JP2770318B2 - Automatic focus detection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focus detection device of an optical device such as a camera for automatically detecting a focus adjustment state of an imaging optical system for forming an optical image of a copy. It is.

[Conventional technology]

2. Description of the Related Art Conventionally, two light images related to substantially the same portion of a subject are guided onto a pair of photoelectric conversion element arrays each including an array of a plurality of photoelectric conversion elements, and an output of the photoelectric conversion element array is calculated to calculate the photoelectric conversion element array. There is an automatic focus detection device that detects the relative displacement of the upper light image and adjusts the focus of the photographing lens based on the detection result. Also, a plurality of specific frequency components of the subject image are extracted from the output of the photoelectric conversion element array using a plurality of filter means (primary filter means, secondary filter means, etc.), and an operation is performed based on these frequency components. There is an automatic focus detection device which detects the relative displacement of the light image and adjusts the focus of the taking lens (Japanese Patent Application Laid-Open No.
No. 87511, JP-A-59-142506, JP-A-60-151
607, JP-A-61-209413).

[Problems to be solved by the invention]

However, in the conventional automatic focus detection device, each filter means always extracts the frequency component of the subject image. For example, even if calculation is performed using only the frequency component extracted by the primary filter means, Even when the relative displacement of the image can be detected, all the filter means are operated. Therefore, there is a problem that it takes time to detect the relative displacement. Further, since a memory such as a RAM for storing data of the extracted frequency components is required for each filter means, there is a problem that the number of memories is large.

An object of the present invention is to provide an automatic focus detection device that activates a secondary filter means to detect a relative displacement of an optical image when a relative displacement of the optical image cannot be detected even when calculation is performed using the primary filter means. With the goal.

[Means for solving the problem]

In order to achieve the above object, the present invention provides primary filter means for extracting a first spatial frequency component, first focus detection means for performing focus detection based on the extracted spatial frequency component, Secondary filter means for extracting a second spatial frequency component from the extracted spatial frequency component, second focus detecting means for performing focus detection based on the spatial frequency component extracted by the secondary filter means, And determining means for operating the secondary filter means and the second focus detecting means when the focus detecting means determines that the focus cannot be detected.

[Action]

According to the automatic focus detection device having the above configuration, the secondary filter is operated when the focus cannot be detected even when the primary filter is used, so that the focus can be detected only with the frequency components extracted by the primary filter. Can reduce the time for extracting the frequency component by the secondary filter means. Further, when the focus is detected by using the frequency component extracted by the secondary filter means, since the frequency component data is formed by using the secondary filter means from the frequency component data extracted by the primary filter means, There is no need to provide an extra memory capacity such as a RAM for creation processing and creation data, and data creation is quick.

〔Example〕

FIG. 1 shows an embodiment of a schematic configuration of a camera provided with an automatic focus detection device according to the present invention. The automatic focus detecting device 1 includes a photographing lens 2, focus detecting means 3, defocus amount determining means 4, lens position detecting means 5, lens driving means 6, and control means 7. The photographing lens 2 guides a light beam 9 emitted from the subject 8 to the focus detecting means 3. The focus detection means 3 has a photoelectric conversion element array (not shown), and calculates the output of the photoelectric conversion element array to detect a relative displacement of a light image by the subject 8 on the photoelectric conversion element array. It is.

Further, the defocus amount determining means 4 determines whether the photographing lens 2 is based on the displacement detection signal output from the focus detecting means 3.
Is determined. The lens position detecting means 5 detects the current position of the taking lens 2. The lens driving unit 6 drives the photographing lens 2 based on the defocus amount signal of the defocus amount determining unit 4. 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 when the focus detection means 3 outputs a focusing signal, the photographing lens 2 Is stopped.

FIG. 2 shows an embodiment of the mechanism configuration of the focus detecting means 3. The focus detecting means 3 includes a main mirror 10, a sub mirror 11, and a focus detecting optical system 12. This primary mirror 10
Is for splitting the light beam 9 passing through the taking lens 2 into a finder optical system (not shown) and a sub-mirror 11. The sub mirror 11 further splits the light beam 9 split by the main mirror 10 into a focus detection optical system 12 and a filter surface 13.

The focus detection optical system 12 is a photoelectric conversion element array 141, 14
2, 143, separator lens 15, aperture mask 16, module mirror 17, condenser lens 181, 182, 183 and field stop 1
It consists of nine. Photoelectric conversion element array 141, 142, 1
Reference numeral 43 denotes an arrangement of a plurality of CCD image pickup devices and the like, which are formed on one chip on the focal plane 14 of the separator lens 15. The separator lens 15 is a separator lens pair 151, 152,
153, and the split light beam 9 is supplied to the photoelectric conversion element array 14
1, 142, 143. The aperture mask 16 has circular or oblong openings 161, 162, and 163, and limits the light flux 9 input to the separator lens 15. The module mirror 17 guides the light flux 9 passing through the condenser lenses 181, 182, 183 to the separator lens 15.
The field stop 19 has rectangular openings 191, 192, and 193 and is disposed near the focal plane, and limits the field of view of the light beam 9 input to the focus detection optical system 12.

FIG. 3 shows a light receiving section of the photoelectric conversion element arrays 141, 142, 143 (hereinafter, referred to as a CCD including a light receiving section, a storage section, and a transfer section of the photoelectric conversion element). The photoelectric conversion element array 141 includes a reference part 141a, a reference part 141b, and a photoelectric sensor 141c. Similarly, the photoelectric conversion element array 142 includes a reference part 142a.
The photoelectric conversion element array 143 includes a reference portion 143a, a reference portion 143b, and a photoelectric sensor 143.
c. The photoelectric sensors 141c, 142c, and 143c are disposed on one side of the reference portions 141a, 142a, and 143a, respectively, in the longitudinal direction, and output signals according to the amount of received light. The accumulation time of the CCD in the accumulation unit is controlled by a signal corresponding to the amount of received light. As shown in FIG. 4, the photoelectric conversion element arrays 141, 142, and 143 are provided with focus detection areas 21, 22, and 23 (hereinafter, referred to as first islands 12 and 23, respectively) located at the center of the photographing screen 20 in the viewfinder.
The displacement detection signal is output based on the light image of the subject 8 projected on the second island 22 and the third island 23).

An area 24 indicated by a dotted line in the center of the imaging screen 20 displays an area where focus detection is performed for the photographer. The display unit 25 is turned on when focusing is performed.

The number of pixels X of the reference portions 141a, 142a, 143a and the number of pixels Y of the reference portions 141b, 142b, 143b are, for example, as shown in FIG. In this example, the number of pixels X in the reference portion is 34, and the number of pixels Y in the reference portion is 44.
In 142, the number of pixels X in the reference portion is 44 and the number of pixels Y in the reference portion is Y
Consists of 52 pieces.

In the automatic focus detection device 1, the reference portions 141a, 142a, 143a
Is divided into a plurality of blocks, and the divided blocks are compared with all the data of the reference units 141b, 142b, and 143b to perform focus detection. Then, among the focus detection results in each block, the data of the rearmost pin is used as the focus detection data of each of the islands 21, 22, and 23, and the focus detection data of each of the islands 21, 22, and The photographing lens 2 is driven based on the data of the photographing magnification to bring the lens into focus.

Next, a range (a defocus range) for detecting the amount of defocus (that is, the amount of defocus in the optical axis direction between the planned focal plane of the imaging optical system and the object image plane) from the photoelectric conversion element arrays 141, 142, and 143. Will be described with reference to FIGS. 5 to 7.

FIG. 5 is an enlarged view of the reference portions 141a, 142a, and 143a corresponding to the islands 21, 22, and 23 shown in FIG. In the figure, the numerical values shown in each of the reference portions 141a, 142a, and 143a are the differences (that is, the space) in which the data of each pixel of the reference portions 141a, 142a, and 143a shown in FIG. (Frequency component). Also,
This difference data indicates a specific spatial frequency component extracted (filtered) from the pixel data (first spatial frequency component extracting means). The difference data may be two or one. However, the spatial frequency components are different from every third spatial frequency component, and the numerical values are also different.

The numerical values in the reference portions 141a, 142a, 143a of the islands 21, 22, 23 are 30 in the first island 21, 40 in the second island 22, and 30 in the third island 23. In addition, the reference parts 141a, 142a,
It is obtained in the same manner as the numerical value of the difference data of 143a. That is,
The numerical values of the reference portions 141b, 142b, 143b are
Forty, the second island 22 has 48, and the third island 23 has forty.

Next, block division in each of the islands 21, 22, and 23 will be described. That is, the first island 21 is divided into two blocks of K1 (1 to 20) and K1 (11 to 30) from the difference data at the upper end, and these are referred to as a first block BL1 and a second block BL2, respectively. In the second island 22, three of K2 (1 to 20), K2 (11 to 30), and K2 (21 to 40) are obtained from the left end difference data.
Divided into three blocks, the third block BL3 and the fourth block, respectively.
Block BL4 and fifth block BL5. In the third island 23, K3 (1 to 20) and K3 (11
30) divided into two blocks, each of which is the ninth block
BL9 and the tenth block BL10.

Further, the second island 22 detects difference data of which the extraction frequency has been changed in order to focus on a subject composed of low frequency components (second spatial frequency component extraction means), and converts the difference data into sixth block BL6, It is divided into a seventh block BL7 and an eighth block BL8 and used for focus detection data. That is, the data of each pixel of the reference unit 142a and the reference unit 142b is, for example, obtained every 7th difference, a sum between the adjacent difference data is obtained, and the sum data is used as a sixth block BL6. That is, the number of data of the difference data 6 is 36 in the reference unit 142a and 44 in the reference unit 142b.
The data number of the sum of the sixth block BL6 is 35 in the reference unit 142a.
And 43 in the reference section 142b. And this reference part 14
The 25 blocks on the left of the 35 blocks of 2a are referred to as a seventh block BL7,
The 25 blocks become the eighth block BL8.

In the above description, the intervals of the difference are set at seven intervals, but the larger the interval, the more low frequency components can be extracted.
That is, the intervals of the differences may be intervals other than every seven intervals.

In this focus detecting means, the rear focus is set when the image interval when the optical images of the reference portion and the reference portion match is larger than a predetermined interval, the front focus is set when the image interval is smaller than the predetermined interval, and the focus is set at the predetermined interval. Therefore, the defocus range in the divided blocks is such that the blocks farther from the optical center in each island cover the rear focus side.

FIG. 6 shows the reference portion 142a and the reference portion of the second island 22.
142b is shown in an enlarged manner, and the defocus range of the fourth block BL4 divided into blocks will be described with reference to FIG.
That is, in order to focus on the image of the fourth block BL4 of the reference unit 142a, the data of the block BL41 located at the center of the reference unit 142b, that is, the data of the image located at the 15th to 34th positions from the left end of the reference unit 142b and This is when the data K2 (11 to 30) of the four blocks BL4 match. When the image coincidence is on the left side of the reference portion 142b, the front pin is set, and the maximum number of shift data of the front pin (hereinafter, referred to as shift pitch) is 14. On the other hand, if the image coincides with the right side of the reference portion 142b, the rear focus is set, and the maximum shift pitch of the rear focus is 14 pieces.

The same applies to the first island 21 and the third island 23. That is, as shown in FIG. 7, in the third block BL3, the front pin side shift pitch is 4, and the rear pin side shift pitch is 24. In the fifth block BL5,
The front pin side shift pitch is 24, and the rear pin side shift pitch is 4. Also, the first block BL1 and the ninth block BL
In No. 9, the number of front pin side shift chips is 5, and the number of rear pin side shift pitches is 15, and the second block BL2 and the tenth block
In BL10, the front pin side shift pitch is 15, and the rear pin side shift pitch is 5. Further, in the sixth block BL6, there are four shift pitches on both the front pin side and the rear pin side.

In the seventh block BL7, the front-pin-side shift pitch is four,
The rear pin side shift pitch is 14, and in the eighth block BL8, the front pin side shift pitch is 14, and the rear pin side shift pitch is 4. However, since the shift pitch overlaps with the sixth block BL6, In the seventh block BL7, four to fourteen shift pitches on the rear pin side are used.
The defocus range is set to the shift pitches of 14 to 14 pieces.

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

A central control circuit (hereinafter referred to as a microcomputer) 26 controls the entire camera, calculates exposure and the like, extracts a first spatial frequency component (primary filter means), and detects a focus based on the extracted spatial frequency component. (First focus detecting means), and a second spatial frequency component is extracted based on the extracted spatial frequency component (secondary filter means). The spatial frequency component extracted by the secondary filter means (Second focus detection means) based on
When the first focus detection means determines that the focus cannot be detected, the secondary filter means and the second focus detection means are operated (determination means). The lens circuit 27 transmits data specific to the photographing lens 2 (interchangeable lens) mounted on the camera body (not shown) to the microcomputer 26. The focus detection data output circuit 28 corresponds to the focus detection means 3 of FIG. 1, and converts an analog output of the photoelectric conversion element array into a digital output and transmits the digital output to the microcomputer 26. The luminance detecting circuit 29 detects the brightness of the subject 8 by measuring the light beam 9 passing through the photographing lens 2 and transmits an apex value Bvo corresponding to the brightness to the microcomputer 26. The film sensitivity reading circuit 30 reads the film sensitivity from a film (not shown) and transmits an apex value Sv corresponding to the film sensitivity to the microcomputer 26.

The display circuit 31 displays the exposure information and the focus state of the taking lens 2. The encoder 32 detects the rotation amount of the lens drive motor 33 and outputs a pulse number corresponding to a predetermined rotation amount of the lens drive motor 33 to a lens drive control circuit 34 described later. The lens drive control circuit 34 is a microcomputer
The motor drive direction signal and the motor stop signal are input from 26, and the drive of the lens drive motor 33 is controlled based on these signals.

Further, a counter is provided inside the microcomputer 26. This counter detects the extension position of the photographing lens 2 from the infinity position, and counts up or down with respect to the pulse number. In addition, a power switch (main switch) described later
SW ₁ is turned on, further, when being driven taking lens 2 is the taking lens 2 has been retracted to the infinity position, the counter is adapted to be reset.

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

Power switch SW ₁ is intended to start or stop the operation of the camera by being opened and closed. One-shot circuit 37, in conjunction with the opening and closing of the power switch SW ₁ generates a predetermined pulse, the pulse microcomputer 26
Is to be entered. Shooting preparation switch SW ₂ is intended to be opened and closed by operation of the release switch (not shown), when the shooting preparation switch SW ₂ is turned on, so that the focus detection operation is started. Limit switch
The SW ₃ is turned on when the photographing lens 2 is retracted to an infinity position or when the photographing lens 2 is extended to the forefront. The selection switch SW ₄ selects an automatic focus adjustment mode (hereinafter, referred to as AF mode) or a focus detection display mode (hereinafter, referred to as FA mode). When the selection switch SW ₄ is turned on, the FA mode is set. When turned off, the camera enters AF mode.

 Next, the operation of the camera having the above configuration will be described.

First, the power switch SW ₁ is once turned on, the one-shot circuit 37 outputs pulses to the interrupt input terminal INTO of the microcomputer 26, the microcomputer 26 executes the flowchart of the interrupt operation shown in FIG. 9.

That is, the microcomputer 26 prohibits the focus detection operation by the on the shooting preparation switch SW ₂ (step # 1), or not this interruption operation due to the on power switch SW _1, or by off interrupt input of the microcomputer 26 The determination is made based on the voltage input to the terminal IP1 (step # 2). And
If this input voltage is a high voltage, steps # 3 to # 11
Without performing the processing of, the power to the lens circuit 27 and the like is stopped,
The microcomputer 26 enters an operation standby state (steps # 12 and # 1).
3). If this input voltage is a low voltage, the power switch S
W ₁ determines the ON state, and prohibits the operation of the counter in the microcomputer 26 (Step # 3), the flag to be used for execution of the flowchart, and initially sets the output terminal such 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 retraction signal of the photographing lens 2 is input to the lens drive control circuit 34, and the photographing lens 2 is retracted in the direction of the infinite position (step # 6). Then, the photographing lens 2 is retracted to the infinity position, and the limit switch SW ₃
Is turned on (step # 7). When the limit switch SW ₃ is turned on at step # 7, it stops the driving of the photographic lens 2 (step # 8). At the same time, the counter in the microcomputer 26 is reset, and the number of pulses according to the rotation amount of the lens drive motor 33 is counted (steps # 9 and # 10). Then, allow interruption of the focus detecting operation by the on shooting preparation switch SW ₂ (step # 11).

Then, the output terminal OP1 is set to a low voltage to set the lens circuit 27.
It stops power to such, to wait the operation to the photographing preparation switch SW ₂ and the like is depressed (step # 12, # 13).

The photographing preparation switch SW ₂ when the operation waiting state of the step # 13 when it is turned on, the microcomputer 26 executes the flowchart of the interrupt operation shown in FIG. 10.

That is, the microcomputer 26 initially sets flags used for execution of the flowchart and output terminals of the microcomputer 26 (step # 21). Further, the timer provided in the microcomputer 26 is reset, and then the timer is started (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 set the lens circuit 27.
And the like (Step # 24). Next, data including a coefficient for converting the focal length data of the photographing lens 2, the open aperture value, the defocus amount, and the like into a pulse number 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 the difference data is stored (steps # 26, # 27). Next, the defocus amounts of the above-mentioned islands 21, 22, and 23 are calculated, exposure calculation is performed, and the calculation results are displayed on the display circuit 31 (step #).
28 to # 30).

Next, it is determined whether the mode is the FA mode or the AF mode (step # 31). If the mode is the 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 the calculated amount. (Step # 32). On the other hand, if the mode is the FA mode in step # 31, the process proceeds to step # 34 without performing the process of step # 32. At step # 34, it determines the opening and closing of the shooting preparation switch SW _2. Then, if photographing preparation switch SW ₂ is turned on, and resets the flag AFSF (step # 35), the process returns to step # 25, step #
Repeat the process from 25. On the other hand, if the shooting preparation switch SW ₂ is turned off at step # 34, turns off the power supply circuit 36 stops power to the lens circuit 27 and the like (step # 36),
Shooting preparation switch SW ₂ and the like to wait operation until pressed (step # 37). When the shooting preparation switch SW ₂ and the like is depressed, the process proceeds to the flow chart of Figure 9.

Next, each island 2 shown in step # 28 of FIG.
The subroutine of the defocus amount calculation of 1, 22, and 23 will be described with reference to FIGS. 11 to 14.

FIG. 11 shows the defocus amounts of the islands 21, 22, and 23 as the first.
The calculation is performed in the order of the island 12 (step # 41), the second island 22 (step # 41), and the third island 23 (step # 41). FIG. 12 to FIG.
A specific flowchart of defocus amount calculation of 21, 22, and 23 is shown.

FIG. 12 shows a subroutine for calculating the defocus amount of the first island 21 (step # 41). As described above, the first island 21 includes the first block BL1 and the second block BL1.
Block BL2, these blocks BL1, BL2
A predetermined value "-K" is stored in the variables DF1 and DF2 for storing the respective defocus amounts (steps # 51 and # 52). The predetermined value “−K” is a value of a front focus state that cannot be obtained in each of the blocks BL1 and BL2, and is output as a defocus amount when focus detection is not possible in the first island 21 (hereinafter referred to as low contrast). .

Next, a flag LCF1 indicating the state of the low contrast in the first island 21 is set (step # 53). And the first
The focus state (front focus state, rear focus state, focus state) of the block BL1 is detected and the defocus amount DF is calculated (step # 54). If focus calculation is possible from the calculation result, the flag LCF1 is reset. And the calculated defocus amount DF
Is a variable DF that stores the defocus amount of the first block BL1.
1 (steps # 55 to # 57), and the process proceeds to step # 58.

On the other hand, if it is determined in step # 55 that focus detection cannot be performed, step # 58 is skipped without performing steps # 56 and # 57.
Move to

Next, the focus state of the second block BL2 is detected and the defocus amount DF is calculated (step # 58). If the focus result cannot be detected from the calculation result, it is determined whether the flag LCF1 is set. . Then, when the flag LCF1 is reset, that is, when the focus detection is disabled in the determination of step # 55, the process proceeds to step # 55.
Move to 62. If the flag LCF1 is set in step # 60, the second step # 42 shown in FIG.
Island 22 defocus amount calculation subroutine (13th
(Figure).

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

In step # 62, an inter-block defocus amount ΔDF used in an averaging processing routine described later is determined. Then
The magnitude of the defocus amount DF1 and the magnitude of the defocus amount DF2 are determined, and the larger the defocus amount, that is, the defocus amount of the subject closer to the photographing lens 2 (camera) is determined as the first defocus amount.
The defocus amount DFIS1 of the island 21 is set. That is,
When the defocus amount DF1 is larger than the defocus amount DF2, the defocus amount DF1 is set to the defocus amount DFIS1 of the first island 21, and conversely, when the defocus amount DF2 is larger than the defocus amount DF1, The focus amount DF2 is set as the defocus amount DFIS1 of the first island 21 (steps # 63 to # 67).

In steps # 64 and # 65, the difference between the defocus amount DF1 and the defocus amount DF2 is the inter-block defocus amount ΔDF.
If smaller, the average of the defocus amount DF1 and the defocus amount DF2 is calculated.
The defocus amount DFIS1 is set to 1 (step # 68). Then, when the processes of steps # 66, # 67, and # 68 are completed, the process proceeds to step # 42 of FIG.

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

First, variables storing the defocus amounts of the third block BL3, the fourth block BL4, and the fifth block BL5, respectively.
A predetermined value "-K" is set in DF3, DF4 and DF5 (steps # 71 to # 73), and a flag LCF2 indicating the state of low contrast in the second island 22 is set (step # 74). Then, the focus state detection and the defocus amount DF of each block BL3, BL4, BL5 are calculated (steps # 75, # 79, # 8).
3). That is, the third block BL3 in step # 75
If the focus can be detected from the calculation result of the defocus amount DF, the flag LCF2 is reset, and the obtained defocus amount is calculated.
The DF is stored in the variable DF3 (steps # 76 to # 78), and the process proceeds to step # 79. Conversely, if it is determined that the focus detection cannot be performed, the processing in steps # 77 and # 78 is not performed and step # 7 is performed.
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 CLF2 is reset, and the defocus amount DF is stored in the variable DF4 (steps # 80 to # 80). 82), proceed to step # 83. Conversely, if it is determined that focus detection is impossible, step #
The process proceeds to step # 83 without performing the processes of 81 and # 82.

Similarly, for the defocus amount DF of the fifth block BL5, if the focus can be detected from the calculation result of step # 83, the flag LCF2 is reset, and the defocus amount DF is stored in the variable DF5 (steps # 84 to ##). 86), proceed to step # 87. Conversely, if it is determined that focus detection is impossible, step #
The process proceeds to step # 87 without performing the processes of 85 and # 86.

In step # 87, it is determined whether or not the low contrast flag LCF2 is set. When the flag LCF2 is not set, that is, in steps # 76, # 80, #
If it is determined that the focus detection cannot be performed in each of the determinations at 84, the defocus amount (average processing width) ΔDF between blocks used in the averaging processing routine described later is determined (step # 88). Next, the magnitude of each defocus amount DF3, DF4, DF5 of each block BL3, BL4, BL5 is determined, and the largest defocus amount MAXDF is extracted (step # 89). And
If there is no other block smaller than the average processing width ΔDF, the defocus amount MAXDF is set to the second island 2
Assuming a defocus amount DFIS2 of 2 (steps # 90 and # 91),
When one or more other blocks smaller than the average processing width ΔDF are present, averaging is performed using only the defocus amount MAXDF and the defocus amount of the other blocks smaller than the average processing width ΔDF (average processing). The average value is used as the defocus amount DFIS2 of the second island 22 (step # 9).
2). When the processing of steps # 91 and # 92 is completed,
The process proceeds to the defocus amount calculation subroutine (FIG. 14) for the third island 23 in step # 43 shown in FIG.

When it is determined in step # 87 that the flag LCF2 is set, every third difference data is re-organized into every seventh difference data in order to focus on a subject having low frequency components (step # 87). # 93). That is, for example, l ₁ the data of the pixel, l _2, ..., ln, ... and when the differential data 2 every _{is, dDn = l 1 -l 5,} ..., l 5 -l 9, ..., ln-
ln ₊₄ , ... The difference data of every seventh is dDm = 1
₁ −l ₉ ,..., Lm−lm _+8,. Every seventh difference data dDm is obtained by taking the sum of every third difference data dDn. In other words, the difference data of 7 every _{is, dDm = dD 1 + dD 5} , ..., dDm + dDm +4, ... = l 1 -l 5 + l 5 -l 9, ..., l n-4 -ln + ln-ln +4, ... = L ₁ -l ₉ , ..., l _n-4 -ln ₊₄ , ... = l ₁ -l ₉ , ..., lm-lm ₊₈ , ... Here, n = m + 4.

Further, the sum between the adjacent pieces of the difference data dDm is calculated, a new data sequence dDw (m) = dDm + dDm _{+ 1} is calculated, and the focus is detected in the sixth block BL6 by using the calculated data. Calculate the defocus amount DF (Step # 9)
4) If the focus can be detected, the flag LCF2 is reset, and the defocus amount DF6 of the sixth block BL6 is set as the defocus amount DFIS2 of the second island 22 in the step # 4.
The process proceeds to step 3 (steps # 95 to # 97). On the other hand, if the focus cannot be detected in step # 95, the focus is detected in the seventh block BL7 to detect the focus state and the defocus amount.
DF is calculated (step # 98). If focus detection is possible (step # 99), the flow returns to step # 96 to set the flag LCF2.
Is reset, and the defocus amount of the seventh block BL7 is set as the defocus amount DFIS2 of the second island 22, and the routine goes to the step # 43. On the other hand, if focus detection is not possible in step # 99, focus detection is performed in the eighth block BL8,
The focus state detection and the defocus amount DF are calculated (step # 100), and if focus detection is possible (step # 10)
1) Returning to step # 96, the flag LCF2 is reset, and the defocus amount of the eighth block BL8 is set as the defocus amount DFIS2 of the second island 22, and the process proceeds to step # 43. On the other hand, if the focus cannot be detected in step # 101, the process proceeds to step # 43 without performing the processes of steps # 96 and # 97.

FIG. 14 shows a subroutine for calculating the defocus amount of the third island 23 (step # 43). First, a predetermined value “−K” is stored in variables DF9 and DF10 for storing the respective defocus amounts of the ninth block BL9 and the tenth block BL10 (steps # 111 and # 112). Next, a flag LCF3 indicating the state of the low contrast in the third island 23 is set (step # 113). Then, the focus state detection of the ninth block BL9 and the defocus amount DF are calculated (step # 11).
4) If the focus can be detected, the flag LCF3 is reset, and the obtained defocus amount DF is stored in the defocus amount DF9 of the ninth block BL9 (steps # 115 to # 117).
On the other hand, if it is determined in step # 115 that the focus detection cannot be performed, the process of steps # 116 and # 117 is not performed and step # 1 is performed.
Move to 18.

Next, the detection of the focus state of the tenth block BL10 and the defocus amount DF are calculated (step # 118). If the focus detection is not possible from this calculation result, it is determined whether or not the flag LCF3 is set. Then, when the flag LCF3 is reset, that is, when the focus detection is disabled in the determination in step # 115, the process proceeds to step # 122. When the flag LCF3 is set, the flow shifts to the exposure calculation subroutine of step # 29 shown in FIG. 10 (steps # 119 and # 120). on the other hand,
If it is determined in step # 119 that focus detection is possible, the process proceeds to step # 112 without performing step # 120.

In step # 122, an inter-block defocus amount ΔDF of an averaging processing routine described later is determined. Next, the magnitude of the defocus amount DF9 and the defocus amount DF10 are determined,
The larger defocus amount is defined as the defocus amount DFIS3 of the third island 23 (steps # 123 to # 127).

If the difference between the defocus amounts DF9 and DF10 is smaller than the average processing width ΔDF in steps # 124 and # 125, the defocus amounts DF9 and DF10 are averaged. Is the defocus amount DFIS3 of the third island 23 (step # 128). Then, when the processes of steps # 126, # 127, and # 128 are completed, the process proceeds to step # 29 in FIG.

Next, the exposure calculation subroutine shown in step # 29 of FIG. 10 will be described with reference to FIG.

First, an open luminance value (apex value) BV0 corresponding to the brightness of the subject 8 is input from the luminance 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 BV0, film sensitivity value SV, and microcomputer 26 are determined in advance in step # 27 of FIG.
The exposure value E is calculated from the sum of the open aperture value AV0 input to
V (EV = BV0 + SV + AV0) is calculated (step # 13)
3).

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

Next, the process of calculating the drive amount of the photographing lens 2 shown in step # 32 of FIG. 10 will be described. In the process of step # 32, how the subject is distributed is divided into patterns based on the defocus amounts of the islands 21, 22, and 23, and an optimal defocus amount calculation procedure is selected for each pattern. Thus, an optimal driving amount of the photographing lens 2 is obtained. Here, the means for selecting the calculation procedure will be briefly described.

First, it is determined whether the mode is the FA mode or the AF mode. In the case of the FA mode, the distance measurement of the second island 22 is prioritized. If the distance measurement of the second island 22 is possible, the driving amount of the photographing lens 2 is determined based on the defocus amount DFIS2 of the second island 22. If it is determined that the distance cannot be measured for the second island 22, the driving amount of the photographing lens 2 is determined based on the defocus amount of the nearest island. In other words, in the FA mode, shooting is often performed with a still subject in the center, and if the defocus amount is obtained based on ranging over a wide range, it is not clear which island is selected and displayed. To measure the distance in the center of the shooting screen,
The defocus amount DFIS2 of the island 22 is given priority.

On the other hand, in the AF mode, the islands 21, 22, 23
When any one of the subjects 8 can detect the focus, the defocus amount of the closest island, that is, the island having the largest defocus amount, the focal length data of the photographing lens 2, and the distance to the subject Is calculated based on the calculation result, and the calculation procedure of the defocus amount is changed according to the calculation result. In other words, basically, if the shooting magnification is large, the main subject always exists at the center of the shooting screen, and the defocus amount DFIS2 of the second island 22 is prioritized. Also, if the shooting magnification is small, the shooting will include the background, and the distribution of the distance to the subject will be large, and the main subject is often located close to the camera. I do. FIG. 16 shows an example of a value used as a guide for determining the photographing magnification and a procedure for selecting a calculation means based on the value.

That is, for example, in the case of the AF mode, the calculation means is selected when the focal length f of the photographing lens 2 is 35 mm. If the focal length f is equal to or greater than 35 mm and the imaging magnification βdf of the nearest island is smaller than a predetermined magnification βH (for example, 1/25), the photographic lens 2 is adjusted based on the defocus amount of the nearest island. Determine the drive amount. On the other hand, when the photographing magnification βdf exceeds the predetermined magnification βH, the second island 2
The defocus amount DFIS2 of 2 is prioritized, and if the distance measurement of the second island 22 is impossible, the drive amount of the photographing lens 2 is determined based on the defocus amount of the closest diode.

Further, if the focal length f is less than 35 mm, 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. Therefore, even if the object on the closest island is focused on in the distance distribution, the object detected on the other island is within a considerable range within the depth of field. Because it can be included in

In the case of the FA mode, regardless of the focal length f,
The defocus amount DFIS2 of the second island 22 is prioritized. If the second island 22 cannot be measured, the driving amount of the photographing lens 2 is determined based on the defocus amount of the closest island.

Here, the calculation means of the above-described photographing magnification βdf will be described.

The photographing magnification βdf is given by the following equation based on the focal length f and the subject distance x from the camera.

βdf = f / x Since the data of the focal length f is input from the photographing lens 2, when the subject distance x is obtained, the photographing magnification βdf is calculated. The subject distance x is obtained by the following formula using the defocus amount DFx from the infinity position of the photographing lens 2 to the subject position.

x = f ² / DFx However, since the photographing lens 2 is not a single thin ideal lens, the principal point is located at the front and back, and the principal point is different due to a change in the focal length, the subject distance x is an approximate value from the above equation. Is required.

On the other hand, the defocus amount Dfo from the infinity position to the current position of the photographing lens 2 is obtained from the number of pulses corresponding to the rotation amount (number) N of the lens drive motor 33 stored in the counter inside the microcomputer 25, The relationship is as follows.

N = k · DFo where the value of the coefficient k is determined based on the number of pulses and the like.

From the above equation, the defocus amount DFo is DFo = N / k. Then, the defocus amount DF from the current position of the taking lens 2 to the subject position is DFx = DFo + DF. Subject distance x from these ^{equations, x = f 2 / DFx =} f 2 / (N / k + DF) Therefore, imaging magnification Betadf becomes βdf = f / x = (N / k + DF) / f.

Further, separately from the above equation, the photographing magnification βdf is the drive amount ΔN from the current position of the photographing lens 2 to the subject position (ΔN = DF ·
Using k), βdf = (N + ΔN) / f · k.

Next, the subroutine for performing the averaging process will be described with reference to the flowchart of the second island 22 (steps # 88 and # 9 in FIG. 13).
This will be described using 2) as an example.

The average processing width ΔDF of step # 88 in FIG. 13 is obtained according to a subroutine shown in FIG. First, it is determined whether or not the previous averaging process has been performed by using the flag WZF2 (step # 141). That is, when the previous averaging process is performed, the flag WZF2 is set. Then, if the previous average processing is performed, set the coefficient k ₁ "1.5", if the previous average processing is performed to set the coefficient k _{1 "1"} (step # 142, # 143) . Setting the coefficient k ₁ reason, or averaging process is performed by variation of the distance measurement values, to prevent or not done, once the average processing performed when the second and subsequent spread Average treatment width This is also to increase the possibility (probability) of performing the averaging process.

Next, the photographing magnification βdf detected at the time of the previous distance measurement is determined, and when the photographing magnification βdf is “1/20” or more, the coefficient k ₂
Is set to “1”, and when the shooting magnification βdf is from “1/20” to “1/50”, the coefficient k ₂ is set to “0.5” and the shooting magnification βdf is set to “1 /
"In the following cases the coefficient k _2" 50 0 "(step # 1
45 to # 149), and the process proceeds to step # 150. The reason for setting the coefficient k ₂ is to possibly occupied by the same subject into a plurality of blocks in the same island as the shooting magnification βdf high increases.

Next, in step # 150, a reference average processing width ΔDF1 is set based on the aperture value FNo. That is, the depth of focus δ obtained by the product of the aperture value FNo. At the time of photographing and the allowable confusion circle diameter ε is set as the reference average processing width ΔDF1 for storing the resolution of the photographed image.

Then, by multiplying the coefficient k ₁ and the coefficient k ₂ in the reference average processing width? Df1, averaging width ΔDF is determined, further flag WZF2 is reset (step # 15
1). Thereafter, the flow shifts to step # 89 shown in FIG.

The flag for determining whether or not the previous averaging process has been performed is determined by the first island 21 and the third island 21.
23 has the same flag as WZF2. When the averaging process is performed, the flag WZF2 is set. When the previous averaging process is not performed, the flag WZF2 is reset.

Here, the calculation of the defocus amount of each block and the determination of the focus detection failure will be described with reference to FIG. 18 (a) using the third block BL3 as an example (steps # 75 to # 78 in FIG. 13).

First, in the defocus range from the position where the front pin side shift pitch is four (shift pitch “−4”) to the position where the rear pin side shift pitch is 24 (shift pitch “24”), the reference unit 142
While shifting (shifting) the data of b, the data of the third block BL3 and the reference unit 14 at each shift position are shifted.
Find correlation H3 (I) with 2b data (step #
161).

 This correlation H3 (I) is expressed by the following equation.

Here, K2 indicates a difference data string of the reference unit 142a, and S2 indicates a difference data string of the reference unit 142b.

Next, the correlation H3 at each shift position described above
The best correlation among (I), that is, the correlation H3
The shift amount IM at which the value of (I) is minimized (IM = MIN3H3
(I)｝) is extracted (step # 162). Next, an interpolation operation between each pitch is performed using the value of each point of the correlation H3 (I) (step # 163).

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

XM = IM + {H3 (IM-1) -H3 (IM + 1)} / [MIN
{H3 (IM-1), H3 (IM + 1)}-H3 (IM)] / 2 The reason for performing this interpolation operation is that when one pitch shift is converted into a defocus amount, it is as large as about 1000 μm. This is for performing accurate distance measurement by compensating for.

The interpolation pitch XM obtained in this way is multiplied by a coefficient α determined by the pitch length of the optical system and the photoelectric conversion element array, and converted into a defocus amount DF (DF = XM · α) (step # 164). Next, the contrast (brightness / darkness) value C (3) of the data of the third block BL3 is obtained as the sum of adjacent data of the reference unit 142a (step # 165).

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

Subsequently, an interpolation value YM of the minimum value of the correlation H3 (I) is obtained, and the interpolation value YM and the contrast value C (3) are obtained.
Is obtained (step # 167).

The interpolation YM and the ratio value R (3) are expressed by the following equation.

YM = H3 (IM)-| H3 (IM-1) -H3 (IM + 1) | / 2R
(3) = C (3) / YM Focus detection is possible only when both the contrast value C (3) thus obtained and the ratio value R (3) satisfy the set values, and the contrast value C (3) or the ratio Value of R
If either one of (3) is not satisfied, focus detection is disabled (low contrast determination). That is, first, the third
It is determined whether or not the block BL3 has been able to detect the focus in the previous routine processing by using the detection flag NLB3 (step # 168). This is to reduce the determination level when focus detection has been possible last time, and to prevent unstable determination of whether or not focus detection is possible for a subject at the very end of the focus detection determination level. In other words, the determination level is determined for the subject just before the focus detection determination level.
Set predetermined values C1 and R1 to Cth and Rth, respectively (step #
169).

Then, in step # 168, if the focus cannot be detected last time or the first routine processing, that is, if the detection flag NLB3 has been reset, the photographing magnification βLS when photographing at the current position of the photographing lens 2 is performed. An operation is performed (step # 170).

The photographing magnification βLS is obtained by calculating the above-described photographing magnification βdf, that is, by substituting “0” into the defocus amount DF of βdf = (N / k + DF) / f.

Then, the product of the photographing magnification βLS and the focal length f is obtained. If the product is equal to or larger than a predetermined value f / βth (for example, βth is 1/15 or more for a 300 mm lens), the determination level Cth, Rt
The predetermined values C4 and R4 larger than the predetermined values C1 and R1 are set to h (steps # 171 and # 172). That is, step # 1
The determination levels Cth and Rth are stricter than in the case of 69.

If it is less than the predetermined value f · βth in step # 171, the maximum local contrast value CLth of the third block BL32 is calculated (step # 173). If the local contrast value CLth is larger than a predetermined value, that is, if a flag CL described later is set, the determination level
Cth is set to a predetermined value C2. If the value is smaller than the predetermined value, that is, if the flag CL is reset, the determination level Ct is set.
h is set to a 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 or not the flag AFSF is set. If the flag AFSF is set, a predetermined value R2 is set as the determination level Rth, and if the flag AFSF is reset, the determination level Rth
Is set to a predetermined value R3 (steps # 177 to # 179). However, the relationship between the predetermined values R2 and R3 is set in advance so that R1 <R2 <R3 <R4.

After a predetermined value is set for each of the determination levels Cth and Rth (steps # 169, # 172, # 178, # 17)
9) 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 NLB3 is set, and the contrast value C (3) or the ratio is set. Is smaller than the judgment level Cth or the judgment level Rth, the detection flag NLB3 is reset (step # 18).
0 to # 182). After that, processing such as calculation of the defocus amount of the fourth block BL4 and determination of the inability to detect the focus, which are shown after step # 79 in FIG. 13, are performed.

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

As the detection flag NLB3, the detection flag NLB may be set for each island, and the determination level may be relaxed based on the detection flag NLB. In other words, if the focus is detected once and a large defocus amount is detected,
By driving the lens, the image interval approaches the basic image interval.
Therefore, the image itself of the reference portion is also, for example, the fourth block,
The image in the fifth block may be shifted to the third block and the fourth block by expanding the image interval by driving the lens. In such a case, focus detection becomes impossible in the third block. Therefore, a flag indicating low contrast for each island
The LCF may be stored in another flag LCFN, and this flag LCFN may be determined at the time of distance measurement of each island instead of the detection flag NLB.

That is, in the case of a long focal length lens having an extremely large lens driving range (lens extension amount of 40 mm or more), a high magnification is set so that the lens position satisfies the above condition. If you try to detect the focus for the subject,
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 a completely different image is projected between the reference portion 142a and the reference portion 142b. Further, since the magnification is low, a completely different subject is projected.
In such a blurred state, the optical system passes only an extremely low frequency component, so that focus detection cannot be normally performed.
However, as shown in FIG. 18 (b), when the persons A and B are arranged side by side, the data (high-frequency component) for distinguishing the persons A and B does not pass through the optical system.
Each of the images of the persons A and B projected on the reference portion 142b and the reference section 142b has substantially the same waveform, and the image of the person A and the image of the person b may be erroneously determined to determine that the focus can be detected.

On the other hand, if the lens position is at infinity and the magnification is low, the focus is to be detected on a near-view, high-magnification subject.
Even in such a case, the optical system passes only very low frequency components, so that detailed data does not pass. However,
Since the magnification is high, the image interval in the reference portion 142a or the reference portion 142b is extremely large, and different portions of the same subject are projected on the reference portion 142a and the reference portion 142b. Therefore, since the reference portion 142a and the reference portion 142b do not project different subjects, the determination levels Cth and Rth are set to be strict.

Also, in step # 161 and step # 165,
The correlation function H3 (I) and the contrast value C (3) of the third block BL3 were calculated. As shown in FIG. 19, the other blocks BL1, BL2, BL4, BL5, BL9, and BL10 are similarly obtained. be able to.

Next, the local contrast value CLt in the step # 173
The operation of h will be described. A noise amount Cnoise generated by the photoelectric conversion element array or the like is superimposed on the contrast value determination level Cth in step # 173. Although the magnitude of the noise itself of the noise amount Cnoise does not change, the waveform of the noise varies, so that the minimum true subject contrast value CMIN required for focus detection is as follows.

Cth = CMIN + MAX {Cnoise} where CMIN {MAX} Cnoise} Therefore, the noise amount Cnoise is small, and the contrast value is determined to be the determination level Cth despite the fact that focus detection is originally possible.
, It may be determined that the focus cannot be detected. Therefore, when the maximum noise amount Cnoise occurs, it is predicted that noise also exists in each part of the third block BL3. Therefore, the contrast limit is determined for each difference data of the third block BL3 according to the following equation.

However, the value P is selected from predetermined value data set in advance and a value equal to or less than “20”.

In the determination of 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 manner as when the noise is small. That is, as shown in FIGS. 20 to 22, there are a plurality of determination routines for determining the contrast limit. That is, in the determination routine of FIG. 20, for example, a data block subdivided for every seven difference data from the third block BL3 is extracted, and if even one of the data blocks is equal to or more than a predetermined value CLth, In addition, the judgment level of the total contrast value is relaxed.

That is, this determination routine first resets the flag CL and also resets the variable q (step #
191). Next, the data of the third block BL3 is replaced with the data K2
Data block consisting of (7) difference data from (1) to K2 (8) Is extracted, and this data block CLOC is compared with a predetermined value CLth1 (steps # 192 and # 193). If at least one of the data blocks CLOC is equal to or greater than the predetermined value CLth1, the flag CL is set (step # 194), and the contrast value determination level is relaxed.

On the other hand, each difference data of the data block CLOC is a predetermined value C
If it is less than Lth1, the variable q is incremented to extract a data block CLOC including the difference data from the data K2 (2) to K2 (9) of the third block BL3, and compare this data block CLOC with a predetermined value CLth1. (Step #
195, # 193). Then, the data block CLOC continues until a single data is equal to or more than the predetermined value CLth1, or a data block CLOC including difference data from the data K2 (13) to K2 (20) of the third block BL3 is extracted. (Steps # 192 to # 196). As a result, if the value is less than the predetermined value CLth1 in all the data blocks CLOC, the flag CL
Shifts to the flowchart of FIG.

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

That is, this determination routine extracts the maximum value [MAX {K2 (j)}] and the minimum value [MIN {K2 (j)}] from the data K2 (1 to 20) of the third block BL3, and extracts these maximum values. The difference CLOC between [MAX ｛K2 (j)｝] and the minimum value [MIN ｛K2 (j)｝] (CLOC = MAX ｛K2 (j)｝-MIN ｛K2
(J)｝) is obtained (steps # 201 to # 203). Next, the flag CL is reset (step # 204), and the difference CLOC
Is compared with a predetermined value CLth2 (step # 205). And
If the value is equal to or larger than the predetermined value CLth2, the flag CL is set (step # 206), and the judgment level of the contrast value is relaxed. On the other hand, if the difference CLOC is less than the predetermined value CLth2, the flow shifts to the flowchart of FIG.

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

That is, in this determination routine, first, the variable j is set to "1", the variables CL1 and CL2 are reset, and the flag CL
Is reset (step # 211). Next, the data K2 (1) of the third block BL3 is compared with the predetermined value CLth3, and when the data K2 (1) is equal to or more than the predetermined value CLth3, "1" is added to the variable CL1. At this time, "1" is added to the variable CL2 (steps # 212 to # 215). Then, the product of the variable CL1 and the variable CL2 is obtained. If the product CL1 · CL2 is equal to or larger than the predetermined value CLth4, the flag CL is set (step # 217), and the judgment level of the contrast value is relaxed. On the other hand, if the product CL1 · CL2 is less than the predetermined value CLth4, the variable j is incremented, and all the data K2 of the third block BL3 are incremented.
With respect to (20), the processing of steps # 212 to # 215 is performed (steps # 212 to # 219). As a result, if the products CL1 and CL2 are less than the predetermined value CLth4 even after all the data have been processed, the flow shifts to the flowchart of FIG. 18A with the flag CL kept reset.

Next, the averaging process routine in step # 92 of FIG. 13 will be described. This averaging processing routine has several processing means, and each processing means is shown in FIGS.
This will be described with reference to FIG.

In the averaging process routine of FIG. 23, the contrast value C (3) obtained in steps # 165 and # 167 of FIG.
And a weighting function W (I) based on the ratio value R (3), and a weighted average of the defocus amount of each block is calculated using the weighting function W (I). In addition,
The weight function W (I) is, for example, a contrast value C
(3) itself or the ratio value R (3) itself may be used. That is, first, the variable I is set to "3" (step # 217). Then, each block BL3, BL4, BL5
The difference between the largest defocus amount MAXDF of the respective defocus amounts DF3, DF4, and DF5 and the defocus amount DF3 is obtained, and this difference is compared with the average processing width ΔDF. If it exceeds, the weight function W (3) is set to "0". Then, the variable I is incremented, and the defocus amount MAXDF, the defocus amount DF4, and the defocus amount DF5
Is calculated, and the difference is compared with the average processing width ΔDF. When the difference exceeds the average processing width ΔDF, the weight function W
(4) and the weight function W (5) are set to "0" (steps # 222 to # 225). That is, the averaging process is performed using the defocus amount within the average processing width ΔDF among the defocus amounts DF3, DF4, DF5 of the blocks BL3, BL4, BL5. Next, weighted averaging is performed using the weight function W (I) processed as described above, and this average value is set as the defocus amount DFIS2 of the second island 22 (step # 226).

 That is, the defocus amount DFIS2 is given by the following equation.

DFIS2 = ｛DF3 · W (3) + DF4 · W (4) + DF5 · W
(5) {/ (W (3) + W (4) + W (5)}} Then, a step # 227 of setting the wide zone flag WZF2. After that, the flow shifts to the defocus amount calculation subroutine of step # 43 in FIG.

In the averaging processing routine shown in FIG. 24, the correlation function is recalculated by combining the maximum correlation position IM among the correlation functions, and a plurality of blocks at the preceding and succeeding correlation positions IM + 1 and IM-1. It is supposed to.
That is, all the blocks BL3, BL4, BL5 have an average processing width Δ
If smaller than DF (average processing target), the second island 22
Correlation function H3,4,5 (IM), H3,4,5 with data K2 (1-40)
(IM-1), H3,4,5 (IM + 1) are recalculated and reinterpolated, and this value is used as the defocus amount of the second island 22.
Set to DFIS2 (steps # 231 and # 232). Also, the third
Block BL3 and fourth block BL4 have an average processing width ΔDF
Is smaller than the data K2 (1 to 30), the correlation function H3,4
(IM), H3,4 (IM-1), H3,4 (IM + 1) are recalculated, reinterpolated, and this value is set as the defocus amount DFIS2 (steps # 233, # 234). Further, the fourth block BL4
If the fifth block BL5 is smaller than the average processing width ΔDF, the correlation function H4,5 (IM), H4,5 (I
M-1), H4,5 (IM + 1) are recalculated and reinterpolated to set this value as the defocus amount DFIS2 (step # 23).
5, # 236). In step # 235, the third block BL3
If the fifth block BL5 is smaller than the average processing width ΔDF, the process proceeds to step # 232, and the wide zone flag WZF2 is set (step # 237).
The process proceeds to the defocus amount calculation subroutine of step # 43 in FIG.

Here, the arithmetic expressions of the correlation functions H3,4,5 (IM), H3,4 (IM), H4,5 (IM) of the above-described steps # 232, # 234, # 236 are shown.

In the averaging processing routine of FIG. 25, the correlation functions H (IM), H (IM−1), H
(IM + 1) are added, and the processing after the interpolation calculation is performed using the addition result. That is,
When all the blocks BL3, BL4, BL5 are smaller than the average processing width ΔDF, the correlation functions H3,4,5 (IM), H3,4,5 (IM−1),
H3,4,5 (IM + 1) is calculated as follows (step #
241, # 242).

H3,4,5 (IM-1) = H3 (IM-1) + H4 (IM-1) + H5
(IM-1) H3,4,5 (IM) = H3 (IM) + H4 (IM) + H5 (IM) H3,4,5 (IM + 1) = H3 (IM + 1) + H4 (IM + 1) + H5
(IM + 1) When the third block BL3 and the fourth block BL4 are smaller than the average processing width ΔDF, the correlation function H3,4 (I
M), H3,4 (IM-1), H3,4 (IM + 1) are calculated as in the following equations (steps # 243 and # 244).

H3,4 (IM-1) = H3 (IM-1) + H4 (IM-1) H3,4 (IM) = 3 (IM) + H4 (IM) H3,4 (IM + 1) = H3 (IM + 1) + H4 (IM + 1) Further, when the fourth block BL4 and the fifth block BL5 are smaller than the average processing width ΔDF, the correlation function H4,5
(IM), H4,5 (IM-1), H4,5 (IM + 1) are calculated as follows (steps # 245 and # 246).

H4,5 (IM-1) = H4 (IM-1) + H5 (IM-1) H4,5 (IM) = H4 (IM) + H5 (IM) H4,5 (IM + 1) = H4 (IM + 1) + H5 (IM + 1) In step # 245, when the third block BL3 and the fifth block BL5 are smaller than the average processing width ΔDF, the correlation functions H3,5 (IM), H3,5 (IM−1), H3,5 (IM +
1) is calculated as shown below (step # 247).

H3,5 (IM-1) = H3 (IM-1) + H5 (IM-1) H3,5 (IM) = H3 (IM) + H5 (IM) H3,5 (IM + 1) = H3 (IM + 1) + H5 (IM + 1) After completing the calculation of the correlation functions in steps # 242, # 244, # 246, and # 247, re-interpolation is performed, and this value is set as the defocus amount DFIS2 (step # 248). That is, the defocus amount DFIS2 is given by the following equation.

DFIS2 = α ・ IM + α ・ (1/2) ・ ｛H (IM-1) -H (IM
+1)｝ / [MIN ｛H (IM−1), H (IM + 1)｝ − H (I
M)] Then, the wide zone flag WZF2 is set (step # 249), and thereafter, the process proceeds to the defocus amount calculation subroutine of step # 43 in FIG.

Next, the sixth block BL of steps # 93 to # 95 in FIG.
The defocus amount calculation subroutine No. 6 will be described with reference to FIG.

First, the difference data string K2 used in the blocks BL3, BL4, BL5
Differences are taken at every seventh from (j) and S2 (j), and the sum data strings KW (j) and SW (j) between adjacent differences are obtained (step # 251). The sum data strings KW (j) and SW (j) are expressed by the following equation using the difference data string input in step # 26 of FIG.

KW (m) = K2 (m) + K2 (m + 1) + K2 (m + 4) + K2
(M + 5) SW (l) = S2 (l) + S2 (l + 1) + S2 (l + 4) + S2
(L + 5) Next, the correlation function H6 (I) is obtained, and the shift amount IM at which the value of the correlation function H6 (I) is minimized (IM = MIN {H6 (I)})
Is extracted (steps # 252 and # 253). This correlation function H6
(I) is as follows.

Here, as described above, the correlation function H6 (I) is obtained by removing the data at both ends from the data string of the reference unit 142a because the correlation function H6 (IM) near the minimum shift amount IM at the time of the interpolation calculation described later.
-1), H6 (I), H6 (IM + 1), but also the correlation functions H6 (IM-2), H6 (IM + 2). Reference section 142)
This is for correcting a large deviation of the position corresponding to the data b (see Japanese Patent Application Laid-Open No. 60-47211).

In step # 254, these correlation functions H6 (IM-2), H6
(IM-1), H6 (IM + 1), H6 (IM + 2) are obtained. That is, these equations are Becomes

These correlation functions H6 (IM-2), H6 (IM-1), H6 (IM +
1) A correction operation is performed using H6 (IM + 2) as in the following equation (step # 255).

XM = IM + {H6 (IM-2) -H6 (IM + 2)} / [MIN
{H6 (IM-2), H6 (IM + 2)}-MAX {H6 (IM-1), H
6 (IM + 1)｝] / 2 The defocus amount DF is calculated by multiplying the interpolation pitch XM by a coefficient α.
(DF = XM · α) (step # 256). Next, the contrast value C (6) of the data of the sixth block BL6 is obtained as in the following equation (step # 257).

Subsequently, an interpolation value YM1 of the minimum value of the correlation function H6 (IM) is obtained, and a ratio value R (6) is obtained by using the interpolation value YM1 and the contrast value C (6) as in the following equation (step #) twenty five
8).

YM1 = MAX {H6 (IM-1), H6 (IM + 1)}-｛| H6 (IM
−2) −H6 (IM + 2) |｝ / 2 R (6) = C (6) / {YM1−OF} Then, predetermined values are set for the determination levels Cth6 and Rth6, respectively, and the contrast value C (6) and the ratio are set. When both the values R (6) satisfy the predetermined value, focus detection is possible. When either the contrast value C (6) or the ratio value R (6) is not satisfied, focus detection is disabled. (Steps # 259 and # 260).

After that, the flow shifts to the flowchart of FIG. 13 to perform the process of step # 96 or step # 98.

Next, regarding the means of the interpolation calculation in step # 256,
This will be described with reference to the example of FIG.

First, the data string of the reference unit 142a is set to “3, 2, 1, −1, −2, −3”.
And the data string of the reference unit 142b is “4, 3, 2, 1, −1, −2, −3,
If -4 ", the correlation function is H (0) = 0, H (-1) = 6H
(1) = 6. Here, noise is added to the data sequence of the reference unit 142b, and the data sequence of the reference unit 142b is “4, 3, 2, 0, −1,
-1, -3, -4 ", the correlation function becomes H (0) = 2, H
(−1) = 5.5, H (1) = 6, the influence of noise on the focal point, that is, the correlation function H (IM) is the largest, and the correlation function H (IM−1), H (IM + 1) The effect is relatively small. Therefore, the correlation function H (IM-2), H before and after the correlation function H (IM) is used without using the correlation function H (IM).
The influence of noise is reduced using (IM-1), H (IM + 1), and H (IM + 2).

In step # 258, when a normal interpolation operation as shown in FIG. 18 (a) is performed, an offset amount is generated, so that the interpolation value YM1 is correlated with MAX {H6 (IM-1), H6 (IM + 1)}. The difference OF1 from the function H6 (IM) or MAX ｛H6 (IM-2),
H6 (IM + 2)} and MAX {H6 (IM-1), H6 (IM + 1)}
The value of the ratio R (6) is calculated using the value OF2 set based on the difference OF2 from the difference or the value obtained by subtracting the contrast value C (6).

〔The invention's effect〕

According to the present invention, when the relative displacement of the light image is detected by using the secondary filter means, the data of the frequency component is formed by using the secondary filter means from the data extracted by the primary filter means. Data creation can be speeded up while increasing the efficiency of use of a memory such as a RAM for storing data.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a camera provided with an automatic focus detection device according to the present invention, FIG. 2 is a configuration diagram of a focus detection unit, FIG. 3 is a diagram showing a photoelectric conversion element array, and FIG. FIG. 5 shows a focus detection area of a photographing screen in FIG.
FIGS. 6 and 7 are diagrams illustrating the defocus range of each block, and FIG. 8 is a diagram illustrating an automatic focus detection device according to the present invention using a microcomputer. Circuit block diagram of the camera configured
9 and 10 are flowcharts of the interrupt operation of the microcomputer, FIGS. 11 to 14 are flowcharts showing a subroutine of the defocus amount calculation of the first to third islands, and FIG. 15 is a subroutine of the exposure calculation. FIG. 16 is a diagram for explaining a procedure for selecting a calculating means of the defocus amount, FIG. 17 is a flowchart showing a subroutine for obtaining an average processing width, and FIG. 18 (a) is a defocus amount of the third block. FIG. 18 (b) is a diagram for explaining the calculation and the focus detection impossible determination, FIG. 18 (b) is a diagram for explaining erroneous determination when a person is lined up, and FIG. FIG.
20 to 22 are flowcharts showing a subroutine for determining the contrast limit, FIGS. 23 to 25 are flowcharts showing an averaging process routine, FIG. 26 is a flowchart showing a defocus amount calculation subroutine, and FIG. 27 is an interpolation FIG. 4 is a diagram for explaining means of calculation. DESCRIPTION OF SYMBOLS 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 battery, 36 power supply circuit, 141a , 142a, 143a… Reference part, 141b,
142b, 143b: Reference part, BL1: First block, BL2: Second
Block, BL3: third block, BL4: fourth block,
BL5: Fifth block, BL9: Ninth block, BL10: Tenth
Block, SW ₁ ... power switch, SW ₂ ... shooting preparation switch, SW ₄ ... selection switch.

Continuation of the front page (72) Inventor Hiroshi Ueda 2-30 Azuchicho, Higashi-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Camera Co., Ltd. Kokusai Building Minolta Camera Co., Ltd. (72) Kenji Ishibashi 2-30-30 Azuchicho, Higashi-ku, Osaka-shi, Osaka Osaka Kokusai Building Minolta Camera Co., Ltd. 30 Osaka International Building Minolta Camera Co., Ltd. (56) References JP-A-59-142506 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 7/11

Claims (2)

(57) [Claims] A first filter means for extracting a first spatial frequency component; a first focus detecting means for performing focus detection based on the extracted spatial frequency component; and a first filter means for detecting a focus based on the extracted spatial frequency component. A second filter means for extracting two spatial frequency components, a second focus detection means for performing focus detection based on the spatial frequency components extracted by the second filter means, and a focus by the first focus detection means. An automatic focus detection device comprising: a determination unit that activates the secondary filter unit and the second focus detection unit when it is determined that detection is impossible. 2. The automatic focus detection device according to claim 1, wherein said secondary filter means is set to extract more low frequency components than said primary filter means.