the above conditions at high magnification, and when the lens extension amount is large, the distance is quite long. Dear, when trying to detect focus on a subject with low magnification, in a case like this,
The spatial frequency component of the subject has a considerable high frequency component,
The image interval in the reference portion 142a or the reference portion 142b is extremely small, and completely different images are projected on the reference portion 142a and the reference portion 142b. Furthermore, due to the low magnification, a completely different subject will be projected. In such a blurred state, the optical system passes only extremely low frequency components, so it would normally be impossible to detect the focus.However, as shown in FIG. 18(b), person A.

In the case where persons A and B are lined up, the detailed data (high frequency components) that distinguish between persons A and B do not pass through the optical system.
Each image of B has almost the same waveform, and there are cases where the image of person A and the image of person A are erroneously determined, and it is determined that the focus can be detected.

On the other hand, when the lens position is at infinity and the magnification is low, foreground,
When attempting to detect focus on a subject with high magnification, the optical system passes only extremely low frequency components, so detailed data is not passed. However, since the magnification is high, the image interval in the reference part 142a or the reference part 142b is extremely large, and different parts of the same subject are projected on the reference part 142a and the reference part 142b. Therefore, the reference portion 142a and the reference portion 142
Since a subject different from that in b is not projected, it was decided to make the determination levels Cth and Rth stricter.

Further, in steps #161 and #165, the correlation function 83(I) and contrast value C(3) of the third block BL3 were calculated, but as shown in FIG. 19, other blocks BLI, BL2.

B10, B10, B10, and BLl0 can be similarly determined.

Next, the local contrast value C in step #173 is
Let me explain about Lth's performance. This step #173
The contrast value judgment level Cth at is determined by the noise amount Cn0i generated by the photoelectric conversion element array,
Se is superimposed. Although the size of the noise itself of this noise amount Cnoise does not change, the waveform of the noise varies, so if the last value of the true subject control 1 required for focus detection is CMIN, the judgment level cth is as shown in the following formula. become.

Cth = CMIN + MAX (Cnoise) However, Ct4IN < MAX (Cnoise) Therefore,
Although the noise amount Cnoise is small and it is originally possible to detect focus and points, the contrast value is at the judgment level cth
In some cases, it may be determined that focus cannot be detected because the value does not exceed . Therefore, when the maximum amount of noise Cnoise occurs, it is predicted that noise will also exist in each part of the third block BL3, so the contrast limit is determined using the following formula for each difference data of the third block BL3.

Σl K(j+q)−K(j+q+1) l≧CHI
N+MAX(Cn.

, 1'-1 ise) - P/20 However, the value P is a predetermined value set in advance, and is selected from values of "20" or less.

Furthermore, in determining the contrast limit, when the local contrast value satisfies a predetermined value, the determination level of the contrast value can be determined in the same way as when noise is small. In other words, the means for determining the contrast limit includes a plurality of determination routines, as shown in FIGS. 20 to 22. That is, in the determination routine shown in FIG. 20, for example, a data block subdivided into 7 pieces of differential data is extracted from the third block BL3, and even one piece of data in this data block has a predetermined value CLth.
If it is 1 or more, the determination level for the total contrast 1 to value is relaxed.

That is, this determination routine first resets the flag CL and resets the variable q (step #
191). Next, the data of the third block B10 is converted into a data block CLOC (CLOC- and 1 to 2(j+q)-to 2(j+q+1)) consisting of differential data (7 pieces) from 2(1) to 2(8). l ) and compares this data block CLOC with a predetermined value CLth1 (steps #192 and #193). If this data block CLOC is greater than or equal to the predetermined value CLth1, a flag OL is set (step #194), and the contrast value determination level is relaxed.

On the other hand, if each differential data of the data block CLOC is less than the predetermined value CLth1, the variable q is incremented and the data of the third block BL3 is changed from 2 (2) to 2 (9).
A data block CLOC consisting of the difference data up to
(Steps #195 and #193). The process continues in the same manner until a data block CLOC consisting of differential data from 2 (13) to 2 (20) is extracted (steps #192 to #196). Then, if even one piece of data in the data block CLOC is greater than or equal to the predetermined value CLth1, the flag C[- is set;
If all data blocks CLOC are less than the predetermined value CLth1, the flag CL remains reset and the state shown in FIG.
>Proceed to flowchart 1~.

Further, in FIG. 21, the maximum value and minimum value of the data of the block are extracted, and the presence or absence of local contrast is determined from the difference between these maximum and minimum values.

In other words, this determination routine inputs the data of the third block BL3 from 2 (1 to 20) to the maximum value [MAX(K2(j)
)] and the minimum value [M IN (K2(m )],
These maximum value [MAX(2(j)) ] and minimum value [
MIN(ni2(j)) ] and the difference Cl0C(CLOC
=MAX(K2(jl)MIN(ni2(j))) is calculated (steps #201 to #203). Next, the flag CL is reset (Step #204), and the difference CLOC is compared with a predetermined value C1, th2 (Step #205>. Then, if the predetermined value C[th2] or more, the flag CL is reset. Step #206), the determination level of the contrast value is relaxed. On the other hand, the difference C to OC
If CLth2 is less than the predetermined value CLth2, the flag CL remains reset and the process moves to flowchart 1 to FIG. 18(a).

Furthermore, in FIG. 22, the presence or absence of local con 1 and las 1 is determined by determining whether or not there is a predetermined number or more of data greater than a predetermined level among the data in the block.

In other words, this determination routine first sets the variable j to 1111
+, reset the variables CL1 and C10, and further reset the flag C (step #21).
1). Next, 2(1) is added to the data of the third block BL3.
and a predetermined value CLth3, and the predetermined value CLth3 is determined.
In the above case, add II II II to the variable c l-i,
Next, when 2(1) is below the predetermined value -C1-th3J, add 1'' to the variable C[2 (step #21
2 to #215). Then, the variable CLI and the variable C1
-2 is calculated, and if this product CLI.C10 is greater than or equal to a predetermined value CL t l)4, a flag CL is set (step #217), and the determination levels of Con1 to Last values are relaxed. On the other hand, the product CLI・C], 2 is the predetermined value C
If Lth4 is unvortexed, increment variable j from 1 to
Processing from steps #212 to #215 is performed for 2 (20) on all data in the third block BL3 (
Steps #212 to #219>. As a result, even after processing all data, the product CLI ・C10 remains at the predetermined value CL
If it is less than th4, the flag CL remains set to 1~ and moves to flowchart 1~ in FIG. 18(a).

Next, the averaging processing routine of step #92 in FIG. 13 will be explained. This average processing routine has several processing means, and each processing means is shown in Figs.
This will be explained using FIG. 25.

In the averaging processing routine of FIG. 23, step #165 of FIG. 18(a). Contrast 1~ found in #167
A weighting function W(1) is set based on the value C(3)d5 and the value R(3), and this weighting function W(I) is used to perform a weighted average of the defocus amount of each block. It has become. Note that this weighting function W(1) may be, for example, the contrast l-value C(3) itself or the ratio value R(3) itself.

That is, first, variable I is set to "3" (step #2'l7). Then, each block B [3°B10
, B10 defocus amounts OF3, DF4
, the largest defocus l1(AX
Find the difference between DF and the defocus amount DF3, compare this difference with the average processing width ΔDF, and calculate the difference as the average processing width ΔDF.
When it exceeds, the weighting function W(3) is set to 1101+. Then, the variable ■ is incremented, the difference between the defocus amount HAXDF and the defocus 1jlDF4 and the defocus l1DF5 is calculated, and this difference and the average processing width △
DF, and if this difference exceeds the average processing width ΔDF, change the weighting function W(4) and weighting function W(5) by ○°
' (Steps #222 to #225>. In other words, among the defocus amounts DF3, DF4, and DF5 of each block BL3, B10, and B10, the average processing is performed using the defocus amount within the average processing width ΔDF. Next, weighted averaging is performed using the weighting function W(I) processed as described above, and this average value is applied to the second island 2.
2 defocus amount DFIS2 (step #
226).

In other words, the defocus amount DFI32 is expressed by the following formula.

DFIS2 = (DF3-W(3)+DF4-W(4
)+DF5- W(5))/(W(3)+W(4)
)+W (5)) And wide zone flag WZF2
(Step #227>. Then, the 11th
The process moves to the defocus amount calculation subroutine of step #43 in the figure.

In the average processing routine shown in FIG. 24, the correlation function is recalculated by combining multiple blocks at the maximum correlation position IN, the correlation positions H+1 and IM-1 before and after the maximum correlation function, and the correlation function is roughly calculated. It is designed to perform re-interpolation calculations. That is, the blocks to be averaged (hereinafter referred to as target blocks) obtained in step #90 of FIG. 13 are all blocks BL3. B10. If B10, the data of the second island 22 has a correlation function H3 of 2 (1 to 40), 45 (Ill), 1-13.4.5 (I
N-1), +3, 4.5 (1+H1), and perform rough re-interpolation to set this value to the defocus 1lDFIs2 of the second island 22 (step #231
．． #232). Furthermore, if the third block B10 and the fourth block BL4 are target blocks, the data is 2 (1
~30) with correlation function 1-13.4(I)1), +3.
Recalculate 4(IN-1), +3,4(1+H1),
Re-interpolate and defocus this value Ili DFIS
2 (steps #233 and #234). Furthermore, if the fourth block BL4 and the fifth block BL5 are the target blocks, the correlation functions H4,5 (IN), H4,5 (IM-1), and 2 (11 to 40) are added to the data.
H4,5(I+1) is recalculated, re-interpolated, and this value is set as the defocus amount DFIS2 (Step #2
35° #236). Further, in step #235, if the third block BL3 and the fifth block BL5 are the target blocks, the process moves to step #232, and the wide zone flag WZF2 is set to cell 1 to step #237.
), then the process moves to the defocus amount calculation subroutine of step #43 in FIG.

Here, step #232 described above. #234゜#236
The correlation functions H3,4,5(I M), H3,4(IH
.

The calculation formula for H4,5 (IM) is shown.

83.4.5(IN)=H3,5(I)l)=(l
K2(1)-32(5+I H) l +l to 2(
4)-82(4+j+IH 834(IN)=(1 to 2(1)-32(5+IH
) l + l 2(30)-82(34+IN)
I)/2 +λ1 to 2(jJ=ll)-32(4+j± I N) 1-145(IN)=(l to 2(11L-32(15+)
I old 1 + 1 to 2 (40) - 82 (44 + I N)
l )/2 + , Σ1 is 2Jλ12 (j)-32 (4+j+ I N) In addition, in the averaging routine of FIG. 25, the correlation function of each block to be averaged is )-1(I)l).

H(I H-1) and H(IN+1) are respectively added, and the results of this addition are used to perform processing subsequent to the interpolation calculation. In other words, all blocks B (3°B
10. If B10 is the target block, the correlation function H3
,4,5(IM), H3,4,5(IM-1),
I-13, 4, 5 (I + H1) is calculated as shown in the following formula (steps #241 and #242).

H3,45(I M-1)=83(I H-1)+
)-14(I M-1)+85(I+1) 1-134.5(IN)=83(I)+)-14(I
)ri+H5(IN)H3,45(I+H1)=
H3 (T + H1) + H4 (I + H1) +
H5(■+1) Also, if the third block 8shi3 and the fourth block 8[4 are target blocks, the correlation function H3,4(IN).

H34 (I M-11, H3, 4 (I N+1) is calculated as shown in the formula below (Steps #243. #244>).

83.4(IM-1)-H3(IN-1)+84
(IM-1)H34(IH)-H3(IN)+
H4(I H)H3,4(I )bl) = H3(I
+H1) + H4 (I +H1) Furthermore, if the fourth block BL4 and the fifth block BL5 are the target blocks, the correlation function is 84.5 (IH), 1-14.5 (IN
-1), H4,5 (IH+1) is calculated as shown in the formula below (steps #245 and #246).

H4, 5 (I H-1) - H4 (I M-1) + H5 (
I H-11H4,5(IN)-H4(IM)+
H5(I M)H4,5(I N+1)=H4(I
+H1)+l-15(I N+1) Also, step #
At 245, the third block BL3 and the fifth block BL
5 is the target block, the correlation function f-13,5(I
)ri, +3.5(IN-1), )-13,5(IM
+1) is calculated as shown below (step #247).

1-13.5(IM-1)-H3(1M-1)+H5
(1M-1)H3,5(rH)-l-13(IN)
+85(IN)1-43,5CIN11)=H3
(I ++1) ten I''5 (I thl) and step #24.2. #244. After completing the correlation function calculations in #246 and #247, re-interpolation is performed and this value is set as the defocus amount DFIS2 (step #248).
. In other words, the defocus amount DFIS2 is expressed by the following formula.

1) FIS2-α・l+α・1/2・(H(JHI)-
H(lN-1))/[M IN (t+ (
lN-1), f-1(1++1))-H([8)] Then, set the wide zone flag WZF2 to cell 1 in step #249), and then step #4 in FIG.
Shift to step 3, which calculates the amount of defocus.

Next, the defocus amount calculation routine of the sixth block B10 in steps #93 to #95 in FIG. 13 will be explained using FIG. 26.

First, take the differences from 2(j) and S2(j) to the difference data strings used in blocks BL3, B10, and B10 at every seventh position, and calculate the summation data strings KW(j) and 2(j) between the adjacent difference data. Find 5W(j) (
Step #251>. In this summation data string, there is (j), 5
-(j) is expressed as the following formula using the differential pig sequence input in step #26 of FIG.

to - (m) - to 2 (m) ten to 2 (m+1) + to 2 (m+
4)+2(m+5)SW(1) =32(1)+52
(1+11+32(1+4)+32(++5)) Next, find the correlation function H6(1), and calculate the shift 1 to amount 1 that minimizes the value of the correlation function H6(I) 1 (IN = MIN(H6
m)) is extracted (steps #252 and #253). This correlation function H6(r) is expressed by the following formula.

1-16(1)=-(l KW(2)-or(6+I)
l -4-I Kw(34)-3W(38+
l) l )/2+book I KW(j)-3W(4+j
+I)''Here, calculating the correlation function 1-16(1) by removing the data at both ends from the data string of the reference section 142a as in the above equation is necessary to obtain the correlation function 1-16(1) near the minimum shift amount IH during the interpolation calculation described later. Correlation functions of 1-16 (I Ll), l-16 (IN),
Instead of using H6(IH+1), the correlation function 1-1
6 (I H-2).

H6 (I H-1), l-16 (I H4,1),
In order to use H6(I++2), the correlation function H6(I
This is to correct a large shift in the position corresponding to the data of the reference section 142b at M-2) and H6(f++2) (see Japanese Patent Laid-Open No. 6C-247211).

In step #254, these correlation functions H6 (IH-2
), H6 (TH-1), H6 (1++1),
Find H6 (IH+2). That is, these formulas are: 1-16(IM-2)=-Ll KW(j)-Rwhat(
j+IH+2)H6(IM-1)=Σl KW(j)
-RW(j4I)1+3)H6(I++2)=Σ1(j)-RW(j+rH
+6) Become one.

These correlation functions H6 (IN-2), H6 (IN-1)
, H6(ls+1), l-16(I)l+2) as shown below (step #255)
.

XH=IN+(H6(IN-2)-H6(IH+
2))/[MIN(86(IN-2), )-16(
++42))-MAX(+-16(IM-11,116
(I++1))]/2 The coefficient α is added to the interpolation pitch XH.
(Step #256) to convert to the differential A waste amount DF (DF=XH・α). Next, the sixth block B
Contrast 1-(direction C(6)) of the data of L6 is obtained as shown in the following formula (step #257).

C(6)-Ll KW(j)-KW(++1) Next, find the interpolated value Y)+1 of the minimum value of the correlation function 1-16(IN), and calculate this interpolated value YH1 and the contrast 1 to last value C(6 ) is used to find the ratio value R(6) as shown in the following formula (Step #258>.

Y 1st = HAX(H6(I)l-1), H6(IN
→1))-(H6(I)1-2)-1-(6(IH+2
)l ) /2R(6) −〇 (6) / (111
-OF) Next, set predetermined values for the judgment levels Cth6 and Rtb6, respectively, and set the values C(6)
Focus detection is possible only when both the ratio value R(6) and the ratio value R(6) satisfy a predetermined value, and the focus detection is possible only when both the ratio value R(6) and the ratio value R(6) are not satisfied. (Steps #259, #26
0).

Thereafter, the process moves to flowchart 1 in FIG. 13, and the process of step #96 or step #98 is performed.

Next, regarding the means of interpolation calculation in step #256, the second
This will be explained using the example shown in FIG.

First, the data string of the reference part 142a is '3.2°1, -1
．． -2. -3", and the data string of the reference section 142b is '4'.
．． 3, 2, 1. -1. -2. -3°4'', the correlation function is H(0)=O,!-1(-1)=6. H(1)
=6. Here, noise is added to the data string of the reference section 142b, and the data string of the reference section 142b becomes "4.3.
2. O, -1°1, -3. -4”, the correlation function is H(0) =2.8 (-1)-5,5,H(1)
-6, and the focused point, that is, the correlation function H (IHI
The influence of noise on the correlation function 11 (I
M−1), H(IN) The influence on N+11 is relatively small. Therefore, unless the correlation function H(IN) is a periodic function, the correlation function H(IN) is The correlation functions H(I H-2), H(
I H-1), H (I N+1), H (I N+2)
) to reduce the influence of noise.

Further, in step #258, when a normal interpolation calculation as shown in FIG. 18(a) is performed, the offset amount is
? between tli 11iYH1 color MAX (H6(IN-1)
.

Difference OFI between H6(IN+1)) and correlation function 1-16(IN), AUIHA MAX(H6(IH-2), H6
(IHI2)) and MAX (H6 (I H-1), H6
The ratio value R(6) is calculated using the value OF set based on the difference OF2 from (IN+11) or the value obtained by subtracting the contrast value C(6).

〔Effect of the invention〕

As explained above, in the present invention, the correlation value obtained by comparing two image signals with each other is compared with a judgment value to determine the reliability of the judgment value, and determine whether focus detection is possible. When determining the above, the above judgment value is changed depending on the focal length value, the lens position, the imaging magnification, the focal length value, and the lens position or the focal length value and the imaging magnification.
For example, when using a long focal length lens, when the photographing lens is extended far to focus on a close-up, high-magnification subject, and then focuses on a distant, low-magnification subject, the image pattern received will be considerably out of focus. , when a repeating pattern with low contrast occurs, switching the above judgment value to a strict value reduces the probability of judgment that focus can be detected, and prevents false detection such as focusing on a focus position different from that of the subject you want to focus on. can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of a camera equipped with a focus detection device according to the present invention, Fig. 2 is a mechanical configuration diagram of the focus detection means, Fig. 3 is a diagram showing a photoelectric conversion element array, and Fig. 4 is a diagram showing the interior of the viewfinder. Figure 5 is an enlarged view of the reference portion corresponding to the first to third islands, Figures 6 and 7 are diagrams explaining the defocus range of each block. , FIG. 8 is a circuit block diagram of a camera configured with a focus detection device according to the present invention using a microcomputer, and FIG.
Figure 10 is a flowchart of microcontroller interrupt operation.
11 to 14 are flowcharts showing a subroutine for calculating the defocus amount for the first to third islands, FIG. 15 is a flowchart showing a subroutine for calculating the exposure, and FIG. 16 is a flowchart showing the subroutine for calculating the defocus amount for the first island to the third island. FIG. 17 is a flowchart showing a subroutine for calculating the average processing width; FIG. Figure (b) is a diagram explaining erroneous judgment when people are lined up, Figure 19 is a diagram showing the calculation of the correlation function and contrast value of each block, and Figures 20 to 22 are contrast Flowcharts showing subroutines for determining limits, Figures 23-2
Figure 5 is a flowchart showing the average processing routine, No. 26.
The figure is a flowchart showing the defocus amount calculation subroutine, and FIG. 27 is a diagram explaining the interpolation calculation means. 1...Automatic focus detection device, 2...Photographing lens, 3.
... Focus detection means, 4... Defocus amount determination means,
5... Lens position detection means, 6... Lens drive means, 7... Control means, 8... Subject, 21... First
Island, 22... Second island, 23... Third island, 26... Microcomputer, 27... Lens circuit, 28... Focus detection data output circuit, 34...
Lens control circuit, 35...Power supply battery, 36...Power supply circuit, 141a, 142a, 143a-reference part, 141
b, 142b. 143b... Reference section, BLI... First block, B
10...Second block, B10...Third block,
BL4...4th block, BL5...5th block, B10...9th block, B[10...10th block, SW+...power switch, SW2...imaging premature ejaculation switch, SW4 ...Selection switch. Patent applicant Representative of Minolta Camera Co., Ltd. Patent attorney Etsushi Kotani Patent attorney
Long 1) Masamukai Patent Attorney Takao Ito Figure 20.21 Figure 1111 L8 Figure Column P Figure Reference Section (b) Reference Section

Claims (1)

[Scope of Claims] 1. Light-receiving means for respectively receiving first and second images formed from subject light fluxes that have passed through the first and second parts of the photographic lens, which are sandwiched by the optical axis of the photographic lens. and a means for comparing the first and second image signals with each other to calculate a correlation value for a combination with the highest degree of coincidence; and detecting a relative interval between the two images from the correlation value; A focus detection device comprising: means for calculating a defocus amount from a focus position of an imaging lens; means for detecting a focal length of the imaging lens; means for setting a determination value; What is claimed is: 1. A focus detection device comprising: determining means for determining whether or not focus detection is possible by comparing the focal length; and means for switching the determination value, and switching the determination value depending on the value of the focal length. 2. Light receiving means for respectively receiving the first and second images formed from the subject light beams that have passed through the first and second parts of the photographing lens, which are sandwiched between the optical axis of the photographic lens; means for comparing the second image signals with each other to calculate a correlation value in a combination with the highest degree of coincidence; and detecting a relative interval between the two images from the correlation value, and detecting a relative distance between the two images and a focusing position of the imaging lens. A focus detection device comprising: means for detecting the position of the photographing lens; means for setting a determination value; and focus detection by comparing the correlation value with the determination value. What is claimed is: 1. A focus detection device, comprising: a determination means for determining whether or not it is possible; and a means for switching the determination value; 3. Light receiving means for respectively receiving the first and second images formed from the subject light beams that have passed through the first and second parts of the photographing lens, which are located on either side of the optical axis of the photographic lens; means for comparing the second image signals with each other and calculating a correlation value in a combination with the highest degree of coincidence;
In a focus detection device, the focus detection device includes means for detecting a relative interval between two images and calculating a defocus amount from a focus position of the imaging lens; means for detecting the position of , means for setting a determination value, determination means for comparing the correlation value with the determination value to determine whether focus detection is possible, and means for switching the determination value. A focus detection device, characterized in that the determination value is switched based on position information and focal length values of the photographic lens. 4. Light-receiving means sandwiching the optical axis of the photographic lens and receiving the first and second images formed from the subject light beams that have passed through the first and second parts of the photographic lens, respectively; means for comparing the second image signals with each other to calculate a correlation value in a combination with the highest degree of coincidence; and detecting a relative interval between the two images from the correlation value, and detecting a relative distance between the two images and a focusing position of the imaging lens. In the focus detection device, the focus detection device includes means for detecting a photographing magnification, means for setting a determination value, and focus detection by comparing the correlation value with the determination value. What is claimed is: 1. A focus detection device comprising: determining means for determining whether or not an image is captured; and means for switching the determination value; and switching the determination value depending on the photographing magnification. 5. Light receiving means for respectively receiving the first and second images formed from the subject light beams that have passed through the first and second parts of the photographing lens, which are located on either side of the optical axis of the photographic lens; means for comparing the second image signals with each other to calculate a correlation value in a combination with the highest degree of coincidence; and detecting a relative interval between the two images from the correlation value, and detecting a relative distance between the two images and a focusing position of the imaging lens. In the focus detection device, the focus detection device has means for detecting a focal length of the photographing lens, a means for detecting a photographing magnification,
means for setting a determination value; determination means for comparing the correlation value with the determination value to determine whether focus detection is possible; and means for switching the determination value; A focus detection device characterized in that the judgment value is switched according to the value of .