JP2006030764A - Focus detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a different focus detection area from being selected every time auto-focusing is performed when subject distances are equal on the entire shooting screen.
A focus detection apparatus in which a plurality of focus detection areas as targets for detecting focus information of a photographic lens are set in a shooting screen, and final focus information is determined based on the plurality of focus information. A memory that stores focus information corresponding to one of the detection areas, a focus information comparison unit that sequentially compares the stored focus information and the focus information of another focus detection area, and the focus of the other focus detection area When the information is a value indicating that the distance is a predetermined distance or more than the stored focus information, the focus information of the other focus detection area is stored in the memory, and the comparison operation ends. Final focus information for determining the focus information stored in the memory at the time as the final focus information And a determining unit.
[Selection] Figure 1

Description

  The present invention relates to a focus detection apparatus having a plurality of focus detection areas.

An autofocus camera having a plurality of focus detection areas may have an automatic selection mode in which the camera automatically selects an optimal focus detection area based on the defocus amount of all focus detection areas and performs focus control. Many.
The following techniques are conventionally known for selecting an optimum focus detection area in this automatic selection mode. Patent Document 1 discloses a focus detection device that performs focusing control based on the closest defocus amount among a plurality of defocus amounts. Patent Document 2 discloses an automatic focus adjustment device that calculates a final defocus amount based on a distribution state of defocus amounts in a plurality of focus detection areas.
Japanese Patent No. 2753544 Japanese Patent Laid-Open No. 64-77008

  Here, when performing focusing control based on the closest defocus amount as in Patent Document 1, there are the following problems. For example, the defocus amount of all focus detection areas is almost the same in the state where the subject distance is the same on the entire shooting screen as in the case of shooting a wall. However, since the defocus amount of each focus detection area varies somewhat for each detection operation, the selected focus detection area (the focus detection area detected as being closest) may be different for each detection operation. In other words, since a different focus detection area can be selected for each autofocus while the subject distance is the same on the entire shooting screen, the photographer may be distrusted with the focus control of the camera.

In the technique of the above-mentioned Patent Document 2, it is necessary to store the defocus amounts of all the focus detection areas in the memory. Therefore, the memory capacity increases in proportion to the increase in the number of focus detection areas, and the cost of the camera increases. There was room for improvement in terms of increase.
The present invention is to solve the above-described problems of the prior art, and its purpose is to prevent different focus detection areas from being selected every time autofocus is performed in a state where the subject distance is the same on the entire shooting screen. And it is providing the focus detection apparatus which can suppress the capacity | capacitance of memory with respect to the number of focus detection areas.

  The invention according to claim 1 is a focus detection apparatus in which a plurality of focus detection areas for detecting focus information of a photographing lens are set in a photographing screen, and final focus information is determined based on the plurality of focus information. A memory that stores focus information corresponding to one of the focus detection areas, a focus information comparison unit that sequentially compares the stored focus information and the focus information of another focus detection area, and the other focus detection. When the focus information of the area is a value indicating that the distance is a predetermined distance or more than the stored focus information, the focus information of the other focus detection area is replaced with the memory and stored, and the comparison is performed. Final focus that determines the focus information stored in the memory as the final focus information at the end of the operation And having an information determining unit.

  According to a second aspect of the present invention, in the first aspect of the invention, the focus information comparison unit sequentially compares the stored focus information and the focus information of another focus detection area in consideration of an allowable range based on the depth of focus. When the focus information of the other focus detection area is a value indicating that the focus information of the other focus detection area is nearer than the stored focus information and exceeds the allowable range, The focus information of the focus detection area is stored in the memory instead of the memory.

According to a third aspect of the present invention, in the second aspect of the present invention, a lens data detection unit that detects information about the F value of the photographing lens, and an allowable range calculation unit that calculates the allowable range based on the information about the F value , Further comprising.
The invention according to claim 4 is a focus detection device in which a plurality of focus detection areas to be detected for distance information related to a subject are set in a shooting screen, and final distance information is determined based on the plurality of distance information. A memory that stores distance information corresponding to one of the focus detection areas, a distance information comparison unit that sequentially compares the stored distance information and distance information of another focus detection area, and the other focus detection area If the distance information is a value indicating that the distance information is a predetermined distance or more closer than the stored distance information, the distance information of the other focus detection area is replaced with the memory and stored, and the comparison operation is performed. And a final distance information determination unit that determines the distance information stored in the memory as the final distance information at the end of the step.

In the present invention, the focus information previously stored in the memory is more easily determined as the final focus information than the focus information of the other focus detection areas, and has a higher priority when the subject distance is the same on the entire shooting screen. The focus detection area is selected stably.
Further, according to the present invention, the number of focus information held by the focus detection device is sufficient for two focus detection areas regardless of the number of focus detection areas. Therefore, even if the number of focus detection areas increases, the memory capacity can be suppressed, which is very advantageous in terms of cost.

Hereinafter, an electronic camera which is an embodiment of a focus detection apparatus of the present invention will be described in detail with reference to the drawings (corresponding to the focus detection apparatus of claims 1 to 3).
(Description of electronic camera configuration)
As shown in FIG. 1, the electronic camera of this embodiment includes a photographic lens 100 and a camera body 200.

  The photographic lens 100 includes a photographic lens system 1 formed by combining a plurality of lenses, a diaphragm 2 for limiting the amount of incident light, a drive mechanism 3 for driving the photographic lens system 1, a lens microcomputer 4 and a lens side mount. 5. The lens microcomputer 4 stores information on the correspondence (conversion coefficient) between the defocus amount and the lens drive amount. The lens microcomputer 4 outputs information related to the F value of the taking lens 100 to the camera body 200. The lens side mount 5 is provided with electrical contacts connected to the drive mechanism 3 and the lens microcomputer 4.

The camera body 200 includes a body-side mount 6, an imaging mechanism described later, a focus detection unit 16, a memory 17, and a CPU 18.
The main body side mount 6 is coupled to the lens side mount 5 by a bayonet mechanism, a screw mechanism, or the like, so that the photographing lens 100 can be attached to the camera main body 200 in a replaceable manner. The body-side mount 6 is provided with an electrical contact corresponding to the lens-side mount 5 so that the electrical connection between the lens-side mount 5 and the body-side mount 6 is established when the photographing lens 100 is mounted. .

The photographing mechanism of the camera body 200 includes a quick return mirror 7, a focal plane shutter 8, an image sensor 9, a diffusion screen 10, a condenser lens 11, a pentaprism 12, an eyepiece lens 13, and a superimpose display unit. 14 and a sub-mirror 15 disposed on the back surface of the quick return mirror 7.
The quick return mirror 7, the focal plane shutter 8, and the image sensor 9 are arranged along the optical axis of the photographing lens 100.

  The quick return mirror 7 is tilted in front of the focal plane shutter 8 and the image sensor 9, and is flipped upward to evacuate from the photographing optical path during photographing. On the other hand, the light beam that has passed through the photographing lens 100 in the normal state is reflected upward by the quick return mirror 7 and enters the finder optical system. A part of the quick return mirror 7 is a half mirror that transmits light. Then, a part of the light beam transmitted through the quick return mirror 7 during normal operation is refracted downward by the sub-mirror 15 so that the light beam is guided to the focus detection unit 16.

The image sensor 9 photoelectrically converts a subject image during shooting and outputs an analog image signal. This analog image signal is A / D converted, and then subjected to processing such as gradation correction and white balance in the image processing unit to become photographed image data. The photographed image data is finally stored in a recording medium ( (The illustration of the image processing unit and the recording medium is omitted).
The diffusing screen 10 is located above the quick return mirror 7 so that the light beam reflected by the quick return mirror 7 at normal time once forms an image. The light beam formed on the diffusing screen 10 then passes through the condenser lens 11, the pentaprism 12 and the eyepiece lens 13 and reaches the eyes of the photographer.

The superimpose display unit 14 is configured by LEDs, prisms, and the like for lighting and displaying a position corresponding to the focus detection area on the diffusion screen 10, and is disposed in the vicinity of the pentaprism 12. The superimpose display unit 14 is lit and displayed so that the photographer can visually recognize the focus detection area finally selected by the CPU 18.
As shown in FIG. 2, the focus detection unit 16 includes five sets of focus detection optics including a field mask 21, a condenser lens 22, a diaphragm mask 23, a separator lens 24, and a line sensor 25 connected to the CPU 18. Has a system. In FIG. 2, an opening in the shape of a letter is formed in the field mask 21 corresponding to the three focus detection optical systems in the center, and the field mask 21 corresponding to the focus detection optical systems on both the left and right sides extends in the vertical direction. A rectangular opening is formed. Then, the line sensors 25 corresponding to the respective openings detect the focus, and the focus adjustment states in 11 focus detection areas Ar1 to Ar11 set in the photographing screen are detected ( (See FIG. 3).

The focus detection unit 16 divides the light flux from the subject by the condenser lens 22 and the separator lens 24 corresponding to each focus detection area, forms an image on the line sensor 25, and performs focus detection by the phase difference detection method. The stray light from the focus detection unit 16 is removed by the field mask 21 and the aperture mask 23.
The subject light corresponding to the focus detection area in the shooting screen passes through the shooting lens system 1 and enters the condenser lens 22 through the opening of the field mask 21 corresponding to each focus detection area. The light emitted from the condenser lens 22 passes through the separator lenses 24 arranged in pairs. The two images formed by the separator lens 24 are formed on the corresponding line sensors 25, respectively.

  The light intensity distribution of the two images is detected from the line sensor 25, and two-image interval data based on the light intensity distribution is output to the CPU 18. The interval between the two images on the line sensor 25 takes a predetermined value when the imaging equivalent plane is in focus (focused state). Therefore, the defocus amount (deviation amount and deviation direction from the in-focus position) can be obtained based on the values of the distance between the two image intervals detected by the line sensor 25 and the two image intervals in the focused state.

  Here, in this embodiment, when the defocus amount is negative, the in-focus position is shifted in the far distance direction, and when the defocus amount is positive, the in-focus position is shifted in the near distance direction. Define. That is, in the present embodiment, when comparing a plurality of defocus amounts, the smaller the defocus amount value including the sign, the closer the subject is to the near side closer to the camera.

The memory 17 stores a correspondence relationship between the defocus amount SDf corresponding to one of the focus detection areas and the position number of the focus detection area SAr.
The CPU 18 controls the operation of each part of the camera body 200 and executes various arithmetic processes necessary for automatic exposure and the like. The CPU 18 has a focus information comparison unit 18a, an allowable range calculation unit 18b, and a final focus information determination unit 18c.

  The focus information comparison unit 18a calculates the defocus amount Df for each focus detection area based on the two-image interval data output from the line sensor 25. Further, the focus information comparison unit 18a has data related to the reliability of the defocus amount obtained in consideration of factors such as the contrast value of the subject and the noise of the line sensor 25, and the calculated defocus amount Df. Reliability is determined based on the data.

Further, the focus information comparison unit 18a outputs the calculated defocus amount Df (defocus amount of another focus detection area) and the defocus amount SDf stored in the memory 17 to be described later which is output by the allowable range calculation unit 18b. Compare with the range data.
The allowable range calculation unit 18b calculates an allowable range based on the depth of focus based on information about the F value input from the lens microcomputer 4 via the electrical contact of the main body side mount 6, and compares the data of the allowable range with focus information comparison To the unit 18a.

  The final focus information determination unit 18c replaces the defocus amount SDf stored in the memory 17 with the defocus amount Df of another focus detection area based on the determination result of the focus information comparison unit 18a. At this time, the final focus information determination unit 18c replaces the position number of the focus detection area SAr stored in the memory 17 with a position number corresponding to another focus detection area.

The final focus information determination unit 18c has a counter for determining the end of the comparison operation of the focus information comparison unit 18a. At the end of the comparison operation, the final focus information determination unit 18c determines the defocus amount stored in the memory 17 as the final defocus amount.
(Explanation of functions and effects of electronic camera)
The electronic camera of the present embodiment is configured as described above, and the autofocus operation of the electronic camera of the present embodiment will be described below with reference to the flowchart of FIG. Note that the autofocus operation of the electronic camera is started by an operation such as half-pressing the release button by the photographer.

Step S101: The CPU 18 initializes the position number of the focus detection area SAr in the memory 17 to 0. The position number of the focus detection area SAr indicates which focus detection area in FIG. 3 is the defocus amount SDf stored in the memory 17.
Step S102: The final focus information determination unit 18c of the CPU 18 sets the numerical value j of the counter to 1. Note that the numerical value j of this counter corresponds to the position number of the focus detection area currently processed by the CPU 18.

Step S103: The focus information comparison unit 18a of the CPU 18 calculates the defocus amount Df of the focus detection area for the focus detection area corresponding to the counter value j of the final focus information determination unit 18c.
Step S104: The focus information comparison unit 18a of the CPU 18 determines the reliability of the defocus amount Df in step S103. If the defocus amount Df is reliable (YES side), the CPU 18 proceeds to step S105. On the other hand, if the defocus amount Df is not reliable (NO side), the CPU 18 discards the defocus amount Df in step S103 and proceeds to step S109.

  Step S105: The final focus information determination unit 18c of the CPU 18 determines whether or not the position number of the focus detection area SAr stored in the memory 17 is zero. When the position number of the focus detection area SAr is 0 (YES side), the CPU 18 determines that the defocus amount SDf is not stored in the memory 17 (a reliable defocus amount has not been obtained by the previous time). The process proceeds to step S107. On the other hand, when the position number of the focus detection area SAr is not 0 (NO side), since the defocus amount SDf is stored in the memory 17, the CPU 18 proceeds to step S106.

Step S106: The focus information comparison unit 18a of the CPU 18 determines whether or not the defocus amount Df in step S103 satisfies the condition of Expression (1).
Df <SDf−α (1)
Here, SDf in the above formula (1) is a defocus amount stored in the memory 17, and α is a value of an allowable range related to the focal depth output from the allowable range calculation unit 18b.

  That is, in step S106, the CPU 18 determines whether or not the defocus amount Df is a value indicating a short distance beyond the allowable range α than the defocus amount SDf. In the present embodiment, when the defocus amount SDf is the same as the defocus amount Df, or when the defocus amount SDf is a value indicating a short distance from the defocus amount Df, the CPU 18 gives priority to the defocus amount SDf. Even if the defocus amount Df is a value indicating a shorter distance than the defocus amount SDf, if the value is within the allowable range α based on the depth of focus, there is a high possibility of variation in calculation. Accordingly, also in this case, the CPU 18 gives priority to the defocus amount SDf.

When the defocus amount Df satisfies the condition of formula (1) (YES side), the CPU 18 proceeds to step S107. On the other hand, when the defocus amount Df does not satisfy the condition of the expression (1) (NO side), the CPU 18 discards the data of the defocus amount Df and proceeds to step S109.
Step S107: The final focus information determination unit 18c of the CPU 18 replaces the defocus amount SDf in the memory 17 with the defocus amount Df in step S103.

Step S108: The final focus information determination unit 18c of the CPU 18 replaces the position number of the focus detection area SAr in the memory 17 with the numerical value j of the counter (the position number of the focus detection area currently being processed).
Step S109: The final focus information determination unit 18c of the CPU 18 determines whether or not the numerical value j of the counter is 11 (that is, whether or not the focus detection area currently being processed is the last). If j = 11 (YES side), the CPU 18 proceeds to step S111. On the other hand, if j is not 11 (NO side), the CPU 18 proceeds to step S110.

  Step S110: The final focus information determination unit 18c of the CPU 18 increments the numerical value of the counter, and the CPU 18 returns to step S103 to start processing of the next focus detection area. In the present embodiment, a series of processing from step S103 to step S109 is sequentially performed in the order of the numbers of the focus detection areas Ar1 to Ar11 shown in FIG.

  Step S111: The final focus information determination unit 18c of the CPU 18 determines whether or not the position number of the focus detection area SAr stored in the memory 17 is zero. If the position number of the focus detection area SAr is 0 (YES side), the CPU 18 proceeds to step S112. On the other hand, when the position number of the focus detection area SAr is not 0 (NO side), the final focus information determination unit 18c determines the defocus amount SDf stored in the memory 17 as the final defocus amount, and the CPU 18 The process proceeds to step S113.

Step S112: The CPU 18 displays “Focus detection impossible” on a display unit (not shown) and ends the operation.
Step S113: The CPU 18 reads the position number of the focus detection area SAr from the memory 17. Then, the CPU 18 instructs the superimpose display unit 14 to turn on and display the focus detection area SAr. Thereby, the photographer can visually recognize the position of the focus detection area finally selected by the electronic camera through the eyepiece 13.

  Step S114: The CPU 18 drives the driving mechanism 3 of the photographing lens 100 based on the final defocus amount (defocus amount SDf stored in the memory 17) to adjust the photographing lens system 1 to the in-focus position. This completes the autofocus operation of the electronic camera of this embodiment. After that, when the photographer fully presses the release button, the electronic camera starts photographing the subject.

  Hereinafter, the effect of this embodiment will be described. In the present embodiment, the defocus amount Df is stored in the memory 17 only when the defocus amount Df exceeds the allowable range α and indicates a short distance than the defocus amount SDf of the memory 17. That is, in this embodiment, the focus detection area with the earlier defocus amount calculation order is more likely to be the focus detection area to be finally selected, and the defocus amount calculation order is the priority order of the focus detection area. It becomes.

  Therefore, when autofocusing a subject that is equidistant on the entire shooting screen, a focus detection area with a high priority is stably selected, and a different focus detection area may be selected for each repeated focus detection. Remarkably reduced. In particular, in the present embodiment, since the focus detection area Ar1 at the center of the shooting screen is highly likely to be selected, it is possible for the photographer to shoot with peace of mind without feeling uncomfortable when shooting a subject that is equidistant over the entire shooting screen. Can do.

In the present embodiment, the defocus amount held by the CPU 18 is sufficient for two defocus amounts SDf and Df regardless of the number of focus detection areas. Accordingly, since it is not necessary to simultaneously hold the defocus amount data of the all focus detection area at the time of calculation, the capacity of the memory can be suppressed.
(Correspondence between Claims and Embodiments)
Here, the correspondence between the claims and the embodiment is shown. Note that the correspondence shown below is an interpretation given for reference only, and does not limit the technical scope of the present invention.

The “photographing lens” corresponds to the photographing lens 100. The “focus detection device” corresponds to the focus detection unit 16 and the CPU 18 of the camera body 200. The memory 17 corresponds to “memory”.
The defocus amount SDf corresponds to “stored focus information”, and the defocus amount Df corresponds to “focus information of other focus detection areas”. The focus information comparison unit 18a corresponds to the “focus information comparison unit”. The “final focus information determination unit” corresponds to the final focus information determination unit 18c. The “lens data detection unit” corresponds to the body-side mount 6 of the camera body 200. The “allowable range calculator” corresponds to the allowable range calculator 18b.

(Supplementary items of the embodiment)
As mentioned above, although this invention has been demonstrated by said embodiment, the technical scope of this invention is not limited to the said embodiment.
Although the above embodiment has been described with respect to an example of a focus detection device for an electronic camera, the focus detection device of the present invention can of course be applied to a silver salt camera. The number of focus detection areas in the above embodiment is merely an example, and the present invention can be widely applied to focus detection apparatuses having two or more focus detection areas.

  The order of calculating the defocus amount of the focus detection area in step S110 of the above embodiment may be changed as appropriate. For example, if there is a focus detection area to be preferentially used, the defocus amount may be calculated from the focus detection area. In the above embodiment, the allowable range α is calculated based on the information about the F value. However, the allowable range α may be a fixed value (for example, about 50 μm, which is a general value of the variation width of the defocus value).

In step S106 of the above embodiment, the CPU may determine whether or not the sum of the defocus amount Df and the allowable range α is smaller than the defocus amount SDf (that is, Df + α <SDf).
The focus detection device of the present invention is not limited to the TTL phase difference detection method, and can be similarly applied to a focus detection device that obtains the subject distance by an active method or the like. That is, in the focus detection apparatus in the above case, distance information about a subject is detected by an active method or the like from a plurality of focus detection areas set in the shooting screen, and distance information corresponding to one of the focus detection areas is stored in a memory. Remember. Next, the focus detection apparatus sequentially compares the distance information stored in the memory and the distance information of the other focus detection areas, and the distance information of the other focus detection areas is closer than the distance information in the memory by a predetermined amount or more. In some cases, the distance information of other focus detection areas is stored in memory. And a focus detection apparatus performs a focus detection operation | movement based on the distance information (final distance information) finally memorize | stored in memory.

  The present invention can be applied to a focus detection device of an autofocus camera.

Schematic diagram showing the configuration of the electronic camera of the present embodiment Outline perspective view showing optical system of focus detection unit The figure which shows the arrangement of the focus detection area of the photographing screen Flow chart of autofocus operation in the electronic camera of this embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shooting lens system 2 Aperture 3 Drive mechanism 4 Lens microcomputer 5 Lens side mount 6 Main body side mount 7 Quick return mirror 8 Focal plane shutter 9 Imaging element 10 Diffusion screen 11 Condenser lens 12 Pentaprism 13 Eyepiece 14 Superimpose display unit 15 Sub mirror 16 Focus detection unit 17 Memory 18 CPU
18a Focus information comparison unit 18b Allowable range calculation unit 18c Final focus information determination unit 21 Field mask 22 Condenser lens 23 Aperture mask 24 Separator lens 25 Line sensor 100 Shooting lens 200 Camera body

Claims (4)

A focus detection device in which a plurality of focus detection areas that are targets for detecting focus information of a shooting lens are set in a shooting screen, and final focus information is determined based on the plurality of focus information,
A memory for storing focus information corresponding to one of the focus detection areas;
A focus information comparison unit for sequentially comparing the stored focus information and the focus information of another focus detection area;
When the focus information of the other focus detection area is a value indicating that the distance is a predetermined distance or more than the stored focus information, the focus information of the other focus detection area is replaced with the memory. And a final focus information determination unit that stores the focus information stored in the memory as the final focus information at the end of the comparison operation. The focus information comparison unit sequentially compares the stored focus information and the focus information of another focus detection area in consideration of an allowable range based on the depth of focus,
The final focus information determination unit is configured to detect the other focus when the focus information of the other focus detection area is a value indicating that the stored focus information is close to the focus range beyond the allowable range. The focus detection apparatus according to claim 1, wherein the focus information of an area is stored in the memory by being replaced.   The lens data detection unit that detects information related to the F value of the photographing lens, and an allowable range calculation unit that calculates the allowable range based on the information related to the F value. Focus detection device. A focus detection device in which a plurality of focus detection areas that are targets for detecting distance information about a subject are set in a shooting screen, and final distance information is determined based on the plurality of distance information,
A memory for storing distance information corresponding to one of the focus detection areas;
A distance information comparison unit that sequentially compares the stored distance information and distance information of other focus detection areas;
If the distance information of the other focus detection area is a value indicating that the distance information is closer than the stored distance information by a predetermined amount or more, the distance information of the other focus detection area is replaced with the memory. And a final distance information determining unit that stores the distance information stored in the memory at the end of the comparison operation as the final distance information.

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