JP4736695B2 - camera - Google Patents

Description

  The present invention relates to a camera that performs a focusing operation by using both focus detection using a distance measurement method and focus detection using a contrast method.

  Conventionally, there has been proposed a hybrid AF camera that uses both phase difference detection AF and contrast AF based on an imaging signal (see, for example, Patent Document 1). In such a camera, in order to achieve both high-precision AF and high-speed AF operation, the focusing lens is moved to the vicinity of the in-focus position by the phase difference detection AF, and finally the contrast AF is used. A focusing operation is performed.

JP 2003-279844 A

  However, in order to ensure that the in-focus point can be found under various shooting conditions, the contrast method AF scanning range is increased, and the contrast method is adjusted from a lens position sufficiently away from the in-focus point calculated by distance measurement. It was necessary to start the focusing operation. For this reason, the AF speed cannot be sufficiently increased.

According to the first aspect of the present invention, a phase difference between a subject image formed by a pair of light beams that pass through a pupil at different positions from the subject, and an image sensor that captures the subject image formed by the photographing optical system and outputs an image signal. First focus detection means for obtaining a first position corresponding to the in-focus position obtained by using the image, and a focus evaluation value corresponding to the contrast of the subject image based on the image signal, and the focus obtained using the contrast. and the second focus detection means for obtaining a second position corresponding to the focus position, the first Go focusing and operation of driving the focusing lens to the third position with a difference between a predetermined amount relative to said first position, said first a camera comprising a focus control means performs a second Go focusing operation to drive the focusing lens to the second position after the focusing operation, using said difference between said first position and the second position To a predetermined amount A correction value calculating means for calculating a that correction value, after the correction value is computed, the focusing control means, focusing at positions corresponding to the difference between the first position and the calculated correction value A first focusing operation for driving the lens and a second focusing operation for driving the focusing lens to the second position after the first focusing operation are performed .
The invention according to claim 2 is the camera according to claim 1, further comprising storage means for storing the correction value of the correction value calculation means, wherein the correction value is updated each time a photographing operation is performed. .
According to a third aspect of the present invention, in the camera according to the first aspect, the correction value calculation means can detect a correction value corresponding to the difference and a maximum value of the focus evaluation value in the second focusing operation. based on the minimum correction value, and obtains the correction value in place of the predetermined amount.
According to a fourth aspect of the present invention, in the camera according to the first aspect, there is provided a selection means for selecting execution / non-execution of the calculation by the correction value calculation means.
The invention of claim 5 is the camera according to any one of claims 1 to 4, wherein the camera is an interchangeable lens camera in which an interchangeable lens provided with the photographing optical system is detachable. said storage means is provided in the camera, and the correction value stored in said storage means, characterized in that it is stored in association with the interchangeable lens.
The invention of claim 6 is the camera according to any one of claims 1 to 4, wherein the camera is an interchangeable lens camera in which an interchangeable lens provided with the photographing optical system is detachable. said storage means is provided in the interchangeable lens, the correction value stored in said storage means, characterized in that associated with the camera is stored.
According to a seventh aspect of the present invention, in the camera according to any one of the first to sixth aspects, the correction value calculating means is at least one of an F value, a focal length, a zoom position, and a focus position of the photographing optical system. The correction value is obtained in association with each other.
According to an eighth aspect of the present invention, in the camera according to any one of the first to seventh aspects, the first focus detection unit performs the detection on a plurality of positions in an image plane by the photographing optical system. The correction value calculation means obtains the correction value for each of the plurality of positions.
The invention of claim 9 is the camera according to claim 8,
The correction value calculating means, F value of the imaging optical system, the focal length, the zoom position, the determination of the said correction value in association with at least one position in the image plane by the focus position and the imaging optical system Features.

  According to the present invention, the driving amount corresponding to the difference between the lens position determined to be in focus by the focus detection unit and the lens position at which the focus evaluation value becomes the maximum value, and the maximum focus evaluation value in the second focusing operation. Since the correction movement amount that replaces the predetermined lens movement amount is obtained based on the reference movement amount whose value can be detected, the first focusing operation is performed by the first lens driving amount based on the correction movement amount. Two focusing operations can be performed at higher speed.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a camera according to the present invention, and is a block diagram showing a schematic configuration of the camera. The camera shown in FIG. 1 is an interchangeable lens digital camera, and an interchangeable lens barrel 2 is detachably attached to the camera body 1. Whether the interchangeable lens barrel 2 is attached to the camera body 1 is detected by the attachment / detachment detection sensor 15.

  In the interchangeable lens barrel 2, lenses 3A, 3B and 3C constituting the photographing lens 3 are provided and have a zoom function. By driving the focusing lens 3 </ b> B with the lens driving unit 4, it is possible to adjust the focus of the photographing lens 3. In the interchangeable lens barrel 2, a parameter storage unit 5A that stores lens parameters such as an F value, a focal length, a zoom position, and an in-focus position of the lens, and a movement amount storage unit that stores a correction movement amount described later. 5B is provided. In the present embodiment, the photographing lens 3 having a zoom function is used. However, the photographing lens 3 may not have the zoom function.

  A quick return mirror 6 is provided in the camera body 1 and is arranged on the optical path of the taking lens 3 as shown in FIG. An imaging element 7 is disposed behind (on the right side in the figure) the quick return mirror 6 disposed on the optical path. As the image pickup element 7, an area type CCD sensor, a CMOS sensor, or the like is used. At the time of shooting, the quick return mirror 5 is retracted out of the optical path, and the subject image formed by the shooting lens 3 is projected onto the image sensor 7.

  The quick return mirror 6 includes a main mirror 6a and a sub mirror 6b provided behind the main mirror 6a. When not photographing, subject light reflected by the main mirror 6a passes through a pentaprism 8 to an eyepiece (not shown). Led to the department. On the other hand, part of the subject light is reflected downward by the sub mirror 6 b and enters the AF sensor module 9 provided at the bottom of the camera body 1.

The AF sensor module 9 performs focus detection by a known phase difference detection method.
A field lens 91, a separator lens 92, a line sensor 93, an AF calculation unit 94, and the like are provided. By the separator lens 92, subject images of light beams passing through pupils at different positions are formed on the corresponding line sensors 93. The AF calculation unit 94 calculates a positional shift (defocus amount) of the subject image with respect to the planned focal plane based on a shift (phase difference) between the images formed on the pair of line sensors 93, and the focusing lens 3B. Calculate the amount and direction of movement. The calculation result is transmitted to the CPU 10.

  The image sensor 7 captures a subject image formed by the photographing lens 3 and outputs an image signal. The imaging signal is input to the image processing circuit 14, and a series of image processing is performed to generate image data. Further, a part of the image pickup signal of the image pickup element 7, that is, the image pickup signal of the image pickup area corresponding to the focus detection area provided in the object scene is input to the evaluation value calculation unit 11 which is the second focus detection means. The The evaluation value calculation unit 11 extracts a predetermined spatial frequency component from the imaging signal. The level of the spatial frequency component corresponds to the contrast level of the subject image, and increases as the focal point is approached. Hereinafter, the level of the extracted spatial frequency component is referred to as a focus evaluation value.

  FIG. 2 is a diagram showing the relationship between the lens position of the focusing lens 3B and the focus evaluation value with respect to a subject at an arbitrary distance. When the focusing lens 3B is moved to the lens position D1 where the focus evaluation value reaches a peak, an in-focus image is obtained, and when the focusing lens 3B is displaced from the lens position D1, the focus evaluation value decreases. The focus evaluation value calculated by the evaluation value calculation unit 11 is input to the CPU 10. Also on the camera body 1 side, a movement amount storage unit 12 for storing a correction movement amount described later is provided. When the release button 13 is pressed halfway, a switch for performing an AF operation is turned on, and when the release button 13 is fully pressed, a switch for performing a photographing operation is turned on.

<Operation description>
Next, the focusing operation in the camera of the present embodiment will be described using the flowchart of FIG. Also in the present embodiment, like a conventional hybrid AF type camera, after performing a focusing operation by phase difference AF (hereinafter referred to as a first focusing operation), a hill-climbing type using a focus evaluation value is performed. A final focusing operation (hereinafter referred to as a second focusing operation) is performed by AF. The process of the flowchart shown in FIG. 3 starts when the release button 13 provided on the camera is half-pressed.

  In step S1, focus detection is performed by the AF calculation unit 94 which is the first focus detection means, and a lens driving amount (hereinafter referred to as P1) to the lens position D2 determined to be in focus is obtained. In FIG. 2, a lens position D1 indicates a lens position at which the focus evaluation value is determined to be maximum (peak), and is a lens position determined to be in focus in a second focusing operation described later. Δ is a driving amount difference corresponding to the difference (= D1−D2) between the lens position D2 and the lens position D1. In general, the drive amount difference Δ often does not become zero due to the detection accuracy in the AF calculation unit 94 or the like.

  In step S2, the first focusing operation is performed. If the correction movement amount α ′, which will be described later, is not stored in the storage unit 12, that is, in the first shooting operation of the camera, the first focusing is performed using the predetermined movement amount α set in advance in the camera. When the operation is performed and the corrected movement amount α ′ is stored in the storage unit 12, the corrected movement amount α ′ is used instead of the predetermined movement amount α. Here, the focusing lens 3B is driven by the lens driving amount obtained by subtracting the predetermined movement amount α from the lens driving amount P1 obtained in step S1. As a result, the lens position of the focusing lens 3B is D3.

  In step S3, it is determined whether or not the release button 13 has been fully pressed. If it is determined that the release button 13 has been fully pressed, the process proceeds to step S4, the quick return mirror 6 is mirrored up, and an image is picked up by the image sensor 7. In step S4, the second focusing operation is performed so that the focus evaluation value calculated by the evaluation value calculation unit 11 based on the image signal obtained by the image sensor 7 is maximized. That is, while moving the focusing lens 3B from the lens position D3 in the direction in which the focus evaluation value increases, the focusing lens 3B is moved to the lens position D1 where the detected focus evaluation value reaches its peak.

  FIG. 4 is a diagram for explaining the second focusing operation. The hill-climbing AF starts in the right direction in the figure where the focus evaluation value increases from the lens position D3, and the focusing lens 3B is moved sequentially to the lenses D32, D33, and D34. For example, if the focus evaluation value F (D32) is calculated at the lens position D32, the focus evaluation value F (D32) is compared with the focus evaluation value F (D3) calculated at the lens position D3, and F (D32 ) ≧ F (D3), the lens is determined to increase and the lens is further moved to the right side. Conversely, if F (D32) <F (D3), the lens is determined to decrease and the lens is moved to the left side in the drawing. In the example shown in FIG. 4, it is determined that the lens position has increased to the lens position D33, and the focusing lens 3B is moved to the lens position D34.

  At the lens position D34, it is determined that F (D34) <F (D33), and the focus evaluation value shifts from an increasing tendency to a decreasing tendency. In this case, it is determined that the lens position has passed the peak position of the focus evaluation value. For example, a lens position D1 estimated as a peak is obtained by three-point interpolation described below, and the focusing lens 3B is moved to the lens position D1. Moving.

  In the three-point interpolation calculation, the lens position D1 is calculated using the three sampling points PS1, PS2, and PS3 of the lens positions D32, D33, and D34. Here, the concept of the three-point interpolation operation will be described. First, a straight line L1 passing through the points PS2 and PS3 is calculated. When the slope of the straight line L1 is −K, a straight line L2 passing through the point PS1 with a slope of K is calculated. And the intersection of the straight line L1 and the straight line L2 is calculated | required. It is assumed that the lens position at this intersection is a lens position D1 at which the focus evaluation value reaches a peak.

  In step S5, a driving amount difference Δ is calculated from the lens position D1 and the lens position D2 obtained in step S1. In step S6, a corrected movement amount α ′ that replaces the predetermined movement amount α described above is obtained based on the calculated driving amount difference Δ, and is stored in the storage unit 12 to end a series of focusing operations. If the corrected movement amount α ′ is already stored in the storage unit 12, it is rewritten with the corrected movement amount α ′ calculated in step S6.

  As described above, the correction movement amount α ′ is calculated and stored in the storage unit 12 every time the photographing operation is performed. Then, when the half-pressing operation of the release button 13 is performed next, the first focusing operation in step S2 of FIG. 3 performs the corrected moving amount stored in the storage unit 12 in place of the predetermined moving amount α described above. This is done using α ′. That is, the focusing lens 3B is moved to the lens position D4 in FIG. 2 by the first focusing operation.

  There are various methods for setting the correction movement amount α ′ performed in step S6. For example, as described above, there is a deviation (drive amount) between the lens position D2 determined to be in focus by the AF calculation unit 94 based on the detection accuracy and the lens position D1 determined to be in focus by the second focusing operation. When the difference (Δ) changes for each shooting (distance), if the predetermined movement amount α is always used in the first focusing operation, the lens driving amount (α + Δ) in the second focusing operation is different for each shooting.

  Therefore, a method of setting the correction movement amount α ′ so that the lens driving amount in the second focusing operation is the same as the predetermined lens movement amount α even when the deviation (drive amount difference) Δ changes can be considered. When the drive amount difference Δ is used, the correction movement amount α ′ in this case is set as α ′ = α−Δ. In other words, if the lens drive amount in the second focusing operation (in this case, the drive amount from D4 to D1 in FIG. 2) is to be set to P3, for example, the correction movement amount α ′ is expressed as α ′ = P3−Δ. Should be set.

  As can be seen from FIG. 4, when performing hill-climbing AF, the peak can be detected by starting the second focusing operation before the lens position D1 corresponding to the peak in the driving direction. Therefore, in principle, if the correction movement amount α ′ is set so that the focus lens 3B is moved to the front by a one-step driving amount of hill-climbing AF from the lens position D1 in the first focusing operation, the second focusing is performed. The lens driving amount in the operation can be minimized. Even when the position D1 in FIG. 2 is far from D2, the correction movement amount α ′ can be obtained in the same manner as described above only by the sign of Δ being reversed.

  In the example described above, the corrected movement amount α ′ is stored in the storage unit 12 provided on the camera body 1 side, but may be stored in the storage unit 5B provided in the interchangeable lens barrel 2. When storing on the camera body 1 side, it is stored for each lens ID of each interchangeable lens barrel 2 for a plurality of interchangeable lenses that can be attached to the camera body 1. If the interchangeable lens barrel 2 is attached to the camera body 1, the lens ID of the interchangeable lens barrel 2 is detected, and the first focusing operation is performed using the corrected movement amount α ′ of the detected lens ID. Make it. When a new corrected movement amount α ′ (see step S6 in FIG. 3) is calculated by the shooting operation, a corrected movement amount α ′ corresponding to the subject distance at the time of the shooting operation related to the lens ID is newly set. The calculated correction movement amount α ′ is rewritten. If the correction movement amount α ′ stored in the storage unit 12 does not include the correction movement amount α ′ corresponding to the subject distance during the shooting operation, the newly calculated correction movement amount α ′ is additionally stored. To do. Further, when storing on the interchangeable lens barrel 2 side, the camera ID of the mounted camera body 1 is detected, and the correction movement amount α ′ is stored for each camera ID.

  Incidentally, the calculated corrected movement amount α ′ is stored in association with the subject distance at the time of shooting. That is, when shooting at a subject distance of 5 m, it is stored as a correction movement amount α (5 m) ′, and when shooting at a subject distance of 6 m, the subject distance is stored as a parameter, such as α (6 m) ′. Will be. In this case, the correction movement amount α ′ may be stored at every predetermined interval, and an intermediate subject distance may be obtained by an interpolation operation to suppress the amount of data to be stored. Such parameters include the F value of the lens, the focal length, and the zoom position in addition to the subject distance.

[Modification 1]
FIG. 5 is a block diagram showing a first modification of the above-described embodiment, in which a correction storage selection means 20 is provided in the camera shown in FIG. Although not shown, the camera body 1 is provided with a monitor for displaying a preview of the captured image. In the above-described embodiment, as shown in the flowchart of FIG. 3, the correction movement amount α ′ is automatically calculated and rewritten after shooting. For this reason, when the out-of-focus shooting is performed due to camera shake or the like, the correction movement amount α ′ is calculated based on the out-of-focus shooting, and an inappropriate correction movement amount α ′ is stored.

  Therefore, in the first modification, the correction storage selection unit 20 allows the user to select whether or not to calculate / rewrite the correction movement amount α ′. For example, the correction storage selection unit 20 is configured by a selection switch that can be operated by the user. FIG. 6 is a flowchart showing an example of operation when the correction storage selecting means 20 is used, and the same reference numerals are assigned to the same processing steps as those in the flowchart of FIG. Below, it demonstrates centering on a different step.

  If the second focusing operation in step S4 is completed, the process proceeds to step S20, and the captured image is displayed on the monitor provided in the camera body 1 as a preview. In step S21, it is determined whether or not a selection operation by the correction storage selection unit 20 has been performed. If it is determined to be selected in step S21, processing is performed in the order of step S5 and step S6, and the process proceeds to step S23 to turn off image display.

  On the other hand, if it is determined in step S21 that it is not selected, the process proceeds to step S22, and it is determined whether or not a predetermined time has elapsed since the preview started. If it is determined in step S22 that the predetermined time has not elapsed, the process returns to step S21. If it is determined that the predetermined time has elapsed, the process proceeds to step S23 and the image display is turned off. That is, if it is determined that the selection is not made in step S21, the processing in step S5 and step S6 is skipped, and the correction movement amount α ′ is calculated / rewritten based on an inappropriate image such as a defocused image. Can be prevented.

  In the first modification described above, the selection operation is performed for each captured image. However, in addition to the selection switch described above, the setting of the camera is in a state where the correction movement amount α ′ is calculated / rewritten. A setting switch that can select a state in which these are not performed may be provided in the correction storage selection unit 20. When the setting switch is set so that no correction is performed, no operation relating to the correction movement amount α ′ is performed. For example, such a state is set when it is not desired to rewrite the correction movement amount α ′ stored on the lens side. On the other hand, when it is set to the state to perform correction, the operation as shown in FIG. 6 is performed.

[Modification 2]
FIG. 7 is a block diagram showing a second modification, in which the area selection means 21 is provided in the camera shown in FIG. The AF module 9 in Modification 2 is configured so that focus detection can be performed in a plurality of focus detection areas set in the object scene. As a selection method by the area selection means 21, there are a case where the camera performs it automatically and a case where the user performs it manually. When performing manually, the area selection means 21 is comprised by the area selection button for selecting one of the some focus detection areas set to the object scene.

  For example, an area selection button may be displayed on the monitor, and the focus detection area to be used may be selected by operating it. Regardless of whether the camera is selected automatically or by the user, the correction movement amount α ′ described above is calculated / rewritten in association with the selected focus detection area and stored for each focus detection area. . In this case, the correction movement amount α ′ is calculated / rewritten using the position of the focus detection area and the image height position as parameters.

  As described above, in the camera according to the present embodiment, the shift Δ between the lens position D2 determined to be in focus by the AF calculation unit 94 and the lens position D1 determined to be in focus in the second focusing operation. Even when the angle changes, the driving amount of the first focusing operation in the next shooting is determined in consideration of the deviation Δ. As a result, the second focusing operation can be performed with a constant driving amount without being affected by the shift Δ, and the focusing speed can be improved.

  In addition, since the correction movement amount α ′ is calculated and rewritten corresponding to the combination of the camera body 1 and the interchangeable lens barrel 2, even if the difference Δ is different for each combination, it is affected by the difference Δ. Therefore, highly accurate AF can be performed at a high speed.

  In the above-described embodiment, the hybrid AF camera configured to perform distance measurement using a part of the subject light flux that has passed through the photographing lens has been described as an example. However, the present invention provides an external light type distance measuring device. The present invention can be similarly applied to the provided hybrid AF camera. In addition, the present invention is not limited to the above embodiment as long as the characteristics of the present invention are not impaired.

1 is a diagram illustrating an embodiment of a camera according to the present invention, and is a block diagram illustrating a schematic configuration of the camera. FIG. It is a figure which shows the relationship between the lens position of the focusing lens 3B, and a focus evaluation value. It is a flowchart explaining a focusing operation | movement. It is a figure explaining the 2nd focusing operation. It is a block diagram which shows a 1st modification. It is a flowchart which shows the operation example of a 1st modification. It is a block diagram which shows the 2nd modification.

Explanation of symbols

1: Camera body 2: Interchangeable lens barrel 3: Shooting lens 3B: Focusing lens 4: Lens drive unit 5A: Parameter storage unit 5B, 12: Movement amount storage unit 7: Image sensor 9: AF module 10: CPU
11: Evaluation value calculation unit 94: AF calculation unit

Claims (9)

An image sensor that captures a subject image formed by the imaging optical system and outputs an image signal;
First focus detection means for obtaining a first position corresponding to an in-focus position obtained using a phase difference of a subject image by a pair of light beams passing through pupils at different positions from the subject;
Second focus detection means for obtaining a focus evaluation value corresponding to the contrast of the subject image based on the image signal and obtaining a second position corresponding to the in-focus position obtained using the contrast ;
A first focusing operation for driving the focusing lens to a third position having a difference from the predetermined amount with respect to the first position , and a second for driving the focusing lens to the second position after the first focusing operation . a camera comprising a focus control means performs a focusing operation,
Correction value calculation means for calculating a correction value instead of the predetermined amount using a difference between the first position and the second position ;
After the correction value is calculated, the focus control means is configured to drive a focusing lens to a position corresponding to a difference between the first position and the calculated correction value; A camera that performs a second focusing operation for driving the focusing lens to the second position after one focusing operation . The camera of claim 1,
The camera further comprises storage means for storing the correction value of the correction value calculation means, and the correction value is updated each time a photographing operation is performed . The camera of claim 1,
The correction value calculating means, a correction value corresponding to the difference, the maximum value of the focus evaluation value in the second Go focusing operation on the basis of the detectable minimum correction value, a correction value in place of the predetermined amount A camera characterized by seeking. The camera of claim 1,
A camera comprising selection means for selecting execution / non-execution of calculation by the correction value calculation means. In the camera according to any one of claims 1 to 4,
The camera is an interchangeable lens camera in which an interchangeable lens provided with the photographing optical system is detachable,
The storage means is provided in the camera,
Correction value stored in said storage means, a camera, characterized in that stored in association with the interchangeable lens. In the camera according to any one of claims 1 to 4,
The camera is an interchangeable lens camera in which an interchangeable lens provided with the photographing optical system is detachable,
The storage means is provided in the interchangeable lens,
Wherein the correction value stored in the storage unit, a camera, characterized in that associated with the camera is stored. In the camera according to any one of claims 1 to 6,
The correction value calculating means, a camera, characterized in that the F value of the imaging optical system, the focal length, in association with at least one zoom position and focus position determining the correction value. In the camera according to any one of claims 1 to 7,
The first focus detection means can perform the detection for a plurality of positions in an image plane by the photographing optical system,
The camera according to claim 1, wherein the correction value calculation means obtains the correction value for each of the plurality of positions. The camera according to claim 8, wherein
The correction value calculating means, F value of the imaging optical system, the focal length, the zoom position, the determination of the said correction value in association with at least one position in the image plane by the focus position and the imaging optical system Features a camera.

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