JP2008070428A - Focus adjustment device and camera - Google Patents

Abstract

A focus adjustment apparatus capable of performing appropriate focus adjustment on a target object.
A first focus detection unit that detects an image corresponding to a focus detection area set in an image plane by an optical system to detect a defocus amount of the optical system, and an optical system. Based on the contrast information of the image, the detection range of the second focus detection unit 6 that detects the focus evaluation value of the optical system 1 and the first focus detection unit 2 corresponding to the focus detection area is divided into a plurality of first blocks. At least one of the first dividing means 4, the second dividing means 6 for dividing the detection range of the second focus detecting means 6 corresponding to the focus detection area into a plurality of second blocks, and the plurality of first blocks. And a control unit 8 that adjusts the focus of the optical system 1 based on the defocus amount detected for and the focus evaluation value detected for at least one of the plurality of second blocks.
[Selection] Figure 1

Description

  The present invention relates to a focus adjustment device that uses different focus detection (adjustment) methods, and a camera using the focus adjustment device.

  Conventionally, a phase difference detection method AF (hereinafter referred to as phase difference AF) and a contrast type AF based on an imaging signal (hereinafter referred to as contrast AF) are used together, and a phase difference is detected. It is known to finely adjust the focus adjustment by contrast AF after driving the photographic lens to near the in-focus position by AF (see, for example, Patent Document 1).

JP 2001-281530 A

  However, when both subjects with different distances exist in the focus detection area, the focus detection area is divided into a plurality of blocks in phase difference AF, and the influence of the subject distance is selected by selecting a block for obtaining a defocus amount. Even if it is going to be excluded, when the focus evaluation value is detected by contrast AF, the focus evaluation value for each subject having a different distance is detected, so that it is not possible to perform appropriate focus adjustment on the target subject. .

The focus adjustment apparatus according to the present invention of claim 1 includes a first focus detection unit that detects an image corresponding to a focus detection area set in an image plane by the optical system and detects a defocus amount of the optical system; The detection range of the second focus detection means for detecting the focus evaluation value of the optical system and the first focus detection means corresponding to the focus detection area is divided into a plurality of first blocks based on the contrast information of the image by the optical system. Detecting at least one of the plurality of first blocks, the second dividing means for dividing the detection range of the second focus detection means corresponding to the focus detection area into a plurality of second blocks And a control unit that adjusts the focus of the optical system based on the defocus amount and the focus evaluation value detected for at least one of the plurality of second blocks.
According to a second aspect of the present invention, in the focus adjustment apparatus according to the first aspect, the first dividing unit is configured to be able to select whether or not to perform the division, and the second dividing unit includes the first dividing unit. When the dividing means performs the division, it is divided into the second blocks, and when the first dividing means does not perform the division, it is not divided into the second blocks.
According to a third aspect of the present invention, in the focusing apparatus according to the first or second aspect, the number of divisions and the range of division of the second block are made to coincide with the number of divisions of the first block and the range of division, respectively. It is.
According to a fourth aspect of the present invention, in the focus adjustment apparatus according to the third aspect, the control means selects one of the first blocks based on a defocus amount regarding the plurality of first blocks, and relates to the selected first block. Focus adjustment is performed based on the defocus amount and the focus evaluation value related to the second block corresponding to the selected first block.
According to a fifth aspect of the present invention, in the focus adjustment apparatus according to the third aspect, the control means corresponds to the second block corresponding to the first block selected based on the detection results of the first focus detection means regarding the plurality of first blocks. When the focus cannot be adjusted with the focus evaluation value of the block, the focus adjustment is performed based on the focus evaluation values of the plurality of second blocks as a whole.
A camera according to a sixth aspect of the invention includes the focus adjustment device according to any one of the first to fifth aspects.
The invention according to claim 7 is a defocus amount obtained by detecting an image corresponding to a focus detection area set in an image plane by the optical system, and a focus evaluation value detected by contrast information of the image by the optical system, The defocus amount detected for at least one of the plurality of first blocks obtained by dividing the focus detection area and the focus detection area is applied to the focus adjustment method for adjusting the focus of the optical system based on The focus adjustment of the optical system is performed based on the focus evaluation value detected for at least one of the plurality of second blocks obtained in this way.
The invention according to claim 8 is the focus adjustment method according to claim 7, wherein the division number and division range of the second block are made to coincide with the division number and division range of the first block, respectively. .

  According to the present invention, even when subjects with different shooting distances exist in the focus detection area, the subject to be detected for the defocus amount is different from the subject to be detected for the focus evaluation value. Therefore, it is possible to detect the focus evaluation value with high speed and high accuracy reflecting the defocus amount with respect to the target subject.

  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. The camera according to the present embodiment is a hybrid AF type camera capable of performing focus adjustment using at least one of phase difference AF and contrast AF, and FIG. 1 is a block diagram illustrating the configuration of the main part thereof. .

  The camera is provided with a phase difference AF detection element 2, an imaging element 5, a lens drive control unit 8, and a control circuit 100. The control circuit 100 includes a CPU, ROM, RAM, and various peripheral circuits. Functionally, the control circuit 100 includes an AF-CCD control unit 3, a defocus amount calculation unit 4, a contrast calculation unit 6, and a lens drive amount calculation unit 7. Yes. Subject light is incident on the imaging element 5 and the phase difference AF detection element 2 via the imaging optical system 1. The photographing optical system 1 may be provided integrally in the camera, or may be provided in a separate lens barrel that can be attached to and detached from the camera.

  The photographing optical system 1 is provided with a focus adjustment lens (not shown), and the focus adjustment of the photographing optical system 1 can be performed by moving the focus adjustment lens in the optical axis direction by the lens drive control unit 8. it can. The subject light that has passed through the photographic optical system 1 is imaged on the imaging surface of the imaging device 5. Part of the subject light also enters the phase difference AF detection element 2 provided at a position optically equivalent to the imaging element 5.

  The phase difference AF detection element 2 includes, for example, a pupil division type focus detection optical system that divides a focus detection light beam into a pair of focus detection light beams that pass through different regions of the exit pupil of the photographing lens 1, and a pair of divided pairs. And a pair of CCD line sensors that receive a light beam and output a light reception signal corresponding thereto. The CCD line sensor of the phase difference AF detection element 2 is controlled by the AF-CCD control unit 3, and the light reception signal output from the CCD line sensor is read into the AF-CCD control unit 3. The AF-CCD control unit 3 inputs the read light reception signal to the defocus amount calculation unit 4.

  The defocus amount calculation unit 4 calculates an image plane displacement amount (hereinafter referred to as a defocus amount) of the imaging plane with respect to the planned focal plane of the photographing lens 1 based on the accumulated signal output from the AF-CCD control unit 3. Calculate. That is, each of the subject images by the pair of defocus amount detection light beams that pass through different areas of the exit pupil of the photographing lens 1 is formed on each of the pair of CCD line sensors.

  The pair of subject images on the CCD line sensor approach each other in a so-called front pin state in which the photographing lens 1 forms a sharp image of the subject before the planned focal plane, and conversely forms a sharp image of the subject behind the planned focal plane. In the so-called rear pin state, they move away from each other. In a focused state that connects a sharp image of the subject on the planned focal plane, the pair of subject images relatively match. Therefore, by calculating the correlation between the signals output from the pair of CCD line sensors and calculating the relative positional deviation amount (relative interval) between the two images, the focus adjustment state of the photographing lens 1, that is, the defocus amount is obtained. It is done.

  The contrast calculation unit 6 selects an image pickup signal for the contrast AF area from the image pickup signal output from the image pickup element 5, extracts a high-frequency component from the image pickup signal, and performs a known focus evaluation value calculation. In a focused state in which the photographic lens 1 forms a sharp image on the image sensor 5, the blur of the edge of the subject image is minimized and the contrast is maximized, so that the focus evaluation value is also maximized.

  The lens drive amount calculation unit 7 calculates the lens drive amount based on the defocus amount calculated by the defocus amount calculation unit 4. The lens drive control unit 8 moves the focus adjustment lens in the optical axis direction based on the lens drive amount calculated by the lens drive amount calculation unit 7. Thereby, the focus adjustment state of the photographic lens 1 is adjusted by the phase difference AF.

  On the other hand, when performing contrast AF, the lens drive control unit 8 drives the focus adjustment lens to a position where the focus evaluation value calculated by the contrast calculation unit 6 is maximized while driving the focus adjustment lens. This contrast AF is a so-called hill climbing method. As a focus adjustment method based on the focus evaluation value, a method may be used in which the focus adjustment lens is scan-driven within a predetermined range to calculate the relationship of the focus evaluation value with respect to the lens position and the focus adjustment is performed based on this relationship. Good.

  FIG. 2 is a diagram showing an AF area on the image plane and a detection area of the phase difference AF detection element 2. In the example shown in FIG. 2, five AF areas 20a to 20e are arranged. In the AF areas 20b and 20d, phase difference detection areas 2b and 2d by line sensors arranged in the horizontal direction in the figure are arranged, and the AF area 20c. , 20e are provided with phase difference detection areas 2c, 2e by line sensors arranged in the vertical direction in the figure. In the center AF area 20a, a phase difference detection area 2a by line sensors arranged in the left-right direction and a phase difference detection area 2a 'by line sensors arranged in the up-down direction are arranged. When phase difference AF is performed, one of these phase difference detection areas is selected.

  Contrast detection areas are set in the AF areas 20a to 20e in FIG. 2 corresponding to the phase difference detection areas 2a to 2e and 2a '. When calculating the above-described focus evaluation value, calculation is performed based on the imaging signals of the pixels included in the contrast detection area. 3A and 3B are diagrams showing the relationship between the phase difference detection area and the contrast detection area. FIG. 3A shows the AF area 20b and the phase difference detection area 2b. FIG. 3B shows the AF area 20b and the contrast. The detection area 21b is shown. In the present embodiment, the range f ′ of the contrast detection region 21b is set to be the same as the detection range f of the phase difference detection region 2b.

  FIG. 4 is a flowchart for explaining the focus adjustment operation in the present embodiment. In step S101, the focus detection signal is read from the phase difference AF detection element 2 into the AF-CCD control unit 3, the defocus amounts of the phase difference detection areas 2a to 2e are calculated, and any one phase difference detection area is selected. To do. For example, when it is a condition to focus on the closest subject, a phase difference detection region in which the defocus amount indicates the closest distance is selected. Hereinafter, a case where the phase difference detection region 2b illustrated in FIG. 3 is selected will be described as an example.

  In step S102, based on the focus detection signal of the phase difference AF detection element 2 corresponding to the selected phase difference detection region 2b, whether or not the condition for dividing the phase difference detection region 2b into a plurality of blocks is satisfied. judge. Conditions for block division include (a) not MF, (b) short focal length, and the like.

  If it is determined in step S102 that the division condition is satisfied, the process proceeds to step S103. If it is determined that the division condition is not satisfied, the process proceeds to step S110. When the process proceeds to step S110, the focus adjustment lens is driven based on the defocus amount of the selected phase difference detection region 2b. In step S111, the quick return mirror is raised, and the process proceeds to step S112 to perform contrast AF. In step S112, contrast AF is performed using the imaging signal of the entire contrast detection area 21b.

  On the other hand, when the process proceeds from step S102 to step S103, the selected phase difference detection area 2b is divided into a plurality of blocks in step S103. In the example shown in FIG. 3A, the phase difference detection area 2b is divided into five blocks Ba to Be. Note that the method of dividing the phase difference detection region 2b is a well-known technique (see, for example, JP-A-8-15603), and a description thereof is omitted here.

  In step S104, the defocus amount is calculated for a block whose defocus amount has not been calculated among the five divided blocks Ba to Be. In step S105, it is determined whether or not the defocus amount calculation has been completed for all the blocks Ba to Be. If it is determined in step S105 that the process has not been completed, the process returns to step S104. If it is determined that the process has been completed, the process proceeds to step S106. In this way, the defocus amount is calculated for all the blocks Ba to Be in the phase difference detection area 2b.

  In step S106, an adopted block used for the phase difference AF is determined from the five blocks Ba to Be. Here, description will be made assuming that the block Bc is determined as the adopted block. There are various conditions for determining the adopted block. As an example, the adopted block having the closest defocus amount is determined as the adopted block. In step S107, the focus adjustment lens is driven based on the defocus amount of the block Bc employed in step S106. In step S108, the quick return mirror is moved up.

  In step S109, as shown in FIG. 3, the range f ′ of the contrast detection area 21b is set to be the same as the detection range f of the AF area 20b, and the five blocks Ba ′ to Be ′ to be divided are also phase difference detection areas. Match with the blocks Ba to Be of 2b. Then, the block Bc ′ corresponding to the block Bc adopted in the phase difference AF (that is, the position and the range coincide with each other) is set as the adopted block in the contrast AF.

  In step S113, a well-known contrast AF is performed using the image pickup signal in the range of the adopted block Bc 'to obtain a focus position. In step S114, it is determined whether or not the in-focus position is determined by the contrast AF in step S113. If the in-focus position is determined, the process proceeds from step S114 to step S115, and the focus adjustment lens is driven to the determined in-focus position.

  On the other hand, if the in-focus position has not been determined, the process proceeds from step S114 to step S116, and the focus adjustment lens is driven to a predetermined position. For example, the lens is moved to the lens position obtained by the phase difference AF. When the hill-climbing method is adopted for the contrast AF in step S113, the in-focus position may be searched for by the contrast AF of scan driving and moved to that position. In this way, when the focus adjustment lens is driven based on the contrast AF, a series of focus adjustment operations are terminated.

  Note that, when the focus position cannot be determined by the focus evaluation value based on the imaging signal of the block Bc ′, the whole of the divided five blocks Ba ′ to Be ′ before proceeding to step S115 as in the above-described embodiment. That is, the focus evaluation value based on the imaging signal of the contrast detection area 21b may be obtained and the process of step S114 may be performed again. Thereby, the situation where it cannot focus is avoided as much as possible.

The camera according to the present embodiment described above has the following operational effects.
(1) One of the blocks Bc is selected based on the defocus amounts regarding the plurality of blocks Ba to Be, and the defocus amount regarding the selected block Bc and the focus evaluation value regarding the block Bc corresponding to the selected block Bc Based on the focus adjustment, it is possible to prevent the defocus amount detection target from being different from the focus evaluation value detection target, and the defocus amount is reflected to the target main subject. Thus, it is possible to detect the focus evaluation value with high speed and high accuracy. Furthermore, by making the number of divisions and the range of division of the blocks Ba ′ to Be ′ coincide with the number of divisions and the range of division of the blocks Ba to Be, the detection targets are more easily matched. In the above-described embodiment, one block is adopted, but a plurality of blocks may be adopted.
(2) When the phase difference detection area 2b is divided, the contrast detection area 21b is also divided, and when the phase difference detection area 2b is not divided, the contrast detection area 21b is also not divided, thereby controlling the defocus amount. And the detection range of the focus evaluation value can be matched.
(3) When focus adjustment cannot be performed with the focus evaluation value of the block Bc ′ corresponding to the selected block Bc, focus adjustment is performed based on the focus evaluation values of the plurality of blocks Ba ′ to Be ′. Thus, it is possible to reduce the occurrence of a situation where focusing cannot be performed.

  The embodiment described above is merely an example, and the present invention is not limited to the above embodiment as long as the characteristics of the present invention are not impaired. For example, the number of AF areas, the number of block divisions, and the like are not limited to those described above, and are applicable not only to the camera focus adjustment device but also to other imaging devices.

It is a block diagram explaining one Embodiment of the camera by this invention. It is a figure which shows arrangement | positioning of AF area and a phase difference detection area on an image surface. It is a figure which shows the relationship between a phase difference detection area and a contrast detection area, (a) shows AF area 20b and phase difference detection area 2a, (b) shows AF area 20b and contrast detection area 21b. It is a flowchart explaining the focus adjustment operation | movement in this Embodiment.

Explanation of symbols

  1: imaging optical system, 2: phase difference AF detection element, 2a to 2e: phase difference detection area, 3: AF-CCD control unit, 4: defocus amount calculation unit, 5: image sensor, 6: contrast calculation unit, 7: Lens drive amount calculation unit, 8: Lens drive control unit, 20a to 20e: AF area, 21a to 21b: Contrast detection region, 100: Control circuit, Ba to Be and Ba ′ to Be ′: Block

Claims (8)

First focus detection means for detecting an image corresponding to a focus detection area set in an image plane by the optical system and detecting a defocus amount of the optical system;
Second focus detection means for detecting a focus evaluation value of the optical system based on contrast information of an image by the optical system;
First dividing means for dividing the detection range of the first focus detecting means corresponding to the focus detection area into a plurality of first blocks;
Second dividing means for dividing the detection range of the second focus detecting means corresponding to the focus detection area into a plurality of second blocks;
Control for performing focus adjustment of the optical system based on the defocus amount detected for at least one of the plurality of first blocks and the focus evaluation value detected for at least one of the plurality of second blocks. And a focus adjustment device. The focus adjustment apparatus according to claim 1,
The first dividing unit is configured to be able to select whether or not to perform the division,
The second dividing means divides into the second blocks when the first dividing means performs division, and does not divide into the second blocks when the first dividing means does not perform division. A focusing device characterized by that. The focusing apparatus according to claim 1 or 2,
The focus adjustment apparatus characterized in that the number of divisions and the range of division of the second block are made to coincide with the number of divisions and the range of division of the first block, respectively. The focus adjustment apparatus according to claim 3.
The control unit selects one of the first blocks based on the defocus amounts related to the plurality of first blocks, and corresponds to the defocus amount related to the selected first block and the selected first block. A focus adjustment device that performs focus adjustment based on the focus evaluation value related to the second block. The focus adjustment apparatus according to claim 3.
The control means has a plurality of second blocks when focus adjustment cannot be performed with the focus evaluation value of the second block corresponding to the first block selected based on the detection result of the first focus detection section regarding the plurality of first blocks. A focus adjustment apparatus that performs focus adjustment based on a focus evaluation value of two blocks as a whole.   A camera comprising the focus adjustment device according to claim 1. Based on a defocus amount obtained by detecting an image corresponding to a focus detection area set in an image plane by the optical system, and a focus evaluation value detected by contrast information of the image by the optical system, the optical In the focus adjustment method for adjusting the focus of the system,
About the defocus amount detected for at least one of the plurality of first blocks obtained by dividing the focus detection area, and at least one of the plurality of second blocks obtained by dividing the focus detection area A focus adjustment method, wherein the focus of the optical system is adjusted based on the detected focus evaluation value. The focus adjustment method according to claim 7,
The focus adjustment method, wherein the number of divisions and the range of division of the second block are made to coincide with the number of divisions and the range of division of the first block, respectively.

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