JP2770408B2 - Focus detection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus detection device that calculates a defocus amount from an in-focus position of a photographic lens by a so-called phase difference detection method.

[Prior Art] Conventionally, in focus detection by a so-called phase difference detection method, the reliability of a shift amount from a focusing position of a photographing lens calculated for a low-brightness or low-contrast subject, that is, a defocus amount is low. Various proposals have been made to prevent the focus from being undetectable due to the low temperature, and to prevent erroneous detection of a different subject in the focus position detection area, and to improve the focus position detection accuracy and detection speed. For example,
According to 61-186917, the image signal received in the focus detection area has low contrast, so when the reliability of the calculated defocus amount is low, the defocus amount is calculated a plurality of times, and the defocus amount is calculated. In this example, the photographing lens is driven by using the average value of (1) and the focus is automatically adjusted. Also, Japanese Patent Application Laid-Open Nos. 61-55618 to 61-55620 disclose a focus detection area divided into three blocks, calculate a defocus amount of each block, and obtain an image under the shooting condition. The width of the defocus amount corresponding to the depth of field is calculated, and the difference between the defocus amounts of the respective blocks is compared with the width of the defocus amount so that all the defocus amounts of the respective blocks are within the depth of field. In this case, the average value of the defocus amounts of the respective blocks is used as the defocus amount of the focus detection area. If at least one of the blocks is out of the depth of field, a warning is issued that focusing is impossible, or The figure shows that the photographing lens is driven (focused on the nearest object) based on the defocus amount for the nearest object among the defocus amounts within the depth of field.

[Problems to be solved by the invention]

By the way, the method disclosed in Japanese Patent Application Laid-Open No. 61-186917 reduces the influence of an error included in the defocus amount due to low contrast by taking an average value of the defocus amount for a plurality of times, thereby improving the focus position detection accuracy. Is to improve. However, since the number of calculations is increased, there is a disadvantage that the detection speed of the focal position is reduced. In particular, it is disadvantageous to divide the focus detection area into a plurality of blocks and calculate the defocus amount for each block.

In addition, the above JP-A-61-55618-55620,
When the objects in each block are within the depth of field, the focus is adjusted to the average value of the focal lengths of those objects. However, the amount of defocus detected from each block in the focus detection area may vary depending on the condition of the subject luminance, the contrast state of the received light image, and the like, and the average processing for performing the simple averaging described above does not provide suitable focus detection. There are cases. Further, in the low contrast state, the focus position detected in each block may be a subject different from the subject to be focused (main subject), and in such a case, it may not be possible to perform suitable focus detection.

The present invention has been made in view of the above problems, and has as its object to provide a focus detection device that performs an averaging process on a defocus amount of each block and quickly calculates a suitable defocus amount in a focus detection area. .

[Means for Solving the Problems] In order to solve the above problems, a first focus detection device includes:
Means for intercepting the optical axis of the photographing lens in the focus detection area, respectively receiving first and second images formed from subject light fluxes respectively passing through the first and second portions of the photographing lens; Means for comparing the two image signals with each other in each block obtained by dividing the area into a plurality of blocks to calculate a minimum correlation value, and detecting a relative interval between the two images from the minimum correlation value A focus detection device that calculates a defocus amount from the in-focus position of the imaging lens to extract a block to be subjected to defocus amount calculation processing from a minimum correlation value of each block; In each block, a contrast calculating means for calculating a contrast value from the image signal, and a defocus amount and a contrast value of each of the extracted blocks are added. On average is obtained and a calculating means for calculating a defocus amount of the focus detection area.

Further, the second focus detection device includes a first focus detection area that sandwiches the optical axis of the taking lens and that is formed from a subject light beam that has passed through the first and second portions of the taking lens.
Means for receiving the second image and a second image, respectively, and means for comparing the two image signals in each block obtained by dividing the focus detection area into a plurality of blocks to calculate a minimum correlation value, In a focus detection device that detects a relative distance between two images from the minimum correlation value and calculates a defocus amount from a focus position of the imaging lens, a weight value is set based on a minimum correlation value of each block. Setting means; and calculating means for calculating a defocus amount of the focus detection area by performing a weighted average of the defocus amount of each block and the weight value.

Further, the third focus detection device is the same as the second focus detection device, further comprising an extraction unit that extracts a block to be subjected to an averaging process from the minimum correlation value of each block, wherein the minimum correlation value of the extracted block is Is used to calculate the correlation value of the focus detection area.

Further, the fourth focus detection device includes a first focus detection device that sandwiches an optical axis of the photographing lens in the focus detection area and is formed from a subject light flux that has passed through the first and second portions of the photographing lens.
Means for receiving the second image and a second image, respectively, and means for comparing the two image signals in each block obtained by dividing the focus detection area into a plurality of blocks to calculate a minimum correlation value, In a focus detection device that detects a relative distance between two images from the minimum correlation value and calculates a defocus amount from a focus position of the imaging lens, a minimum correlation value between the blocks and the minimum correlation value Adding means for adding the correlation values at the shift positions separated by the same pitch back and forth from the shift position corresponding to the above, and performing an interpolation operation on the added correlation values to calculate a defocus amount in the focus detection area. Calculation means.

The fifth focus detection device may further include, in the fourth focus detection device, extraction means for extracting a block to be subjected to the addition operation of the correlation value from the minimum correlation value of each block. The correlation value of the focus detection area is calculated based on the minimum correlation value.

The sixth focus detection device may include a first focus detection region that sandwiches the optical axis of the photographing lens and that is formed from a subject light beam that has passed through the first and second portions of the photographing lens.
Means for receiving the second image and a second image, respectively, and means for comparing the two image signals in each block obtained by dividing the focus detection area into a plurality of blocks to calculate a minimum correlation value, In a focus detection device which detects a relative interval between two images from the minimum correlation value and calculates a defocus amount from a focus position of the imaging lens, a correlation value is recalculated from the minimum correlation value of each block. Extracting means for extracting a block to be subjected to the above, recalculating means for recalculating a minimum correlation value in the block by using an area obtained by combining the extracted blocks as one block, and detecting the focus from the minimum correlation value. Calculating means for calculating the defocus amount of the area.

[Action]

In the first focus detection device configured as described above, a minimum correlation value is calculated for each of a plurality of blocks in the focus detection area, and a block to be subjected to defocus amount calculation processing is determined from the minimum correlation value. Is extracted. A defocus amount and a contrast value are calculated for each extracted block, and a weighted average process is performed on the defocus amount and the contrast value of each block. Then, the defocus amount of the focus detection area is calculated from the weighted average value.

In the second focus detection device, the minimum correlation value and the defocus amount are calculated for each block in the focus detection area. A weight value corresponding to each block is set from the minimum correlation value, a weighted average value is calculated from the set weight value and the defocus amount of each block, and the defocus of the focus detection area is calculated from the weighted average value. The amount is calculated.

In the third focus detection device, a minimum correlation value is calculated in each block in the focus detection area, and a block for performing averaging processing is calculated from the minimum correlation value. Further, a defocus amount is calculated for the calculated block, and a weight value corresponding to the block is set from the minimum correlation value. Then, a weighted average value is calculated from the defocus amount of each block and its weight value, and the defocus amount of the focus detection area is calculated from the weighted average value.

Further, in the fourth focus detection device, in each block in the focus detection area, a minimum correlation value and a correlation value at a shift position separated by the same pitch back and forth from a shift position corresponding to the minimum correlation value are calculated, The minimum correlation values of each block and the correlation values at the shift positions separated in the same direction from the shift position corresponding to the minimum correlation value are respectively added, and a new correlation value is calculated. Then, the minimum correlation value is calculated from the interpolation calculation of these new correlation values,
The defocus amount of the focus detection area is calculated from the minimum correlation value.

Further, in the fifth focus detection device, a minimum correlation value is calculated in each block in the focus detection area, and a block to be subjected to the addition operation of the correlation value is calculated from the minimum correlation value. Next, for each of the calculated blocks, a correlation value at a shift position separated by the same pitch back and forth from the shift position corresponding to the minimum correlation value is calculated. The correlation values at the shift positions separated in the direction are added to each other, and a new correlation value is calculated. Then, the minimum correlation value is calculated from the interpolation calculation of these new correlation values, and the defocus amount of the focus detection area is calculated from the minimum correlation value.

In the sixth focus detection device, the minimum correlation value is calculated for each block in the focus detection area, and the block whose correlation value is to be recalculated is calculated from the minimum correlation value. Then, the minimum correlation value is calculated again for one block obtained by combining the calculated blocks, and the defocus amount of the focus detection area is calculated from the minimum correlation value.

〔Example〕

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

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 film surface 13.

The focus detection optical system 12 is a photoelectric conversion element array 141, 142,
143, separator lens 15, aperture mask 16, module mirror 17, condenser lenses 181, 182, 183 and field stop 19
It is composed of Photoelectric conversion element arrays 141, 142, 14
Reference numeral 3 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 beam 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 focus detection areas 21, 22, and 23 (hereinafter, referred to as first islands 21 and 22, 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).

A region 24 indicated by a dotted line in the center of the photographing screen 20 displays a region 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 each of the divided blocks is 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 difference data area of the reference portions 141a, 142a, 143a corresponding to the islands 21, 22, 23 shown in FIG. In the figure, each of the reference portions 141a, 142a,
The numerical value shown in 143a is the reference part 141a, 1 shown in FIG.
Data for each pixel 42a and 143a is detected every third pixel, and the number of differences (that is, spatial frequency components) obtained by taking the difference between them is shown. The difference data indicates a component of a specific spatial frequency extracted (filtered) from the pixel data (first spatial frequency component extracting means). The difference data is two or one.
It may be every other. 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, K1 (1 to 20) and K1 (11 to 30), from the difference data at the upper end, and sets them 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. Third island
In 23, K3 (1-20), K3 (11-
30) divided into two blocks, and the ninth block BL
9, and the tenth block BL10.

Further, the second island 22 detects difference data whose 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, 7th block BL7 and 8th block
It is divided into blocks 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, a difference is obtained every seven, and the sum of the difference data is obtained between adjacent data. The sum data is used as the sixth block BL6. That is, the number of difference data every seventh is 36 in the reference unit 142a and 44 in the reference unit 142b.
The number of data in the sixth block BL6 is 35 in the reference unit 142a,
In the reference part 142b, the number is 43. And this reference part 142a
The 25 blocks on the left side are the seventh block BL7, and the 25 blocks on the right side are 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. Further, the first block BL1 and the ninth block BL9
In the example, the front pin side shift pitch is 5 and the rear pin side shift pitch is 15, and the second block BL2 and the tenth block BL1
In the case of 0, 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, but since the shift pitch overlaps with the sixth block BL6, In the seventh block BL7, 4 to 14 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 focuses on the basis of the extracted spatial frequency component. Detection (first focus detection means), and further, a second spatial frequency component is extracted based on the extracted spatial frequency component (secondary filter means), and the spatial frequency extracted by the secondary filter means is extracted. Focus detection is performed based on the component (second focus detection means), and 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). Lens circuit 27
Denotes a photographing lens 2 mounted on a camera body (not shown)
(Interchangeable lens) This is for transmitting data unique 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 flux 9 passing through the photographing lens 2, and outputs an apex value B VO corresponding to this brightness to the microcomputer.
26 to communicate. 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 amount of each of the islands 21, 22, and 23 as the first island 21 (step # 41) and the second island 22.
(Step # 41), Third Island 23 (Step # 41)
12 to 14 show a specific flowchart of the defocus amount calculation of each of the islands 21, 22, and 23.

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.
A predetermined value "-K" is stored in variables DF1 and DF2 which are divided into blocks BL2 and store the respective defocus amounts of these blocks BL1 and BL2 (steps # 51 and # 52). This 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 cannot be performed on the first island 21 (hereinafter referred to as low contrast). You.

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 DF1 that stores the defocus amount of the first block BL1.
(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 detection of the focus state of the second block BL2 and the defocus amount DF are calculated (step # 58). If focus calculation is possible from this calculation result, it is determined whether or not the flag LCF1 is set. When the flag LCF1 is reset, that is, when the focus detection is enabled in the determination in step # 55, the process proceeds to step # 62.
Move to When the flag LCF1 is set in step # 60, the defocus amount calculation subroutine for the second island 22 in step # 42 shown in FIG.
(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 (average processing width) ΔDF used in an averaging processing routine described later is determined. Next, the defocus amount DF1 and the defocus amount DF2
The defocus amount of the subject closer to the photographing lens 2 (camera) is determined as the defocus amount DFIS1 of the first island 21. That is, the defocus amount DF1 is equal to the defocus amount DF2.
If the defocus amount DF1 is larger than the defocus amount DF2, the defocus amount DF2 is set to the defocus amount DFIS1 of the first island 21. Defocus amount DFI
S1 is set (steps # 63 to # 67).

If the difference between the defocus amounts DF1 and DF2 is smaller than the average processing width ΔDF in steps # 64 and # 65, the defocus amounts DF1 and DF2 are averaged, and the average value is calculated. Is the defocus amount DFIS1 of the first island 21 (step # 68). And step # 6
After completing the processing of 6, # 67 and # 68, step # 42 in FIG.
Move to

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

First, a variable DF for storing the defocus amount of each of the third block BL3, the fourth block BL4, and the fifth block BL5.
3. A predetermined value "-K" is set in DF4 and DF5, respectively (steps # 71 to # 73), and a flag LCF2 indicating the state of the 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, if the focus can be detected from the calculation result of the defocus amount DF of the third block BL3 in step # 75, the flag LCF2 is reset and the obtained defocus amount DF
Is stored in the variable DF3 (Steps # 76 to # 78), and the routine goes to Step # 79. Conversely, if it is determined that focus detection cannot be performed, the processing in steps # 77 and # 78 is not performed and step # 79 is performed.
Move to

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, and the defocus amount DF is stored in the variable DF4 (steps # 80 to ##). 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, if the defocus amount DF of the fifth block BL5 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 # 84). 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, #
When it is determined that the focus can be detected in each of the determinations in step 84, the average processing width Δ used in the averaging processing routine described below is used.
The DF is determined (step # 88). Next, each block BL
The magnitude of each of the defocus amounts DF3, DF4, DF5 of 3, BL4, BL5 is determined, and the largest defocus amount MAXDF is extracted (step # 89). If there is no other block whose difference from the defocus amount MAXDF is smaller than the average processing width ΔDF, the defocus amount MAXDF is set to the second island 22.
(Steps # 90 and # 91), and if there is at least one other block in which the difference is smaller than the average processing width ΔDF, the defocus amount MAXDF and the difference are the average processing width. Averaging is performed only with the defocus amounts of other blocks smaller than ΔDF (average processing), and the average value is used as the defocus amount DFIS2 of the second island 22 (step # 92). When the processes of steps # 91 and # 92 are 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 every _{three, dDn = l 1 -l 5,} ..., l 5 -l 9, ..., ln- ln +
₄ , ... Also, _every seventh difference data is dD m = l ₁ -l
₉ , ..., l ml m + ₈ , ... Every seventh difference data dDm is obtained by taking the sum of every third difference data dDn every third. That is, _every seventh difference data is dD m = dD ₁ + dD ₅ ,..., DD m + dD m + ₄ ,... = L ₁ -l ₅ + l ₅ -l ₉ , ..., l n- _4- l n + l nl n + ₄ ,... = l ₁ -l ₉ ,…, l n− ₄ -l n + ₄ ,… = l ₁ -l ₉ ,…, lm m + ₈ ,. Here, n = m + ₄ .

Further, the sum between adjacent differences of the difference data dD m is calculated, a new data sequence dD W (m) = dD m + dD m + ₁ is calculated, and the focus is detected in the sixth block BL6 using this, The focus state is detected and the defocus amount DF is calculated (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 above-mentioned step # 43.
(Steps # 95 to # 97). Meanwhile, step #
If the focus cannot be detected at 95, the focus is detected at the seventh block BL7 to detect the focus state and the defocus amount DF.
Is calculated (step # 98), and 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 # 11).
7). On the other hand, if it is determined in step # 115 that the focus detection cannot be performed, the process proceeds to step # 118 without performing the processes of steps # 116 and # 117.

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. When the flag LCF3 is set, that is, when the focus detection is disabled in the determination in step # 115, the process proceeds to step # 115.
Move to 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 # 122 without performing the process of step # 120.

In step # 122, an average processing width ΔDF of an averaging processing routine described later is determined. Next, the magnitude of the defocus amount DF9 and the defocus amount DF10 is determined, and the larger defocus amount is determined by 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) BVO 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, the open brightness value BVO and the film sensitivity value SV are stored in the microcomputer 26 in advance in step # 27 of FIG.
The exposure value E is calculated from the sum of the open aperture value A VO
Calculate V (EV = B VO + S V + A VO) (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 object 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 case of the AF mode, when any one of the subjects 8 among the subjects on each of the islands 21, 22, and 23 can detect the focus, the defocus of the closest island, that is, the island having the largest defocus amount is performed. The photographing magnification is calculated based on the amount, the focal length data of the photographing lens 2 and the distance to the subject, 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. Then, the focal length f is 35 mm or more, and the imaging magnification β df of the nearest island is a predetermined magnification β H (for example, 1/25 magnification).
If smaller, the driving amount of the photographing lens 2 is determined based on the defocus amount of the nearest island. On the other hand, if the photographing magnification β df exceeds the predetermined magnification β H, the defocus amount DFIS2 of the second island 22 is prioritized. If the second island 22 cannot be measured, the defocus amount of the closest island is The driving amount of the photographing lens 2 is determined based on the driving amount.

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 β df is expressed by the following equation based on the focal length f and the subject distance x from the camera.

β df = 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 β df
Is calculated. The object distance x is determined by the photographing lens 2
Defocus amount DFx from infinity position to subject position
Is calculated using the following equation.

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 DF _O from infinity position of the taking lens 2 to the current position is determined from the rotation amount (number) number of pulses corresponding to the N of the lens driving motor 33 stored in the counter of the microcomputer 26 , The relationship is as follows:

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

Then, the defocus amount DFx from the defocus amount DF of the current position of the defocus amount DF _O taking lens 2 to the focal position of the subject, the DFx = DF _O + DF. From these equations, the subject distance x is: x = f ² / DFx = f ² / (N / k + DF) Therefore, the imaging magnification β df is β df = f / x = (N / k + DF) / f.

Further, separately from the above equation, the photographing magnification β df is a drive amount ΔN (ΔN = DF · D) from the current position of the photographing lens 2 to the subject position.
k), β df = (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 β df detected during the previous distance measurement is determined. If the photographing magnification β df is “1/20” or more, the coefficient
Set k ₂ to “1” and change the magnification β df from “1/20” to “1/5”.
In the case of “0”, the coefficient k ₂ is set to “0.5”, and the photographing magnification β df
There "1/50" to coefficient k ₂ in the following cases is set to "0" (step # 145 to # 149), 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 imaging magnification beta df is high increases.

Next, in step # 150, a reference average processing width ΔDF1 is set based on the aperture value F No. at the time of shooting. That is, the depth of focus δ determined by the product of the aperture value F No. at the time of shooting and the allowable confusion circle diameter ε is set as the reference average processing width ΔDF1 for storing the resolution of the shot 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 WZF2. When the previous averaging process is performed, the flag WZF2 is set. When the previous averaging process is not performed, the flag WZF2 is reset.

Next, the calculation of the defocus amount of each block and the determination of whether or not focus detection is possible will be described using the third block BL3 as an example (13
Steps # 75 to # 78) will be described with reference to FIG.

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 at each shift position and the reference unit 142
A correlation function H3 (I) with the data of b is obtained (step # 1)
61).

 This correlation function 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 function H3 at each shift position described above
The best correlation among (I), that is, the correlation function H3
The shift position IM that minimizes the value of (I) is extracted (step # 162). Next, an interpolation operation between each pitch is performed using the value of each point of the correlation function H3 (I) (step # 16).
3).

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)} / [2 ·
｛MIN (H3 (IM-1), H3 (IM + 1))-H3 (I
M)｝] The reason why this interpolation calculation is performed is that when one pitch shift is converted into a defocus amount, it is as large as about 1000 μm, and accurate distance measurement is performed by compensating for this pitch gap.

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 the differences between the 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 function H3 (I) is obtained, and the interpolation value YM and the contrast value C (3) are obtained.
Is obtained (step # 167).

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

YM = H3 (IM)-| H3 (IM-1) -H3 (IM + 1) | / 2 R (3) = C (3) / YM The contrast value C (3) thus obtained and the ratio value R ( 3) focus detection is possible only when both satisfy the set values, and the contrast value C (3) or the ratio value R
If either one of (3) is not satisfied, focus detection is disabled (low contrast determination). That is, first, the third
A determination is made as to whether the block BL3 has been able to perform focus detection in the previous routine processing, 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.
The predetermined values C1 and R1 are set in 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 is reset, the photographing magnification β LS when photographing at the current position of the photographing lens 2 is performed. Is calculated (step # 170).

This photographing magnification β LS is calculated by the above-described photographing magnification β df,
That is, “0” is substituted for the defocus amount DF of β df = (N / k + DF) / f.

Then, the product of the photographing magnification β LS and the focal length f is obtained. If this value is equal to or larger than a predetermined value f · β th (for example, β th is 1/15 or more for a 300 mm lens), the determination level C t
predetermined values C4 and R4 larger than predetermined values C1 and R1, respectively, for h and Rth
Is set (steps # 171 and # 172). That is, the determination levels C th and R th are stricter than in the case of step # 169.

If it is less than the predetermined value f · βth in step # 171, the maximum local contrast value CLth of the third block BL3 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, and if smaller than the predetermined value, that is, if the flag CL is reset, the determination level C
The predetermined value C3 is set to th (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 C th and R th (steps # 169, # 172, # 178, and # 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) is set. Alternatively, when at least one of the ratio values R (3) is smaller than the judgment level Cth or the judgment level Rth, the detection flag NLB3 is reset (steps # 180 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 in step # 79 and thereafter in FIG. 13, are performed.

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.

Here, the reason why the determination levels C th and R th are strict when the value is equal to or more than the predetermined value f · β th in step # 172 will be described.

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 C th and R th 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. The noise level C noise generated by the photoelectric conversion element array or the like is superimposed on the contrast value determination level C th in step # 173. Although the magnitude of the noise itself of the noise amount C noise does not change but the waveform of the noise varies, if the minimum true object contrast value required for focus detection is C MIN, the determination level C th is as follows: become.

C th = C MIN + M AX ｛C noise｝ However, C MIN ≪ M AX ｛C noise｝ Therefore, the noise amount C noise is small, and the contrast value is judged to be C despite the fact that focus detection is originally possible.
In some cases, it is determined that the focus cannot be detected because it does not exceed th. Therefore, when the maximum noise amount C noise occurs,
Since it is predicted that noise exists in each part of the third block BL3, the contrast limit is determined for each difference data of the third block BL3 according to the following equation.

However, the value P is a predetermined value set in advance, and is selected from values 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 the predetermined value CLth1, 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 C LOC is compared with a predetermined value CLth1 (steps # 192 and # 193). If the data block C LOC is equal to or more than the predetermined value CLth1, the flag CL
Is set (step # 194) to relax the contrast value determination level.

On the other hand, each difference data of the data block C LOC is a predetermined value C
If it is less than Lth1, the variable q is incremented to extract a data block C LOC consisting of difference data from the data K2 (2) to K2 (9) of the third block BL3, and this data block C LOC and a predetermined value CLth1 are extracted. Compare with (Step #
195, # 193). Similarly, data K2 (13) to K2 (2
The process is continued until the data block CLOC including the difference data up to 0) is extracted (steps # 192 to # 196). Then, if at least one of the data blocks C LOC is equal to or more than the predetermined value CLth1, the flag CL is set. If all data blocks C LOC are less than the predetermined value CLth1, the flag CL remains reset. The flow shifts to the flowchart in 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.

In other words, this determination routine extracts the maximum value [MAX {K2 (j)}] and the minimum value [M IN {K2 (j)}] from the data K2 (1 to 20) of the third block BL3, These maximum value [MAX {K2 (j)}] and minimum value [MIN {K2 (j)}]
C LOC (C LOC = MAX ｛K2 (j)｝ − M IN ｛K2
(J)｝) is obtained (steps # 201 to # 203). Next, the flag CL is reset (step # 204), and the difference C LOC is set.
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 C LOC is less than the predetermined value CLth2, the flag
The flow shifts to the flowchart in FIG. 18 (a) while the CL remains reset.

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. In the case of, "1" is set to the variable CL2
Is added (steps # 212 to # 215). And the variable
The product of CL1 and the variable CL2 is calculated, and the products CL1 and CL2 are set to the predetermined value CL.
If th4 or more, the flag CL is set (step # 21)
7) Relax the contrast level judgment level. 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 (2
With respect to (0), the processes from steps # 212 to # 215 are performed (steps # 212 to # 219). As a result, if the products CL1 and CL2 are less than the predetermined value CLth4 even after all data processing is completed, the flow shifts to the flowchart of FIG. 18A with the flag CL kept reset.

Next, the averaging calculation of the focus detection device according to the present invention will be described by taking step # 92 in FIG. 13 as an example. There are several processing methods for the averaging processing, and each processing method will be described with reference to FIGS. 23 to 25.

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, the largest defocus amount M among the respective defocus amounts DF3, DF4, DF5 of the blocks BL3, BL4, BL5.
The difference between AXDF and the defocus amount DF3 is obtained, and the difference is compared with the average processing width ΔDF. When the difference exceeds the average processing width ΔDF, the weight function W (3) is set to “0”. And
The variable I is incremented, the difference between the defocus amount MAXDF, the defocus amount DF4 and the defocus amount DF5 is determined, and this 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 # 22).
Five). That is, the averaging process is performed using the defocus amount within the average processing width ΔDF among the defocus amounts DF3, DF4, and DF5 of the blocks BL3, BL4, and 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, the wide zone flag WZF2 is set (step # 227). 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 following correlation positions IM + 1 and IM-1. It is designed to calculate. That is, if the blocks to be averaged (hereinafter referred to as target blocks) obtained in step # 90 in FIG. 13 are all the blocks BL3, BL4, BL5, the data K2 (1 to 40) of the second island 22 And the correlation function H3,4,5 (IM), H3,4,5
(IM-1), H3, 4, 5 (IM + 1) are recalculated, and reinterpolated, and this value is set as the defocus amount DFIS2 of the second island 22 (steps # 231 and # 232). Further, if the third block BL3 and the fourth block BL4 are target blocks, the correlation function H3,4 (IM), H is used for the data K2 (1 to 30).
3,4 (IM-1) and H3,4 (IM + 1) are recalculated and re-interpolated to set this value as the defocus amount DFIS2 (steps # 233 and # 234). Further, if the fourth block BL4 and the fifth block BL5 are target blocks, the data K2 (11
~ 40) and the correlation functions H4,5 (IM), H4,5 (IM-1), H4,5
(IM + 1) is recalculated and reinterpolated to set this value as the defocus amount DFIS2 (steps # 235 and # 236).
If it is determined in step # 235 that the third block BL3 and the fifth block BL5 are the target blocks, 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 the figure.

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 process routine of FIG. 25, the correlation functions H (IM) and H (IM−
1), H (IM + 1) are added, and the processing after the interpolation calculation is performed using the addition result. That is, if all the blocks BL3, BL4, BL5 are target blocks, the correlation functions H3, 4, 5 (IM), H3, 4, 5 (IM-1), H
3,4,5 (IM + 1) is calculated as shown below (step #
241, # 242).

H3,4,5 (IM-1) = H3 (IM-1) + H4 (IM-1) + H
5 (IM-1) If the third block BL3 and the fourth block BL4 are target blocks, the correlation functions H3,4 (IM), H3,4 (IM
-1), H3,4 (IM + 1) is calculated as in the following equation (steps # 243 and # 244).

H3,4 (IM-1) = H3 (IM-1) + H4 (IM-1) H3,4 (IM) = H3 (IM) + H4 (IM) H3,4 (IM + 1) = H3 (IM + 1) + H4 (IM + 1) Further, if the fourth block BL4 and the fifth block BL5 are target blocks, the correlation functions H4,5 (IM), H4,5 (IM
-1), H4,5 (IM + 1) are calculated as shown below (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 (I M + 1) In step # 245, the third block BL3 and the fifth block
If the block BL5 is the target block, the correlation function H3,5 (I
M), H3,5 (IM-1), H3,5 (IM + 1) are 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) When the calculation of the correlation functions in steps # 242, # 244, # 246, and # 247 is completed, a re-interpolation operation 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 · I M + α · 1/2 · ｛H (IM-1) −H (IM
+1) / [M IN {H (IM-1), H (IM + 1)}-H
(IM)] Then, the wide zone flag WZF2 is set (step # 249), and thereafter, the flow shifts to a 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 6 will be described with reference to FIG.

First, the difference data string K2 used in blocks BL3, BL4, and 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 = M IN {H6 (I)})
Is extracted (steps # 252 and # 253). This correlation function H6
(I) is as follows.

Here, the correlation function H6 (I) is obtained by removing the data at both ends from the data sequence of the reference unit 142a as in the above equation, when the correlation function H6 (I
Instead of using M-1), H6 (IM), H6 (IM + 1), the correlation functions H6 (IM-2), H6 (IM-1), H6 (IM +
1) In order to use H6 (IM + 2), the correlation function H6 (IM−
2) This is for correcting a large shift of the position corresponding to the data of the reference portion 142b at H6 (IM + 2).
-247211).

In step # 254, these correlation functions H6 (IM-2), H
6 (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 (I
M + 1) and H6 (IM + 2) are used to perform an interpolation operation as in the following equation (step # 255).

XM = IM + {H6 (IM-2) -H6 (IM + 2)} / [M IN
{H6 (IM-2), H6 (IM + 2)} − M AX ｛H6 (IM−
1), H6 (IM + 1)｝] / 2 The defocus amount D is obtained by multiplying the interpolation pitch XM by a coefficient α.
It is converted to F (DF = XM · α) (step # 256). Next, the contrast value C of the data of the sixth block BL6
(6) is obtained as in the following equation (step # 257).

Subsequently, an interpolation value Y M1 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 Y M1 and the contrast value C (6) as in the following equation ( Step # 25
8).

Y M1 = M AX {H6 (IM-1), H6 (IM + 1)}-｛| H6
(IM-2) −H6 (IM + 2) |｝ / 2 R (6) = C (6) / {Y M1−OF} Then, predetermined values are set for the determination levels C th6 and R th6, respectively, and the contrast value is set. C (6) and ratio value R (6)
Are focus-detectable only when both satisfy the predetermined values, and when either the contrast value C (6) or the ratio value R (6) is not satisfied, the focus detection is disabled (steps # 259 and # 259). 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,
-4 ", the correlation function is H (0) = 0, H (-1) = 6, H
(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, and 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) Is relatively small. Therefore, as long as the correlation function H (IM) is not a periodic function, the correlation function H (IM) before and after the correlation function H (IM) is used without using the correlation function H (IM).
2), H (IM-1), H (IM + 1), H (IM + 2) are used to reduce the influence of noise.

In step # 258, if a normal interpolation operation as shown in FIG. 18 (a) is performed, an offset amount is generated. Therefore, from the interpolation value Y M1 to M AX ｛H6 (IM-1), H6 (IM + 1). The difference OF1 between｝ and the correlation function H6 (IM), or MAX ｛H6 (IM
-2), H6 (IM + 2)} and MAX {H6 (IM-1), H6 (I
M + 1)｝ difference OF2 or contrast value C (6)
Using the value OF set based on the value obtained by subtracting
The calculation of (6) is performed.

〔The invention's effect〕

As described above, in the present invention, the defocus of this focus detection area is determined by the weighted average of the contrast value or the minimum correlation value of each block in the focus detection area and the defocus amount of each block. Since the amount is calculated, the error of the defocus amount calculated in each block is averaged, the variation of the defocus amount of each block due to the variation of the subject brightness can be reduced, and the main subject within the depth of field can be reduced. , A suitable focus position can be detected stably. Furthermore, by extracting the block to be subjected to the weighted averaging process based on the minimum correlation value, the defocus amount is calculated using only highly reliable data, so that more reliable detection is possible.

Also, the three types of correlation values generated by adding the minimum correlation values of each block of the focus detection area and the correlation values at shift positions separated by the same pitch back and forth from the shift position corresponding to the minimum correlation value are generated. Since the minimum correlation value is calculated by interpolation and the defocus amount of the focus detection area is calculated from the minimum correlation value, errors in the defocus amount calculated from the minimum correlation value are averaged in the same manner as described above. In addition, it is possible to reduce the variation in the defocus amount of each block due to the variation in the luminance of the subject, and to stably detect a suitable focus position for the main subject within the depth of field.

In addition, a block that detects the focus of a subject within a predetermined focal length is calculated from the defocus amount of each block, and the entire block is regarded as one block again.
Since the minimum correlation value is calculated and the defocus amount of the focus detection area is calculated from the minimum correlation value, the variation of the defocus amount of each block due to the variation of the subject brightness is reduced, and the focus detection area is obtained. The main subject can be detected from the plurality of subjects competing for perspective, and a suitable focus position for the subject can be stably detected.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a camera provided with a focus detection device according to the present invention, FIG. 2 is a configuration diagram of a mechanism of focus detection means, FIG. 3 is a diagram showing a photoelectric conversion element array, and FIG. FIG. 5 is a view showing a focus detection area of the photographing screen of FIG. 5, FIG. 5 is an enlarged view of a reference portion corresponding to the first to third islands, and FIGS. 6 and 7 are views for explaining a defocus range of each block. FIG. 8 is a circuit block diagram of a camera in which a focus detection device according to the present invention is configured using a microcomputer, and FIG.
11 and 14 are flowcharts showing a subroutine for defocus amount calculation of the first to third islands, and FIG. 15 is a flowchart showing a subroutine for exposure calculation. FIG. 16 is a view for explaining a procedure for selecting a defocus amount calculating means, FIG. 17 is a flowchart showing a subroutine for obtaining an average processing width, and FIG. 18 (a) is a calculation of the defocus amount of the third block. FIG. 18 (b) is a diagram for explaining determination of focus detection failure, FIG. 18 (b) is a diagram for explaining erroneous determination when a person is lined up, and FIG. 19 is a diagram for explaining calculation of a correlation function and a contrast value of each block. Figure, 20th
FIG. 22 to FIG. 22 are flowcharts showing a subroutine for determining a contrast limit, FIG. 23 to FIG. 25 are flowcharts showing an averaging process routine, FIG. 26 is a flowchart showing a defocus amount calculation subroutine, and FIG. It is a figure explaining means of. 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 section, BL1 First block, BL2 Second block, BL3 Third block, BL4 Fourth block, BL5
... 5th block, BL9 ... 9th block, BL10 ... 1st
0 block, SW ₁ ... Power switch, SW ₂ ... Shooting preparation switch, SW ₄ ... Selection switch.

Continued on the front page (72) Inventor Kenji Ishibashi 2-3-3 Azuchicho, Chuo-ku, Osaka-shi, Osaka Osaka International Building Minolta Camera Co., Ltd. (72) Inventor Toshio Kaida 2 Azuchicho, Chuo-ku, Osaka-shi, Osaka No. 3-13 Osaka International Building Minolta Camera Co., Ltd. (72) Inventor Hiroshi Ueda 2-3-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Osaka International Building Minolta Camera Co., Ltd. (72) Inventor Noriyuki Okisu Osaka International Building Minolta Camera Co., Ltd. 2-3-3 Azuchicho, Chuo-ku, Osaka City, Osaka (56) References JP-A-62-187829 (JP, A) JP-A-59-68713 (JP, A) 61-269106 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 7/11

Claims (6)

(57) [Claims] 1. A means for receiving first and second images formed from a light beam of a subject passing through first and second portions of a taking lens, respectively, sandwiching an optical axis of the taking lens in a focus detection area. And means for calculating the minimum correlation value by comparing the two image signals with each other in each block obtained by dividing the focus detection area into a plurality of blocks,
A focus detection device that detects a relative distance between two images from the minimum correlation value and calculates a defocus amount from a focus position of the imaging lens, wherein a defocus amount calculation process is performed from the minimum correlation value of each block. Extraction means for extracting a target block of the above; contrast calculation means for calculating a contrast value from the image signal in each of the extracted blocks; and a weighted average of the defocus amount and the contrast value of each of the extracted blocks Calculating means for calculating the defocus amount of the focus detection area. 2. A means for receiving a first image and a second image formed from a subject light beam passing through a first portion and a second portion of the taking lens, respectively, sandwiching an optical axis of the taking lens in a focus detection area. And means for calculating the minimum correlation value by comparing the two image signals with each other in each block obtained by dividing the focus detection area into a plurality of blocks,
In a focus detection device for calculating a defocus amount from a focus position of the imaging lens by detecting a relative interval between two images from the minimum correlation value, a weight value is set based on a minimum correlation value of each block. A focus detection device comprising: a setting unit; and a calculation unit that calculates a defocus amount of the focus detection area by performing a weighted average of a defocus amount of each block and the weight value. 3. The focus detection device according to claim 2, further comprising an extraction unit for extracting a block to be subjected to an averaging process from the minimum correlation value of each block. 4. A means for receiving first and second images formed by subject light beams passing through first and second portions of the photographing lens, respectively, sandwiching the optical axis of the photographing lens in the focus detection area. And means for calculating the minimum correlation value by comparing the two image signals with each other in each block obtained by dividing the focus detection area into a plurality of blocks,
A focus detection device that detects a relative distance between two images from the minimum correlation value and calculates a defocus amount from a focus position of the imaging lens; and a minimum correlation value between the blocks and the minimum correlation value. Adding means for respectively adding the correlation values at the shift positions separated by the same pitch before and after from the shift position corresponding to, and performing an interpolation operation on the added correlation values to calculate a defocus amount in the focus detection area. A focus detection device comprising: a calculation unit. 5. The focus detection device according to claim 4, further comprising an extraction unit for extracting a block to be subjected to the addition operation of the correlation value from a minimum correlation value of each of the blocks. 6. A means for receiving a first image and a second image formed from a subject light beam passing through a first portion and a second portion of the photographing lens, respectively, sandwiching the optical axis of the photographing lens in the focus detection area. And means for calculating the minimum correlation value by comparing the two image signals with each other in each block obtained by dividing the focus detection area into a plurality of blocks,
A focus detection device that calculates a defocus amount from a focus position of the imaging lens by detecting a relative interval between two images from the minimum correlation value, and recalculates a correlation value from the minimum correlation value of each block. Extraction means for extracting a block to be subjected to the above, recalculation means for recalculating a minimum correlation value in the block with an area obtained by combining the extracted blocks as one block, and detecting the focus from the minimum correlation value. A focus detection device comprising: a calculation unit configured to calculate a defocus amount of an area.