JPH07181366A - Automatic focusing camera and automatic focusing method of camera - Google Patents

Abstract

PURPOSE:To shorten the focus detecting arithmetic time during scanning drive, eliminate the missing of a subject even at a high-speed scanning drive, and surely detect the subject when the subject is out of the frame. CONSTITUTION:A pair of subject images formed by the luminous flux passed through a photographing optical system 3 is received and converted into a pair of subject image data according to the light intensity distribution, and the correlation degree is arithmetically operated while relatively shifting the subject image data to detect the focusing state of the photographing optical system 3. When the reliability of the detection result of the focusing state is high, the photographing optical system 3 is driven on the basis of the detected focusing state, and when the focusing state can not be detected, or the reliability of the detection result is low, the photographing optical system 3 is scanning- driven, and the quantity of the subject image data is more limited than during non-scanning drive to arithmetically operate the Correlation degree on the basis of the less subject image data, and the focusing of the photographing optical system 3 is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focusing camera for driving a photographing optical system to scan between a near range and an infinity when focus detection is impossible, and an automatic focusing method for the camera.

[0002]

2. Description of the Related Art A subject image formed by a focus detection optical system is received by a charge storage type image sensor, and an output of the image sensor is arithmetically processed to defocus a subject image plane with respect to a planned focal plane of a photographing optical system. Detect the amount,
There is known an automatic focusing camera that drives a focusing lens according to the defocus amount to achieve focusing of a photographing optical system. With this type of camera, the defocus amount cannot be calculated because the contrast of the subject image is insufficient, or when it is determined that the calculated defocus amount is unreliable, In order to find the position of the focusing lens that can calculate the defocus amount with high contrast and high reliability, the focusing lens is scanned and driven between the closest end and the infinite end to perform focus detection.

[0003]

However, the above-described conventional automatic focusing camera has the following problems. There is a limit to the amount of defocus that can be detected by the focus detection device.Therefore, if the amount of movement of the focusing lens of the photographic optical system in the focus detection interval from focus detection to the next focus detection is large, the focus of the subject during scan You may miss a position.

This problem will be described in detail with reference to FIG. FIG. 13 is a diagram showing the position of the focusing lens of the photographic optical system during scanning drive, and FIG. 13A shows the case where the movement amount of the focusing lens in the focus detection interval is smaller than the detectable defocus amount. In b), the movement amount of the focusing lens in the focus detection interval is larger than the detectable defocus amount. In the figure, P1 to P6 indicate the position of the focusing lens of the photographing optical system at the focus detection time during scanning drive. W indicates the range of the defocus amount that can be detected at each of the focusing lens positions P1 to P6, and Q indicates the focus position of the focusing lens with respect to the subject. FIG.
In the scanning drive as shown in (a), since the ranges W of detectable defocus amounts at the focusing lens positions P1, P2, P3, and P4 overlap with each other, the focus position Q may not be missed. Absent. However, when the amount of movement of the focusing lens in the focus detection interval becomes larger than the detectable defocus amount, FIG.
As shown in (b), when the range W of the detectable defocus amount does not overlap and the focus position Q is located within the range W, the focus position Q may be missed.

In an automatic focusing camera of the pupil division type image shift detection system, an image sensor receives a pair of object images formed by light fluxes passing through different parts of the exit pupil of the photographing optical system, and outputs from the image sensor. The pair of subject image data is relatively shifted to perform a correlation calculation, and the focus adjustment state of the focusing lens is detected from the relative positional relationship of the detected pair of subject images. Therefore, if the focus detection calculation time is long during scanning drive,
The state becomes as shown in 3 (b).

In order to solve such a problem, during the scanning drive, the shift range of the focus detection correlation calculation is limited in accordance with the scanning drive direction of the focusing lens to shorten the focus detection calculation time. A camera has been proposed (see, for example, JP-A-63-172211). That is, since the focus detection calculation time becomes long if the correlation calculation is performed with the same shift amount as during the normal focus detection even during the scanning drive, the shift range of the focus detection correlation calculation is limited to shorten the focus detection calculation time. .

However, the object of shortening the calculation time may not be sufficiently achieved only by limiting the shift range in the focus detection correlation calculation according to the scanning drive direction of the focusing lens during the scanning drive. In addition, when the moving subject is photographed while holding the camera with a hand, the moving subject may be out of the focus detection area (hereinafter, referred to as subject frame removal), and thus focus detection may be impossible. In such a case, if the shift range is limited only to the scanning drive direction,
Even if the subject returns to the focus detection area after the start of scanning drive, focus detection becomes impossible.

An object of the present invention is to shorten the focus detection calculation time during the scanning drive so that the subject is not missed even when the scanning drive is performed at a high speed, and even if the subject frame is missed, it is ensured. An object of the present invention is to provide an automatic focusing camera capable of detecting a subject and an automatic focusing method for the camera.

[0009]

FIG. 1 showing a first embodiment.
The present invention will be described in association with
A focus detection optical system 7 that forms a pair of subject images by the light flux from the subject that has passed through the photographing optical system 3, and a pair of subject images that are formed by the focus detection optical system 7 are received to form a light intensity distribution. The image sensor 8 that outputs a pair of subject image data corresponding to the image sensor 8 and the pair of subject image data that are output from the image sensor 8 are relatively shifted to calculate the correlation degree, and the photographing is performed based on the calculated correlation degree. Focus detection means 11 for detecting the focus adjustment state of the optical system 3, drive means 17 for driving the photographing optical system 3 based on the focus adjustment state detected by the focus detection means 11, and focus detection by the focus detection means 11. Of the focus detection result and the reliability of the focus detection result. When the determination unit 12 determines that the focus detection result has high reliability, the focus detection unit 11 determines Driving the photographing optical system 3 by the drive means 17 on the basis of the detected focusing state, determination means 1
If it is determined that the focus detection result is low or the focus detection result is low in reliability, the driving unit 1
7, the photographing optical system 3 is scan-driven, and the focus detection means 11
Control means 14 for detecting the focus of the photographing optical system 3 by
15 and an autofocus camera with. Then, the focus detection unit 11 achieves the above object by limiting the amount of subject image data used in the calculation of the degree of correlation during the scanning drive of the photographing optical system 3 as compared with during the non-scanning drive.
The focus detection means 11 of the automatic focusing camera according to claim 2,
During scanning drive of the photographing optical system 3, the correlation degree is calculated using only the data of the central portion of the subject image data. The focus detecting means 11 of the automatic focusing camera according to the third aspect is configured to thin out the object image data and calculate the degree of correlation during the scanning drive of the photographing optical system 3. According to a fourth aspect of the present invention, the focus detection optical system 7 forms a pair of subject images by the light flux from the subject that has passed through the photographing optical system 3.
An image sensor 8 that receives a pair of subject images formed by the focus detection optical system 7 and outputs a pair of subject image data corresponding to the light intensity distribution; and a pair of image sensors output from the image sensor 8. While relatively shifting the subject image data, calculate the degree of correlation at each shift amount,
A focus detection unit 11 that detects the focus adjustment state of the photographing optical system 3 based on the degree of correlation, and a drive unit 17 that drives the photographing optical system 3 based on the focus adjustment state detected by the focus detection unit 11. The determination means 12 for determining whether or not the focus detection means 11 can detect the focus and the reliability of the focus detection result, and when the determination means 12 determines that the reliability of the focus detection result is high, the focus detection means 11 detects the result. When the photographing optical system 3 is driven by the driving means 17 based on the focus adjustment state and the determination means 12 determines that the focus detection result is low or the focus detection result is low, the drive means is driven. The present invention is applied to an automatic focus adjustment camera provided with control means 14 and 15 for scanning and driving the photographing optical system 3 by 17, and for performing focus detection of the photographing optical system 3 by the focus detecting means 11. It is. Then, the focus detection means 11
Achieves the above object by making the relative shift amount of the pair of subject image data in the calculation of the correlation degree during the scanning drive of the photographing optical system 3 larger than during the non-scanning drive.
Control means 14, 15 of the automatic focusing camera according to claim 5.
Means that the scanning drive of the photographing optical system 3 is not performed after the determination unit 12 determines that the focus detection result is highly reliable. The automatic focusing camera according to claim 6 receives a pair of subject images formed by a light flux that has passed through a photographing optical system, converts the pair of subject images into a pair of subject image data according to a light intensity distribution, and the pair of subject image data. Is relatively shifted, the correlation degree is calculated to detect the focus adjustment state of the photographic optical system, and when the detection result of the focus adjustment state is highly reliable, the photographic optical system is adjusted based on the detected focus adjustment state. The present invention is applied to an automatic focus adjusting method for a camera, which is driven to detect the focus of the photographing optical system 3 by scanning the photographing optical system when the focus adjustment state cannot be detected or the reliability of the detection result is low. The above object is achieved by limiting the amount of subject image data used in the calculation of the degree of correlation during scanning driving of the photographing optical system as compared with during non-scanning driving. According to the seventh aspect of the automatic focus adjusting method of the camera, the degree of correlation is calculated using only the central portion of the subject image data during the scanning drive of the photographing optical system. In the automatic focus adjusting method for a camera according to the present invention, the degree of correlation is calculated by thinning out subject image data during scanning drive of the photographing optical system. According to a ninth aspect of the present invention, a pair of subject images formed by the light flux that has passed through the photographing optical system is received and converted into a pair of subject image data according to the light intensity distribution, and the pair of subject image data is relative. The focus adjustment state of the photographic optical system is detected by calculating the degree of correlation in each shift amount while shifting to the right.When the detection result of the focus adjustment state is highly reliable, the photographic optical system is based on the detected focus adjustment state. When the focus adjustment state cannot be detected or the reliability of the detection result is low, the present invention is applied to a camera automatic focus adjustment method in which the photographing optical system is scan-driven to detect the focus of the photographing optical system 3. The above object is achieved by increasing the relative shift amount of the pair of subject image data in the calculation of the degree of correlation during scanning driving of the photographing optical system as compared with during non-scanning driving. In the automatic focus adjustment method for a camera according to the tenth aspect, the scanning drive of the photographing optical system is not performed after the highly reliable detection result of the focus adjustment state is obtained.

[0010]

The pair of subject images formed by the light flux passing through the photographing optical system 3 is received and converted into a pair of subject image data corresponding to the light intensity distribution, and the pair of subject image data is relatively shifted. While calculating the degree of correlation, shooting optical system 3
The focus adjustment state of is detected. When the reliability of the focus adjustment state detection result is high, the photographing optical system 3 is driven based on the detected focus adjustment state, and when the focus adjustment state cannot be detected or the detection result reliability is low. The scanning optical system 3 is driven to scan, the amount of the subject image data is limited as compared with that during non-scanning driving, the correlation degree is calculated based on the less subject image data, and the focus of the photographing optical system 3 is detected. As a result, the scale of the correlation calculation processing during scan driving can be made smaller than the scale during non-scan driving, and the correlation calculation time is shortened, so the focus detection interval during scan driving is also shortened, and scan driving is performed at high speed. Even when performing, the subject is less likely to be missed, and the subject can be reliably detected even when the subject frame is missed. Also, the photographing optical system 3
A pair of subject images formed by the light flux that has passed through the received light is received and converted into a pair of subject image data according to the light intensity distribution, and the correlation degree at each shift amount while relatively shifting the pair of subject image data. To calculate the shooting optical system 3
The focus adjustment state of is detected. When the reliability of the focus adjustment state detection result is high, the photographing optical system 3 is driven based on the detected focus adjustment state, and when the focus adjustment state cannot be detected or the detection result reliability is low. , The photographing optical system 3 is driven to scan, the relative shift amount of a pair of subject image data is made larger than that during non-scanning drive, and the degree of correlation is calculated.
The focus of the photographing optical system 3 is detected. As a result, the scale of the correlation calculation processing during scan driving can be made smaller than the scale during non-scan driving, and the correlation calculation time is shortened, so the focus detection interval during scan driving is also shortened, and scan driving is performed at high speed. Even when performing, the subject is less likely to be missed, and the subject can be reliably detected even when the subject frame is missed.

Incidentally, in the section of means and action for solving the above problems for explaining the constitution of the present invention, the drawings of the embodiments are used for the purpose of making the present invention easy to understand. It is not limited to.

[0012]

【Example】

First Embodiment FIG. 1 is a functional block diagram showing the configuration of the first embodiment. An interchangeable lens 2 is attached to the camera body 1. A photographing optical system 3 is provided in the lens 2, and a light flux from a subject passing through the photographing optical system 3 is split by a main mirror 4 composed of a half mirror toward a sub mirror 5 and a finder 6. The light beam further deflected in the body bottom direction by the sub-mirror 5 is guided to a focus detection optical system 7 arranged near the planned focal plane of the photographing optical system 3.

FIG. 2 shows the structures of the focus detection optical system and the charge storage type image sensor. The focus detection optical system 7 includes a field mask 71 having an opening 70 and a condenser lens 7.
2. A diaphragm mask 7 having a pair of diaphragm openings 73, 74
5. It has a pair of re-imaging lenses 76 and 77. The charge storage image sensor 8 has a pair of light receiving portions 80 and 81. The primary image of the object formed by the photographing optical system 3 in the vicinity of the opening 70 on the optical axis is re-imaged by the focus detection optical system 7 on the light receiving portions 80 and 81 of the image sensor 8 as a pair of secondary images. .

In the structure described above, the pair of aperture openings 73 and 74 are projected by the condenser lens 72 onto the pair of regions 31 and 32 symmetrical with respect to the optical axis of the surface 30 near the exit pupil of the photographing optical system 3. The light flux passing through this area first forms a primary image near the field mask 71. The primary image formed in the opening 70 of the field mask 71 further includes a condenser lens 72, a pair of aperture openings 73,
After passing through 74, a pair of re-imaging lenses 76 and 77 form a pair of secondary images on the light receiving portions 80 and 81 of the charge storage image sensor 8. The light intensity distributions of the pair of secondary images are photoelectrically converted by the light receiving units 80 and 81 to become an electrical subject image signal.

Returning again to the explanation of FIG. A pair of electric subject image signals of the image sensor 8 is taken into a microcomputer 16 (hereinafter referred to as a microcomputer), and a focus detection calculation unit 11 calculates a relative positional relationship between the pair of subject image signals by image shift calculation. Then, the defocus amount DEF between the image plane of the photographing optical system 3 and the planned focal plane is detected.

<First Focus Detection Computation Processing Executed During Non-scanning Driving> First, focus detection computation processing executed during normal focus detection, that is, non-scanning driving (hereinafter referred to as first computation processing) Will be explained. The subject image data is Ai and Bi (where i = 1 to 20). First, the correlation amount C is calculated by the differential correlation algorithm shown in Expression 1.
Find (L).

## EQU1 ## C (L) =. SIGMA. | A (i + L) -B (i) | In Expression 1, Σ represents the summation operation of i = j to j + 7. L is an integer and is a relative shift amount in units of the pitch of the light receiving elements of the pair of light receiving element output data. The range of L is -12 to +12. Furthermore, j
Is a value corresponding to the shift amount L, and is 7 when L = 0, for example.

FIG. 3 shows the calculation result by the mathematical expression 1. In the figure, the abscissa represents the subject image data Ai and the ordinate represents the subject image data Bi, and the positions of the combinations for calculating the respective differences are represented by white circles and black circles. Also,
The number of summation operations is eight, and in the figure, addition is performed in the diagonally lower right direction by white circle ○ comrades or black circle ● comrades. The value of the correlation amount C (L) of the calculation result is the shift amount L on the horizontal axis.
It is taken and represented by a white circle. When the scale of the first arithmetic processing from FIG. 3 is defined as the number of arithmetic operations that take the absolute value of the difference, it is 25 × 8 = 200 because it is the total number of white circles and black circles.

FIG. 8 is an explanatory diagram of a procedure for calculating the defocus amount from the correlation amount C (L). The calculation result of Equation 1 is
As shown in FIG. 8A, the correlation amount C (L) becomes the minimum when the shift amount L = kj (kj = 2 in FIG. 8A) in which the subject image data has a high correlation. Next, Formula 2 to Formula 3 3
Minimum value C for continuous correlation using the point interpolation method
The shift amount x that gives (L) min = C (x) is determined.

[Formula 2] x = kj + D / SLOP

## EQU3 ## C (x) = C (kj)-| D |

## EQU00004 ## D = {C (kj-1) -C (kj + 1)} / 2

## EQU00005 ## SLOP = MAX {C (kj + 1) -C (k
j), C (kj-1) -C (kj)} Further, based on the shift amount x obtained by the above equation, the defocus amount DEF with respect to the planned focal plane of the subject image plane can be obtained by the following equation.

[Expression 6] DEF = KX · PY · x In Equation 6, PY is a pitch in the arrangement direction of the light receiving elements forming the light receiving portion of the image sensor, and KX is a conversion coefficient determined by the configuration of the focus detection optical system.

<Second Focus Detection Calculation Processing Executed During Scanning Driving> Next, the focus detection calculation processing executed during scanning driving (hereinafter referred to as the second calculation processing) will be described. (1) Calculation process with large shift amount (see FIG. 4) During normal focus detection, the shift amount L is changed by 1 in the range of −12 to +12 to calculate the correlation amount C (L).
On the other hand, when the focus is detected during the scan driving, the correlation amount C (L) is calculated by changing the shift amount L by 2 in the range of −12 to +12 as shown in FIG. By thus increasing the shift amount L and calculating the correlation amount C (L), the focus detection accuracy is reduced, but the calculation scale is reduced and the calculation time is shortened. The scale of the second arithmetic processing of this system is 13 × 8 = 104.

(2) Calculation processing for limiting subject data (see FIG. 5) In normal focus detection, the calculation of the correlation amount C (L) in Expression 1 is performed by changing the parameter i from j to j + 7. On the other hand, at the time of focus detection during scan driving, the correlation amount C is changed by changing the parameter i from j ′ to j ′ + 3 as shown in FIG.
(L) is calculated. By thus limiting the object data and calculating the correlation amount C (L), the focus detection accuracy is reduced, but the calculation scale is reduced and the calculation time is shortened. The scale of the second arithmetic processing of this method is 25
× 4 = 100.

(3) Calculation processing for thinning out subject data
(See FIG. 6) At the time of normal focus detection, the calculation of the correlation amount C (L) of Formula 1 is performed by changing the parameter i one by one, while at the time of focus detection during scan driving, it is shown in FIG. Parameter i
Is changed by 2 to calculate the correlation amount C (L). By thus thinning out the object data and calculating the correlation amount C (L), the focus detection accuracy is reduced, but the calculation scale is reduced and the calculation time is shortened. The scale of the second arithmetic processing of this method is 25 × 4 = 100.

(4) Arithmetic processing combining (1) and (2) (see FIG. 7) During focus detection during scan driving, as shown in FIG. 7, the shift amount L is 0 depending on the scan driving direction. To +14 (in this case, the sign + side of the shift amount corresponds to the focus shift amount in the scanning drive direction), and the shift amount is further increased. Further, the parameter i is changed from j ′ to j ′ + 3 to calculate the correlation amount C (L). By performing the calculation of the correlation amount C (L) in this manner, the focus detection accuracy is lowered, but the calculation scale is reduced and the calculation time is shortened. The scale of the second arithmetic processing of this method is 9 × 4 = 3
It becomes 6.

In the above description of the focus detection calculation, the subject image data Ai, Bi may be raw data of the output signal of the image sensor 8 or may be data obtained by filtering the raw data.

Returning to the explanation of FIG. Impossible judgment unit 1
2 checks whether the defocus amount DEF calculated by the focus detection calculation unit 11 is reliable, or whether the focus detection calculation unit 11 can perform focus detection calculation according to the contrast of the subject image data. Focus amount D
When the reliability of the EF is low, or when the contrast of the subject image data is low and the focus detection calculation by the focus detection calculation unit 11 is impossible, the focus detection is determined to be impossible and a focus detection impossible signal is generated.

<Focus Detection Impossible Judgment> When the correlation degree of the subject data is low, the minimum value C (X) of the interpolated correlation amount becomes large as shown in FIG. 8B. Therefore, when C (X) is a predetermined value or more, it is determined that the reliability is low. Alternatively, in order to standardize C (X) with the contrast of the subject data, if the value obtained by decrementing C (X) by SLOP, which is a value proportional to the contrast, is a predetermined value or more, it is determined that the reliability is low. Alternatively, when the SLOP that is a value proportional to the contrast is less than or equal to a predetermined value, the subject has low contrast and the calculated defocus amount D
It is determined that the reliability of EF is low.

When the degree of correlation of subject data is low, as shown in FIG. 8C, the correlation amount C (L) is within the shift range.
The minimum value C (X) cannot be obtained because there is no drop in In such a case, it is determined that focus detection is impossible.

Before the focus detection calculation unit 11 performs the focus detection calculation, the contrast of the subject image data may be directly detected by the following equation to determine the focus detection failure.

## EQU7 ## Cnt = Σ | A (i) -A (i + 1) | In the above equation, Σ represents the sum of i = 1 to m−1. When the contrast value Cnt is equal to or less than the predetermined value, the subject has low contrast, and it is determined that only the defocus amount DEF with low reliability can be obtained even if the focus detection calculation unit 11 performs the focus detection calculation. The impossibility determining unit 12 applies the above conditions alone, or applies a plurality of conditions and satisfies any one of the conditions, determines that the focus cannot be detected and generates a focus undetectable signal.

Returning to the explanation of FIG. Impossible judgment unit 1
When it is determined that the focus can be detected by No. 2, the first drive control unit 14 included in the microcomputer 16 controls the rotation direction and the rotation amount of the motor 17 according to the defocus amount DEF. The motor 17 is connected to the photographing optical system 3 and is driven so that the photographing optical system 3 moves in the optical axis direction so that the defocus amount DEF becomes 0, and the in-focus state of the photographing optical system 3 is achieved. . On the other hand, when the inability determination unit 12 determines that focus detection is impossible, the second drive control unit 15 included in the microcomputer 16 finds the in-focus point and the photographing optical system 3 is close to the photographing optical system 3 regardless of the defocus amount DEF. The motor 17 is controlled so as to be scan driven for an infinite period. If the focus cannot be detected even if the scan driving is performed, the scan driving is ended in a predetermined procedure. For example, when the scan drive is started, the drive is performed in the close-up direction, the light is inverted in the infinite direction at the close-up end, and when the focus detection is still impossible when the infinite end is reached, the scan drive is ended.

Further, during the scanning drive by the second drive control unit 15, the focus detection calculation unit 11 performs the focus detection calculation by the above-mentioned second calculation processing, and the above-described first detection except during the scanning drive.
The focus detection calculation is performed by the calculation process of. As described above, the focus detection calculation having a small calculation scale is performed during the scan driving, so that the calculation time can be shortened, and it is possible to prevent the subject from being overlooked during the scan driving which occurs when the calculation time is long in the related art.

FIG. 9 shows the focus detection calculation unit 11 and the inability judgment unit 1.
2 is an operation flowchart of the microcomputer 16 which constitutes the first drive control unit 14 and the second drive control unit 15. The operation of the first embodiment will be described with reference to this flowchart. When the power of the camera is turned on, the operation starts from step S100, and the charge accumulation operation of the image sensor 8 is performed in step S101. In step S102, the subject image data is read from the image sensor 8 and the process proceeds to step S103 to check whether or not the photographing optical system 3 is currently being driven for scanning. If the scanning drive is in progress, the process proceeds to step S105, and the defocus amount DEF is calculated by subjecting the subject image data to the second calculation process described above. If the scanning drive is not in progress, the process proceeds to step S104, and the defocus amount DEF is calculated by subjecting the subject image data to the first calculation process described above.

In step S106, the above-described focus detection inability determination is performed, and in the following step S107, it is determined whether focus detection is impossible. If focus detection is not possible, the process proceeds to step S109, and if focus detection is possible, step S10.
Go to 8. If focus detection is possible, step S108.
Then, the drive amount of the photographing optical system 3 is determined based on the calculated defocus amount DEF, and the motor 17 is controlled to drive the photographing optical system 3 to the in-focus position. When the driving is completed, the process returns to step S101 and the above-described operation is repeated. Note that the process may return to step S101 before the driving ends in step S108. On the other hand, if focus cannot be detected,
In step S109, it is determined whether or not the scanning drive is in progress. When the scanning drive is in progress, the process returns to step S101, and the above-described operation is repeated while continuing the scanning drive. If the scan drive is not in progress, the process proceeds to step S110, and it is determined whether or not focus detection has been possible in the past. If yes, the scan drive is not started and the process returns to step S101 to repeat the above operation. Otherwise, the process proceeds to step S111.
In step S111, scan driving is started and then step S111 is performed.
Returning to 101, the above operation is repeated.

In this way, once the focus can be detected, the scanning drive thereafter is prohibited.
Scanning drive is not frequently performed. It should be noted that in step S110, the process may always proceed to step S111. If focus detection cannot be performed even if the scanning drive is performed from the closest distance to infinity, the scanning drive is ended according to an operation flowchart (not shown). further,
In the above-described embodiment, the second calculation process is selected during the scan driving, but the condition of the subject brightness is further added, and the second calculation is performed when the scan driving is in progress and the charge accumulation time is long at low brightness. You may make it select a process. Furthermore, in the above-described embodiment, the first arithmetic processing is selected except during the scan driving. However, when the condition of the subject brightness is further added and the charge accumulation time is long even when the brightness is low even during the scan driving, The second arithmetic process may be selected.

-Second Embodiment- FIG. 10 is a functional block diagram showing the structure of the second embodiment. It should be noted that devices similar to those shown in FIG. 1 are designated by the same reference numerals, and differences will be mainly described. In the second embodiment, the impossibility determining unit 12 inputs the subject image data directly from the image sensor 8 and performs the focus detection impossibility determination before the focus detection calculation processing by the focus detection calculation unit 11 during the scan driving. In such a configuration, the focus detection calculation unit 1
In No. 1, the focus detection calculation is performed only during the scanning drive. In this way, since focus detection calculation is not performed during scan driving, the calculation time can be shortened, and it is possible to prevent the subject from being overlooked during scan driving, which occurred when the calculation time was long in the past. The calculation processing of the focus detection non-determination during the scan driving is performed according to Expression 7, and the scale of the calculation processing in this case is 19 when the number of calculations taking the absolute value of the difference is defined.

11 and 12 show the focus detection calculation unit 11, the inability judgment unit 12, the first drive control unit 14, and the second drive control unit 1.
6 is an operation flowchart of the microcomputer 16 that constitutes part 5 of FIG. The operation of the second embodiment will be described with reference to this flowchart. When the power of the camera is turned on, step S20
The operation is started from 0, and the process proceeds to step S201 to make the image sensor 8 perform the charge accumulation operation. Step S2
In 02, the subject image data is read from the image sensor 8, and in the following step S203, it is determined whether or not the photographing optical system 3 is currently being driven for scanning. If the scanning drive is in progress, the process proceeds to step S204. If the scanning drive is not in progress, the process proceeds to step S206. When scanning is being driven, step S20
4, the contrast of the subject image data is detected by the above-described mathematical expression 7, and the focus detection impossibility determination (first focus detection impossibility determination) is performed. Then, in step S205, the result of the first focus detection inability determination is determined. If focus detection is not possible, the process proceeds to step S210, and if focus detection is possible, step S210 is performed.
Proceed to 206.

In step S206, the subject image data is subjected to the first arithmetic processing to calculate the defocus amount DEF. Further, in step S207, a focus detection impossibility determination (FIGS. 8B and 8C, second focus detection impossibility determination) based on the correlation calculation result is performed. In step S208, the result of the second focus detection inability determination is determined. If focus detection is not possible, the process proceeds to step S210, and if focus detection is possible, the process proceeds to step S209. If the scan driving is performed, the scan driving is ended when the process proceeds from step S208 to step S209. In step S209, the drive amount of the photographic optical system 3 is determined based on the calculated defocus amount DEF, and the motor 17 is controlled to control the photographic optical system 3.
To the in-focus position. When driving is completed, step S2
Returning to 01, the above operation is repeated. Note that step S
You may make it return to step S201 before drive completion in 209.

On the other hand, if it is determined in the first or second focus detection impossibility that focus detection is impossible, step S
In 210, it is determined whether or not the scanning drive is in progress. When the scanning drive is in progress, the process returns to step S201 and the above-described operation is repeated while continuing the scanning drive.
Proceed to 211. In step S211, it is determined whether or not focus detection has been possible in the past. If yes, the scanning drive is not started and the process returns to step S201 to repeat the above-described operation. If no, the process proceeds to step S212. .
In step S212, scan driving is started and then step S2
Returning to 01, the above operation is repeated.

By doing so, once focus detection becomes possible, subsequent scanning drive is prohibited.
Scanning drive is not frequently performed. It should be noted that in step S211, the process may always proceed to step S212. If focus detection cannot be performed even if the scanning drive is performed from the closest distance to infinity, the scanning drive is ended according to an operation flowchart (not shown).

In the structure of the above embodiment, the photographing optical system 3 is the photographing optical system, the focus detection optical system 7 is the focus detection optical system, the image sensor 8 is the image sensor, and the focus detection calculation unit 11 is the focus detection means. The motor 17 serves as a driving unit, the inability judgment unit 12 serves as a judgment unit, and the first drive control unit 1
The fourth drive controller 15 and the second drive controller 15 constitute control means.

[0039]

As described above, according to the present invention, the focus detection calculation processing of a scale smaller than the normal calculation processing scale is performed during the scanning drive of the photographing optical system. The focus detection interval is shortened in accordance with the shortening of, and the missing of the subject during scan driving is reduced. Further, the scanning drive can be performed at a higher speed than in the past, and the transition from the state in which the subject is undetectable due to blurring to the in-focus state can be achieved in a short time. Furthermore, the time from the start of scan drive to the end is shorter for a subject with a completely low contrast in which focus detection is not possible even if scan drive is performed, and the time from the start of scan drive to the end is reduced as in the past. It is possible to reduce the discomfort given to the photographer because of the long length. Further, according to the present invention, since it is not necessary to limit the shift range in the correlation calculation processing, focus detection can be reliably performed when the subject returns to the focus detection area even when the subject frame is missed.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing a configuration of a first embodiment.

FIG. 2 is a perspective view showing the configuration of a focus detection optical system according to the first embodiment.

FIG. 3 is an explanatory diagram of first arithmetic processing.

FIG. 4 is an explanatory diagram of second arithmetic processing.

FIG. 5 is an explanatory diagram of another second arithmetic processing.

FIG. 6 is an explanatory diagram of another second arithmetic processing.

FIG. 7 is an explanatory diagram of another second arithmetic processing.

FIG. 8 is an explanatory diagram of focus detection impossibility determination.

FIG. 9 is an operation flowchart of the first embodiment.

FIG. 10 is a functional block diagram showing the configuration of the second embodiment.

FIG. 11 is an operation flowchart of the second embodiment.

FIG. 12 is a flowchart showing the operation of the second embodiment following FIG. 11.

FIG. 13 is a diagram showing a position of a focusing lens of a photographing optical system during scanning driving.

[Explanation of symbols]

 1 Body 2 Lens 3 Photographic Optical System 4 Main Mirror 5 Sub Mirror 6 Finder 7 Focus Detection Optical System 8 Image Sensor 11 Focus Detection Calculation Unit 12 Impossible Judgment Unit 14 First Drive Control Unit 15 Second Drive Control Unit 16 Microcomputer 17 Motor

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Claims (10)

[Claims] 1. A focus detection optical system for forming a pair of subject images by a light flux from a subject that has passed through a photographing optical system, and a light intensity for receiving a pair of subject images formed by the focus detection optical system. An image sensor that outputs a pair of subject image data corresponding to the distribution, and a correlation degree is calculated while relatively shifting a pair of subject image data output from the image sensor. Based on the correlation degree of the calculation result, Focus detecting means for detecting a focus adjustment state of the photographing optical system, driving means for driving the photographing optical system based on the focus adjustment state detected by the focus detecting means, whether or not focus detection by the focus detecting means is possible, and The determination means for determining the reliability of the focus detection result, and when the determination means determines that the reliability of the focus detection result is high, it is detected by the focus detection means. The drive means drives the photographing optical system based on the focus adjustment state, and if the determination means determines that the focus detection result is low or the focus detection result is low, the drive means In the automatic focusing camera, the focus detection means scans and drives the photographing optical system, and the focus detection means controls focus detection of the photographing optical system. Is an auto-focusing camera characterized by limiting the amount of subject image data used in calculating the degree of correlation as compared with that during non-scanning drive. 2. The automatic focus adjustment camera according to claim 1, wherein the focus detection unit calculates the degree of correlation using only the data of the central portion of the subject image data during the scanning drive of the photographing optical system. An autofocus camera that is characterized. 3. The automatic focus adjustment camera according to claim 1, wherein the focus detection unit thins out the subject image data during scan driving of the photographing optical system to calculate a correlation degree. Focusing camera. 4. A focus detection optical system that forms a pair of subject images by a light flux from the subject that has passed through the photographing optical system, and a light intensity by receiving the pair of subject images formed by the focus detection optical system. An image sensor that outputs a pair of subject image data according to the distribution, and a pair of subject image data output from this image sensor are relatively shifted, and the correlation degree at each shift amount is calculated. Focus detecting means for detecting the focus adjustment state of the photographing optical system, driving means for driving the photographing optical system based on the focus adjustment state detected by the focus detecting means, and focus detection by the focus detecting means. The determination means for determining the availability and the reliability of the focus detection result, and when the determination means determines that the reliability of the focus detection result is high, the focus detection means When the photographing optical system is driven by the driving unit based on the focus adjustment state detected by the detection unit, and the determination unit determines that the focus detection result is low or the focus detection result is low, the focus detection result is low. An automatic focus adjustment camera, comprising: a control unit that scans and drives the photographing optical system by the driving unit and performs focus detection of the photographing optical system by the focus detection unit, wherein the focus detection unit is the photographing optical system. The automatic focus adjustment camera is characterized in that the relative shift amount of the pair of subject image data in the calculation of the degree of correlation is set to be larger during the scanning drive than in the non-scanning drive. 5. The automatic focusing camera according to any one of claims 1 to 4, wherein the control unit performs the photographing after the determination unit determines that the focus detection result has high reliability. An automatic focusing camera characterized by not performing scanning drive of an optical system. 6. A pair of subject images formed by a light flux passing through a photographing optical system is received and converted into a pair of subject image data according to a light intensity distribution, and the pair of subject image data is relatively shifted. While calculating the correlation degree to detect the focus adjustment state of the photographing optical system, when the reliability of the detection result of the focus adjustment state is high, drive the photographing optical system based on the detected focus adjustment state, In the automatic focus adjustment method of a camera, wherein the photographing optical system is scan-driven when the focus adjustment state cannot be detected or the reliability of the detection result is low, and the photographing optical system is scan-driving. Is an automatic focus adjustment method for a camera, characterized in that the amount of subject image data used in the calculation of the degree of correlation is limited as compared with that during non-scan driving. 7. The camera automatic focusing method according to claim 6, wherein the degree of correlation is calculated using only the central portion of the subject image data during scanning drive of the photographing optical system. Automatic focus adjustment method. 8. The automatic focus adjustment method for a camera according to claim 6, wherein the correlation between the subject image data is thinned out to calculate the degree of correlation during the scanning drive of the photographing optical system. Method. 9. A pair of subject image data formed by a light flux passing through a photographing optical system is received and converted into a pair of subject image data corresponding to a light intensity distribution, and the pair of subject image data is relatively shifted. While calculating the correlation degree in each shift amount, the focus adjustment state of the photographing optical system is detected, and when the reliability of the detection result of the focus adjustment state is high, the photographing optical system is based on the detected focus adjustment state. In the automatic focus adjustment method of a camera for driving the image pickup optical system to detect the focus of the image pickup optical system by scanning driving the image pickup optical system when the focus adjustment state cannot be detected or the reliability of the detection result is low. During the scan driving, the relative shift amount of the pair of subject image data in the calculation of the degree of correlation is set to be larger than that during the non-scan driving. 10. The automatic focusing method for a camera according to claim 6, wherein the scanning drive of the photographing optical system is performed after a highly reliable detection result of the focusing state is obtained. A method for automatically adjusting the focus of a camera, characterized by not performing.