JPH0215218A - Focus detecting device - Google Patents

Abstract

PURPOSE:To stably detect focusing of an object with an overall low contrast by extracting part of data from plural pieces of data by a local contrast extracting means and deciding whether the object has a high contrast difference, or not. CONSTITUTION:The title device is to detect contrast based on optical images of the object in focus detecting areas 21 to 23 located in the central part of a photographic screen 20 in a finder. In an automatic focus detecting device, data on picture elements of the reference parts 141a to 143a in photoelectric conversion element arrays 141 to 143 divided into plural blocks, and each of them is compared with entire data in reference parts 141b to 143b to detect a focus. Part of data is extracted out of plural pieces of data, and according to it, a decision level is altered to compare each data. As a result, an object which has an overall low contrast but a locally high contrast difference can be detected stable focusing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a focus detection device for an optical device such as a camera, which detects the focus adjustment state of an imaging optical system that forms an optical image of a subject.

[Conventional technology]

Conventionally, two optical images relating to substantially the same part of a subject are guided onto a pair of photoelectric conversion element arrays consisting of a plurality of photoelectric conversion element arrays, and the outputs of the photoelectric conversion element arrays are calculated and displayed on the photoelectric conversion element array. There is an automatic focus detection device that detects the relative displacement of an optical image, detects the focus from this detection result, and adjusts the focus of the photographic lens.

With this type of automatic focus detection device, for example, when the contrast of the subject is low, the determination as to whether focus detection is possible becomes unstable, and accurate focus detection becomes impossible.
The photographic lens may cause slight vibrations.

In consideration of such a case, the focus detection determination level is changed depending on whether or not the previous detection result indicates that focus detection was possible, and stable focus detection is performed (Japanese Patent Application Laid-Open No. 60-247210). ), and when the contrast value is less than a predetermined value, contrast signals detected a plurality of times are averaged, and this average value is used for focus detection (Japanese Patent Laid-Open No. 186917/1983).

[Problem to be solved by the invention]

However, in the automatic focus detection device disclosed in Japanese Patent Application Laid-Open No. 60-247210, for example, the optical image of the object has a locally high contrast difference, and focus detection can be performed using this local contrast. Even in such a case, if the contrast of the object as a whole is low, it will be determined that focus cannot be detected.

In addition, even with the automatic focus detection device disclosed in JP-A-61-186917, if the contrast of the subject as a whole is low, the contrast signal is averaged even if there is a locally high contrast difference, resulting in poor focus detection response. There is a problem that it becomes worse.

SUMMARY OF THE INVENTION An object of the present invention is to provide a focus detection device that can perform stable focus detection for objects that have a locally high contrast difference.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a focus detection device having a focus detection area for detecting the contrast of an optical image of a subject, in which a part of data is extracted from a plurality of pieces of data from the focus detection area. a local contrast extracting means for extracting a local contrast; a determination level setting means for setting a determination level according to data from the local contrast extracting means; and determining means for determining whether or not.

Further, in claim 2, the local contrast extraction means extracts a predetermined number of adjacent data from among the data from the focus detection area, and calculates a data block CLCO formed by summing these differences, and the determination level is It is changed according to the data block CLCO.

Furthermore, in claim 3, the local contrast extraction means extracts a maximum value and a minimum value from the data from the focus detection area, and the determination level is changed according to the difference between the maximum value and the minimum value. It was to so.

Further, in claim 4, the local contrast extracting means selects a first predetermined value or less and a second predetermined value from among the data from the focus detection area.
Data below a predetermined value are extracted, and the determination level is changed according to the number of data.

[Effect]

According to the focus detection device having the above configuration, the determination level is changed according to a part of data extracted from a plurality of data from the focus detection area, and whether or not the focus can be detected is determined according to this determination level. It will be judged.

Further, a predetermined number of adjacent pieces of data are extracted from among the data from the focus detection area, and a data block CLCO is calculated by summing the differences between them, and the determination level is changed according to the data block CLCO.

Further, the determination level is changed according to the difference between the maximum value and the minimum value extracted from the data from the focus detection area.

Further, the determination level is changed depending on the number of data extracted from the data from the focus detection area that is equal to or greater than the first predetermined value and equal to or less than the second predetermined value.

〔Example〕

FIG. 1 shows an embodiment of the schematic configuration of a camera equipped with an automatic focus detection device according to the present invention. The automatic focus detection device 1 is composed of a photographing 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. This photographing 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 detects the relative displacement of the optical image due to the subject 8 on the photoelectric conversion element array by performing nose processing on the photoelectric conversion element array (not shown). It is something to do.

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 current position of the photographic 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 No. 2.

FIG. 2 does not show an example of the mechanical configuration of the focus detection means 3. The focus detection means 3 is composed of a main mirror 1o, a submirror 11, and a focus detection optical system 12. This main mirror 1o 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 branched by the main mirror 10 to a focus detection optical system 12 and a film surface 13.

The focus detection optical system 12 includes a photoelectric conversion element array 141.
142.1/1.3, separator lens 15, aperture mask 16, module mirror 17, and condenser lens 18
1, 182, 183, a field stop 19, etc. The photoelectric conversion element arrays 141, 142, 143 are arrays of a plurality of COD imaging elements, etc., and are formed one depth above the focal plane 14 of the separator lens 15. The separator lens 15 has a pair of separator lenses 151.degree. The aperture mask 16 has a circular or oval opening 16.
1,162,163, and limits the light flux 9 input to the separator lens 15. The module mirror 17 guides 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 to limit the field of view of the light beam 9 input to the focus detection optical system 12.

FIG. 3 shows the photoelectric conversion element arrays 141, 142.14.
3 (hereinafter referred to as a CCD 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 141.
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 14
3 is a reference part 143a, a reference part 143b and a photoelectric sensor 14
It consists of 3C. The photoelectric sensor 141c.

142c and 143c are reference portions 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 of COD in the storage section is controlled by a signal corresponding to the amount of received light. Further, as shown in FIG. 4, the photoelectric conversion element arrays 141, 142, 143 have focus detection areas 21, 22, 23 (hereinafter referred to as first islands 21, 22, 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.

Number of pixels in each of the reference portions 141a, 142a, and 143a×
, and the number of pixels Y in the reference parts 141b, 142b, and 143b, for example, as shown in FIG. The number of pixels Y in the reference part is 4
In the photoelectric conversion element array 142, the reference part has a pixel number X of 44, and the reference part has a pixel number Y of 52.

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, 142b, 143b to perform focus detection. Then, among the focus detection results in each block, the data of the rearmost focus is used for each island 2.
1, 22.23, and the focus detection data of each island 21°22.23 and the photographing lens 2.
The photographic lens 2 is driven and focused based on the photographing magnification data.

Next, the photoelectric conversion element arrays 141, 142.14
3 shows the means for determining the range (defocus range) for detecting the defocus amount (that is, the defocus amount is the amount of deviation in the optical axis direction between the intended focal plane of the imaging optical system and the subject image plane). This will be explained using FIG.

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 portions 141a, 14 of each island 21, 22.23
2a, 143a are the values for the first island 2
1, there are 30 pieces, 40 pieces on the second island 22, and 30 pieces on the third 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) and 1 (11) are calculated from the upper end difference data.
-30) are divided into two blocks, the first block BL1 and the second block B[2. In the second island 22, the differential data at the left end is divided into three blocks: 2 (1 to 20), 2 (11 to 30), and 2 (21 to 40), and the third block BL3 and the fourth block are divided into three blocks, BL3 and BL3, respectively. B[4, fifth block BL5. 3rd island 2
3, the differential 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 BL9 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 difference 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 BL6 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.

J) In the above, the interval between the differences was set at every seventh interval, 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 IC blocks, the block far from the optical center within each island has the back 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, the data of the block B [41 located at the center of the reference section 142b, that is, the image located 15th to 34th from the left end of the reference section 142b, and the data of the fourth block BL4 must be combined with the data of the fourth block BL4. (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. In other words, as shown in Figure 7,
In the third block BL3, the front pin side deviation pitch is 4g,
The rear pin side deviation pitch is 24, and the fifth block BL
In No. 5, the number of deviation pitches on the front pin side is 24 and the number of deviation pitches on the rear pin side is 4.

Furthermore, in the first block BL1 and the ninth block BL9, the number of front pin side deviation pitches is 5 and the number of rear pin side deviation pitches is 15, and in the second block B1-2 and the tenth block BLIO, the number of front pin side deviation pitches is 15. There are 15 pitches and 5 rear pin side deviation pitches. Furthermore, the 6th block B
At L6, 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,
The rear pin side deviation pitch is 14, and the 8th block BL
8, the front pin side deviation pitch is 14 and the rear pin side deviation pitch is 4, but since the deviation pitch overlaps with the sixth block BL6, in the seventh block 817, the deviation pitch is 4 to 14 on the rear pin side. In the eighth block BL8, 4 to 14 deviation pitches on the front pin side are set as 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 a first spatial frequency component (primary filter means), and performs focus detection based on this extracted spatial frequency component. (first focus detection means), further extracting a second spatial frequency component based on the extracted spatial frequency component (secondary filter means), (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 two IIi degree detection circuits are for the photographing lens 2.
The brightness of the subject 8 is detected by measuring the luminous flux 9 that has passed through the apex m B corresponding to this brightness.
It transmits VO to the microcomputer 26. The film sensitivity reading circuit 3o reads the film sensitivity from a film (not shown) and transmits the apex value sv corresponding to this film sensitivity 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 photographing lens 2 from the infinite position, and is designed to count down to VXt, which is a count up to the number of pulses. Also, when the power switch (main switch) SWl of the rear 'rli is turned on and the photographing lens 2 is driven and the photographing lens 2 is retracted to the infinity position, the counter is reset. Become (Xru.

The power supply battery 35 directly supplies power to the microcomputer 26 and switches described below, and supplies power to other circuits (this is via a power supply circuit 36 described later. Power is supplied to circuits such as the lens circuit 27 and the focus detection data output circuit 28 based on the fli control signal.

The power switch SW1 starts or "stops" the operation of the camera when the power switch SW1 is opened or closed.The one-shot circuit 37 generates a predetermined pulse in conjunction with the opening or closing operation of the power switch SW+. This is input 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 SW3 is turned on when the photographing lens 2 is retracted to the infinite 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 SW1 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 I (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 SW1 is determined to be on, and the operation of the counter in the microcomputer 26 is prohibited (Step #3), the flag used for executing the flowchart, and the output terminals of the microcomputer 26. is initially set (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 camera waits until 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 projection quasi-leprosy 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 sets the flags used to execute flowchart 1 and the output terminals of the microcomputer 26 from the initial cell 1 to step #21). Furthermore, microcontroller 2
The timer set in 6 is reset, and then this timer is started from 1 (step #22).Then, the flag AFS indicating that this is the first focus adjustment operation is reset.
Step #23), output terminal OP1
is set to high voltage and supplies power to the lens circuit 27 etc. (
Step #24). Next, data including coefficients for converting the focal length, 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). and,
Difference data is input from the focus detection data output circuit 28, and this difference data is stored in step #26. #27
). Next, the defocus amount of each of the islands 21, 22, and 23 described above is calculated, and furthermore, an exposure calculation is performed, and the results of these calculations are displayed on the display circuit 31 (step #
28~#30).

Next, it is determined whether the mode 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 driven based on this. (Step #32). on the other hand,
If it is FA mode in step #31, step #32
The process proceeds to step #34 without performing the above process. In step #34, it is determined whether the photographing preparation switch SW2 is opened or closed.

If the photographing preparation switch SW2 is on, the flag AFSF is reset (step #35), the process returns to step #25, and the process from step #25 is repeated. On the other hand, in step #34, the shooting preparation switch SW
If 2 is off, the power supply circuit 36 is turned off to stop power to the lens circuit 27 etc. (step #36), and the operation is put on standby until the fu shadow preparation switch SW2 etc. is pressed (step #37). And the shooting preparation switch SW2
When ``etc.'' is pressed, the process moves to flowchart 1~ in FIG.

Next, the subroutine for calculating the defocus amount for each island 21, 22, and 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.
(Step #41), and the 12th
14 to 14 show specific flowcharts of 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 reduced. As described above, this first island 21 is divided into the first block B and the second block BL2, and the variables DPI and DF2 that store the respective defocus amounts of these blocks 811 and 812 are set to predetermined values. II K II is stored (steps #51, #52). This predetermined value #
K II is a value for a front focus state that cannot be obtained in each block BL1.8L2, and is output as a defocus amount when focus cannot be detected in the first island 21 (hereinafter referred to as low contrast).

Next, a flag LCF1 indicating the low contrast state at the first island 21 is set (step #53). Then, detection of the focus state (front focus state, back focus state, focused state tI!4) of the first block BL1 and defocus amount D
Calculate F Step #54. ), If focus detection is possible from this calculation result, reset flag 1 and CF 1 to 1 and store the obtained defocus amount DF in the variable DFI that stores the defocus amount of the M1 block 81.1 ( Steps #55 to #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, step #58)G detects the focus state of the second block BL2 and calculates the defocus IDF. If focus detection is possible from this calculation result, flag L
Determine whether CF1 is set.

Then, when the flag LCF1 is reset, that is, when focus detection is determined to be possible in the determination at step #55, the process moves to step #62. Also,
When the flag LCF1 is set in step #60, the process moves to the defocus amount calculation subroutine for the second island 22 (FIG. 13) in step #42 shown in FIG. 11.

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, the magnitude of the defocus amount DF1 and the defocus lDF2 is determined, 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 as the defocus amount of the first island 21. IDFIS1. In other words, defocus l D
When FI is larger than the defocus amount DF2, the defocus fliD
F1 is the defocus amount DFISI of the first island 21
And conversely, the defocus acid DF2 is the defocus amount D
When it is larger than F1, the defocus amount DF2 is set to the first
The island 21 is defocused @DFIS1 (steps #63 to #67).

Also, step #64. Defocus amount DF1 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 amount DF1 and the defocus fiDF2 are averaged, and this average value is set as the defocus amount DFISI 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.
A predetermined value of 11 is set in variables DF3, DF4, and DF5 that store the respective defocus amounts of block BL5.
Set K11 (Steps #71 to #73)
), sets a flag LCF2 indicating the low contrast state at the second island 22 (step #74). and,
The focus state detection and defocus fitDF of each block BL3, B10, and B10 are calculated (steps #75, #79, and #83). i.e. step #
If focus detection is possible from the calculation result of the defocus amount DF of the third block BL3 by 75, the flag LCF2 is set.
and set the obtained defocus amount DF to variable DF3.
(Steps #76 to #78), Step #7
Move to 9. Conversely, if focus detection is determined to be impossible,
Step #7 without performing steps #77 and #78
Move to 9.

Similarly, for the defocus amount DF of the fourth block BL4, if the focus can be detected from the calculation result of step #79,
The flag LCF2 is reset, the defocus amount DF 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 BL5, if focus detection is possible from the calculation result of step #83,
The flag LCF2 is reset, the defocus amount DF is stored in the variable DF5 (steps #84 to #86), and 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 block BL3. B10. Each defocus amount DF3 of B10.

The magnitude of DF4 and DF5 is determined, and the largest defocus amount HAX 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 Ii DFIS2 of the second island 22.
#91), if there is one or more other blocks whose difference is smaller than the average processing width ΔDF, the defocus amount of the other block whose difference is smaller than the average processing width ΔDF from the defocus 1HAXDF; Perform the average with just (
averaging process), and this average value is used as the defocus IDE 132 of the second island 22 (step #92). And step #91. When the process of #92 is completed, the process moves to the defocus maximum calculation subroutine for the third island 23 (FIG. 14) of step #43 shown in FIG. 11.

Further, when it is determined in step #87 that the flag LCF2 is set to 1~, the difference data of every third difference is reorganized into the difference data of every seventh difference in order to focus on the subject consisting of low frequency components. (Step #93). That is,
For example, if the pixel data is +21. ρ2. ..., Q mouth,
..., then the difference data for every third data is dDn =
Q+ −c5 , −, Q5ρ9. ..., ρn−ρj
l+4. ...becomes... The difference data for every 7th place is dDm-ρ1-ρ9. ..., ρm-Qm+8.・・・
・What should I do? The difference data dDm for every seventh data is obtained by taking the sum of the difference data d[)n for every third data. In other words, the difference data for every 7th position is dDm = dD+ +dD5 , =・, d[)m
+dl) m+4 , -...-ρ1-ρ5+ρ5-ρ9
．． ..., +2n-4-Q, n+ρn-ρn+4.・・・
・-+2? -1! 9,-,ρn-4-l2Q44.
-...=ρ1-ρ9. ..., ρm-ffm→8.・・・
・It becomes. However, n=m+4.

Furthermore, take the sum of the adjacent difference data clDm,
New lj data string dDW(m) = dj)m +dl)
m41 is used to perform focus detection in the sixth block BL6, and to calculate focus state detection J5 and defocus ftDF (Step #94). If focus detection is possible, reset flag LCF2. , the defocus IDF6 of the sixth block BL5 is set as the defocus amount DFIS2 of the second island 22 and the process moves to step #43 (steps #95 to #97).
If focus detection is not possible in step 95, focus detection is performed in the seventh block BL7 to detect the focus state, and calculate 15 and defocus amount DF (step #98), and if focus detection is possible (step #98). 99), return to step #96, reset the flag LCF2, and set the seventh block BL7.
The defocus amount is set as the defocus amount DFIS2 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,
Perform focus detection in block BL8, detect focus state and calculate defocus amount DF (Step #100)
, if focus detection is possible (step #101), return to step #96, reset the flag LCF2, and set the defocus amount of the eighth block BL8 to the second island 2.
2 as the defocus amount DFIS2 in step #4.
Move to 3.

On the other hand, if focus detection is impossible in step #101, step #96. Step #4 without performing the process in #97
Move to 3.

FIG. 74 shows the calculation of the defocus amount of the third island 23 (
The subroutine of step #43) is shown.

First, a variable D "9° DF
A predetermined value "l K I+" is stored in the IO (steps #111 and #112).Next, a flag LCF3 indicating the low contrast state at the third island 23 is set (step #113). Detect the focus state of the 9th block BL9 and calculate the defocus IDF (Step #114). If focus detection is possible, flag L C
Reset F3 and set the obtained defocus IDF to the 9th
Store it in the defocus amount DF9 of block BL9 (
Steps #115 to #117). Meanwhile, step #11
If it is determined in step #5 that focus detection is impossible, step #116
．． The process moves to step #118 without performing the process #1''+7.

Next, detect the focus state of the 10th block BL''IQ and calculate the defocus fiDF (Step #118)
, If focus detection is impossible from this calculation result, flag L is set.
It is determined whether CF3 is set to Sera 1 or not. Then, when the flag LCF3 has been reset, that is, when focus detection is determined to be impossible in the determination at step #115, the process moves to step #122. Also,
When the flag LCF3 is set, the process moves to the exposure calculation subroutine of step #29 shown in FIG. #
The process moves to step #122 without performing the process of step #120.

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 @DF10, and the one with the larger defocus amount is set as the defocus IDFIS3 of the third island 23 (Steps #123 to #127>
.

Also, step #124. Defocus amount O at #125
The difference between F9 and defocus amount 0F10 is the average processing width ΔD
When it is smaller than F, the defocus amount 0[9 and the defocus IDEIO are averaged, and this average value is set as the defocus amount DFIS3 of the third island 23 (step #128). And step #126. #127
．． After completing the process #128, step #2 in Figure 10
Move to 9.

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

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

Subsequently, the 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
Calculate svo+sv+Aν0> (step #1
33).

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, the defocus amount of each island 21, 22, 23 is divided into patterns to see if the subject is distributed like this, and the optimal defocus amount calculation procedure is selected for each pattern. Thus, the optimum driving amount 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 FA mode, shots are often taken with a stationary subject in the center, and when the amount of defocus is determined based on distance measurement over a wide range, it is clear whether the island is selected and displayed. Therefore, the defocus IDF of the second island 22 performs distance measurement in the center of the shooting screen.
We decided to give priority to TS2.

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 for the focal length f of the photographic lens 2 at 35#I.

If the focal length f is 35 mm or more and the photographing magnification βdf of the nearest island is smaller than a predetermined magnification βH (for example, magnification 1/25>), then the photographing is performed based on the defocus amount of the nearest island. The driving amount of the lens 2 is determined. On the other hand, when the imaging magnification βdf exceeds the predetermined magnification β11, the defocus amount DFIS2 of the second island 22 is determined.
If priority is given to the second island 22 and distance measurement is not possible,
The driving amount of the photographing lens 2 is determined based on the defocus amount of the nearest island.

Roughly speaking, if the focal length f is less than 35 fH, 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 l1llIf becomes shorter, the depth of field becomes deeper, so even if you focus on the object 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 FA mode, regardless of the focal length f,
Priority is given to the defocus fiDFIS2 of the second island 22, and if the second island 22 cannot be measured, the photographing lens 2 is set based on the defocus amount of the nearest island.
Determine the amount of drive.

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

This photographing magnification βdf is determined by the following formula from the focal length @j f and the subject distance MX from the camera.

βdf=f/x Since the data on the focal point v0 and distance f is input from the photographing lens 2, the photographing magnification βdf is calculated by determining the subject distance l11i×. Further, this object distance X is determined using the differential focus 1DFx from the infinity position of the photographing lens 2 to the object position as shown in the following equation.

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 point changes depending on the change in focal length, so from the above equation, the subject distance X can be calculated as an approximate value. Desired.

On the other hand, the defocus IDE 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 value 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 +D
It becomes F. From these formulas, the subject distance X is x=f 2
/DFx = f 2 / (+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 βdf is the driving amount ΔN (ΔN=DF−) from the current position of the photographing lens 2 to the subject position.
k), it can also be obtained as βdf=(N+ΔN)/f−.

Next, the flowchart of the second island 22 regarding the subroutine that performs the averaging process (step #88 in FIG.
．． #92) will be explained as an example.

The average processing width ΔDF in step #88 in FIG.
It 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).

That is, when the previous averaging process is performed, the flag -ZF2
is set. Then, if the averaging process was performed last time, the coefficient is set to 1 to "1.5", and if the previous averaging process was not performed, the coefficient is set to 1 to LL I I+ (
Step #142. #143). The reason for setting the coefficient to 1 is to prevent average processing from being performed or not performed due to variations in distance measurement values.If average processing is performed by -degrees, the average processing width is widened and the second processing is performed. This is to increase the possibility (probability) that the averaging process will be performed thereafter.

Next, the photographing magnification βdf detected during the previous distance measurement is determined, and if the photographing magnification βdf is greater than or equal to "'1/20", the coefficient 2 is set to "1", and the photographing magnification βdf is
If the shooting magnification βdf is "1/20" to "1/50", set the coefficient 2 to "0.5", and if the imaging magnification βdf is "1/50" or less, set the niha coefficient 2 to "O".
If it is set to step #145 to #149), the process moves to step #150. The reason for setting the coefficient to 2 is
This is because when the photographing 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.
〇F1 is set to the standard average processing width based on . In other words, the focus quarantine δ obtained from the product of the aperture value F No at the time of photographing and the allowable circle of confusion diameter ε is set as the standard average processing width ΔDFI for preserving the image resolution.

Then, by multiplying the reference average processing width 〇F1 by the coefficient 1 and the coefficient 2, the average processing width ΔDF is determined, and the flag WZF2 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 averaging process was performed last time. Flag WZF2 is set, and if no averaging process was performed last time, it is reset.

Here, regarding the calculation of the defocus amount of each block and the determination that focus detection is not possible according to the present invention, 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 411! While shifting the data of the reference part 142b in the differential 1-cass range from the position a (shift pitch ``-4'') to the rear bin side displacement pitch ``24''), each Third block 6[3 in shift position
The correlation function H3 (
I) is determined (step #161).

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

H3(1)=(1 to 2(1)-32(5+Il l +
2 (20) - 32 (24, where 2 is the reference part 14)
2a shows the difference data string, and S2 shows the difference data string of the reference section 142b.

Next, the correlation function H3(1
), that is, the correlation function H3(I
) is extracted at the shift position [ where the value of ) is the minimum (step #162). Next, interpolation calculation between each pitch is performed using the value of 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=IM+(H3(IN-1)-H
3(IN+1))/[MIN(H3(IN-1), H3
(IN+1)L-83(IN)]/2 The reason for performing this interpolation calculation is that when converted to a defocus amount, one pitch deviation is large, approximately 1000 μm, and by compensating for this pitch difference, accurate distance measurement can be achieved. This is to do this.

The thus obtained interpolation pitch XH 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 a defocus amount DF (DF=XHα) (step #164). Next, the contrast (brightness and darkness) value C(3) of the data of the third block BL3 is determined by the reference section 142.
Find it as the sum of the differences between adjacent data of a (step #1
65).

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

C(3)-Σl K2(j)-2(j+1)J"1 Next, find the interpolated value YH of the minimum value of the correlation function H3(1), and use this interpolated value 11fYH and the contrast value C(
Find the ratio R(3) to 3) (step #167)
.

These interpolated values YH and the ratio 1tllR(3) are expressed by the following equation.

YM = 83(IM)-11-13(IN-11-
1-43(H1+1) l /2R(3) =C(3
) /YH Focus detection is possible only when both the con1 to last value C(3) and the ratio value R(3) obtained in this way satisfy the set value, and the last value C(3) or the ratio value to con1 value R
If any one of (3) is not satisfied, focus detection is determined to be impossible (low contrast determination). That is, first, the third
It is determined whether or not the focus of block BL3 was able to be detected in the previous routine processing using 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 at the very edge of the focus detection judgment level, the judgment levels Cth and Rth are set to predetermined values C1 and R1, respectively.
(Step #16).

Then, in step #168, it is determined that the previous focus cannot be detected or the first routine processing is performed, that is, the detection flag NLB
3 has been reset to 1 or more, the photographing magnification βLS 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 determined by substituting 'O'' for the defocus amount DF where βdf=(N/+DF>/f).

Then, the product of the photographing magnification β[S and the focal length l1lltf is calculated, and this product is a predetermined value f·βth (for example, 300
In the case of an M lens, βth is 1/15 or more), the determination levels Cth and Rth are set to predetermined values C1 and Rth, respectively.
Predetermined values C4 and R4 larger than R1 are set (step #171.R172). In other words, the judgment level c th is higher than in the case of step #16.

Rth will be tough.

If it is less than the predetermined value f·βth in step #171,
Maximum local contrast value CLt of third block BL3
Calculate h (step #173). and local]
If the value CL th is larger than a preset predetermined value (), that is, if the flag CL described later is set to cell 1, the predetermined value C2 is set to the determination level cth. , if it is smaller than the predetermined value, that is, if the flag CL is reset, the determination level cth is set to the predetermined value C3.
(Steps #174 to #176). however,
The relationship between the predetermined values C2 and C3 is set in advance so that C1<C2<C3<C4.

Next, it is determined whether flag 8 FSF is set, and if it is set, a predetermined value R2 is set to the determination level Rth, and if it is reset, a predetermined value R3 is set to the determination level Rth ( Step #177~
#179). However, the relationship between the predetermined values R2 and R3 is R1
It is set in advance so that <R2<R3<R4.

After each of the determination levels Cth and Rlh is set to a predetermined value (steps #169 and #172,
R178, R179), when the contrast value C(3) is larger than the judgment level C1h and the ratio value R<3) is larger than the judgment level Rth, the detection flag N is set.
If LB3 is set to 1-shi, contrast 1-last value C(3) or ratio value R(3), the judgment level cth
Alternatively, when it is smaller than the determination level Rth, the detection flag NLB3 is reset (steps #180 to #
182). Thereafter, processing such as calculating the defocus amount and determining whether focus detection is possible in the fourth block BL4 shown after step #79 in FIG. 13 is performed.

Note that the detection flag NLB3 may be set for each island, and the determination level may be relaxed based on the detection flag NLB3. 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 portion itself, for example, the image that was in the fourth and fifth blocks may be shifted to the third and fourth blocks as the distance between the images increases due to lens driving. In such a case, focus detection becomes impossible in the third block. Therefore, instead of indicating the low contrast for each island, the flag LCF may be stored in a separate flag LCFH, and this flag LCFN may be determined during distance measurement 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 m or more), the lens position must satisfy the above conditions at high magnification, that is, when the lens extension amount is large, it will produce a very distant view and at low magnification. When trying to detect focus on a subject 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 is usually 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 interval between images falling on the reference section 142a or the reference section 142b is extremely large, and different parts of the same subject are projected on the reference section 142a and the reference section 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.

Furthermore, in steps #161 and #165, the correlation function H3(I) and contrast value C(3) of the third block 8[3 were calculated, but as shown in FIG. B10.

B10, BL5, B10, and BLl0 can be similarly determined.

Next, the local contrast value C in step #173 is
The calculation of Lth will be explained. This step #173
The contrast value judgment level cth at
Se is superimposed. Although the size of the noise itself of the noise amount Cnoise does not change, the waveform of the noise varies, so if CMIN is the minimum true object contrast value required for focus detection, the determination level cth is as shown in the following equation.

Cth = CMIN + MAX (Cnoise) However, CMIN < MAX (Cnoise) Therefore,
Even though the noise amount Cnoise is small and focus detection is originally possible, it may be determined that focus detection is impossible because the contrast value does not exceed the determination level cth. 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 for each difference data of the third block BL3 according to the formula below. .

se) 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 data block of this data block has a predetermined value ctth.
If it is equal to or greater than i, the determination level of the total contrast value is relaxed.

That is, this determination routine first resets the flag CL and resets the variable q to 1 (step #191>).Then, the data of the third block BL3 is changed from 2(1) to 2(8). Output data block C consisting of differential data (7 pieces) up to and compare this data block CLOC with a predetermined value C weight. Step #192
．． #193). If this data block CLOC is equal to or greater than the predetermined value CLth1, a flag CL 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
) is extracted, and this data block CLOC and a predetermined value CL t are extracted.
Compare with h 1 (step #195. #193).

In the same way, successive numbers are added to the data 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 a predetermined value CL th 1, the flag C
If L is set to 1 to 1 and less than the predetermined value CLth1 in all data blocks CLOC, the process moves to the flowchart of FIG. 18(a) with the flag CL remaining reset.

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 1 to last 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 TN(K2(j)) ], and calculate the difference CLOC between these maximum value [MAX(K2(j)) ] and minimum value [MIN(K2(j)) ]. (
C1, oc = M AX (K2 (j)) M IN (K
2(j)) ) (steps #201 to #203
). Next, step #20 to reset the flag CL.
4) Compare the difference CLOC with a predetermined value CLth2 (step #205). Then, if it is less than the predetermined value CLth2, set the flag CL to cell 1 (step #206).
, the determination level of the contrast value is relaxed. On the other hand, if the difference CLOC is less than the predetermined value CLth2, the flag CL
remains reset and proceeds to the flowchart of FIG. 18(a).

Furthermore, in FIG. 22, the presence or absence of local contrast 1 to last is determined by determining whether 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
+ and reset variables CL1 and Cl-2 to 1~
and further resets the flag CL (step #21
1). Next, 2(1) is added to the data of the third block BL3.
and a predetermined value CLth3, and when it is greater than or equal to the predetermined value CLth3, '1' is added to variables 01 to 1, and then 2 is added to the data.
When (1) is less than or equal to the predetermined value -CLth3, ((1I+) is added to the variable C[2 (steps #212 to #215).

Then, calculate the product of the variable CL1 and the variable CL2, and if the product CL1 and Cl2 is greater than or equal to a predetermined value CL th 4, set the flag CL (step #217).
, the determination level of the contrast value is relaxed. On the other hand, product C
If 1,1・Cl2 is less than the predetermined value CLth4, the variable "is incremented, and all data in the third block BL3 is set to 2 (for 20>, steps #212 to #
Perform processing up to step 215 (steps #212 to #2'1
9>. As a result, even after processing all data, 'ff
4CLI If Cl2 is at the predetermined value CLth4, the flag CL remains at reset 1~ and the process 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 includes several processing means, and each processing means will be explained using FIGS. 23 to 25.

In the averaging processing routine of FIG. 23, step #165 of FIG. 18(a). Con 1 - Las 1 found in #167
A weighting function W(I) is set based on the ~ value C(3) and the ratio 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 #217). And each block B 3゜B10,
Each defocus amount of B10 DF3, DF4,
Largest defocus 1i of DF5 = HAXDF
and the defocus amount DF3, and compare this difference with the average processing width ΔDF. If this difference exceeds the average processing width ΔDF, the weighting function W(3) is set to 0''. Increment I, defocus amount HAXD
F, defocus 1DF4 and defocus amount DF5
and compare this difference with the average processing width ΔDF,
When this difference exceeds the average processing width ΔDF, the weighting function W
(4) and weighting function W(5) to 11011 (steps #222 to #225>. In other words, each block BL
3, B10, and B10 each defocus amount DF3
, DF4, and DF5, the average processing is performed using a defocus amount within the average processing width ΔDF. Next, weighted averaging is performed using the weighting function W(1) processed as described above, and this average value is set as the defocus@DF 132 of the second island 22 (step #226).

In other words, the defocus MDFIS2 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 -
ZF2 is set to 1- (step #227). Thereafter, the process moves to the defocus amount calculating subroutine of step #43 in FIG.

In the averaging processing routine shown in FIG. 24, a plurality of blocks are combined at the maximum correlation position IN, the correlation positions IH+1 and IM-1 before and after the correlation function, and the correlation function is calculated 100 times. It is designed to perform re-interpolation calculations. That is, if the blocks to be averaged (hereinafter referred to as target blocks) obtained in step #90 of FIG. )
and the correlation function H3, 45 (IN), +3.4.5 (IN
-1), 1-13.4.5 (IN+1) is calculated as 100,
Roughly re-interpolate and set this value to the defocus 1DFIs2 of the second island 22 (step #231
．． #232). Furthermore, if the third block BL3 and the fourth block BL4 are target blocks, the data has 2 (1
~30), the correlation function is 83.4 (I M), H3,4 (
I M-1), recalculate H3,4 (I M+1),
Re-interpolate and set this value to defocus IDFIS2 (steps #233 and #234>.Furthermore, the fourth
If block 8[4 and fifth block BL5 are the target blocks, the correlation function H4 is set to 2 (11 to 40) in the data.
,5(IN), H4,5(IN-1), H4,5(
IH+1) is recalculated, re-interpolated, and this value is set as the defocus amount DFIS2 (step #235゜#
236). Further, in step #235, if the third block total 3 and the fifth block BL5 are the target blocks,
The process moves to step #232, and the wide zone flag -ZF2 is set (step #237), and 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 N), H3H45(I
The calculation formula for N) is shown below.

H3,4,5(IM)-H3,5(IM)=(2
(1)-82(5+IN)4(IN).

+ 2(4)-82(4+j+I H) +34(IN)=(l K2(1)-32(5+IN)
l + l to 2(3)-32(4+j+I H) H4,5(IN)=(l K2(11)-82(15+
IH) l +1 to 2(j)-s2(4+j+ I N
) Also, in the averaging processing routine of FIG. 25, the correlation function H(IN) of each block to be subjected to averaging processing.

H(lN-1) and H(I)l+1) are respectively added, and this addition result is used to perform processing subsequent to the interpolation calculation. That is, all blocks BL3.

B10. If B10 is the target block, the correlation function H
3,4,5(IN), H3,4,5(IM-1)
, H3, 4, 5 (I H+1) are calculated as shown below (steps #241 and #242).

1-13.4.5(IN-1)=H3(IN-1)+l
”4([t-1)+1-15(I H-1) 1-13.4.5(1)=83(IN)+l-14(I
N)+H5(IN)+3,4.5(IH+1)=H3(
rH+1)+1-14(IN+1) 10H5(I)1+
1) Furthermore, if the third block BL3 and the fourth block BL4 are target blocks, the correlation function 1-13.4(I)
11゜1-13.4 (I M-1), H3,4 (i
N+1) is calculated as shown below (step #243.
#244>.

+3.4 (I Ll) = +3 (I Ll) + f-t
4(I Ll)H3, 4(I M)=H3(I H)
+ H4 (I H) H3,4 (I N+1) = H3 (
I ++11+ H4(IN+1) Furthermore, if the fourth block BL4 and the fifth block BL5 are target blocks, the correlation function H4,5(rMl, l-(4,5(
T H−T), l−14,5(IN+1) are calculated as shown in the following formula (steps #245 and #246).

H4,5(IN-1)=H4(IN-1)+l-15(
1-1) 1-14.5(IN)=H4(I)l)+H5
(Nl)H4,5(1N+1)=H4(IN+1)+H
5(Ill+1) Also, in step #245, if the third block BL3 and the fifth block BL5 are the target blocks, the correlation function H3,5(IN), 1-13.5(
IN-1) and 1-13.5 ([+1) are calculated as shown in the following formula (step #247).

1-13,5(IM-1)-+3(IM-1h-+
5(IH-1)+3,5(IN)-1-13JIH)
+85(IN)H3,5(IN+4)=H3(
I N+1) 15 (I N+1) And step #242. #244. #246, #247
After completing the calculation of the correlation function, re-interpolation is performed and this value is set to defocus 1DFIs2 (step #
248). In other words, the defocus amount DFI32 is expressed by the following formula.

DFIS2-α・IN→-α・1/2・(+-1(lN
-1)-1-1(IH+1))/[MIN (H(lN
-1), H(1N+1)) -1-1(IN)] Then, set the wide zone flag WZF2 in step #249), and then step #43 in FIG.
The defocus amount calculation moves to step 4.

Next, the defocus amount calculation subroutine of the sixth block BL6 of steps #93 to #95 in FIG. 13 will be explained using FIG. 26.

First, take the difference between the difference data strings used in blocks BL3, B10, and B10 by 2(j) and 82(j) at every seventh position, and then calculate the summation data string KW(j) and the adjacent data of this difference data. SW l) is determined (step #251). In this summation data string, -(j), 3
The expression j) is expressed as the following formula using the differential data string input in step #26 of FIG.

KW (m) = 2 (m) 10 to 2 (m+1) 10 to 2 (
m+4)+ to 2(m+5)311I(+) -32(
11+32(1+1)+32(+44)+32(1+5
) Next, find the correlation function H6(1), and calculate the correlation function 1-16
Schiff l-quantity IN (1=MI
Extract N(+-16(I))) (Step #25
2. #253). This correlation function H6(1) is expressed by the following formula.

H6(I)=(l K14(2)-3W(6+I)
l + l to W(34)-8W(38B +I) )/2 + Σ l KW(j)-
3W(4+j+I)J23 Here, to obtain the correlation function 86(1) by removing data at both ends from the data string of the reference section 142a as in the above equation,
During the interpolation calculation described later, correlation functions 86 (IH-1), H6 (IN), H6 (IH+) near the minimum shift amount IH are
1) rather than using the correlation function 86 (IL2).

H6 (I H-1), H6 (J N+1), H6 (
J N+2), the correlation function H6(I M-2
), H6(I )l+2) to correct a large shift in the position corresponding to the data of the reference portion 142b (see Japanese Patent Laid-Open No. 60-247211).

In step #254, these correlation functions)-16(IH
-2), H6(IN-1), 1-(6(IH+1)
, find H6(1→2). That is, these formulas are as follows.

These correlation functions 1-46 (IN-2), H6 (H4-
11, H6 (IH+1) and H6 (IN+21) are used to perform interpolation calculations as shown below (step #255).

XH= IN +(H6(1N4-2)-1-164old2))/[MIN(H6(1-2), l-16(I
)l+2))-MAX(H6(1H-1), H6(I
H+1) month/2 Multiply the interpolation pitch XH by a coefficient α to defocus, I
DF (DF=XH-ark: Conversion Suru (Step #2
56>. Next, the contrast value c(6) of the data of the sixth block BL5 is determined as shown in the following formula (step #257>).

Next, the correlation function 86 (interpolated value Y of the minimum value of [1)) 11
is determined, and the ratio value R(6) is determined using the interpolated value Yold and the contrast value c(6) as shown in the following formula (step #258).

YH1=MAX()-16(IN-1), H6(1M
+1)) -(H6(IN-2)-86(IN+2)l
) /2R(6)=C(6)/(Y141-OF) Then, predetermined values are set for the judgment levels Cth6 and Rth6, respectively, and the contrast value C(6) and the ratio value R are set.
Focus detection is enabled only when both (6) satisfy predetermined values, and when either contrast value C(6) or ratio value R(6) is not satisfied, focus detection is disabled (step # 259, #260>.

After that, the process moves to the flowchart of 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 set to "3.2°1, -1".
．． -2. -3'', and the data string of the reference section 142b is set to 4.
3.2.1. -1. -2. -3゜=4'', the correlation function is l-1(0) -〇, H(-1>-6, H(
1) becomes =6. Here, noise is added to the data string of the reference section 142b, and the -7-ta string tfi of the reference section 142b
When changing to "4.3.2.O,-1°1,-3.-4", the correlation function becomes H(0) =2.8 (-1) =5.
5.8 (1) = 6, the effect of noise on the focused point, that is, the correlation function H(IN) is the largest, and the effect on the correlation functions H(I H-1), HCI N+1) is relatively small. Become. Therefore, the correlation function 1-1(11
4) is not a periodic function, the correlation function)((IN)
The correlation functions before and after the correlation function 1-1 (114))-1(lN-2), H(I M-1),
N+1) and H(IN+2) are used to reduce the influence of noise.

Furthermore, in step #258, if a normal interpolation calculation as shown in FIG. 18(a) is performed, an offset amount will occur.
Interpolated value Y old to M AX (H6(I)l-1).

Difference O between H6(IN+1)) and correlation function H6(IN)
F1, Aiha MAX (H6 (I H-2), H6
(IN+2)) and MAX(H6(IN-1), H6
(IN+season) difference OF2 or contrast value C
The ratio value R(6) is calculated using the value OF set based on the value obtained by subtracting (6).

(Effects of the Invention) The present invention extracts some data from a plurality of pieces of data and determines whether the subject has a high contrast difference, so even if the contrast of the subject as a whole is low, it is locally high. If the subject has a contrast difference, it can be determined that focus detection is possible.

That is, for example, in the case of a slit-shaped object or when there is a locally high contrast difference such as the edge of the object, stable focus detection cannot be performed even if the contrast of the object as a whole is low. can.

In addition, since it determines whether focus detection is possible by extracting block data that is the sum of differences between a predetermined number of adjacent pieces of data, it is possible to reduce the effects of noise and achieve accurate focus detection without sacrificing responsiveness. It can be carried out.

Furthermore, since it is determined whether focus detection is possible according to the difference between the maximum value and the minimum value of data, stable focus detection can be performed even for a subject with a narrow slit width.

In addition, since it is determined whether focus detection is possible according to the number of pieces of data that are greater than or equal to the first predetermined value and less than or equal to the second predetermined value, it is possible to reduce the influence of noise and to accurately capture even slit-shaped objects. Focus detection can be performed.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a schematic diagram of a camera equipped with an automatic focus detection device according to the present invention, FIG. 2 is a mechanical diagram of a focus detection means, and FIG. 3 is a photoelectric conversion element array. Figure 4 is a diagram showing the focus detection area of the photographing screen in the finder, and Figure 5 is a diagram showing the focus detection area of the photographing screen in the finder.
FIG. 6 is an enlarged view of the reference portion corresponding to the islands to the third island. FIG. 7 is a diagram explaining the defocus range of each block,
FIG. 8 is a circuit block diagram of a camera configured with an automatic focus detection device according to the present invention using a microcomputer, FIGS. 9 and 10.
The figure is a flowchart of microcontroller interrupt operation, No. 11.
14 are flowcharts showing subroutines for calculating the defocus amount of the first island to the third island,
FIG. 15 is a flowchart showing a subroutine for exposure calculation, FIG. 16 is a diagram explaining a procedure for selecting a defocus amount calculation means, and FIG. 17 is a flowchart 1 to 18 showing a subroutine for calculating an average processing width. Figure (a) is the third
Figure 18(b) is a diagram explaining the calculation of the defocus amount of a block and determination that the focus cannot be detected. Figure 18 (b) is a diagram explaining erroneous determination when people are lined up. Figure 19 is the correlation between each block. Figures 20 to 22 are flowcharts 1 and 23 to 25 showing subroutines for contrast limit determination.
FIG. 26 is a flowchart showing the average processing routine, FIG. 26 is a flowchart showing the defocus amount calculation subroutine, and FIG. 27 is a diagram illustrating means for interpolation calculation. 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, 14.1a, 142a, 143a... Reference section,
141b, 142b. 143b... Reference section, BLl... 1st block 1] Tsuku,
BL2...second block, B1-3...third block, BL4...fourth block, Bl-5...
5th block, B10...9th block, BLlo...
...10th block, SW+...power switch, W2...shooting preparation switch, Wa...selection switch.

Claims (1)

[Claims] 1. In a focus detection device having a focus detection area for detecting the contrast of an optical image of a subject, local contrast extraction for extracting some data from a plurality of data from the focus detection area. means, a determination level setting means for setting a determination level according to data from the local contrast extraction means, and determining whether focus detection is possible by comparing the determination level with data from the focus detection area. What is claimed is: 1. A focus detection device comprising: determination means for determining a focus. 2. The local contrast extraction means extracts a predetermined number of adjacent pieces of data from the data from the focus detection area, and sums up the differences between them to create a data block CLC.
O is calculated, and the judgment level is the above data block CLCO.
2. The focus detection device according to claim 1, wherein the focus detection device is configured to be changed in accordance with. 3. The local contrast extraction means extracts the maximum value and minimum value from the data from the focus detection area, and the determination level is changed according to the difference between the maximum value and the minimum value. The focus detection device according to claim 1, characterized in that: 4. The local contrast extraction means extracts data equal to or greater than a first predetermined value and equal to or less than a second predetermined value from among the data from the focus detection area, and the determination level is changed according to the number of pieces of data. The focus detection device according to claim 1, characterized in that: